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Low Health Literacy and Health Outcomes: An Updated
Systematic Review
Nancy D. Berkman, PhD; Stacey L. Sheridan, MD, MPH; Katrina E. Donahue, MD, MPH; David J. Halpern, MD, MPH; and
Karen Crotty, PhD, MPH
Background: Approximately 80 million Americans have limited
health literacy, which puts them at greater risk for poorer access to
care and poorer health outcomes.
Purpose: To update a 2004 systematic review and determine
whether low health literacy is related to poorer use of health care,
outcomes, costs, and disparities in health outcomes among persons
of all ages.
Data Sources: English-language articles identified through MEDLINE,
CINAHL, PsycINFO, ERIC, and Cochrane Library databases and
hand-searching (search dates for articles on health literacy, 2003
to 22 February 2011; for articles on numeracy, 1966 to 22
February 2011).
Study Selection: Two reviewers independently selected studies that
compared outcomes by differences in directly measured health lit-
eracy or numeracy levels.
Data Extraction: One reviewer abstracted article information into
evidence tables; a second reviewer checked information for accu-
racy. Two reviewers independently rated study quality by using
predefined criteria, and the investigative team jointly graded the
overall strength of evidence.
Data Synthesis: 96 relevant good- or fair-quality studies in 111
articles were identified: 98 articles on health literacy, 22 on nu-
meracy, and 9 on both. Low health literacy was consistently asso-
ciated with more hospitalizations; greater use of emergency care;
lower receipt of mammography screening and influenza vaccine;
poorer ability to demonstrate taking medications appropriately;
poorer ability to interpret labels and health messages; and, among
elderly persons, poorer overall health status and higher mortality
rates. Poor health literacy partially explains racial disparities in some
outcomes. Reviewers could not reach firm conclusions about the
relationship between numeracy and health outcomes because of
few studies or inconsistent results among studies.
Limitations: Searches were limited to articles published in English.
No Medical Subject Heading terms exist for identifying relevant
studies. No evidence concerning oral health literacy (speaking and
listening skills) and outcomes was found.
Conclusion: Low health literacy is associated with poorer health
outcomes and poorer use of health care services.
Primary Funding Source: Agency for Healthcare Research and
Quality.
Ann Intern Med. 2011;155:97-107. www.annals.org
For author affiliations, see end of text.
The term “health literacy” refers to a set of skills that
people need to function effectively in the health care
environment (1). These skills include the ability to read
and understand text and to locate and interpret informa-
tion in documents (print literacy); use quantitative infor-
mation for tasks, such as interpreting food labels, measur-
ing blood glucose levels, and adhering to medication
regimens (numeracy); and speak and listen effectively (oral
literacy) (2, 3).
Approximately 80 million U.S. adults are thought to
have limited health literacy, which puts them at risk for
poorer health outcomes. Rates of limited health literacy are
higher among elderly, minority, and poor persons and
those with less than a high school education (4). Numer-
ous policy and advocacy organizations have expressed con-
cern about barriers caused by low health literacy, notably
the Institute of Medicine’s report Health Literacy: A Pre-
scription to End Confusion in 2004 (5) and the U.S. De-
partment of Health and Human Services’ report National
Action Plan to Improve Health Literacy in 2010 (6).
To understand the relationship between health literacy
level and use of health care services, health outcomes, costs,
and disparities in health outcomes, we conducted a system-
atic evidence review for the Agency for Healthcare Re-
search and Quality (AHRQ) (published in 2004), which
was limited to the relationship between print literacy and
health outcomes (7). We found a consistent association
between low health literacy (measured by reading skills)
and more limited health-related knowledge and compre-
hension. The relationship between health literacy level and
other outcomes was less clear, primarily because of a lack of
studies and relatively unsophisticated methods in the avail-
able studies.
In this review, we update and expand the earlier review
(7). Since 2004, researchers have conducted new and more
sophisticated studies. Thus, in synthesizing the literature,
See also:
Print
Editors’ Notes ..............................98
Editorial comment..........................129
Related article..............................87
Web-Only
Appendix Tables
Appendix Figure
Supplement
Conversion of graphics into slides
Annals of Internal Medicine Review
www.annals.org 19 July 2011 Annals of Internal Medicine Volume 155 • Number 2 97
we can now consider the relationship between outcomes
and health literacy (print literacy alone or combined with
numeracy) and between outcomes and the numeracy com-
ponent of health literacy alone.
METHODS
We developed and followed a protocol that used stan-
dard AHRQ Evidence-based Practice Center methods. The
full report describes study methods in detail and presents
evidence tables for each included study (1).
Literature Search
We searched MEDLINE, CINAHL, the Cochrane Li-
brary, PsycINFO, and ERIC databases. For health literacy,
our search dates were from 2003 to May 2010. For nu-
meracy, they were from 1966 to May 2010; we began at an
earlier date because numeracy was not addressed in our
2004 review. For this review, we updated our searches be-
yond what was included in the full report from May 2010
through 22 February 2011 to be current with the most
recent literature. No Medical Subject Heading terms spe-
cifically identify health literacy–related articles, so we con-
ducted keyword searches, including health literacy,literacy,
numeracy, and terms or phrases used to identify related
measurement instruments. We also hand-searched refer-
ence lists of pertinent review articles and editorials. Appen-
dix Table 1 (available at www.annals.org) shows the full
search strategy.
Study Selection
We included English-language studies on persons of
all ages whose health literacy or that of their caregivers
(including numeracy or oral health literacy) had been mea-
sured directly and had not been self-reported. Studies had
to compare participants in relation to an outcome, includ-
ing health care access and service use, health outcomes, and
costs of care. For numeracy studies, outcomes also included
knowledge, because our earlier review had established the
relationship between only health literacy and knowledge.
We did not examine outcomes concerning attitudes, social
norms, or patient–provider relationships.
Data Abstraction and Quality Assessment
After determining article inclusion, 1 reviewer entered
study data into evidence tables; a second, senior reviewer
checked the information for accuracy and completeness.
Two reviewers independently rated the quality of studies as
good, fair, or poor by using criteria designed to detect
potential risk of bias in an observational study (including
selection bias, measurement bias, and control for potential
confounding) and precision of measurement.
Data Synthesis and Strength of Evidence
We assessed the overall strength of the evidence for
each outcome separately for studies measuring health liter-
acy and those measuring numeracy on the basis of infor-
mation only from good- and fair-quality studies. Using
AHRQ guidance (8), we graded the strength of evidence as
high, moderate, low, or insufficient on the basis of the
potential risk of bias of included studies, consistency of
effect across studies, directness of the evidence, and preci-
sion of the estimate (Table 1). We determined the grade
on the basis of the literature from the update searches. We
then considered whether the findings from the 2004 review
would alter our conclusions. We graded the body of evi-
dence for an outcome as low if the evidence was limited to
1 study that controlled for potential confounding variables
or to several small studies in which all, or only some, con-
trolled for potential confounding variables or as insufficient
if findings across studies were inconsistent or were limited
to 1 unadjusted study. Because of heterogeneity across
studies in their approaches to measuring health literacy,
numeracy, and outcomes, we summarized the evidence
Context
Several studies show that people with low health liter-
acy skills have poorer health-related knowledge and
comprehension.
Contribution
This updated systematic review of 96 studies found that
low health literacy is associated with poorer ability to un-
derstand and follow medical advice, poorer health out-
comes, and differential use of some health care services.
Caution
No studies examined the relationship between oral literacy
(speaking and listening skills) and outcomes.
Implication
Although it is challenging, we need to find feasible ways
to improve patients’ health literacy skills and reduce the
negative effects of low health literacy on outcomes.
—The Editors
Table 1. Strength of Evidence Grades and Definitions
Grade Definition
High High confidence that the evidence reflects the true effect.
Further research is very unlikely to change our confidence
in the estimate of effect.
Moderate Moderate confidence that the evidence reflects the true
effect. Further research may change our confidence in the
estimate of effect and may change the estimate.
Low Low confidence that the evidence reflects the true effect.
Further research is likely to change our confidence in the
estimate of effect and is likely to change the estimate. The
evidence was graded as low if findings were limited to
only 1 or a few studies that controlled for potential
confounding or the preponderance of evidence was based
on studies that did not control for potential confounding.
Insufficient Evidence either is unavailable or does not permit estimation
of an effect. Inconsistent findings across studies were
generally graded as insufficient, as was evidence limited to
1 study that did not control for potential confounding.
Review Outcomes Related to Low Health Literacy
98 19 July 2011 Annals of Internal Medicine Volume 155 • Number 2 www.annals.org
through consensus discussions and did not conduct any
meta-analyses.
Role of the Funding Source
AHRQ reviewed a draft report and provided copyright
release for this manuscript. The funding source did not
participate in conducting literature searches, determining
study eligibility, evaluating individual studies, grading evi-
dence, or interpreting results.
RESULTS
First, we present the results from our literature search
and a summary of characteristics across studies, followed
by findings specific to health literacy then numeracy. We
generally highlight evidence of moderate or high strength
and mention only outcomes with low or insufficient evi-
dence. Where relevant, we comment on the evidence pro-
vided through the 2004 review. Tables 2 and 3summarize
our findings and strength-of-evidence grade for each in-
cluded health literacy and numeracy outcome, respectively.
Characteristics of Reviewed Studies
We identified 3823 citations and evaluated 1012 full-
text articles (Appendix Figure, available at www.annals
.org). Ultimately, we included 96 studies rated as good or
fair quality. These studies were reported in 111 articles
because some investigators reported study results in multi-
ple publications (98 articles on health literacy, 22 on nu-
meracy, and 9 on both). We found no studies that exam-
ined outcomes by the oral (verbal) component of health
literacy. Of the 111 articles, 100 were rated as fair quality.
All studies were observational, primarily cross-sectional de-
signs (91 of 111 articles). The Supplement (health literacy)
and Appendix Table 2 (numeracy) (both available at www
.annals.org) present summary information for each in-
cluded article.
Studies varied in their measurement of health literacy
and numeracy. Commonly used instruments to measure
health literacy are the Rapid Estimate of Adult Literacy in
Medicine (REALM) (9), the Test of Functional Health
Literacy in Adults (TOFHLA) (10), and short TOFHLA
(S-TOFHLA). Instruments frequently used to measure nu-
meracy are the Schwartz–Woloshin Numeracy Test (11)
and the Wide Range Achievement Test (WRAT) math
subtest (12).
Studies also differed in how investigators distinguished
between levels or thresholds of health literacy—either as a
continuous measure or as categorical groups. Some studies
identified 3 groups, often called inadequate,marginal, and ad-
equate, whereas others combined 2 of the 3 groups. Because
evidence was sparse for evaluating differences between mar-
ginal and adequate health literacy, our results focus on the
differences between the lowest and highest groups.
Studies in this update generally included multivariate
analyses rather than simpler unadjusted analyses. They varied
considerably, however, in regard to which potential con-
founding variables are controlled (Supplement and Appendix
Table 2). All results reported here are from adjusted analyses
that controlled for potential confounding variables, unless
otherwise noted.
Relationship Between Health Literacy and Outcomes
Use of Health Care Services and Access to Care
Emergency Care and Hospitalizations. Nine studies ex-
amining the risk for emergency care use (13–21) and 6
examining the risk for hospitalizations (14–19) provided
moderate evidence showing increased use of both services
among people with lower health literacy, including elderly
persons, clinic and inner-city hospital patients, patients
with asthma, and patients with congestive heart failure.
Outcomes did not differ among adolescents with HIV or
among children (based on parents’ health literacy) (19,
21). Studies in our 2004 review also found increased hos-
pitalizations (7).
Preventive Services. Four studies provided moderate ev-
idence of a lower probability of mammography screening
(18, 22–24) and influenza immunizations (22, 23, 25, 26)
in low health literacy groups. Two of the mammography
studies were conducted in a nationally representative
sample of elderly persons. Our 2004 report found sim-
ilar results (7).
Health Care–Related Skills
Taking Medications Appropriately. Six studies provided
moderate evidence that low health literacy is related to
poorer skills in taking medications. Three studies directly
observed whether participants take prescription medica-
tions appropriately and generally found poorer skills
among those with low health literacy (27–29). In 1 good-
quality study, patients with coronary heart disease and low
health literacy were less likely to identify all of their med-
ications (27). Patients with HIV and low health literacy
scored significantly lower during a mock exercise that mea-
sured management of medication (28). Elderly persons
with low health literacy were less able to open and take
their medications (29).
Three analyses examined other measures of taking
medications properly—self-reported use of nonstandard-
ized dosing instruments (such as kitchen spoons), observa-
tion of use of common dosing instruments, and biological
test results (30–32). The 2 dosing-instrument studies re-
ported poorer performance among persons with low health
literacy (31, 32).
Interpreting Labels and Health Messages. Studies pro-
vided moderate evidence that low health literacy is associated
with poorer interpretation of labels (prescription medications
and nutrition) and health messages. Adult patients with low
health literacy in primary care clinics were less able to describe
how they would take 5 medications and had a greater proba-
bility of misunderstanding instructions on 1 or more labels
(33). In an unadjusted analysis, they were also less able to
correctly interpret 4 of 5 primary medication labels and were
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www.annals.org 19 July 2011 Annals of Internal Medicine Volume 155 • Number 2 99
Table 2. Health Literacy Outcome Results: Strength of Evidence and Summary of Findings, 2004 and 2011
Outcome Study Design Articles (Articles
Controlling for
Confounding),
n (n)
Low vs. Adequate Health Literacy Strength of
Evidence: 2011
2004 2011 2004 2011
Access to care Cohort
Cross-sectional
0
1 (1)
4 (4)
6 (5)
No difference Inconsistent Insufficient
Access to insurance Cross-sectional 0 1 (1) NA: no studies Decrease Low
Adherence Cohort
Cross-sectional
2 (0)
2 (1)
7 (7)
10 (10)
Inconsistent Inconsistent Insufficient
Alcohol and drug use Cross-sectional 1 (1) 2 (2) No difference Inconsistent Insufficient
Asthma self-care Cross-sectional 1 (1) 1 (1) Decrease Decrease Low
Asthma severity and
control
Cross-sectional 0 2 (1) NA: no studies Inconsistent Insufficient
Chronic disease Cohort
Cross-sectional
1 (1) 2 (0)
5 (3)
No difference Inconsistent Insufficient
Colon cancer screening Cross-sectional 0 5 (5) NA: no studies Decrease Insufficient
Dental disease Cross-sectional 0 2 (2) NA: no studies Inconsistent Insufficient
Diabetes control and
related symptoms
Cross-sectional 3 (2) 8 (7) Inconsistent Inconsistent Insufficient
Diabetes
self-management
Cross-sectional 0 1 (1) NA: no studies Decrease Low
Emergency care visits Cohort
Cross-sectional
0
0
6 (4)
3 (3)
NA: no studies Increase Moderate
Seeking health-related
information
Cross-sectional 0 1 (1) NA: no studies No difference Low
Health status
Adolescents Cross-sectional 0 1 (1) NA: no studies Decrease Low
All adults Cross-sectional 2 (2) 1 (1) Decrease No difference Low
Health status and
quality of life
Elderly persons Cohort
Cross-sectional
0
1 (0)
1 (1)
5 (4)
Decrease Decrease Moderate
Specific diseases Cross-sectional 2 (0) 7 (7) No difference Inconsistent Insufficient
Mental and physical
functioning:
elderly persons
Cohort
Cross-sectional
0 3 (2)
2 (2)
NA: no studies Inconsistent Insufficient
Healthy lifestyle
(physical activity,
eating habits, and
seat belt use)
Cross-sectional 0 5 (4; for some
outcomes)
NA: no studies Inconsistent Insufficient
HIV risk and sexual
behavior
Cohort
Cross-sectional
0
0
1 (1)
2 (2)
NA: no studies Inconsistent Insufficient
HIV severity and
symptoms
Cohort
Cross-sectional
3 (0) 1 (1)
4 (3)
Inconsistent No difference in 4 studies Low
Hospitalization Cohort
Cross-sectional
2 (2)
0
4 (3)
2 (2)
Increase Increase Moderate
Hypertension control Cross-sectional 1 (1) 2 (2) No difference Inconsistent Insufficient
Immunization
Influenza Cohort
Cross-sectional
0
1 (1)
1 (1)
3 (3)
Decrease Decrease Moderate
Pneumococcal Cohort
Cross-sectional
0
1 (1)
1 (1)
1 (1)
Decrease Inconsistent Insufficient
Interpreting labels and
health messages
Cross-sectional 0 5 (4) NA: no studies Decrease Moderate
Knowledge Cohort
Cross-sectional
1 (0)
9 (7)
NA Decrease NA: analysis not repeated Not
re-evaluated
Mammography Cross-sectional 1 (1) 4 (4) Decrease Decrease Moderate
Mental health
symptoms
Cohort
Cross-sectional
1 (0)
4 (2)
2 (1)
8 (4)
Decrease Greater in 8 studies Low
Mortality: elderly
persons
Cohort 0 3 (3) NA: no studies Increase High
Obesity and weight Cohort
Cross-sectional
0
0
1 (0)
4 (1)
NA: no studies Inconsistent Insufficient
Pap tests Cross-sectional 1 (1) 3 (3) Decrease Decrease Low
Prostate cancer control Cross-sectional 1 (1) 1 (1) No difference Decrease Low
Review of prescription
information
Cross-sectional 0 1 (1) NA: no studies Decrease Low
Self-efficacy Cross-sectional 0 6 (5) NA: no studies Inconsistent Insufficient
Continued on following page
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100 19 July 2011 Annals of Internal Medicine Volume 155 • Number 2 www.annals.org
less likely to look at auxiliary labels (34). Another study found
that persons with low health literacy were less likely to under-
stand nutrition labels (35). In a third study, mothers with low
literacy in Nepal had poorer ability to give an organized health
narrative (36).
Disease Prevalence and Severity
Mental Health Outcomes. Although 8 of 10 studies
found that patients with low health literacy were more
likely to have symptoms of depression or to be considered
depressed, we judged the strength of evidence as low (14,
19, 26, 37–43). Despite the general consistency of results,
only 1 depression study rigorously controlled for potential
confounders. In our earlier review, studies evaluating de-
pression were inconsistent (7).
Severity and Symptoms of HIV Infection. Studies con-
cerning HIV infection severity and health literacy were
judged as low strength of evidence because most included
limited control for confounding and had small sample
sizes. Four studies (1 unadjusted) did not find differences
in HIV infection severity by health literacy (19, 40, 44,
45). In contrast, low health literacy was associated with less
intensity of symptoms in 1 study that controlled only for
Hispanic ethnicity (38). Our earlier review, limited to un-
adjusted analyses, found inconsistent results (7).
Global Health Status of Elderly Persons
Five studies found poorer health status among elderly
persons with low health literacy (18, 22, 25, 26, 46– 49); we
judged the evidence to be moderate. Studies included 1 good-
quality, nationally representative sample (22); patients in Chi-
cago, Illinois (18, 47); Prudential Medicare managed care en-
rollees (25, 48); and elderly persons in Korea (46). Two
unadjusted analyses—one of elderly persons in Pittsburgh,
Pennsylvania, and in Memphis, Tennessee (26), and a second
of the Prudential Medicare sample that was included in our
2004 review (49)—also found the same result.
Death
Higher all-cause mortality rates of elderly persons were
related to lower health literacy in 2 large, good-quality
Table 2—Continued
Outcome Study Design Articles (Articles
Controlling for
Confounding),
n (n)
Low vs. Adequate Health Literacy Strength of
Evidence: 2011
2004 2011 2004 2011
Smoking Cross-sectional 3 (1) 2 (2) Inconsistent Inconsistent Insufficient
STD (testing) Cross-sectional 1 (1) 1 (1) Increase Increase Low
Taking medications
appropriately
Cohort
Cross-sectional
0
0
1 (1)
5 (5)
NA: no studies Decrease Moderate
Costs Cohort 1 (1) 2 (2) No difference Inconsistent Insufficient
Disparities Cohort
Cross-sectional
0
1 (1)
1 (1)
5 (5)
Health literacy mediates racial
disparity in 1 study
Health literacy partially mediates
racial disparities in some
outcomes; no differences in
ethnicity; and sex differences
for 1 outcome
Race, ethnicity,
and sex: low
NA ⫽not applicable; Pap ⫽Papanicolaou; STD ⫽sexually transmitted disease.
Table 3. Numeracy Outcome Results: Strength of Evidence and Summary of Findings, 2011*
Outcome Study Design Articles (Articles
Controlling for
Confounding),
n (n)
Low vs. Adequate Numeracy Strength of Evidence
Accuracy of risk perception Cross-sectional 6 (4) Inconsistent Insufficient
Behavior Cross-sectional 1 (0) No difference Insufficient
Disease prevalence and severity Cross-sectional 5 (4) Inconsistent Insufficient
Knowledge Cross-sectional 5 (4) Inconsistent Insufficient
Self-efficacy Cross-sectional 3 (0) Decrease Low
Skills Cohort
Cross-sectional
1 (1)
5 (4)
Taking medication (n⫽4): inconsistent
Interpretation of health information
(n⫽2): decrease
Taking medication: insufficient
Interpretation of health
information: low
Quality of life Cross-sectional 1 (1) Decrease Low
Use of health care services Cross-sectional 2 (2) Inconsistent Insufficient
Disparities Cross-sectional 3 (3) Numeracy partially mediates relationship
between race and 2 outcomes and
between sex and 1 outcome
Low
*Numeracy studies were not included in the 2004 review.
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www.annals.org 19 July 2011 Annals of Internal Medicine Volume 155 • Number 2 101
studies, after participants’ demographic characteristics,
health status, and other factors were controlled for;
strength of evidence was high (48, 50, 51). The inadequate
health literacy group in the Prudential Medicare sample
had higher mortality rates than the adequate health literacy
group, after cognitive functioning (hazard ratio, 1.27 [95%
CI, 1.03 to 1.57]) (50) and baseline measures of disease,
physical functioning, and healthy lifestyle (hazard ratio,
1.52 [CI, 1.26 to 1.83]) were controlled for (48). Elderly
persons with limited health literacy in the Pittsburgh and
Memphis sample also had higher all-cause mortality rates
(hazard ratio, 1.75 [CI, 1.27 to 2.41]) (51).
Additional Outcomes: Low or Insufficient Evidence
We judged the evidence of a relationship between
health literacy and the following outcomes as insufficient
because of inconsistent results: access to care (13, 14, 19,
23, 26, 52–57), self-efficacy (19, 58– 61), various health
behaviors (18, 19, 26, 35, 48, 57, 62–70), adherence to
medication regimens and procedures (18, 19, 40, 44, 58,
71–82), prevalence of chronic disease (35, 48, 83), preva-
lence of specific diseases (14, 26, 46, 84), asthma severity
and control (17, 21), dental disease (57, 85), diabetes con-
trol and complications (42, 86– 89), hypertension control
(90, 91), health-related quality of life among elderly per-
sons (25, 46– 48, 84), and health status among adults with
specific diseases (38, 56, 92–96).
We graded the evidence as low when it consisted of
few studies or unadjusted analyses. Outcomes included
colorectal screening (18, 23, 59, 97, 98), Papanicolaou
screening (18, 23, 99), acceptance of HIV testing (100),
access to health insurance (101), seeking health-related in-
formation (102), asthma self-care (16), diabetes self-
management (103), review of prescription information
(104), prostate cancer control (105), and adult (106) and
adolescent (69) health status.
Potential Mediators and Moderators of the Effect of
Health Literacy
Mediators in the causal pathway between health liter-
acy and health outcomes are factors that explain all or part
of the relationship. Knowledge, patient self-efficacy,
norms, and stigma may mediate the association between
health literacy and at least some outcomes, such as adher-
ence and diabetes control (40, 56, 58, 72, 73, 77, 89).
Moderators affect the magnitude or direction of a re-
lationship. Social support and characteristics of the health
care system may moderate the relationship between health
literacy and both adherence and blood pressure control
(76, 77, 90).
Costs of Health Care
Two studies about differences in costs of health care
by health literacy level found inconsistent results (insuffi-
cient strength of evidence) (14, 107). The studies exam-
ined different payment sources (Medicaid and Medicare)
and services. Our earlier review found no relationship be-
tween literacy and Medicaid costs (108).
Disparities in Use of Health Care Services or Health
Outcomes
Eight studies examined whether health literacy medi-
ates disparities in use of health care services or health out-
comes (109). One study examined whether health literacy
moderates disparities.
Health literacy mediated disparities between white and
black participants for many health outcomes; however, we
judged the evidence as low because only 1 study examined
each outcome, and findings from 1 outcome cannot be
generalized to other outcomes that have not been tested.
Outcomes include the inability to work because of a long-
term illness or health condition (83), health status and
influenza vaccination among elderly persons (22), physical
and mental health domains of quality of life among Medi-
care enrollees (25), prostate-specific antigen levels among
patients with newly diagnosed prostate cancer (105), non-
adherence to HIV medication regimens (72), lack of health
insurance for children (101), and misinterpretation of
medication labels (110). Health literacy did not mediate
racial disparities in mammography screening or dental
checkups (22), glycemic control (111), parents’ difficulty
in understanding labels of over-the-counter medications
(22, 101), or vaccination rates among elderly persons (25).
We also judged the evidence as low concerning health
literacy as a mediator of outcome differences between eth-
nicities or genders; only 1 study was available to answer
each question. Health literacy was not found to mediate
differences in health status between Hispanic and white
participants (22). In contrast, health literacy explained gen-
der differences in interpreting medication label instructions
(110).
In 1 study, health literacy was not found to be a mod-
erator of disparities in health outcomes. The relationship
between mortality and health literacy did not differ for
black and white persons or for males and females (51).
Relationship Between Numeracy and Outcomes
Twenty-two studies examined the relationship be-
tween numeracy and various outcomes, including use of
health care services, health, and disparities. No studies ad-
dressed differences in costs.
Two studies examined differences in use of health care
services (breast and colorectal cancer screening) by nu-
meracy level and found inconsistent results (insufficient
strength of evidence) (112, 113).
In relation to health outcomes, we judged 3 outcomes
as low evidence. Poorer self-efficacy in managing asthma
and diabetes was related to poor numeracy in 3 studies
(114–116). Similarly, less skill in interpreting health infor-
mation (nutrition labels and health plan information) was
related to poor numeracy in 2 studies (only 1 adjusted for
potential confounders) (35, 54). One study found that
poorer asthma-specific quality of life was related to poor
Review Outcomes Related to Low Health Literacy
102 19 July 2011 Annals of Internal Medicine Volume 155 • Number 2 www.annals.org
numeracy; the relationship was mediated by self-efficacy
(115).
The relationship between numeracy and other out-
comes was judged as insufficient; findings either were in-
consistent or were supported by only 1 unadjusted analysis.
These outcomes included accuracy of risk perception (11,
117–119, 131), knowledge (32, 112, 114, 120, 121), skills
in taking medications (28, 30, 32, 35, 54, 122, 123), self-
management behavior (114), and disease prevalence and
severity (35, 65, 103, 114, 116).
The evidence of numeracy mediating disparities was
low and was limited to racial differences in glycemic con-
trol (111) and medication management (123) and gender
differences in medication management (28).
DISCUSSION
Our updated review expands findings from the 2004
review in important ways. The 2004 review concluded that
low health literacy was associated with poorer health-
related knowledge and comprehension. The update shows
that low health literacy is also associated with differential
use of certain health care services, including increased hos-
pitalizations and emergency care and decreased mammog-
raphy screening and influenza immunizations. Differences
in health-related outcomes include a poorer ability to dem-
onstrate taking medications properly and interpret medica-
tion labels and health messages and, among elderly per-
sons, poorer overall health status and higher mortality.
Evidence is emerging that lower health literacy can mediate
(explain or partially explain) racial disparities in health out-
comes. The effect was demonstrated across several studies,
each measuring a different outcome. In contrast, we did
not find a relationship between health literacy and costs or
other types of disparities. In both cases, only a few studies
examined these relationships. Similarly, the body of evi-
dence concerning the relationship between low numeracy
and outcomes is very new and still inconclusive. A broader
evidence base is needed to understand this relationship,
including the relative importance of the print literacy and
numeracy aspects of health literacy.
Newer studies addressed many of the methodological
concerns identified in our previous review. Most impor-
tant, the majority of studies in our updated review evalu-
ated outcome differences by using multivariate analyses
that controlled for potential confounding variables. These
techniques produced less biased and more meaningful es-
timates of the direction and magnitude of the relationship
between health literacy and outcomes. However, the final
selection of confounding variables differed across studies,
making synthesis of the literature difficult. Because studies
were conducted in various settings and measured different
outcomes, this may be appropriate to some extent. Many
studies, however, controlled for educational attainment
(which is highly correlated with health literacy), and some
controlled for variables that would be expected to be in the
causal pathway or to mediate the relationship between
health literacy and outcomes. This “overadjustment” may
underestimate the effect of health literacy (124).
Studies are beginning to identify and isolate variables
that can mediate the relationship between health literacy
and outcomes. Important explanatory factors include
health-related knowledge, self-efficacy, and beliefs (such as
stigma related to one’s disease). Including control variables
based on an analytic framework or causal model in future
research would help clarify the pathway of effect between
health literacy and health outcomes.
Because no gold standard exists for measuring health
literacy, studies differ not only in the tools used but also in
specifications of thresholds for distinguishing between
health literacy levels. We found only sporadic evidence of
differences between an occasionally measured middle cate-
gory of health literacy and adequate health literacy. Early
evidence suggests that the threshold level at which limited
health literacy is negatively related to a health outcome
may differ across outcomes (125). In future research, jus-
tification for the choices of health literacy thresholds based
on the outcomes examined would lead to evidence that
more meaningfully describes differences and thus identifies
populations that are appropriate for different interventions.
Findings from our review can be considered in light of
4 other recent reviews that examined the relationship be-
tween health literacy and health outcomes. Each focused
on a narrower patient population and settings and fewer
outcomes, specifically children (evaluating their health lit-
eracy or that of their parents or caregivers) (126, 127),
ambulatory care patients (128), and working-age adults
(129). Their findings were generally similar to ours, in-
cluding low health literacy being related to less health-
related knowledge and poorer health status but were incon-
sistent regarding the relationship between low health
literacy and overall use of health care services, overall
health behavior, and disease severity. Another recent sys-
tematic review found, as we did, a mixed relationship be-
tween low health literacy and cost (130).
Given these and our reviews, we believe it is unlikely
that we missed any meaningful body of work. Many pub-
lished studies report no relationship between health literacy
and outcomes, making selective reporting unlikely. Also,
although we restricted our review to English-language arti-
cles, we found a growing body of literature that measured
participants’ health literacy in languages other than
English.
Although the field has made advances, work remains
to be done. Limited data were available from nationally rep-
resentative or other large samples. Moreover, many studies
were conducted in just 1 clinic or in other narrowly defined
patient populations. Some smaller studies may have lacked
sufficient statistical power to detect differences among
health literacy levels or selected uncommon health literacy
thresholds because of limitations in their sample distribu-
tion. Therefore, larger studies and those that would add to
ReviewOutcomes Related to Low Health Literacy
www.annals.org 19 July 2011 Annals of Internal Medicine Volume 155 • Number 2 103
our confidence in the applicability of the evidence to a
broader population are needed.
Regardless of these limitations, our updated review
should enhance the public’s awareness that low health lit-
eracy can play a substantial role in the interrelationship
among patient characteristics, use of health care services,
and resulting health outcomes. Finding ways to reduce the
effects of low health literacy on health outcomes warrants
the attention of policymakers, clinicians, and other
stakeholders.
From RTI International, Research Triangle Park; University of North
Carolina at Chapel Hill, Chapel Hill; and Duke University, Durham,
North Carolina.
Disclaimer: The authors of this report are responsible for its content.
Statements in this report should not be construed as endorsement by the
Agency for Healthcare Research and Quality or the U.S. Department of
Health and Human Services.
Acknowledgment: The authors thank Audrey R. Holland, Anthony J.
Viera, Loraine G. Monroe, Michelle Brasure, Elizabeth Harden, Eliza-
beth Tant, and Ina F. Wallace for their assistance in conducting the
systematic review. They also thank Kathleen N. Lohr, Meera Viswana-
than, and Dan Jonas for their input on standard Agency for Healthcare
Research and Quality Evidence-based Practice Center protocols. Finally,
they thank Kathleen N. Lohr, Anthony J. Viera, and Jonathan M. Farber
for their input on prior drafts of this manuscript and Loraine G. Monroe
for her assistance in preparing the manuscript.
Financial Support: This project was funded by the Agency for Health-
care Research and Quality, U.S. Department of Health and Human
Services (under contract HHSA-290-2007-10056-1).
Potential Conflicts of Interest: Disclosures can be viewed at www.acponline
.org/authors/icmje/ConflictOfInterestForms.do?msNum⫽M11-0110.
Requests for Single Reprints: Nancy D. Berkman, PhD, Program on
Health Care Quality and Outcomes, Division of Health Services and
Social Policy Research, RTI International, PO Box 12194, 3040 Corn-
wallis Road, Research Triangle Park, NC 27709-2194; e-mail: berkman@rti
.org.
Current author addresses and author contributions are available at
www.annals.org.
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of caregiver literacy. Pediatrics. 2010;125:e1104-8. [PMID: 20368322]
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Review Outcomes Related to Low Health Literacy
106 19 July 2011 Annals of Internal Medicine Volume 155 • Number 2 www.annals.org
tion formats. J Gen Intern Med. 2003;18:884-92. [PMID: 14687273]
119. Haggstrom DA, Schapira MM. Black-white differences in risk perceptions
of breast cancer survival and screening mammography benefit. J Gen Intern Med.
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120. Vavrus F. Girls’ schooling in Tanzania: the key to HIV/AIDS prevention?
AIDS Care. 2006;18:863-71. [PMID: 17012074]
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[PMID: 19188645]
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19644651]
MANUSCRIPT PROCESSING AND TURNAROUND
Annals sends about half of submitted manuscripts for peer review and
publishes about 10% of submitted material. The 2010 processing and
notification turnaround time for manuscripts that were rejected without
external peer review was within 1 week for more than 95% of submitted
manuscripts. The processing and notification turnaround time for manu-
scripts that were received and rejected after external peer review was
within 4 weeks for 50% and within 8 weeks for 98%.
ReviewOutcomes Related to Low Health Literacy
www.annals.org 19 July 2011 Annals of Internal Medicine Volume 155 • Number 2 107
Current Author Addresses: Dr. Berkman: Program on Health Care
Quality and Outcomes, Division of Health Services and Social Policy
Research, RTI International, PO Box 12194, 3040 Cornwallis Road,
Research Triangle Park, NC 27709-2194.
Dr. Sheridan: 5039 Old Clinic Building, CB 7110, University of North
Carolina at Chapel Hill, Chapel Hill, NC 27599.
Dr. Donahue: Department of Family Medicine, University of North
Carolina at Chapel Hill, CB 7595, 590 Manning Drive, Chapel Hill,
NC 27599.
Dr. Halpern: Durham Medical Center, 4220 North Roxboro Road,
Durham, NC 27704.
Dr. Crotty: W228 S2406 Oriole Drive, Waukesha, WI 53186.
Author Contributions: Conception and design: N.D. Berkman, S.L.
Sheridan, K.E. Donahue, D.J. Halpern.
Analysis and interpretation of the data: N.D. Berkman, S.L. Sheridan,
K.E. Donahue, D.J. Halpern, K. Crotty.
Drafting of the article: N.D. Berkman, S.L. Sheridan, K.E. Donahue,
D.J. Halpern.
Critical revision of the article for important intellectual content: N.D.
Berkman, S.L. Sheridan, K.E. Donahue, D.J. Halpern, K. Crotty.
Final approval of the article: N.D. Berkman, S.L. Sheridan, K.E. Dona-
hue, D.J. Halpern.
Statistical expertise: D.J. Halpern.
Obtaining of funding: N.D. Berkman, S.L. Sheridan.
Administrative, technical, or logistic support: N.D. Berkman, K. Crotty.
Collection and assembly of data: N.D. Berkman, S.L. Sheridan, K.E.
Donahue, D.J. Halpern, K. Crotty.
131. Davids SL, Schapira MM, McAuliffe TL, Nattinger AB. Predictors of
pessimistic breast cancer risk perceptions in a primary care population. J Gen
Intern Med. 2004;19:310-5. [PMID: 15061739]
132. Laramee AS, Morris N, Littenberg B. Relationship of literacy and heart
failure in adults with diabetes. BMC Health Serv Res. 2007;7:98. [PMID:
17605784]
Annals of Internal Medicine
W-34 19 July 2011 Annals of Internal Medicine Volume 155 • Number 2 www.annals.org
Appendix Table 1. Search Strategy
Search Number, by Date and
Database
Search Terms Articles
Returned,
n
May 2009
PubMed
1 Numeracy 173
2 Numeracy; limits: Humans, English 146
3 “health literacy” 789
4 “health literacy”; limits: Entrez Date from 2003, Humans, English 586
5 #2OR#4 716
6 Literacy 39 075
7 “rapid estimate functional health literacy” OR real* 215 538
8 #6 AND #7 920
9 “test of functional health literacy” OR tofhl* 295
10 #6 AND #9 295
11 “Hebrew health literacy test” OR HHLT 6
12 “medical achievement reading test” OR MART 1202
13 #6 AND #12 23
14 “newest vital signs” OR NVS 203
15 #6 AND #14 6
16 “short assessment of health literacy” OR SAHLSA 170
17 #6 AND #16 170
18 “wide range achievement test” OR WRAT 290
19 #6 AND #18 77
20 “nutritional literacy” OR “literacy assessment for diabetes” OR LAD OR SIL OR “single item numeracy screener”
OR DAHL OR “demographic assessment” OR BEHKA OR “brief estimate” OR “diabetes numeracy” OR
“medical data interpretation” OR “subjective numeracy” OR “numeracy test”
18 220
21 #6 AND #20 264
22 #8 OR #10 OR #11 OR #13 OR #15 OR #17 OR #19 OR #21 1661
23 #8 OR #10 OR #11 OR #13 OR #15 OR #17 OR #19 OR #21; limits: Entrez Date from 2003, Humans, English 729
24 #5 OR #23 1310
25 #5 OR #23; limits: Editorial, Letter, Case Reports 58
26 #24 NOT #25 1252
PubMed
1 “rapid estimate of adult literacy” 104
2 “test of functional health literacy” 290
3 “Hebrew health literacy test” 6
4 “medical achievement reading test” 0
5 Medical achievements reading test 68
6 “newest vital signs” 1
7 “short assessment of health literacy” 170
8 “wide range achievement test” 219
9 “literacy assessment for diabetes” 225
10 “nutritional literacy” 3
11 “single item numeracy screener” 0
12 #1 OR #2 OR #3 OR #4 OR #5 OR #6 OR #7 OR #8 OR #9 OR #10 OR #11 991
13 #1 OR #2 OR #3 OR #4 OR #5 OR #6 OR #7 OR #8 OR #9 OR #10 OR #11; limits: Entrez Date from 2003,
Humans, English
473
14 #1 OR #2 OR #3 OR #4 OR #5 OR #6 OR #7 OR #8 OR #9 OR #10 OR #11; limits: Entrez Date from 2003,
Humans, Editorial, Letter, Case Report, English
5
15 #13 NOT #14 468
PubMed
1 Literacy [tw] 5516
2 Literacy [tw]; limits: Entrez Date from 2003, Humans, English 2337
3 Literacy [tw]; limits: Editorial, Letter, Case Reports 243
4 #2 NOT #3 2226
CINAHL
1 “health literacy” 34
Cochrane Library
1 “health literacy” 61
PsycINFO
1 “health literacy” 65
ERIC
1 “health literacy” 34
Summary: Update,
May 2009
Total unduplicated titles and abstracts through electronic database searches 2855
Continued on following page
www.annals.org 19 July 2011 Annals of Internal Medicine Volume 155 • Number 2 W-35
Appendix Table 1—Continued
Search Number, by Date and
Database
Search Terms Articles
Returned,
n
December 2009
PubMed
1 Numeracy 213
2 Numeracy; limits: Human, English 169
3 “health literacy” 964
4 “(“2009/01/01”[Entrez Date]: “3000”[Entrez Date]) AND (“health literacy”); limits: Humans, English 110
5 #2 OR #4; limits: Humans, English 273
6 Literacy 41 096
7 “rapid estimate of adult literacy” OR real* 232 562
8 #6 AND #7 968
9 “test of functional health literacy” OR tofhl* 326
10 #6 AND #9 326
11 “Hebrew health literacy test” OR HHLT 7
12 “medical achievement reading test” OR MART 1300
13 #6 AND #12 26
14 “newest vital signs” OR NVS 220
15 #6 AND #14 8
16 “short assessment of health literacy” OR SAHLSA 187
17 #6 AND #16 187
18 “wide range achievement test” OR WRAT 302
19 #6 AND #18 83
20 “nutritional literacy” OR “literacy assessment for diabetes” OR LAD OR SIL OR “single item numeracy screener”
OR DAHL OR “demographic assessment” OR BEHKA OR “brief estimate’ OR “diabetes numeracy” OR
“medical data interpretation’ OR “subjective numeracy” OR “numeracy test”
18 849
21 #6 AND #20 282
22 #8 OR #10 OR #11 OR #13 OR #15 OR #17 OR #19 OR #21 1773
23 (“2009/01/01”[Entrez Date]: “3000”[Entrez Date]) AND (#8 OR #10 OR #11 OR #13 OR #15 OR #17 OR #19
OR #21); limits: Humans, English
86
24 #5 OR #23 342
25 #5 OR #23; limits: Editorial, Letter, Case Reports 24
26 #24 NOT #25 318
CINAHL
1 “health literacy”; limits: English, non-MEDLINE 37
2 “health literacy”; limits: 1/1/2009–12/31/2010, exclude MEDLINE records, English; search modes—Boolean/
Phrase
37
Cochrane Library “health literacy”; 2009–present 5
PsycINFO
1 “health literacy”; 2009–present, English, no Editorials, no Letters 74
2 “health literacy”; limits: 1/1/2009–12/31/2010, English; search modes—Boolean/Phrase 74
ERIC
1 “healthy literacy”; 2009–present, English 9
Summary: Update,
December 2009
Total unduplicated titles and abstracts through electronic database searches 397
May 2010
PubMed
1 Numeracy 243
2 “health literacy” 1084
3 #1OR#2 1285
4 Literacy 42 702
5 “rapid estimate of adult literacy” OR real* 245 476
6 #4 AND #5 1000
7 “test of functional health literacy” OR tofhl* 154
8 #4 AND #7 154
9 “Hebrew health literacy test” OR HHLT 1
10 #4 AND #9 1
11 “medical achievement reading test” OR MART 1358
12 #4 AND #11 28
13 “newest vital signs” OR NVS 261
14 #4 AND #13 11
15 “short assessment of health literacy” SAHLSA 49
16 #4 AND #15 49
17 “wide range achievement test⬙OR WRAT 303
18 #4 AND #17 84
Continued on following page
W-36 19 July 2011 Annals of Internal Medicine Volume 155 • Number 2 www.annals.org
Appendix Table 1—Continued
Search Number, by Date and
Database
Search Terms Articles
Returned,
n
19 “nutritional literacy” OR “literacy assessment for diabetes’ OR LAD OR SIL OR “single item numeracy screener”
OR DAHL OR “demographic assessment” OR BEHKA OR “brief estimate” OR “diabetes numeracy” OR
“medical data interpretation” OR “subjective numeracy” OR “numeracy test”
19 266
20 #4 AND #19 303
21 #6 OR #8 OR #10 OR #12 OR #14 OR #16 OR #18 OR #20 1522
22 #3 OR #21 2561
23 #22; limits: Humans, English 2042
24 #23; limits: Editorial, Letter, Case Reports 93
25 #23 NOT #24 1949
26 (#25) AND “20/10/01”[Entrez Date]: “3000”[Entrez Date]; sort by publication date 106
CINAHL
1 Analogous terms were used to conduct searches 39
PsycINFO
1 Analogous terms were used to conduct searches 68
Cochrane Library
1 Analogous terms were used to conduct searches 44
ERIC Analogous terms were used to conduct searches 8
Summary: Update,
May 2010
Total unduplicated titles and abstracts through electronic database searches 244
December 2010
PubMed
1 Numeracy 295
2 “health literacy” 1322
3 #1OR#2 1563
4 Literacy 44 669
5 “rapid estimate of adult literacy” OR real* 262 208
6 #4 AND #5 1062
7 “test of functional health literacy” OR tofhl* 175
8 #4 AND #7 175
9 “Hebrew health literacy test” OR HHLT 1
10 #4 AND #9 1
11 “medical achievement reading test” OR MART 1433
12 #4 AND #11 28
13 “newest vital signs” OR NVS 281
14 #4 AND #13 12
15 “short assessment of health literacy” OR SAHLSA 56
16 “short assessment of health literacy” OR SAHL 306
17 #15 OR #16 306
18 #4 AND #17 56
19 “wide range achievement test” OR WRAT 314
20 #4 AND #19 86
21 “nutritional literacy” OR “literacy assessment for diabetes” OR LAD OR SIL OR “single item numeracy screener”
OR DAHL OR “demographic assessment” OR BEHKA OR “brief estimate” OR “diabetes numeracy” OR
“medical data interpretation” OR “subjective numeracy” OR “numeracy test”
19 820
22 #4 AND #21 319
23 #6 OR #8 OR #10 OR #12 OR #14 OR #18 OR #20 OR #22 1622
24 #3 OR #23 2896
25 #24; limits: Humans, English 2291
26 #24; limits: Editorial, Letter, Case Reports 121
27 #25 NOT #26 2180
28 (#27) AND “2010/03/01“[Entrez Date]: “3000”[Entrez Date]) AND “0”[Entrez Date]: “3000”[Entrez Date]; sort
by publication date
169
CINAHL
1 “health literacy”; limits: English, non-MEDLINE
2 “health literacy”; limits: 3/1/2010–12/07/2010; exclude MEDLINE records, English
Summary: CINAHL,
December 2010
54
Cochrane Library
1 “health literacy”; limit: 2010–present 6
PsycINFO
1 “health literacy”; limits: English, no Editorials, no Letters
2 “health literacy”; limits: 3/1/2010–12/07/2010, English
Continued on following page
www.annals.org 19 July 2011 Annals of Internal Medicine Volume 155 • Number 2 W-37
Appendix Table 1—Continued
Search Number, by Date and
Database
Search Terms Articles
Returned,
n
Summary: PsycINFO,
December 2010
51
ERIC
1 “health literacy”; limits: 3/1/2010–12/07/2010, English 5
Summary: Update,
December 2010
Total unduplicated titles and abstracts through electronic database searches 285
February 2011
PubMed
1 Numeracy 310
2 “health literacy” 1404
3 #1OR#2 1656
4 Literacy 6982
5 “rapid estimate of adult literacy” OR real* 268 409
6 #4 AND #5 415
7 “test of functional health literacy” tofhl* 180
8 #4 AND #7 180
9 “Hebrew health literacy test” OR HHLT 1
10 #4 AND #9 1
11 “medical achievement reading test” OR MART 1833
12 #4 AND #11 7
13 “newest vital signs” OR NVS 288
14 #4 AND #13 10
15 “short assessment of health literacy” OR SAHLSA 56
16 SAHL 253
17 #15 OR #16 308
18 #4 AND #17 56
19 “wide range achievement test” OR WRAT 318
20 #4 AND #19 30
21 “nutritional literacy” OR “literacy assessment for diabetes” OR LAD OR SIL OR “single item numeracy screener”
OR DAHL OR “demographic assessment” OR BEHKA OR “brief estimate” OR “diabetes numeracy” OR
“medical data interpretation” OR “subjective numeracy” OR “numeracy test”
19 793
22 #4 AND #21 63
23 #6 OR #8 OR #10 OR #12 OR #14 OR #18 OR #20 OR #22 657
24 #3 OR #23 2021
25 #24; limits: Humans, English 1617
26 #24; limits: Editorial, Letter, Case Reports 117
27 #25 NOT #26 1511
28 #27 AND (2010/12:2011/02 [edat]) 16
29 #25; limits: Published in the last 3 years 756
30 #29; limits: Review 80
31 #28 OR #30 95
CINAHL
1 “health literacy”; limits: English, non-MEDLINE
2 “health literacy”; limits: 12/2010–2/2011, English, exclude MEDLINE records
Summary: CINAHL,
February 2011
11
1 “health literacy”; 2010–present 4
PsycINFO
1 “health literacy”; limits: English, Humans, no Editorials, no Letters
2 “health literacy”; limits: 12/2010–2/2011, English
Summary: PsycINFO,
February 2011
21
ERIC
1 “health literacy”; limits: 12/2010–2/2011, English 1
Summary: Update,
February 2011
53
W-38 19 July 2011 Annals of Internal Medicine Volume 155 • Number 2 www.annals.org
Appendix Figure. Summary of evidence search and selection.
Titles and abstracts identified
through electronic database
searches (n = 3823)
Articles identified through
hand-searches
(n = 88)
Total articles retrieved
(n = 3911)
Citations excluded
(n = 2899)
Intervention articles reviewed
(n = 50 [47 studies])
Full-text articles retrieved
(n = 1012)
Articles included in full review
(n = 204)
Poor quality
(n = 43 [32 on health outcomes])
Full-text articles excluded (n = 808)
Studies that do not measure literacy or health
literacy: 350
Studies with no original data: 220
Studies with no health outcomes (i.e.,
descriptive only or have such outcomes as
likability or satisfaction): 194
Studies answering KQ 1 where literacy (not
numeracy) is measured and the only study
outcome is knowledge: 17
Studies examining normal reading development
in children: 6
Ecological data only: 5
Studies in which the outcome is limited to
dementia or cognitive impairment: 4
Systematic evidence review only: 3
Studies about dyslexia: 2
Studies published in abstract form only: 3
Unable to obtain the article: 2
Intervention studies not designed to test health
literacy: 2
Articles included in outcomes review
Health literacy (n = 98 [84 studies])
Numeracy (n = 22 [21 studies])
KQ ⫽key question.
www.annals.org 19 July 2011 Annals of Internal Medicine Volume 155 • Number 2 W-39
Appendix Table 2. Overview of Numeracy Studies
Study, Year
(Reference)
Design Numeracy Instrument Quality
Score
Study Sample Outcomes Variables Used in
Multivariate Analysis
Aggarwal et al,
2007 (112)
Cross-sectional 5-item test adapted from the
Black–Toteson Numeracy
Test
Fair 264 patients at 4 ambulatory care
clinics affiliated with a U.S.
urban academic medical center
Knowledge, use of
health care services
Age, race, education,
primary care
provider, FH of
disease
Apter et al,
2009 (115)
Cross-sectional Asthma Numeracy
Questionnaire
Fair 80 patients with moderate or
severe asthma recruited from
urban medical practices in
Philadelphia
Quality of life,
self-efficacy
Age, Latino ethnicity
Cavanaugh et al,
2008 (114)
Cross-sectional WRAT-3, Diabetes
Numeracy Test
Fair 398 patients from 2 primary care
clinics and 2 endocrinology
clinics at 3 U.S. hospitals
Knowledge (unadjusted),
self-efficacy
(unadjusted), behavior
(unadjusted), disease
severity
Age, sex, race, income,
type of diabetes,
years since
diagnosis, clinic site
Ciampa et al,
2010 (113)
Cross-sectional 1 item from the Lipkus
Numeracy Test
Fair 1436 participants in the Health
Information Technology Survey
Use of health care
services
Age, sex, race, income,
education, health
insurance
Davids et al,
2004 (131)
Cross-sectional Test adapted from the
Schwartz–Woloshin
Numeracy Test
Fair 254 patients in 2 U.S. academic
general medicine clinics
Accuracy of risk
perception
Age, race, education,
income, FH of breast
cancer, age at
menses, age at first
live birth, number of
breast biopsies
Estrada et al,
2004 (30)
Prospective cohort 6 items (including 3 items
adapted from the
Schwartz–Woloshin
Numeracy Test)
Fair 143 patients in anticoagulation
management clinics in 1 U.S.
university and 1 U.S. VA-based
hospital
Medication management
skills
Age
Haggstrom and
Schapira,
2006 (119)
Cross-sectional Schwartz–Woloshin
Numeracy Test
Fair 207 patients in a general
medicine clinic at a U.S.
academic medical center
Accuracy of risk
perception
Age, race, FH, family
income, insurance,
education
Hassan and
Heptulla,
2010 (103)
Cross-sectional Newest vital sign Fair 200 parents or caregivers of
children with diabetes receiving
care at a U.S. diabetes clinic
Glycemic control Race, language,
income, education
Hibbard et al,
2007 (54)
RCT: data analyzed
cross-sectionally
15-item scale adapted from
the Lipkus Numeracy Test
Fair 303 community-dwelling U.S.
adults
Skill (unadjusted), use of
health care services
(unadjusted)
None
Huizinga et al,
2008 (65)
Cross-sectional WRAT-3 Fair 169 patients in a U.S. academic
primary care clinic
Disease prevalence or
severity
Age, sex, race, income,
education, REALM
Lokker et al,
2009 (122)
Cross-sectional WRAT math subtest Fair 182 caregivers of patients at
general pediatric clinics at 3
academic medical centers
Medication management
skills
Age, sex, race,
education
Osborn et al,
2009 (111)
Cross-sectional Diabetes Numeracy Test Good 383 patients at 2 primary care
and 2 diabetes specialty clinics
located at 3 medical centers
Disease prevalence and
severity (numeracy as
a mediator of
relationship between
race and HbA
1c
)
Age, year of diagnosis,
diabetes, insulin use,
African American
Osborn et al,
2010 (116)
Cross-sectional WRAT math subtest Fair 383 patients at 2 primary care
and 2 diabetes specialty clinics
located at 3 medical centers
Disease severity
measured through
glycemic control
Age, African American,
years since
diagnosis, insulin,
diabetes self-efficacy
Portnoy et al,
2010 (121)
Cross-sectional 3-item test adapted from the
Schwartz–Woloshin
Numeracy Test
Fair 246 residents of Baltimore and
Salt Lake City
Knowledge Age, site, REAL-G
(genetic testing
literacy measure),
session length
Rothman et al,
2006 (35)
Cross-sectional WRAT-3 Fair 200 patients at 1 U.S. academic
primary care clinic
Skill (unadjusted),
disease prevalence or
severity (unadjusted)
None
Schwartz et al,
1997 (11)
RCT: data analyzed
cross-sectionally
Schwartz–Woloshin
Numeracy Test
Fair 287 patients at a U.S. VA hospital
who received a mailed survey
Accuracy of risk
perception
Age, income,
education, frame of
information
Sheridan and
Pignone, 2002
(117)
RCT: data analyzed
cross-sectionally
Schwartz-Woloshin
Numeracy Test
Fair 62 medical students in a U.S.
medical school
Accuracy of risk
perception
(unadjusted)
None
Sheridan et al,
2003 (118)
RCT: data analyzed
cross-sectionally
Schwartz–Woloshin
Numeracy Test
Fair 357 patients in a U.S. academic
general medicine clinic
Accuracy of risk
perception
(unadjusted)
None
Vavrus, 2006 (120) Cross-sectional Unspecified numeracy test Fair 277 students from 4 school
districts in Tanzania
Knowledge Sex, literacy,
household spending,
parents’ education,
television in home,
siblings, electricity,
sewage
Waldrop-Valverde
et al, 2009 (28)
Cross-sectional Woodcock–Johnson Applied
Problems subtest
Fair 155 patients at HIV clinics or
participants in an AIDS
drug-assistance program in
Miami
Medication management
skills (numeracy as a
mediator of the
relationship between
sex and capacity to
manage medications)
Sex, time since HIV
diagnosis, education,
health literacy
Continued on following page
W-40 19 July 2011 Annals of Internal Medicine Volume 155 • Number 2 www.annals.org
Appendix Table 2 —Continued
Study, Year
(Reference)
Design Numeracy Instrument Quality
Score
Study Sample Outcomes Variables Used in
Multivariate Analysis
Waldrope-Valverde
et al, 2010 (123)
Cross-sectional Woodcock–Johnson Applied
Problems subtest
Fair 207 patients at HIV clinics or
participants in an AIDS
drug-assistance program in
Miami
Medication management
skills (numeracy as a
mediator of the
relationship between
race and capacity to
manage medications)
Female, African
American, time since
HIV diagnosis
Yin et al, 2007 (32) Cross-sectional TOFHLA numeracy subtest Fair 292 caregivers of young children
at the pediatric emergency
department in a U.S. urban
academic medical center
Knowledge, medication
management skills
Caregiver education,
country of origin,
language, SES, age
of children, regular
health care provider,
experience in health
care setting
FH ⫽family history; HbA
1c
⫽hemoglobin A
1c
; RCT ⫽randomized, controlled trial; REAL-G ⫽Rapid Estimate of Adult Literacy in Genetics; REALM ⫽Rapid Estimate
of Adult Literacy in Medicine; SES ⫽socioeconomic status; TOFHLA ⫽Test of Functional Health Literacy in Adults; VA ⫽Veterans Affairs; WRAT-3 ⫽Wide Range
Achievement Test, 3rd edition.
www.annals.org 19 July 2011 Annals of Internal Medicine Volume 155 • Number 2 W-41