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RESEARCH ARTICLE
Changes in the use practitioner-based
complementary and alternative medicine over
time in Canada: Cohort and period effects
Mayilee Canizares
1,2
*, Sheilah Hogg-Johnson
3,4
, Monique A. M. Gignac
2,3,4
, Richard
H. Glazier
3,5,6,7
, Elizabeth M. Badley
2,3
1Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada, 2Krembil Research Institute,
University Health Network, Toronto, Ontario, Canada, 3Dalla Lana School of Public Health, University of
Toronto, Toronto, Ontario, Canada, 4Institute for Work and Health, Toronto, Ontario, Canada, 5Institute for
Clinical Evaluative Sciences, Toronto, Ontario, Canada, 6Department of Family and Community Medicine,
University of Toronto, Toronto, Ontario, Canada, 7Department of Family and Community Medicine,
St. Michael’s Hospital, Toronto, Ontario, Canada
*mcanizar@uhnres.utoronto.ca
Abstract
Background
The use of complementary and alternative medicine (CAM) is growing. However the factors
contributing to changes over time and to birth cohort differences in CAM use are not well
understood.
Setting
We used data from 10186 participants, who were aged 20–69 years at the first cycle of data
collection in the longitudinal component of the Canadian National Population Health Survey
(1994/95-2010/11). We examined chiropractic and other practitioner-based CAM use with a
focus on five birth cohorts: pre-World War II (born 1925–1934); World War II (born 1935–
1944); older baby boomers (born 1945–1954); younger baby boomers (born 1955–1964);
and Gen Xers (born 1965–1974). The survey collected data every two years on predispos-
ing (e.g., sex, education), enabling (e.g., income), behavior-related factors (e.g., obesity),
need (e.g., chronic conditions), and use of conventional care (primary care and specialists).
Results
The findings suggest that, at corresponding ages, more recent cohorts reported greater
CAM (OR = 25.9, 95% CI: 20.0; 33.6 for Gen Xers vs. pre-World War) and chiropractic use
than their predecessors (OR = 2.2, 95% CI: 1.7; 2.8 for Gen Xers vs. pre-World War). There
was also a secular trend of increasing CAM use, but not chiropractic use, over time (period
effect) across all ages. Factors associated with cohort differences were different for CAM
and chiropractic use. Cohort differences in CAM use were partially related to a period effect
of increasing CAM use over time across all ages while cohort differences in chiropractic use
were related to the higher prevalence of chronic conditions among recent cohorts. The use
of conventional care was positively related to greater CAM use (OR = 1.8, 95% CI: 1.6; 2.0)
PLOS ONE | https://doi.org/10.1371/journal.pone.0177307 May 11, 2017 1 / 17
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OPEN ACCESS
Citation: Canizares M, Hogg-Johnson S, Gignac
MAM, Glazier RH, Badley EM (2017) Changes in
the use practitioner-based complementary and
alternative medicine over time in Canada: Cohort
and period effects. PLoS ONE 12(5): e0177307.
https://doi.org/10.1371/journal.pone.0177307
Editor: Russell Jude de Souza, McMaster
University, CANADA
Received: October 26, 2016
Accepted: April 25, 2017
Published: May 11, 2017
Copyright: ©2017 Canizares et al. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which
permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: Access to the data is
through the Statistics Canada Research Data
Centres (RDC) Program. RDCs are operated under
the provisions of the Statistics Act in accordance
with all the confidentiality rules. Researchers with
approved projects by Statistics Canada can access
the data. For more information on how to access
the data see http://www.statcan.gc.ca/eng/rdc/
process.
Funding: Access to the data is through the
Statistics Canada Research Data Centres (RDC)
and chiropractic use (OR = 1.2, 95% CI: 1.1; 1.4) but did not contribute to changes over time
or to cohort differences in CAM and chiropractic use.
Conclusion
The higher CAM use over time and in recent cohorts could reflect how recent generations
are approaching their healthcare needs by expanding conventional care to include CAM
therapies and practice for treatment and health promotion. The findings also underscore the
importance of doctors discussing CAM use with their patients.
Introduction
Conventional or mainstream medicine continues to be the main source of healthcare in Can-
ada and elsewhere. However, a significant number of people choose complementary and alter-
native medicine (CAM) for wellness and/or treatment [1,2]. The increasing demand for CAM
may reflect a diversification of preferences for different types of healthcare services and an
increasing emphasis on health promotion and self-care by the public [3]. For example, studies
show that while many adults use CAM therapies to treat specific symptoms such as chronic
pain, others also report using CAM for general health maintenance [4–6]. Therefore, the grow-
ing interest in CAM raises questions about the patterns of CAM use over time in the context
of use of conventional medicine in the population. Understanding the changes in patterns of
CAM and conventional care use has important implications for planning and improving the
healthcare system as well as for medical education.
Age has been found to be strongly related to CAM use, but studies show an inconsistent pat-
tern. Some studies suggest CAM use peaks at middle age [7–10] while others show that CAM
use increases with increasing age [11,12]. It is not clear if these findings reflect true age effects or
if they are related to birth cohort effects. Cohort effects arise from differences in the experiences
of groups born and growing up in different time periods. These may be differences that are
unique to a particular birth cohort or that accumulate over the lifetime. Only two studies have
examined cohort differences in CAM use [13,14]. Both reported greater CAM use in more
recent cohorts, but used cross-sectional data and could not distinguish cohort effects from age
and period effects (secular changes over time). Period effects are changes in CAM use across all
age groups resulting from widespread societal changes or from events that took place at a partic-
ular point in time. Changes in government policies are often cited as examples of period effects.
Findings from studies examining changes over time in CAM use are not consistent across
CAM therapies and practices. For example, data from the U.S. on national estimates of CAM
use for 2002, 2007, and 2012 found large variability across types of CAM used and over time
[15]. The study found an increased use of acupuncture and homeopathy over time, but no sig-
nificance change in chiropractic use. A Canadian study showed that use of publicly subsidized
chiropractic services by adults over the age of 50 decreased over the decade of the 1990s in one
Canadian province [16]. Several hypotheses related to period differences have been put for-
ward to explain why CAM use may be growing, including the rise of the consumer movement
in healthcare since the 1970’s and the growing use of the Internet [17–19]. The consumer
movement has empowered individuals and encouraged them to take a proactive role towards
healthcare decisions and selection of services [18,20,21]. Additionally, as health information
becomes more readily available online, more individuals are seeking and finding information
about CAM treatments, which they may incorporate into their general healthcare practices
[19].
Changes in the use practitioner-based complementary and alternative medicine over time in Canada
PLOS ONE | https://doi.org/10.1371/journal.pone.0177307 May 11, 2017 2 / 17
Program. RDCs are operated under the provisions
of the Statistics Act in accordance with all the
confidentiality rules. The findings and conclusions
of this paper are those of the authors and do not
represent the official position of Statistics Canada.
This study was partially supported by a CIHR
Operating Grant–Secondary Analysis of Databases
(SEC 117113). The funder had no role in study
design, data collection and analysis, decision to
publish, or preparation of the manuscript.
Competing interests: The authors have declared
that no competing interests exist.
The aging of the population has been proposed as another possible explanation for variations
in CAM use over time. Notably, age effects alone do not appear to explain these changes since
analyses adjusting for age continue to indicate variability across time [22,23]. These variations
may also be related to changes in other factors. For example, cross-sectional studies have found
that CAM use is greater among those with high income and/or educational levels [2,7,9,24].
Yet, the few studies that have controlled for these factors while comparing CAM use across peri-
ods of time have found that changes in income and education were not associated with time
trends in CAM use [23]. Health variables are also important. Studies consistently indicate that
chronic conditions and pain are significantly related to CAM use [7,13,25–27]. Therefore, it is
reasonable to hypothesize that the growing number of people living with chronic conditions
may also underlie the growing trend in CAM use [28–30]. Lastly, the use of CAM in relation to
conventional care has also been examined with inconsistent findings. Some studies suggest that
conventional care users supplement their care with CAM services [31,32]. Others have sug-
gested that patients having difficulties accessing conventional care turn to CAM to meet their
healthcare needs [33,34]. No study, however, has examined changes in CAM use over time in
the context of changing patterns of need for care and of conventional care use.
We drew on 16 years of longitudinal population data to examine variations in CAM use
from 1994 to 2011 We focused on five birth cohorts of Canadians: pre-World War II (born
1925–1934), World War II (born 1935–1944), older baby boomers (born 1945–1954), younger
baby boomers (born 1955–1964), and Generation X (Gen Xers, born 1965–1974). We also
controlled for other factors associated with CAM use that have been reported in the literature
(e.g. chronic conditions, pain). Our goals were to determine 1) whether, in addition to age
effects, there were birth cohort and/or period effects in CAM use, and 2) whether changes in
need for care and changes in the use of conventional medicine contributed to any cohort and/
or period effects, controlling for other factors. We hypothesized that changes in CAM use over
time were, at least partially, related to cohort and period effects, independent of changes over
time in the factors predicting CAM use.
Materials and methods
Canadian National Population Health Survey
We used data from the longitudinal component of the Canadian National Population Health
Survey (NPHS) spanning 16 years (1994–2011) [35]. The target population of the NPHS
included household residents in the ten Canadian provinces in 1994/1995. The survey
excluded persons living on Indian Reserves and Crown Lands, residents of health institutions,
full-time members of the Canadian Forces Bases and some remote areas in Ontario and Que
´-
bec. The survey used a complex sampling design with a multi-stage stratified and cluster selec-
tion (geographic and/or socio-economic strata, geographic clusters, and then dwellings within
each cluster). The NPHS retained individuals who moved to long-term care institutions and
those who died over the course of the survey. The death of a respondent was confirmed against
the Canadian Vital Statistics Database, and the cause and date of death were captured. More
details on the NPHS sampling plan and survey questions is available from Statistics Canada
[35].We restricted the sample to 10186 individuals aged 20–69 years in 1994 who provided at
least three cycles of data.
This paper is based on secondary analyses of data collected by Statistics Canada; as such we
did not obtained direct consent from the survey participants. However, participation in the
survey was voluntary and respondents consented that their data may be used by third parties
upon approval from Statistics Canada. In addition, the University of Toronto Ethics Commit-
tee approved the study.
Changes in the use practitioner-based complementary and alternative medicine over time in Canada
PLOS ONE | https://doi.org/10.1371/journal.pone.0177307 May 11, 2017 3 / 17
Measures
CAM use. CAM use was defined as consulting with any of the following CAM practition-
ers (Yes/No) in the past 12 months: massage therapist, acupuncturist, homeopath or naturo-
path, Feldenkrais or Alexander teacher, relaxation therapist, biofeedback teacher, rolfer,
herbalist, reflexologist, spiritual healer, or religious healer. As in other studies we also included
chiropractors [36]. Because chiropractors exhibit characteristics of both conventional medi-
cine and CAM [37,38], we examined chiropractic use separately from other CAM use. Chiro-
practic use was derived from a separate question: “In the past 12 months, how many times
have you seen or talked on the telephone with a chiropractor about your physical, emotional
or mental health?” Chiropractic use was defined as reporting 1 or more visits.
Age, period, and cohort. We used participants’ date of birth to calculate age for each
cycle and to allocate participants to the five birth cohorts previously noted. The year of the
interview was used as an indicator of period.
Need for care. We used two factors to assess need for care: chronic conditions and pain
that prevents activities. The NPHS collected data on up to 17 individual chronic conditions
that had been diagnosed by a healthcare professional: arthritis, back problems, asthma, aller-
gies (excluding food allergies), bronchitis, emphysema, diabetes, high blood pressure, heart
conditions, stroke, cancer, ulcers, urinary incontinency, dementia, migraine, glaucoma, and
cataracts. We calculated the number of chronic conditions and grouped them as: none, 1, and
2+. For the variable “pain that prevents activities” responses were grouped as: no pain/pain
does not prevent activity or pain prevents activity (few/sometimes/always).
Use of conventional care. At each survey cycle participants reported whether they con-
tacted primary care physicians/general practitioners (PCP) or specialists (excluding eye care)
in the 12 months prior to their interview. An indicator combining use of PCPs and of special-
ists was created: visited both, only PCP, only specialists, none.
Other predictors of CAM use. We included other factors grouped as predisposing,
enabling and behavior-related that previously have been found to be associated with CAM use
[7]: predisposing (sex and education), enabling (household income and having a regular
source of care), and behavior-related (obesity, smoking status, physical activity, and sedentary
lifestyle). Education was measured as years of schooling and was grouped for analyses as: <12
years, 12–15 years, and 16+ years. At each cycle, participants reported if they had a regular
doctor. Household income was categorized into quartiles of the distribution within each sur-
vey year and a separate category representing unknown values was retained for analyses. Obe-
sity was ascertained by using body mass index (BMI) categorized as: underweight (<18.5),
normal weight (18.5–24.9), overweight (25.0–29.9), moderate obese (30.0–34.9), and severe
obese (35.0). Smoking status was assessed by a Statistics Canada derived variable which
grouped participants as current smoker, former smoker, and non-smoker (those who never
smoked) [35]. Responses to a series of questions about participation in leisure time physical
activities such as, walking for exercise, running, gardening, etc. combined with data on walk-
ing or bicycling for commuting were used to group individuals as physically active (during lei-
sure time or active commuting) vs. inactive. Lastly, sedentary lifestyle was defined as those
who reported that they “usually sit during the day and don’t walk around very much.”
Statistical analysis
There is ongoing debate as to the best way to examine the unique effects of age, period, and
cohort [39–41]. Because age, period and cohort are linearly related, the linear effects of the
three factors cannot be modeled simultaneous without imposing restrictions on at least one of
the parameters. For this study, we conceptualized the models within a multilevel framework
Changes in the use practitioner-based complementary and alternative medicine over time in Canada
PLOS ONE | https://doi.org/10.1371/journal.pone.0177307 May 11, 2017 4 / 17
[42,43]. We estimated age and cohort as fixed effects with period as a random effect. We
started with a model unadjusted by period (Model 1). This was a two-level model where
repeated observations were nested within individuals, and age and cohort effects were esti-
mated as fixed effects. We then extended this model by adding another level to account for var-
iability across periods of times (Model 2). This was a hierarchical age-period-cohort (HAPC)
model in which repeated observations were nested within individuals and individuals were
nested within time periods. In subsequent models we added need for care and use of conven-
tional care while adjusting for the other predictors of CAM previously listed. In addition to
examining the effect of need for care and use of conventional care on CAM use, we also exam-
ined whether these factors affected the cohort, age, and period estimates.
We used the SAS/STAT software for all data analyses and the GLIMMIX procedure to esti-
mate the HAPC model [44]. The procedure uses maximum likelihood estimators that adjust
for non-response assuming the data are missing at random. It also uses all available data for
incomplete cases [44]. Although the NPHS uses weights to compensate for the complex multi-
stage sample design, the results of this paper are based on un-weighted analyses. The reason
for this is that the HAPC model cannot incorporate sampling weights at cross-classified levels.
We centered age at 39 years (the mean of the distribution for the five cohorts at baseline (1994/
95)). We used Wald tests to assess the significance of the variables.
Sub-analyses. About 39% of eligible participants died or dropped-out before the end of
the study. To examine the effect of attrition in our findings we compared our main results
with the results of two additional analyses: 1) including indicator variables identifying partici-
pants who dropped-out or died before the end of the study in all models; and 2) analyses with
a restricted sample of participants with complete data in the nine cycles.
Previous studies have suggested that analyses grouping CAM practitioners have the poten-
tial of missing differing patterns of use across practitioners [45]. We, therefore, repeated our
analyses for the CAM practitioners with >1% of use: massage therapy, acupuncture, and
homeopathy/naturopathy.
We also repeated the analyses to examine the contribution of specific chronic conditions to
the results. We chose the conditions that have been reported in the literature to be associated
with CAM use. These conditions were: back pain, arthritis, respiratory (asthma, allergies,
bronchitis, or emphysema), migraine, diabetes, high blood pressure, cardiovascular (heart con-
ditions or stroke), cancer, and other (ulcers, urinary incontinency, dementia, glaucoma,
cataracts).
Nahin et al [46] found that about 25% of individuals who do not use conventional care use
CAM in subsequent years. We, therefore, fitted the final model for CAM use with an addi-
tional variable indicating the use of conventional medicine in the previous cycle of data collec-
tion. This way we could examined whether those not using conventional care had increased
odds of using CAM in the following year.
Results
Descriptive
There were 10186 participants with at least three years of data (13.6% in the pre-World War II
cohort, 15.7% in the World War II, 21.6% in the older baby boomer, 27.3% in the younger
baby boomer, and 21.8% in the Generation X). Overall, 10.0% of the initial sample died and
27.3% dropped-out during follow-up. Between 1994/95 and 2010/11, CAM use increased from
4.8% to 11.2%. In contrast, overall chiropractic use remained virtually constant (9.0% in 1994/
95 vs. 10.2% in 2010/11, respectively). Similar patterns were seen in all birth cohorts. Chiro-
practors were the most common type of practitioner consulted across all cohorts followed by
Changes in the use practitioner-based complementary and alternative medicine over time in Canada
PLOS ONE | https://doi.org/10.1371/journal.pone.0177307 May 11, 2017 5 / 17
massage therapists (Table 1). Generally, users of all types of CAM practitioners had higher
education and/or income. They were less likely to be current smokers, were more physically
active, and more likely to have a sedentary lifestyle. Obese individuals were less likely to con-
sult with other CAM practitioners and more likely to consult with chiropractors. CAM users
also had more chronic conditions and a higher proportion reported pain. In addition, CAM
users reported higher use of conventional care (visits to PCPs and/or specialists) than non
CAM users (Table 2).
CAM use
Changes over time and birth cohort differences. Table 3 presents the results of the
modeling for CAM use. There were significant age differences in CAM use (Table 3, Model 1,
Fig 1A). After accounting for the effects of aging, cohort differences were large and significant;
that is, there was a trend of greater CAM use in each succeeding recent cohort, particularly for
Gen Xers and baby boomers (Table 3, Model 1). Results from the model adjusting for period
effects (Table 3, Model 2) indicated that there was significant variability in CAM use over this
period of time. As illustrated in Fig 1B, there was a trend of increasing CAM use over the years
irrespective of age and cohort. In addition, compared to the unadjusted model, the age and
cohort effects were substantially reduced, although they remained significant. This suggests
that broad societal changes were at least partially manifesting as increases in CAM use over the
lifecourse.
Model 2 was then extended to include predisposing, enabling, and behavior-related factors
(S1 Table, Model 2a). CAM users were more likely to be women, have higher education/
income, to not have a regular source of care, to be current smokers, have normal weight, be
physically active, and to have a sedentary lifestyle. The estimates of the age and cohort effects
remained significant in this model, but were slightly reduced. The model was further extended
by adding need factors (Table 3, Model 3). (Only the estimates for age, cohort, need factors,
and period are presented in the table with the full model presented in S1 Table, Model 3.)
Cohort differences remained significant after accounting for need factors suggesting that there
were cohort differences in CAM use over and above need for care. In addition, the estimate for
the random effect for period was reduced but remained significant. This suggests that the
trend of increasing chronic conditions over time partially underlies the growing CAM use.
The inclusion of use of conventional care did not alter the age and cohort estimates (Table 3,
Model 4).
Role of need for care and use of conventional care. As shown in Table 3 Model 4,
chronic conditions and pain were strong predictors of CAM use. Those with two or more
chronic conditions were more likely to use CAM than those with no chronic conditions
(OR = 1.79, 95% CI (1.64; 1.96)). Similarly, those reporting pain were more likely to use CAM
(OR = 1.81, 95% CI (1.66; 1.98)). The use of conventional care was also a significant and strong
predictor of CAM use. The results indicate that CAM users were also users of conventional
medicine: those consulting with primary care physicians and with specialists had higher odds
of consulting with CAM practitioners.
Chiropractic use
Changes over time and birth cohort differences. Results from the model unadjusted by
period (Table 4, Model 1) showed that the age-trajectory of chiropractic use increased around
middle age, then declined (Fig 2A). In addition to age effects, large and significant cohort dif-
ferences were found (Table 4, Model 1, Fig 2A). Comparing cohorts at corresponding ages
indicates that there was higher chiropractic use for Gen Xers, followed by younger boomers,
Changes in the use practitioner-based complementary and alternative medicine over time in Canada
PLOS ONE | https://doi.org/10.1371/journal.pone.0177307 May 11, 2017 6 / 17
and older boomers when compared to pre-boomers (World War II and pre-World War II
cohorts). As shown by the estimate of the random effect for period, variability across years for
chiropractor use was small and non-significant (Table 4, Model 2, Fig 2B). In addition, com-
pared to the unadjusted model (Model 1), the age and cohort effects were virtually unchanged.
As with CAM use, we included predisposing, enabling, and behavior-related factors to
Model 2 (S2 Table, Model 2a). There were no significant differences in chiropractic use
between men and women. Those with higher income, who were overweight or obese, current
smokers, and physically active were more likely to consult with chiropractors. When these var-
iables were considered, the estimates of the age and cohort effects were reduced but remained
significant.
Model 3 in Table 4 shows the estimates for age, cohort, need factors, and period with the
full model presented in S2 Table, Model 3. The estimates of age effects were slightly reduced,
although they remained significant, while the cohort effect estimates were no longer signifi-
cant. Lastly, Model 4 shows the results of adding the use of conventional care to Model 3.
Although significant, the inclusion of use of conventional care did not alter the age and cohort
estimates.
Role of need for care and use of conventional care. Findings from the fully adjusted
model (Table 4, Model 4) indicate that need for care factors (i.e. chronic conditions and pain)
were significantly associated with chiropractic use, such that having more chronic conditions
and/or pain affecting activities were strong positive predictors of chiropractic use. Further-
more, the use of conventional care was a significant and strong predictor of chiropractic use.
Those consulting with primary care physicians and/or with specialists had higher odds of con-
sulting with chiropractors.
Table 1. Use (%) of practitioners-based complementary and alternative medicine in 1994/95 and 2010/11 by birth cohort. Canadian National Popula-
tion Health Survey (NPHS), 1994–2011.
ALL
(1925–1974)
PRE-WORLD WAR
II
(1925–1934)
WORLD
WAR II
(1935–1944)
OLDER
BABY
BOOMER
(1945–1954)
YOUNGER BABY
BOOMER
(1955–1964)
GENERATION
X
(1965–1974)
CYCLE
1:
1994/
95
CYCLE 9:
2010/11
CYCLE1:
1994/95
CYCLE 9:
2010/11
CYCLE1:
1994/95
CYCLE 9:
2010/11
CYCLE1:
1994/95
CYCLE 9:
2010/11
CYCLE1:
1994/95
CYCLE 9:
2010/11
CYCLE1:
1994/95
CYCLE 9:
2010/11
n10186 6562 1384 665 1596 1061 2205 1577 2778 1886 2223 1373
CAM use
(all practitioners)
14.6 24.5 12.1 11.5 15.4 16.1 17.4 24.1 16.3 29.5 10.8 31.0
Chiropractors 10.7 13.4 9.5 8.4 11.8 9.0 13.0 13.8 11.2 15.7 8.2 15.6
CAM use
a
(other
practitioners)
5.6 15.8 3.8 5.3 5.2 9.2 6.6 14.6 7.3 19.6 3.9 21.8
Massage
therapist
2.4 7.6 1.0 3.5 3.1 5.6 3.2 9.1 4.0 14.2 2.3 15.6
Acupuncturist 0.8 2.4 1.2 1.5 0.8 2.5 1.0 3.4 1.0 3.6 0.3 3.8
Homeopath/
Naturopath
1.2 1.9 0.9 0.4 1.3 1.3 1.7 2.8 2.0 3.4 0.9 2.8
Abbreviations: CAM, Complementary and Alternative Medicine
a
Massage therapist, Acupuncturist, Homeopath/Naturopath, Feldenkrais or Alexander teacher, relaxation therapist, biofeedback teacher, rolfer, herbalist,
reflexologist, spiritual healer, or religious healer
https://doi.org/10.1371/journal.pone.0177307.t001
Changes in the use practitioner-based complementary and alternative medicine over time in Canada
PLOS ONE | https://doi.org/10.1371/journal.pone.0177307 May 11, 2017 7 / 17
Sub-analyses
Our models adjusting for attrition showed no significant differences in CAM use between
those who died, dropped-out, or remained for the duration of the study. Estimates for the fac-
tors associated with CAM use were similar to those obtained in the main analyses. Further
analyses restricted to those who remained for the duration of the study showed that cohort dif-
ferences in CAM use and the relationships of the factors examined remained unchanged.
These analyses did not alter our conclusions.
Table 2. Characteristics of users and non-users of CAM and chiropractic services. Canadian National Population Health Survey (NPHS), 1994–2011.
CAM CHIROPRACTIC
CYCLE 1:
1994/95
CYCLE 9:
2010/11
CYCLE 1:
1994/95
CYCLE 9:
2010/11
USERS NON-USERS USERS NON-USERS USERS NON-USERS USERS NON-USERS
n570 9616 1035 5362 1100 9086 882 5705
Mean number of chronic conditions 1.3 0.9 2.0 1.9 1.4 0.9 2.1 1.9
% with back pain 26.9 15.1 29.2 19.7 41.7 12.6 37.5 18.7
% with arthritis 15.1 13.1 29.2 30.8 17.6 12.6 31.2 30.5
% with migraine 12.1 8.3 13.5 8.5 11.3 8.2 11.8 8.5
% with respiratory 27.8 22.0 44.8 34.4 27.8 21.6 42.3 35.0
% with diabetes 3.5 2.5 5.4 10.3 2.9 2.5 7.1 10.0
% with high blood pressure 7.4 8.9 19.3 30.6 8.6 8.9 23.4 29.6
% with cancer 1.8 1.2 1.5 2.3 1.1 1.3 1.7 2.2
% with cardiovascular 4.2 3.1 5.8 9.5 3.0 3.6 7.8 9.0
% with other
a
17.8 13.2 29.5 31.2 16.0 13.2 28.5 31.3
% with no chronic conditions 34.7 47.6 21.1 22.7 37.0 22.2 19.4 22.9
% with pain 21.9 10.9 21.6 14.8 19.4 10.5 20.1 15.3
Use of conventional care
% consulting with PCP 89.1 77.4 86.1 78.0 85.8 77.1 83.8 78.6
Mean visits to PCP 5.1 3.6 3.7 3.2 4.5 3.6 3.5 3.2
% consulting with specialists 40.0 25.8 37.2 31.9 30.6 26.1 35.0 32.4
Mean visits to specialists 1.8 0.9 1.2 1.0 1.3 1.0 1.0 1.0
Other factors
Predisposing
% women 70.4 53.1 71.5 53.1 54.7 54.0 56.7 55.9
Mean years of education 13.6 12.5 14.4 13.0 12.9 12.5 13.8 13.1
Enabling
Mean household income
b
53.4 50.4 87.4 73.5 53.1 50.2 84.1 74.4
% with regular source of care 87.5 85.7 92.2 90.9 90.3 85.2 92.5 90.9
Behavior-related factors
% obese (BMI 30.0) 45.3 52.0 57.6 67.6 51.5 46.0 66.1 66.1
Smoking status
% Current smokers 30.7 34.8 12.6 20.1 29.5 35.1 15.1 19.6
% Former smokers 34.6 30.2 53.9 49.2 36.7 29.7 54.0 49.3
% physical inactive 52.0 54.3 34.9 40.6 49.5 54.7 36.8 40.1
% with sedentary lifestyle 25.3 19.5 31.1 24.8 21.0 19.7 24.9 25.9
Abbreviations: CAM, complementary and alternative medicine; BMI, Body Mass Index; PCP, Primary Care Physician.
a
ulcers, urinary incontinency, dementia, glaucoma, or cataracts.
b
in Canadian dollars and expressed in thousands.
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The analyses for use of massage therapy, acupuncture, and homeopathy/naturopathy sepa-
rately showed similar patterns and predictors of use over time to those of all CAM use. Fur-
thermore, results from the models including individual chronic conditions suggested that
although back pain was the most common chronic condition reported associated with chiro-
practic use, cohort differences were not explain by cohort differences in back pain. Lastly, the
analyses controlling for use of conventional medicine in the previous cycle of data collection
yielded findings comparable to the main analyses. Results from these analyses are available
upon request.
Discussion
Using data from a large longitudinal national population survey spanning 16 years, this study
examined CAM and chiropractic use among baby boomers, Gen Xers, and pre-boomers in the
Table 3. Results from logistic two-level growth model (1) and hierarchical age-period-cohort models (2–4) for CAM use. Canadian National Popula-
tion Health Survey, 1994–2011.
MODEL 1 MODEL 2 MODEL 3
a
MODEL 4
a
OR (95% CI) OR (95% CI) OR (95% CI) OR (95% CI)
Fixed Effects
Age and Cohort
Linear Age
b
1.09 (1.09;1.10)*** 1.02 (1.01;1.03)*** 1.02 (1.00;1.03)*1.02 (0.99;1.08)
Birth Cohort
(Ref: Pre-World War)
Generation X 25.90 (19.95;33.64)*** 1.70 (1.02;3.00)*** 1.78 (1.03;3.07)*** 1.51 (1.14;2.00)**
Younger Baby Boomer 10.18 (8.00;12.95)*** 1.34 (0.85;2.10) 1.36 (1.01;2.10)*1.25 (1.01;1.61)*
Older Baby Boomer 4.46 (3.58; 5.56)*** 1.17 (0.83;1.63) 1.13 (0.99;1.57)
†
1.12 (0.99;1.40)
World War II 1.74 (1.42; 2.12)*** 0.89 (0.70;1.13) 0.87 (0.69;1.10) 0.94 (0.77;1.15)
Need for Healthcare
Chronic Conditions
(Ref: None)
2+ 1.91 (1.75;2.08)*** 1.79 (1.64;1.96)***
1 1.45 (1.34;1.58)*** 1.40 (1.29;1.52)***
Pain Prevents Activity 1.91 (1.75;2.08)*** 1.81 (1.66;1.98)***
Conventional Care
Physician Visits
(Ref: No visits)
Both 1.78 (1.60;1.97)***
Primary Care Only 1.44 (1.30;1.58)***
Specialists Only 1.21 (1.00;1.47)*
Random Effects
c
Individual 2.17 (2.06;2.28)*** 2.14 (2.04;2.24)*** 1.92 (1.82;2.02)*** 1.92 (1.82;2.02)***
Period 0.20 (0.04;0.35)*** 0.11 (0.01;0.20)*** 0.11 (0.01;0.20)***
Abbreviations: OR, Odd Ratio; 95% CI, 95% Confidence Interval.
*** p<0.0001
** p<0.01
*p<0.05
†
p<0.1.
a
Models also included, predisposing, enabling, and behaviour-related factors. Full models are shown in S1 Table.
b
Age was centered at the mean of the distribution in 1994/95 (39 years). All models also included a quadratic age term.
c
Estimates are variances.
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context of need for care (i.e. chronic conditions and pain) and the use of conventional care
(i.e. visits to physicians). There were substantial cohort differences in CAM and chiropractic
use, with each succeeding recent cohort reporting higher use of these practitioners (e.g. Gen
Xers reported greater CAM use than younger boomers and so on). In addition to cohort differ-
ences there was an increase in CAM use, but not chiropractic use, over time (period effect)
across all ages. Of interest was that different factors underlay cohort differences in CAM and
chiropractic use. Cohort differences in CAM use were partly related to period effects with
greater CAM use over time, whereas differences in chiropractic use were related to differences
in need for care. The use of conventional care was positively related to greater use of CAM and
chiropractic, but was not related to changes over time or cohort differences.
Higher CAM use over time, independent of changes in the individual factors examined, is
in keeping with studies suggesting that the growing interest in CAM reflects societal changes
that have been happening for several decades. These include the rise in medical consumerism,
the self-care movement, and the resurgence of holistic health in the 1970s [17,18,47,48]. In
addition, many physicians are more engaged with CAM practices and therapies than previ-
ously, which may explain some of the findings. For example, a survey of Canadian primary
care physicians found that 12% offered CAM services in their practice [49] and a literature
review found that 40% of physicians referred patients to chiropractors for the management of
chronic pain and back problems [50].
That chiropractic use remained relatively stable between 1994 through 2011 is in accord
with two smaller studies focused on healthcare use in provinces within Canada [16,51]. The
trend is of interest given that there has been an increase in the number of chiropractors during
this time period (15.9 vs. 24.3 per 100000 population in 1997 and 2011, respectively) [52]. The
reasons why use of chiropractic services is not noticeably changing are unknown. It is possible
that, as other CAM therapies and practices have become more widely accepted and used, as
Fig 1. Age, period, and cohort effects for CAM use: Results fromlogistic growth models. Canadian National Population Health Survey, 1994–
2011. Notes: CAM, Complementary and Alternative Medicine; GenX, Generation X; YBB, Younger Baby Boomer; OBB, Older Baby Boomer; WW2, World
War II; pre-WW, pre-World War II. Values for a) are predictions from the fixed partof model 1 in Table 3 and values for b) are predictions from the solution of
the random effects in model 2 in Table 3.
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was found in these data, it has created competition from other healthcare providers [51,53].
Future research would benefit from asking individuals directly about CAM preferences and
choices in care.
In our study, although chronic conditions and pain were strongly associated with higher
CAM use overall, the higher CAM use in Gen Xers and baby boomers was not related to
cohort differences in these factors. Cohort differences in CAM use were partly related to
period effects of increasing CAM use over time. As noted, there have been significant changes
in healthcare consumers’ values and expectations that appear to have had an impact on how
more recent cohorts approach their healthcare choices. The greater CAM use in Gen Xers and
boomers may be because they have been exposed, from an early age, to alternative treatments
as a more normalized part of the healthcare culture. It may also reflect that members of recent
generations share beliefs that are align with the holistic principles of CAM towards healthcare.
Table 4. Results from logistic two-level growth model (1) and hierarchical age-period-cohort models (2–4) for chiropractic use. Canadian National
Population Health Survey, 1994–2011.
MODEL 1 MODEL 2 MODEL 3
a
MODEL 4
a
OR (95% CI) OR (95% CI) OR (95% CI) OR (95% CI)
Fixed Effects
Age and Cohort
Linear Age
b
1.04 (1.03;1.04)*** 1.03 (1.03;1.04)*** 1.01 (1.01;1.02)*** 1.01 (1.01;1.02)***
Birth Cohort
(Ref: Pre-World War)
Generation X 2.16 (1.68;2.77)*** 2.08 (1.58;2.75)*** 1.12 (0.85;1.46) 1.15 (0.88;1.51)
Younger Baby Boomer 1.68 (1.34;2.11)*** 1.64 (1.28;2.09)*** 1.02 (0.80;1.29) 1.04 (0.82;1.32)
Older Baby Boomer 1.25 (1.01;1.53)*** 1.23 (0.99;1.52) 0.87 (0.70;1.08) 0.88 (0.71;1.09)
World War II 1.03 (0.85;1.24) 1.02 (0.84;1.23) 0.83 (0.68;1.01)
†
0.83 (0.69;1.01)
†
Need for Healthcare
Chronic Conditions
(Ref: None)
2+ 2.37 (2.17;2.58)*** 2.31 (2.11;2.52)***
1 1.61 (1.49;1.75)*** 1.58 (1.46;1.72)***
Pain Prevents Activity 1.44 (1.32;1.58)*** 1.43 (1.31;1.57)***
Conventional Care
Physician Visits
(Ref: No visits)
Both 1.22 (1.11;1.35)***
Primary Care Only 1.25 (1.14;1.36)***
Specialists Only 1.01 (0.84;1.23)
Random Effects
c
Individual 2.66 (2.54;2.78)*** 2.66 (2.54;2.78)*** 2.59 (2.47;2.71)*** 2.59 (2.47;2.71)***
Period 0.01(0.00;0.04) 0.01 (-0.02;0.03) 0.01 (-0.01;0.04)
Abbreviations: OR, Odd Ratio; 95% CI, 95% Confidence Interval.
*** p<0.0001
** p<0.01
*p<0.05
†
p<0.1.
a
Models also included, predisposing, enabling, and behaviour-related factors. Full models are shown in S2 Table.
b
Age was centered at the mean of the distribution in 1994/95 (39 years). All models also included a quadratic age term
c
Estimates are variances.
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As such, these generations may use CAM not only for treatment purposes but for health pro-
motion, supporting the idea that CAM is beneficial in maintaining well-being and preventing
illness. It is important for health services researchers and policy makers to understand the rea-
sons why individuals from different generations use CAM to develop appropriate policies. In
contrast, although back pain was the most common chronic condition reported by those using
chiropractic services, back pain alone did not explain cohort differences in chiropractic use.
The greater number of chronic conditions in recent cohorts contributed to the greater chiro-
practic use in these cohorts.
Our finding that use of conventional care did not reduce CAM consumption align with pre-
vious research suggesting that CAM users do not abandon conventional care [11,54,55].
Some proponents of CAM therapies and practices have speculated that since CAM focuses on
preventive care and is less expensive than conventional care, promoting the use of CAM may
help control increasing healthcare costs [34,56]. However, research in this area is too scant to
inform policy decisions. Since in our study we found that CAM users not only use conven-
tional care more frequently but they also use more services, widespread CAM use may not
reduce healthcare costs in this context. As CAM is not covered by the provincial health plans
in Canada, it is likely that growing CAM use will translate into increased out-of-pocket costs
for CAM users. This joint use of conventional care and CAM is also important in light of stud-
ies showing that more than 50% of CAM users do not disclose their CAM use to their conven-
tional healthcare providers [5,57,58]. Studies have shown that when patients disclose CAM
use to their physicians they experience a better patient–physician relationship and improve
quality of care [59,60]. From a policy perspective, understanding more about the patterns of
use of multiple healthcare services in the population is particularly important because the evi-
dence base about the safety and efficacy of CAM is limited. Future research is warranted to dis-
tinguish those who use CAM for treatment and/or for health promotion, as this will have
implications for determining whether, and how CAM or specific forms of CAM can be inte-
grated within the current healthcare delivery system.
Fig 2. Age, period, and cohort effects for chiropractic use: Results from logistic growth models. Canadian National Population Health Survey,
1994–2011. Notes: GenX, Generation X; YBB, Younger Baby Boomer; OBB, Older Baby Boomer; WW2, World War II; pre-WW, pre-World War II. Values
for a) are predictions from the fixed part of model 1 in Table 4 and values for b) are predictions from the solution of the random effects in model 2 in Table 4.
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Strengths and limitations
This study enhances the current literature by drawing upon panel data from a large population
longitudinal survey, providing the most current and comprehensive data available in Canada
describing CAM use. We were able to compare CAM use across different cohorts at the same
chronological age over a period of 16 years. However, the study is not without limitations. The
analyses focused on practitioner-based CAM use and did not include alternative therapies. As
a result, it may under-represent CAM use as people may be using a wide range of alternative
therapies (e.g. taking herbal supplements) without consulting CAM practitioners. Although
the survey collected information on the presence of chronic conditions and pain, it did not
link these conditions and CAM use. Consequently, we were unable to identify the specific con-
ditions for which individuals consulted with CAM practitioners. Also, information is not avail-
able on all the factors that motivate individuals to consult with CAM practitioners. For
example, it is unknown if seeking care from CAM practitioners was by referral from physi-
cians, related to lifestyle and general health and well-being, or if the decision was motivated by
disenchantment with the conventional healthcare system. Lastly, given the longitudinal nature
of the study and the long follow-up time, almost two-fifths of the sample died or dropped-out
during follow-up. However, we were able to examine the impact of these losses on the results
and these did not change our conclusions.
The analyses presented in this paper did not use sample weights. Although it has been sug-
gested that failing to account for the complex design in multilevel analyses can produce biased
parameter estimates, using a single weight combining level-1 and level-2 sampling design ele-
ments––as is the case for the NPHS––can also produce bias results [61]. In keeping with this
notion, a simulation study comparing different methods for incorporating sampling weights
into multilevel models suggested that unless weights are included properly (e.g. properly re-
scale weights at each level) in the estimation, the un-weighted analysis yielded results similar
to those that accounted for the complex design. More specifically, the study found that overall
weighted and un-weighted parameter estimates and standard errors were generally compara-
ble [62]. Furthermore, we fit the two-level models for CAM and chiropractic use adjusting for
the individual level predictors with and without weights. The findings from the weighted anal-
yses were not appreciable different to those from the un-weighted analyses. Taken all these
together we do not expect that the un-weighted analyses presented in this paper affected the
results and conclusions substantially.
Conclusions
Our study adds to the literature by examining the lifecourse trajectories of practitioner-based
CAM use using longitudinal data from a large national population survey. The findings indi-
cate that Gen Xers and younger and older boomers were more likely to consult with CAM
practitioners than pre-boomers, and that CAM use, excluding chiropractors, has increased
over time across all ages (period effect). We also found that CAM users are also users of con-
ventional care. This underscores the importance of doctors asking their patients about their
CAM use. Finally, the increasing trend of CAM use over time highlights the need for continu-
ing efforts to rigorously evaluate the safety, mechanisms, and cost-effectiveness of CAM thera-
pies and practices.
Supporting information
S1 Table. CAM use: Results from logistic growth models a. Canadian National Population
Health Survey, 1994–2011
(DOCX)
Changes in the use practitioner-based complementary and alternative medicine over time in Canada
PLOS ONE | https://doi.org/10.1371/journal.pone.0177307 May 11, 2017 13 / 17
S2 Table. Chiropractic use: Results from logistic growth models a. Canadian National Pop-
ulation Health Survey, 1994–2011
(DOCX)
Acknowledgments
Richard Glazier is supported as a Clinician Scientist in the Department of Family and Commu-
nity Medicine at the University of Toronto and at St. Michael’s Hospital. Access to the data is
through the Statistics Canada Research Data Centres (RDC) Program. RDCs are operated
under the provisions of the Statistics Act in accordance with all the confidentiality rules. For
more information on how to access the data see http://www.statcan.gc.ca/eng/rdc/process.
The findings and conclusions of this paper are those of the authors and do not represent the
official position of Statistics Canada.
Author Contributions
Conceptualization: MC SHJ MAMG RHG EMB.
Data curation: MC.
Formal analysis: MC SHJ.
Funding acquisition: EMB.
Methodology: MC SHJ.
Project administration: MC.
Resources: MC.
Software: MC.
Supervision: SHJ MAMG RHG EMB.
Validation: MC SHJ MAMG RHG EMB.
Visualization: MC SHJ MAMG RHG EMB.
Writing – original draft: MC.
Writing – review & editing: MC SHJ MAMG RHG EMB.
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