Elevated rates of diabetes in Pacific Islanders and Asian subgroups: The Diabetes Study of Northern California (DISTANCE)

ArticleinDiabetes care 36(3) · October 2012with40 Reads
Impact Factor: 8.42 · DOI: 10.2337/dc12-0722 · Source: PubMed
Abstract

OBJECTIVE We estimated the prevalence and incidence of diabetes among specific subgroups of Asians and Pacific Islanders (APIs) in a multiethnic U.S. population with uniform access to care.RESEARCH DESIGN AND METHODS This prospective cohort analysis included 2,123,548 adult members of Kaiser Permanente Northern California, including 1,704,363 with known race/ethnicity (white, 56.9%; Latino, 14.9%; African American, 8.0%; Filipino, 4.9%; Chinese, 4.0%; multiracial, 2.8%; Japanese, 0.9%; Native American, 0.6%; Pacific Islander, 0.5%; South Asian, 0.4%; and Southeast Asian, Korean, and Vietnamese, 0.1% each). We calculated age-standardized (to the 2010 U.S. population) and sex-adjusted diabetes prevalence at baseline and incidence (during the 2010 calendar year). Poisson models were used to estimate relative risks (RRs).RESULTSThere were 210,632 subjects with prevalent diabetes as of 1 January 2010 and 15,357 incident cases of diabetes identified during 2010. The crude diabetes prevalence was 9.9% and the incidence was 8.0 cases per 1,000 person-years and, after standardizing by age and sex to the 2010 U.S. Census, 8.9% and 7.7 cases per 1,000 person-years. There was considerable variation among the seven largest API subgroups. Pacific Islanders, South Asians, and Filipinos had the highest prevalence (18.3, 15.9, and 16.1%, respectively) and the highest incidence (19.9, 17.2, and 14.7 cases per 1,000 person-years, respectively) of diabetes among all racial/ethnic groups, including minorities traditionally considered high risk (e.g., African Americans, Latinos, and Native Americans).CONCLUSIONS High rates of diabetes among Pacific Islanders, South Asians, and Filipinos are obscured by much lower rates among the large population of Chinese and several smaller Asian subgroups.

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Available from: Howard H Moffet, Mar 13, 2014
Elevated Rates of Diabetes in Pacic
Islanders and Asian Subgroups
The Diabetes Study of Northern California (DISTANCE)
ANDREW J. KARTER, PHD
1
DEAN SCHILLINGER, MD
2,3,4
ALYCE S. ADAMS, PHD
1
HOWARD H. MOFFET, MPH
1
JENNIFER LIU, MPH
1
NANCY E. ADLER, PHD
5
ALKA M. KANAYA, MD
2
OBJECTIVE dWe estimated the prevalence and incidence of diabetes among specic sub-
groups of Asians and Pa cic Islanders (APIs) in a multiethnic U.S. population with uniform
access to care.
RESEARCH DESIGN AND METHODS dThis prospective cohort ana lysis included
2,123,548 adult members of Kaiser Permanente Northern California, including 1,704,363 with
known race/ethnicity (white, 56.9%; Latino, 14.9%; African American, 8.0%; Filipino, 4.9%;
Chinese, 4.0%; multiracial, 2.8%; Japanese, 0.9%; Native American, 0.6%; Pacic Islander, 0.5%;
South Asian, 0.4%; and Southeast Asian, Korean, and Vietnamese, 0.1% each). We calculated age-
standardized (to the 2010 U.S. population) and sex-adjusted diabetes prevalence at baseline and
incidence (during the 2010 calendar year). Poisson models were used to estimate relative risks.
RESULTSdThere were 210,632 subjects with prevalent diabetes as of 1 January 2010 and 15,357
incident cases of diabetes identied during 2010. The crude diabetes prevalence was 9.9% and the
incidence was 8.0 cases per 1,000 person-years and, after standardizing by age and sex to the 2010
U.S. Census, 8.9% and 7.7 cases per 1,000 person-years. There was considerable variation among
the seven largest API subgroups. Pacic Islanders, South Asians, and Filipinos had the highest prev-
alence (18.3, 15.9, and 16.1%, respectively) and the highest incidence(19.9, 17.2, and 14.7 cases per
1,000 person-years, respectively) of diabetes among all racial/ethnic groups, including minorities
traditionally considered high risk (e.g., African Americans, Latinos, and Native Americans).
CONCLUSIONSdHigh rates of diabetes among Pacic Islanders, South Asians, and Filipi-
nos are obscured by much lower rates among the la rge population of Chi nese and several smaller
Asian subgroups.
Diabetes Care 36:574579, 2013
A
sians and Pacic Islanders (APIs)
comprised 5% of the U.S. popula-
tion in the 2010 Census, a 43%
increase compared with the 2000 Census
(1). The three largest API subgroups in-
cluded people of Chinese (3.3 million),
South Asian (2.8 million), or Filipino
(2.6 million) ancestry. Most national
health surveys before 2000 classied
Asians as other race or, if recognized,
combined them with Pacic Islanders;
thus, the variation among API subgroups
has been neglected.
Epidemiologic studies and U.S. na-
tional surveillance report that Asians have a
higher prevalence of type 2 diabetes relative
to non-Hispanic whites, but lower than
that of African Americans and Latinos
(2,3). However, aggregation of API sub-
groups may preclude identifying those at
particularly high risk for diabetes (4). A re-
cent report from the U.S. National Health
Interview Survey (NHIS) disaggregated API
subgroups and found substantive differen-
ces in diabetes prevalence (3). Nonetheless,
there is a paucity of published data on the
prevalence and incidence of diabetes
among API subgroups in the U.S (5,6).
Through the Diabetes Study of Northern
California (DISTANCE), we estimated racial/
ethnic differences in the prevalence and in-
cidence of diabetes in a large, multiethnic
cohort of patients receiving care in an inte-
grated health delivery system.
RESEARCH DESIGN AND
METHODS dSubjects were adult
($18 years of age) heal th plan mem bers
of Kaiser Permanente Northern California
(KPNC), a large, int egrated healthcare de-
livery system caring for .3 million peo-
ple who are broadly representative of the
local and statewide population (7). We
studied the prevalence and incidence of
diabetes during the calendar year 2010
(1 January 201031 December 2010),
while excluding subjects not continu-
ously enrolled during the 12 months (1
January 200931 December 2009) prior
to baseline to avoid misclassifying new
enro llees with pre-existing diabetes as in-
cident cases. These criteria resulted in an
eligible adult population of 2,123,548.
Those with unknown race /ethnicity
(n = 419,185) were included in the de-
nominator for our evalu ati on of overall
prevalence and incidence but excluded
from the race-specic analyses. Race/eth-
nicity was ascertained from self-reported
demographic data collected at clinic vis-
its, during heal th plan enrollment, f rom
member surveys, or on intake for hospi-
talization. Self-reported race/ethnicity
was available for 1,704,363 patients
(80%), including white (n = 968,943), La-
tino (n = 253,821), African American (n =
135,934), Filipino (n = 82,781), Chinese
(n = 68,831), Japanese (n = 16,032), Native
American/American Indian/Alaska native
(n = 9,546), Pacic Islander (Hawaiian,
Guamanian, Samoan, or other Pacic
Islander;
n = 7,732), South Asian (Asian
Indian, Pakistani, Bangladeshi, Sri Lankan,
or Nepalese; n = 6,768), Southeast Asian
(Cambodian, Laotian, Burmese, Thai,
ccccccccccccccccccccccccccccccccccccccccccccccccc
From the
1
Division of Research, Kaiser Permanente Northern California, Oakland, California; the
2
Division of
General Internal Medicine, University of California, San Francisco, San Francisco, California; the
3
Center for
Vulnerable Populations, San Francisco General Hospital, University of California, San Francisco, San
Francisco, California; the
4
California Diabetes Program, California Department of Public Health, Sacra-
mento, California; and the
5
Center for Health and Community, University of California, San Francisco, San
Francisco, California.
Corresponding author: Andrew J. Karter, andy.j.karter@kp.org.
Received 16 April 2012 and accepted 13 August 2012.
DOI: 10.2337/dc12-0722
© 2013 by the American Diabetes Association. Readers may use this arti cle as long as the work is properly
cited, the use is education al and not for prot, and the work is not altered . See http://creativecommons.org/
licenses/by-nc-nd/3.0/ for details.
574 DIABETES CARE, VOLUME 36, MARCH 2013 care.diabetesjournals.org
Epidemiology/Health Services Research
ORIGINAL ARTICLE
Page 1
Malaysian, Indonesian; n = 1,876), Korean
(n = 1,130), Vietnamese (n = 1,671), other
and unspecied Asian (n = 101,769), and
multiracial (n = 47,529). We also created
aggregate categories of Asians (Filipino,
Chinese, Japanese, South Asian, Southeast
Asian, Korean, Vietnamese, and other/un-
specied Asian; n = 280,858) and APIs (n =
288,590) to simulate the current categori-
zation u sed for presen ting demographic
data at the national and state level.
The prevalence of clinically recog-
nize d diabetes was estimated overall and
by race/ethnicity as of 1 January 2010
(baseline), based on available administra-
tive data (algorithm detailed i n Table 1).
The inc idenc e rate was estimated by inci-
dent cases of diabetes identied during
the calendar year of 2010 divided by the
population at risk ( n = 1,912,916), which
excluded those with known (prevalent )
diabetes at baseline or incomplete mem-
bership in the previous year (precluding
ability to reliably ascertain if they joined
with pre-existing diabetes). We sex and
age standardized the 2010 U.S. Census
population, yielding rates expected if
our population had the identical demo-
graphic distribution as the U.S. popula-
tion. This will facilitate comparisons
between our ndings and exist ing and fu-
ture national su rveillance reports. We also
estimate d relative risk (RR) of incidence
and prevalence of diabetes (whites as the
reference group) in a series of internally
adjusted Poisson regression models with
log link functions. The base model was
age and sex adjusted, and subsequent
models included potential mediators
(model 1 added census-based, block-level
median income to the base model, and
model 2 added BMI and systolic blood
pressure to model 1).
Study methods and description of t he
KPNC Diab etes Registry (99% sensitivity
basedonchartreviewvalidation)have
been published previously (8,9). How-
ever, in this study, we also used the new
diagnostic criteria of HbA
1c
$6.5% recog-
nized by the American Diabetes Associa-
tion Clinical Practice Recommendations
in 2010 (10). This study was approved by
the institutional review boards of the Kaiser
Foundation Research Institute and Univer-
sity of California, San Francisco.
RESULTSdThe c haracteristics for the
2,123,548 adults members of the study
population differed substantively by race/
ethnicity (Table 2 ). The average age was
49 years, but Vietnamese and Southeast
Asians were younger on average, and Jap-
anese, whites, Chinese, and multiracial
members were older. Multiracial , African
American, Filipino, and Southeast Asian
groups had a greater proportion of women.
BMI (kg/m
2
) was 28.2 on average overall,
and highest in African Americans and Na-
tive Americans and lowest in Vietnamese,
Koreans, Chinese, and Japanese. Systolic
blood pressure was 124 mmHg on average
but highest in African Americans, whites,
and multiracial subjects and lowest in Viet-
namese, Southeast As ians, Koreans, and
South Asians. The median census block-
group level income was $62,600 annually,
with the highest salaries associated with
Koreans, Chinese, South Asians, and Japa-
nese, and lowest with African Americans,
Latinos, and Native Americans.
We identied 210,632 individuals
with prevalent diabetes, yielding an 8.9%
prevalence after standardizing to the 2010
U.S. population (Table 3). The prevalence
increased with age (P , 0.001); men had
higher prevalence than women (10.2% in
men vs. 7.8% in women; P , 0.001). Since
the age and sex patterns were similar across
races/ethnicities, we present age- and sex-
standardized prevalence of diabetes for
each racial/ethnic category and the age-
and sex-adjusted RR (Table 4). Each ethnic
minority group had signicantly higher
diabetes prevalence than whites (reference
group) (7.3%). The highest prevalence
was observed among PacicIslanders
(18.3%; RR 2.43), fo llowed by Filipinos
(16.1%; 2.26), South Asians (15.9%;
2.19), Latinos (14 .0%; 1.88), African
Americans (13.7%; 1.86), Native Ameri-
cans (13.4%; 1.86), multiracial patients
(12.8%; 1.7 4), other/unspecied Asians
(12.1%: 1.59), Southeast Asians (10.5%;
1.46), Japanese (10.3%; 1.46), Vietnam-
ese (9.9%; 0.98 but NS), Koreans (9.9%;
1.31), and Chinese (8.2%; 1.14). The
aggregated categories of Asians and
Asians/Pacic Islanders yielded preva-
lence estimates of 12.2 and 12.3%, respec-
tively (data not shown).
Of the 1,912,916 individuals without
prevalent dia betes on 1 January 2010,
there were 15,357 incident diabetes cases
identied during 2010. After age and sex
standardizing, the incidence density was
7.7 incident cases (95% CI 7.557.79)
per 1,000 person-years. The patterns of
age- and sex-standardized incidence ( and
across races/ethnicities) and internally
adjusted RRs (Table 5) were similar t o
those observed for prevalence. PacicIs-
landers (19.9 cases per 1,000 person-
years; RR 3.08) had the highest incidence
rates, more than triple that of whites, who
had 6.3 cases per 1,000 person-years, fol-
lowed by South Asians (17.2; RR 2.31),
Filipinos (14.7; 2.38), Native Americans
(12.0; 1.93), Latinos (11.2; 1.76), African
Americans (11.2; 1.76), other/unspeci-
ed Asians (10.2; 1.55), multiracial pa-
tients (9.7; 1.50), Japanese (7.5; 1.26),
and Chinese (6.5; 1.02 but NS). We do
notreportincidentratesforKoreans,
Vietnamese, and other Southeast Asians
due t o the low power in th ese small sub-
groups, although we do report the RRs.
The aggregated categories of all Asians
and Asians/Pacic Islanders yielded inci-
dence estimates of 10.4 and 10.6 cases
per 1,000 person-years, respectively
(Fig. 1).
We examined the contribution of sev-
eral possible explanatory factors. The BMI
among the subjects with newly diagnosed
diabetes varied widely across race/ethnic
groups, ranging from 36.2 kg/m
2
in Native
Americans to 27.2 kg/m
2
in Chinese indi-
viduals (Fig. 2). Moreover, the mean BMI
among those identied with incident dia-
betes was consistently higher than in those
with prevalent diabetes (by 12points)
and in individuals who remained normo-
glycemic (by 36 points) . Adjusting for
census block-level income in the Poisson
regression models for prevalence and in-
cidence (model 2 in Tables 4 and 5) im-
parted minimal changes to the age- and
Table 1dClinical recognition of diabetes
Clinical recog nition of diabetes* was based on
any of the following:
1) inpatient diagnosis (principal diagn osis of
ICD-9: 250 )
2) outpatient diagnosis (two or more
diagnoses with ICD-9: 250; excludes
diagnoses collected in the emergency
room or optometry or ophthalmology
depa rtments)
3) second abnormal outpatient laboratory
result (fa sting glucose $126 mg/dL;
random or postchallenge [75 g] glucose
$200 mg/dL; HbA
1c
$6.5%), tested on
separate days, within a 3-year period
4) pharmacy use (prescription for
insulin or oral antihyperglycemic
medications)
*We excluded those newly identied diabetes cases
if they were based on a diagnosis for gestational di-
abetes mellitus (ICD-9: 648.8), identied due to the
use of insulin sensitizers (thiazolidinediones or
metformin) for conditions other than diabetes (e .g.,
lipodys trophy or polycystic ovary syndrome), or
included due to a single criteria without subse quent
diabetes-related utilization withi n a 2-year period.
care. diabetesjournals.org DIABETES CARE, VOLUME 36, MARCH 2013 575
Karter and Associates
Page 2
sex-adj usted point estima tes (mod el 1).
After adjustment for the two available clin-
ical factors (BMI and systolic blood pres-
sure in model 2), the point estimate for the
RR increased for all of the Asian subgroups
but decreased for Pacic Islanders, African
Americans, Latinos, Native Americans, and
multiracial subjects.
CONCLUSIONS dIn a large, inte-
grated healthca re delivery syste m in
which participants have uni form access
to healthcare, both the diabetes prevalence
and incidence rates in the two aggregate API
categories (Asians or APIs) were greater than
whites but lower than Latinos or African
Americans. However, there was substantial
variation across the API subgroups. Pacic
Islanders, South Asians, and Filipinos
had substantially higher prevalence and
incidence than all other ethnic groups,
including African Americans, Latinos, and
Native Americans. Pacic Islanders had
more than three times the incidence of
diabetes relative to whites, compared with
an ;75% higher diabetes incidence among
African Americans and Latinos relative to
whites.
Our ndings are consistent with pre-
vious po pulation-based studies based on
the Behavioral Risk Factor Surveillance
Study (11) and the NHIS (12), which
ranked Asians as intermediate in risk above
Table 2dRace/ethnicity-specic characteristics of our study population (n = 2,123,548); KPNC
Race/ethnicity Sample size Age (years) Sex (% female) BMI (kg/m
2
)
Systolic blood
pres sure (mmHg)
Median household income
in census block (31,000)
White (reference) 968,943 53.6 (18. 0) 56.2% 28.3 (6.4 ) 124.6 (15.1) $65.7 (25.3)
Latino 253,821 44.8 (16. 5) 57.4% 29.7 (6.4 ) 122.3 (14.8) $55.4 (20.8)
African American 135,934 48.8 (17. 5) 60.0% 30.9 (7.5 ) 127.1 (16.1) $50.9 (21.0)
Filip ino 82,7 81 49.1 (16.2) 61.6% 26.6 (4.7) 123.9 (14.7) $64.5 (21.1)
Chinese 68,8 31 51.6 (16.8) 58.5% 24.2 (4.0) 120.1 (15.0) $70.1 (28.4)
Japanese 16,0 32 58.7 (17.7) 62.9% 25.4 (4.9) 123.5 (15.0) $69.7 (26.2)
Native American 9,54 6 47.9 (16.5) 57.7% 30.4 (7 .2) 124.3 (15.3) $56.2 (21.7)
Pacic Islander 7,73 2 46.0 (17.8) 54.4% 29.8 (7 .7) 124.0 (15.3) $58.0 (22.2)
South Asian 6,76 8 43.4 (15.0) 52.0% 26.4 (4 .7) 119.0 (14.8) $69.2 (27.5)
Southeast Asian 1,87 6 37.7 (12.2) 63.0% 26.4 (5 .2) 117.0 (14.0) $51.0 (23.7)
Korean 1,13 0 49.6 (15.7) 50.4% 24.9 (4 .2) 119.9 (14.9) $72.1 (27.6)
Vietnamese 1,67 1 39.5 (11.6) 61.0% 23.9 (4 .1) 114.7 (14.3) $64.1 (25.5)
Other/unspecied Asian 101,769 43.3 (15. 1) 59.9% 25.5 (4.8 ) 119.2 (14.9) $67.2 (26.4)
Multi racial group 47,5 29 55.6 (18.8) 64.4% 28.7 (6.6) 124.5 (15.6) $62.1 (23.8)
Missing race 419,185 40.1 (13. 1 35.4% 27.9 (6.0 ) 122.7 (14.1) $62.1 (24.4)
Overall 2,123,548 48 .8 (17.6) 53.2% 28.2 (6.3) 123.7 (15.1) $62.6 (24.8)
Data are reported as means (SD) unless otherwise no ted. Block-level indicator from the 2010 U.S. Cens us linked to each subjects geocoded address.
Table 3dRace/ethnicity-specic diabetes prevalence and incidence sex and age standardized to the 2010 U.S. population; KPNC
Race/ethnicity Sam ple size Prevalence (%) (95% CI)
Stand ardized relative
difference in
prevalence
Incidence (new cases
per 1,000 person-years)
(95% CI)
Standardized relative
difference in
incidence
White (reference) 968,943 7.25 (7.27.29) Reference 6.3 (6.146.46) Reference
Latino 253,821 14.02 (13.8914.16) 94% 11.17 (10.6811.66) 77%
African American 135,934 13.7 (13.5313.87) 89% 11.22 (10.6111.84) 78%
Filip ino 82,7 81 16.13 (15.916.3 7) 123% 14.68 (1 3.7415.62) 133%
Chinese 68,831 8.15 (7.968.33) 12% 6.5 (5.877.14) 3%
Japanese 16,0 32 10.28 (9.8410.7 1) 42% 7.53 (6 .148.92) 20%
Native American 9,546 13.38 (12.7414.02) 85% 11.97 (9.614.34) 90%
Pacic Islander 7,732 18.27 (17.4419.1) 152% 19.94 (16.1623.71) 216%
South Asian 6,768 15.85 (14.8316.87) 119% 17.16 (11.9922.34) 172%
Southeast Asian 1,876 10.52 (8.4912.55) 45% 11.36 (1.2421.47) 80%
Korean 1,130 9.85 (7.811.91) 36% 2 0.28 (15.7424.82) 222%
Vietnamese 1,671 9.85 (7.5112.2) 36% 4.62 (1.138.1) 227 %
Other/unspecied Asian 101,769 12.12 (11.8812.35) 67% 10.17 (9.38
10.96) 61%
Multi racial group 47,5 29 12.84 (12.5413.14) 77% 9.74 (8.6 310.85) 55%
Missing race/ethnicity 419,185 5.36 (5.215.5) 226% 6.16 (5.696.63) 2 2%
Overall 2,12 3,548 8. 89 (8.868.93) 23% 7.67 (7.557.79) 22%
Denominator includes subjects with known race/ethnicity, directly standardized to the age and sex distribution of the 2010 U.S. Census population. For the
prevalence calculations, this includes 2,123,548 Kaiser Permanente members. For the incidence calculations, those with pre-existing diabetes were excluded, leaving
1,912,916 in the denominator. P , 0.05. Relative difference = (% or rate in ethnic group % or rate in reference)/(% or rate in reference).
576 DIABETES CARE, VOLUME 36, MARCH 2013 care.diabetesjournals.org
Elevated rates of diabetes in Asian subgroups
Page 3
whites and below African Americans, Lati-
nos, and Native Americans. The use of the
aggregated Asian or API categories masks
the variation in risk among the sub-
groups (4). These categories are essentially
weighted averages of the component sub-
groups, with the risk of the larger groups
(Chinese and Filipinos) exerting a stronger
inuence on the overall rate. Thus, the very
high risk experienced among PacicIs-
landers, South Asians, and Filipinos is
masked in the aggregate rate by the much
lower risk among Chinese and Japanese.
Our ndings are consistent with the
NHIS, reporting elevated diabetes preva-
lence among all Asian ethnic groups
combined, but particularly hi gh risk
among Filipinos and South Asians (3).
In the 2004 New York City Health and
Nutrition Examination Survey, the higher
diabetes prevalence observed amo ng
Asians relative to whites was primarily
due to high diabetes prevalence among
South Asians (13). Less national data exist
for Pacic Islanders, but in smaller epide-
miologic studies conducted in Hawaii, di-
abetes prevalence was similarly high
among Pacic Islanders compared with
Japanese and even Filipinos (14).
Phenotypic differences by race/ eth-
nicity were also evident among patients
newly diagnosed with diabetes. Most
noteworthy was that each Asian subgroup
other than Pacic Islanders had a sub-
stantively lower average BMI at diabetes
diagnosis than the remaining groups at
diagnosis. The average BMI values of
Asian subgroups were in fact below the
threshold for ob esity based on National
Heart, Lung, a nd Blood Institute stan-
dards. The World Health Organization
criteria suggested f or use in Asian pop-
ulations (15), with overweight BMI 23
27.5 k g/m
2
and obesity $27.5 kg/m
2
,
are more useful for helping clinicians
identify who to target for behavioral inter-
ventions to reduce diabetes ris k. Com -
pared w ith those with inciden t diabetes,
there was a consistent pattern across race/
ethnic groups of lower BMI among individ-
uals with prevalent diabetes, and even
lower BMI among normoglycemic subjects.
Adjusting for BMI actually increased the RR
for all the Asian subgroups, while attenuat-
ing the RR among the remaining minority
groups. This suggests that Asian subgroups
have an increased prevalence and incidence
of diabetes at comparable levels of BMI
(relative to the white reference group).
Few data on di abetes incidence exist
for APIs, particularly for clinica lly recog-
nized rather than sel f-reported diabetes.
The few existing studies again support the
somewhat misleading impression that
stems from aggregating subgroups into
broad Asian or API categori es (16). The
rate observed in the KPNC cohort adds
several additional subgroups for which
few current diabetes incidence data exist,
notably among Filipinos and South Asians.
Moreover, unlike population-based stud-
ies, this study population received care
in a single integrated healthcare delivery
system, and thus the ndings are not con-
founded by differential access to care across
the racial/ethnic groups.
These ndings may not be represen-
tative of other geographical regions,
heal th plans, o r population- based sam-
ples. Findings are based on a fully insured
population from Northern California;
caution is needed when generalizing to a
wider population. Asian im migrants to
the U.S. may differ signicantly from the
populations from which they originated.
Although California has a longer history
of immigra tion from Asia than other parts
of the U.S., the timing of immi gration
varies along with the degree of accultur-
ation to a Western lifestyle. The time of
residence and acculturation in the U.S.
may alter rates of chronic diseases such as
diabetes, and this effect can change over
time or in subsequent generations. The
stage of life (child, older adults, etc.) when
U.S. resid ence began may also play an
important role. Also, it is unclear as to
what extent the racial/eth nic differences
in screen ing for diabetes could contribute
to our ndings. Screening for diabetes has
increased in recent years, and, over all,
65% of subjects without pre-existing di-
abetes completed a fasting, random, or
postchallenge glucose test during the 2
years prior to study baseline (2008
2009). Modest differences were noted
by race/ethnicity: multiracial subjects
(72%), South Asians (71%), Chinese
(70%), Japanese (68%), Filipinos (67%),
Koreans (66%), whites (65%), African
Americans ( 64%), Native America ns
(63%), Vietnamese (63%), Latinos (62%),
and Pacic Islanders (60%). However, the
race/ethnicity-specic ranking of screening
rates was inconsistent with the ranking in
diabetes risk, suggesting that these screen-
ing differences unlikely accounted for ob-
served differences. The American Diabetes
Association introduced HbA
1c
as a screen-
ing test in their 2010 Clinical Practice Rec-
ommendations (10), and thus it was only
rarely used at the time of the study (only
0.3% of our cohort was screened for diabe-
tes using an HbA
1c
test alone), diminishing
Figure 1dStandardized diabetes incidence rate (per 1,000 person-years) for each race/ethnic
group (2010, KPNC). Identied 15,357 new cases of medically diagnosed diabe tes in 2010 among
the adults ($18 years of age) without pre-existing diabetes in KPNC on 1 Janu ary 2010. The
incidence density was directly stand ardized to the 2010 U.S. Census. All Asian included Filipino,
Chinese, Japanese, South Asian, Southeast Asian, Korean, Vietnamese, unspecied Asian, and
multiracial Asian; API included the identical groups as all Asian with the addition of Pacic
Islan ders.
care. diabetesjournals.org DIABETES CARE, VOLUME 36, MARCH 2013 577
Karter and Associates
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concerns that this may bias ascertainment
given the observed differential association
between glycemia and HbA
1c
by race (17).
It remains unknown to what extent the
rates of undetected diabetes vary across
race/ethnicity, and whether the ethnic dis-
tribution of diabetes would change sub-
stantively if we did not have 19.7% with
missing data regarding ethnicity.
These ndings represent a departure
from the conventional wisdom regarding
diabetes burden among APIs as being
uniformly lower than African Americans
and Latinos but higher than that of
whites. Survei llance statistics aggregating
all APIs obscure the very high diabetes
risk among PacicIslanders,South
Asians, and Filipinos. These groups
would benet from increased diabetes
prevention efforts. Subgroup variation
in diabetes prev alence is not unique to
APIs; variation has been observed among
Latino subgroups (e.g., between Cubans,
Puerto Ricans, and Mexican Americans)
(18,19). Aggregated statistic s may be,
frankly, misle ading.
More work is needed to unders tand
the extent to which subgroup differences
in diabetes burden are attributable to
behavioral factors, socioeconomic status,
education, health literacy, language bar-
riers, or biology. Diabetes is a rapidly
growing public health problem for Asian
Americans (2), and p ublic health promo-
tionmaymoreeffectivelytargetsub-
groups separately given differences in
potential barriers to care (language, culture,
education, and socioeconomics). In re-
sponse to the growing risk of diabetes
among Asians and the paucity of surveil-
lance data, t he Centers for Disease Control
and Preventions National Center for Health
Statistics has begun oversampling Asians in
the National Health and Nutrition Exami-
nation Survey (5). Although the causes of
differing diabetes rates by race/ethnicity are
not well understood, in our efforts to meet
our national objective of eliminating health
disparities, we must continue to monitor
diabetes prevalence and incidence among
the API subgroups, as well as across race s/
ethnicities in general (20).
Acknowledgmentsd DISTANCE and its inves-
tigators were supported by grants from the Na-
tional Institutes of Health (NIH) (R01-DK-081796,
R01-DK-065664, R01-HD046113, and P30-DK-
092924). A.M.K. was supported by NIH grants
1RO1-HL-093009-01 and 1R01-AT-004569-01.
The funding organizations had no role in the
design and conduct of the study; collection,
Table 4dAge- and sex-adjusted, race/ethnicity-specic RR for diabetes prevalence based on a Poisson regression with log link functions;
KPNC (n = 2,123,548)
Race/ethnicity
Base model
(age and sex adjusted)
Model 1 (age, sex, and
income adjusted)
Model 2 (age, sex, income,
systolic blood pressure, and BMI adjusted)
White (reference) Reference Reference Reference
Latino 1.88 (1.861.91); P , 0.0001 1.80 (1.7 81.82); P , 0.0001 1.69 (1.671.71); P , 0.0001
African American 1.86 (1.8 31.89); P , 0.0001 1.73 (1.711.76); P , 0.0001 1.50 (1.471.52); P , 0.0001
Filip ino 2.26 (2.2 22.30); P , 0.0001 2.24 (2.202.28); P , 0.0001 2.74 (2.692.79); P , 0.0001
Chinese 1.14 (1.111.16); P , 0.0001 1.16 (1.131.19); P , 0.0001 1.63 (1.591.67); P , 0.0001
Japanese 1.46 (1.4 01.51); P , 0.0001 1.48 (1.421.54); P , 0.0001 1.88 (1.801.96); P , 0.0001
Native American 1.86 (1.7 6
1.96); P , 0.0001 1.78 (1.681.87); P , 0.0001 1.55 (1.471.64); P , 0.0001
PacicIslander 2.43(2.302.56); P , 0.0001 2.35 (2.232.48); P , 0.0001 2.31 (2.192.44); P , 0.0001
South Asian 2.19 (2. 052.33); P , 0.0001 2.25 (2.112.40); P , 0.0001 2.64 (2.482.82); P , 0.0001
Southeast Asian 1.46 (1.221.74); P , 0.0001 1.39 (1.161.66); P = 0.0004 1.72 (1.432.07); P , 0.0001
Korean 1.31 (1.101.56); P , 0.003 1.36 (1.141.61); P = 0.0006 1.84 (1.542.20); P , 0.0001
Vietnamese 0.98 (0.781.2 4); NS 0.97 (0.7 71.22); NS 1.42 (1.121.80); P = 0.0041
Other/unspecied Asian 1.59 (1.561.63); P , 0.0001 1.61 (1.581.65); P , 0.0001 2.13 (2.09
2.18); P , 0.0001
Multi racial group 1.74 (1. 701.78); P , 0.0001 1.71 (1.671.74); P , 0.0001 1.62 (1.581.66); P , 0.0001
Denominator includes subjects with known race/ethnicity. Census-based (block-level) median income.
Figure 2dBMI among adult ($18 years of age) members of KPNC by race for those with
prevalent diabetes (n = 194,614), newly identied diabetes (n = 13,392), and subjects remaining
normoglycemic (n = 1,496,357) during calendar year 2010. BMI m easured during cal endar year
2009 among the 1,704,363 adult members of KPNC with known ethnicity.
578 DIABETES CARE, VOLUME 36, MARCH 2013 care.diabetesjournals.org
Elevated rates of diabetes in Asian subgroups
Page 5
management, analysis, and interpretation of
data; or preparation, review, and approval of
the manuscript.
No potential conicts of interest relevant to
this article were reported.
A.J.K. conceived the study, researched the
data , and wrote the manuscript. D.S., A.S.A.,
and N.E.A. contrib uted to the discussion.
H.H.M. and J.L. researched the data and re-
viewed and edited the manuscript. A.M.K.
contributed to the discussion and reviewed and
edited the manuscript. A.J.K. is the guarantor
of this work and, as such, had full access to all
the data in the study and takes responsibility
for the integrity of the data and the accuracy of
the data analysis.
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Table 5dAge- and sex-adjusted, race/ethnicity-specic RR (95% CI) for diabetes incidence based on a Poisson regression with log link
functions; KPNC (n = 1,912,916)
Race/ethnicity
Base model
(age and sex adjusted)
Model 1 (age, sex, and
income adjusted)
Model 2 (age, sex, income, systolic
blood pressure, and BMI adjusted)
White (reference) Reference Reference Reference
Latino 1.76 (1.671.84); P , 0.0001 1.68 (1.601.76); P , 0.0001 1.54 (1.461.63); P , 0.0001
African American 1.76 (1.661.87); P , 0.0001 1.64 (1.541.74); P , 0.0001 1.25 (1.181.34); P , 0.0001
Filip ino 2.38 (2.232.54); P , 0.0001 2.37 (2.212.53); P , 0.0001 3.22 (3.003.45); P , 0.0001
Chinese 1.02 (0.921.12); NS 1.04 (0.951.15); NS 1.82 (1.652.01); P , 0.0001
Japanese 1.26 (1.071.50); P = 0.007 1.31 (1.101.55); P , 0.003 1.79 (1.492.15); P , 0.0001
Native American 1.93 (1.582.34); P , 0.0001 1.84 (1.512.25);
P , 0.0001 1.60 (1.311.97); P , 0.0001
Pacic Islander 3.08 (2.563.72); P , 0.0001 2.92 (2.423.53); P , 0.0001 2.61 (2.133.20); P , 0.0001
South Asian 2.31 (1.832.92); P , 0.0001 2.35 (1.852.98); P , 0.0001 3.31 (2.604.22); P , 0.0001
Southeast Asian 1.20 (0.622.30); NS 1.14 (0.592.20); NS 1.91 (0.993.67); NS
Korean 1.13 (0.562.26); NS 1.19 (0.59 2.37); NS 1.66 (0.753.70); NS
Vietnamese 0.99 (0.472.08); NS 1.00 (0.48 2.10); NS 2.10 (1.004.42); P , 0.05
Other/unspecied Asian 1.55 (1.441.68); P , 0.0001 1.57 (1.451.69); P , 0.0001 2.28 (2.102.48); P , 0.0001
Multi racial group 1.50 (1. 361.65); P , 0.0001 1.48 (1.341.63); P , 0.0001 1.45 (1.311.60); P , 0.0001
NS, not statistically signicant at the P , 0.05 level. Denominator includes subjects with known race/et hnicity and without pre-existing diabetes on 1 January 2010.
Census-based (block-level) median income.
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