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The Prevalence and Determinants of Using Traditional Chinese Medicine Among Middle-aged and Older Chinese Adults: Results From the China Health and Retirement Longitudinal Study
JAMDA 16 (2015) 1002.e1e1002.e5
JAMDA journal homepage: www.jamda.com
Original Study
The Prevalence and Determinants of Using Traditional Chinese Medicine Among Middle-aged and Older Chinese Adults: Results From the China Health and Retirement Longitudinal Study Tingting Liu RN, PhD a, Xiang Li BM b, Zhi-Yong Zou MD, PhD c, Changwei Li MD, PhD, MPH b, * a b c
Nell Hodgson Woodruff School of Nursing, Emory University, Atlanta, GA Department of Epidemiology, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA Institute of Child and Adolescent Health, School of Public Health, Peking University, Beijing, China
a b s t r a c t Keywords: Traditional Chinese medicine prevalence determinants chronic diseases
Background: Although traditional Chinese medicine (TCM) is known as an integrative part of China’s health care system, little is known on the prevalence and determinants of using TCM among the middleaged and older Chinese population, especially among those with chronic conditions. Methods: The nationwide survey data of 17,708 Chinese adults aged 45 and older from the China Health and Retirement Longitudinal Study were used to estimate the prevalence of TCM. SAS SURVEYLOGISTIC procedure was applied to identify factors associated with using TCM. Analysis took into account the complex survey design and nonresponse rate. Results: The prevalence of using TCM was 19.3% (95% CI 18.4%e20.1%) among the overall participants and 24.5% (95% CI 23.4%e25.5%) among those with self-reported chronic conditions. Participants with stroke, cardiovascular disease, and chronic kidney diseases were the most frequent users of TCM to treat their conditions. Age, individual income, and family income were associated with TCM use; however, when further controlling for chronic diseases, these variables became nonsignificant. Besides TCM, 4.4% (3.8% e5.0%) and 4.6% (4.0%e5.2%) of the overall participants and those with chronic conditions, respectively, used other forms of complementary and alternative medicine. Conclusions: The prevalence of using TCM was high among the middle-aged and older Chinese population. The use of TCM was mainly driven by chronic conditions. The main conditions that patients used TCM to treat were stroke, cardiovascular disease, and chronic kidney disease. Ó 2015 AMDA e The Society for Post-Acute and Long-Term Care Medicine.
Traditional Chinese medicine (TCM) originated in ancient China and has evolved over 2500 years.1 TCM encompasses a wealth of documented therapeutic resources, mainly including Chinese herb medicine, acupuncture, moxibustion, Chinese massage, cupping, and guasha.1 TCM is considered as a subset of complementary and alternative medicine in the West.2 However, in China, TCM is an integral component of the health care system, where it is practiced side by side with conventional medicine in most hospitals and clinics.3 TCM is also considered as an affordable medical service and is particularly popular among low-income and middle-aged and older Chinese adults. It is projected that the proportion of adults aged 60 years and older will
The authors declare no conflicts of interest. * Address correspondence to Changwei Li, MD, PhD, MPH, Department of Epidemiology, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA 70112. E-mail address: [email protected] (C. Li). http://dx.doi.org/10.1016/j.jamda.2015.07.011 1525-8610/Ó 2015 AMDA e The Society for Post-Acute and Long-Term Care Medicine.
increase from 10% in 2000 to approximately 30% in 2050.4 As China’s population ages rapidly, the trend and prevalence of TCM use among the middle-aged and older population will provide significant information in health care planning and health policy development. However, there are no data on TCM prevalence in China. In addition, TCM is perceived to be effective in treating and managing chronic conditions,5,6 and patients frequently turn to TCM whenever conventional medicine fails to provide anticipated relief in China.7 Considering the large population base and long history of TCM in China, the patterns of TCM use among patients with different chronic conditions would provide valuable information for patients outside China. However, such information was never available. Therefore, the aims of the current study were to estimate the prevalence of TCM use among the middle-aged and older Chinese population and among those with chronic conditions, respectively, using nationwide representative survey data from the China Health and Retirement Longitudinal Study (CHARLS). We further aimed to
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identify factors that are associated with TCM use among people with chronic conditions. Methods Study Population The CHARLS is a representative national survey of Chinese adults aged 45 years or older.8 It was designed to obtain detailed information regarding the dynamics of retirement and how it interacts with health, health insurance, and economic well-being.8 The CHARLS provides comprehensive and detailed information on demographics, health status, physical measures, employment history, pension insurance, retirement, income, and expenditures and assets.8 The comprehensive and multifaceted dataset provided by the CHARLS allows us to estimate the prevalence of TCM among different demographic and socioeconomic groups and to identify the patterns of and factors associated with TCM among people with chronic diseases. The CHARLS baseline survey was conducted in 28 provinces across the country from May 2011 to March 2012. The subjects of the CHARLS were selected using a 4-stage, stratified, cluster sampling method.8 The primary sampling units (PSU) in the CHARLS were administrative villages (cun) in rural areas and neighborhoods (shequ) in urban areas. In the first stage, all counties in China were sorted by regions as defined by the National Bureau of Statistics of China, rural and urban types, and per capita gross domestic products levels. Population sizes and cumulative population sizes were then listed for the sorted counties. A random number r between 0 and 1 was generated, and sampling interval n was calculated as the total population divided by the prespecified targeted number of counties of 150. The first county was selected as the first county that the cumulative population size exceeded the product of the random number r and the sampling interval n. The second county was the first county that the cumulative population size exceeded the sum of r*n plus n. In this manner, 150 counties were selected. And the 150th county was selected as the first county that the cumulative population size exceeded r*nþ149n. In the second stage, 3 PSUs were selected in each county with the probabilities proportional to their population sizes. A total of 450 PSUs located in 150 counties were sampled in this stage. In the third stage, all the households in each selected PSU were first outlined using the CHARLS-GIS software (Beijing, China), which was designed specifically for the CHARLS. Then, a random sample of 24 households was selected among all households with residents aged 45 years or older within each PSU. Finally, for a selected household, one random resident aged 45 years or older was selected as a participant of the survey. If the spouse of the selected resident was aged 45 years or older, the spouse was also included in the survey. The response rate among eligible households was 80.51%. The response rate was higher among rural households than urban households (94.15% vs 68.63%, respectively). The baseline survey was implemented as a face-to-face household interview by trained interviewers. If the participant could not answer questions in the interview, an adult offspring of the participant would be selected as the representative of the participant to answer questions in the interview. Overall, a total of 17,708 individuals within 10,257 households were interviewed in the baseline survey. All the participants were included in the current analysis. The current study was a secondary analysis of the open-access dataset of the CHARLS. The original CHARLS was approved by the Ethical Review Committee of Peking University, and all participants signed informed consent at the time of participation. Definitions and Measures of TCM TCM includes Chinese herbal medicines, acupuncture, moxibustion, Chinese massage, cupping, and guasha. Respondents were
defined as using TCM service if they circled TCM as one of the treatment options to the questions: “Are you now using any of the following treatments to treat or control your disease?” “In your recent visit to a health care provider in the last month, what kind of treatment did you receive?” “During the hospitalization in the past year, what kind of treatment did you receive?” and “How did you treat yourself during the past month?” Covariates All covariates were collected using questionnaires. Demographic variables included age, gender, and living areas (rural vs urban). Socioeconomic status was assessed by income and educational levels. Age was categorized into 6 groups. The first 5 groups have an interval of 5 years, and the last group was defined as 70 years or older. Income variables included self-rated household income levels and sources of individual income. Self-rated household income levels included “very high,” “relatively high,” “average,” “relatively poor,” and “poor.” Sources of individual income included “wage and bonus,” “wage and bonus plus others,” “others,” and “none.” Education was measured as “illiterate,” “less than elementary school,” “elementary school,” “middle school,” “high school,” and “above vocational school.” Health status and functioning were assessed based on self-reports of a number of specific chronic health conditions, including hypertension; dyslipidemia; diabetes; cancer (excluding minor skin cancers); chronic lung diseases (except for tumors or cancer); liver diseases (except for fatty liver; tumors; or cancer); cardiovascular diseases (heart attack; coronary heart disease; angina; congestive heart failure; or other heart problems); stroke; kidney disease (except for cancer or tumor); stomach or other gastrointestinal diseases (except for tumor or cancer); emotional, nervous, or psychiatric problems; memory-related diseases; arthritis; and asthma. Statistical Analysis Continuous variables were reported as mean (SD), and categorical variables were presented as percentages. The prevalence of TCM was estimated taking into account the complex survey design and nonresponse rate.9 SAS PROC SURVEYFREQ procedure was used to estimate TCM prevalence according to different demographic and socioeconomic status among the overall middle-aged and older Chinese population and among those with chronic conditions, respectively. We further estimated the prevalence of TCM that was used specifically for the treatment of each chronic condition. SAS PROC SURVEYLOGISTIC procedure was used to identify significant demographic and socioeconomic predictors of using TCM among participants with chronic conditions, including age, gender, living areas, education, and income. We also evaluated the impact of chronic conditions on the association between demographic and socioeconomic predictors and TCM use by adding all the chronic conditions in the model. Two-sided P values are provided, and P less than .05 was considered significant. All the analyses were performed using SAS version 9.3 (SAS Institute Inc., Cary, NC). Results A total of 17,708 CHARLS participants were included in the current analysis. The characteristics of the participants are shown in Table 1. Among all the participants, 47.62% were male, 66.45% lived in rural areas, 55.94% had no individual income, only 25.61% were illiterate, most of the participants rated their household income level as average or below, and approximately two-thirds of the participants had at least 1 chronic condition.
T. Liu et al. / JAMDA 16 (2015) 1002.e1e1002.e5 Table 1 Characteristics of the Participants, n ¼ 17,708 % Gender Male Female Living areas Rural residents Urban residents Self-rated household income levels Very high Relatively high Average Relatively poor Poor Individual income types Wage and bonus Wage and bonus plus others Others None Age groups 45e50 50e55 55e60 60e65 65e70 70 Education Illiterate Less than elementary school Elementary school Middle school High school Above vocational school Having at least 1 chronic condition
Table 2 The Prevalence of Using Traditional Chinese Medicine Among the Overall Middleaged and Older Chinese Population (n ¼ 17,708) and Those With Chronic Conditions (n ¼ 11,807) by Demographic and Social Economic Status
47.62 52.38 66.45 33.55 0.23 3.05 53.20 31.76 11.77 17.45 3.11 23.50 55.94 21.39 14.84 19.65 15.31 9.93 18.88 25.61 16.65 21.31 21.17 8.61 6.65 65.54
Using TCM Among the Overall Participants As shown in Table 2, a total of 19.3% of the participants used TCM. TCM use did not differ between genders or living areas; however, its use increased with self-rated household income levels and age. People with low or high education levels had higher proportions of TCM use compared with those with middle school education. Approximately 4.4% of the participants used other forms of complementary and alternative medicine (CAM). Detailed information on the distribution of these non-TCM CAM is presented in supplementary Table S1. Using TCM Among Participants With Chronic Conditions The distribution of TCM use among participants with chronic conditions is also shown in Table 2. The prevalence of TCM was much higher than that in the overall participants (24.5% vs 19.3%, respectively). The prevalence increased with age, but did not differ by living areas and education levels. In addition, female patients and patients with lower self-rated household income levels were more likely to use TCM. The distribution of using non-TCM CAM is shown in supplementary Table S2. TCM Used by People With Different Chronic Conditions The prevalence of TCM used for the treatment of chronic conditions is shown in Table 3. Patients with stroke, chronic kidney disease, and cardiovascular disease were the most frequent users of TCM to treat their conditions. On the other hand, patients with memoryrelated disease, diabetes, or hypertension were least likely to use TCM to treat their disease; however, the prevalence of TCM was still above 11%.
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Overall Participants
Participants With Chronic Conditions
Prevalence (95% CI), %
Prevalence (95% CI), %
Overall 19.3 (18.4e20.1) Gender Male 18.6 (17.3e19.9) Female 19.9 (18.8e21.1) Age groups 45e50 14.8 (12.8e16.9) 50e55 15.8 (14.1e17.5) 55e60 19.6 (17.4e21.8) 60e65 21.5 (19.6e23.3) 65e70 23.1 (20.2e26.1) 70 23.8 (21.6e26.0) Living areas Rural residents 18.8 (18.0e19.5) Urban residents 19.8 (17.7e21.9) Self-rated household income levels Very high 12.6 (1.0e24.2) Relatively high 17.6 (12.8e22.3) Average 17.4 (16.3e18.6) Relatively poor 21.8 (20.1e23.5) Poor 24.3 (21.6e27.1) Individual income types Wage and bonus 13.0 (11.4e14.6) Wage and bonus 18.1 (9.8e26.4) plus others Others 24.4 (22.3e26.5) None 18.9 (17.9e19.9) Education Illiterate 20.2 (18.8e21.6) Less than elementary 19.8 (18.0e21.6) school Elementary school 19.2 (17.2e21.2) Middle school 16.9 (15.1e18.7) High school 18.2 (14.9e21.5) Above vocational 23.8 (18.4e29.2) school
P
P
24.5 (23.4e25.5) .1208
<.0001
.3393
23.0 (21.5e24.4) 25.8 (24.2e27.4)
.0098
20.2 22.9 24.0 26.0 26.4 27.2
.001
(17.7e22.6) (20.4e25.3) (21.3e26.6) (23.7e28.4) (22.8e30.1) (24.7e29.7)
24.5 (23.5e25.5) 24.2 (21.6e26.7)
.7915
<.0001
16.7 21.0 23.0 25.7 29.5
(0e34.9) (14.3e27.7) (21.5e24.5) (23.7e27.6) (26.0e33.0)
.0019
<.0001
19.4 (16.8e22.1) 20.3 (12.6e27.9)
.0008
27.3 (24.8e29.8) 24.5 (23.3e25.8) .032
26.3 (24.4e28.1) 25.5 (23.1e27.9) 24.8 22.2 22.1 23.1
.1377
(22.0e27.6) (19.9e24.6) (18.5e25.7) (18.4e27.7)
CI, confidence interval.
Factors Associated With TCM Use Among People With Chronic Conditions The multivariate logistic regression results are shown in Table 4. Age, sources of individual income, and self-rated household income levels were significant predictors of TCM use among patients with chronic conditions. However, when further controlling for chronic diseases, only sources of individual income remained significant. In
Table 3 The Prevalence of Using TCM Specifically for the Treatment of Chronic Conditions (n ¼ 11,807) Prevalence (95% CI), % Stroke Kidney disease Heart disease Cancer Chronic digestive disease Lung disease Liver disease Arthritis Dyslipidemia Memory-related disease Diabetes Hypertension CI, confidence interval.
40.5 24.4 23.2 21.0 20.0 19.4 19.3 19.1 14.1 13.1 11.9 11.1
(34.5e46.4) (21.1e27.8) (20.5e26.0) (13.7e28.3) (18.4e21.5) (16.4e22.3) (15.6e22.9) (17.8e20.4) (11.0e17.3) (8.9e17.4) (9.4e14.4) (9.6e12.6)
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T. Liu et al. / JAMDA 16 (2015) 1002.e1e1002.e5
Table 4 The Effects of Socioeconomic Status and Chronic Conditions on the Use of Traditional Chinese Medicine Variables
Model 1, n ¼ 10,852
Model 2, n ¼ 10,819
OR
OR
95% CI
Per 1 year increase in age 0.99 (0.98e1.00) Female vs. male 0.89 (0.78e1.01) Education Illiterate 1.38 (0.98e1.92) Less than elementary 1.30 (0.92e1.83) school Elementary school 1.26 (0.88e1.81) Middle school 1.26 (0.89e1.79) High school 1.24 (0.85e1.81) Above vocational Ref d school Individual income sources Wage and bonus 1.12 (0.91e1.37) Wage and bonus 1.22 (0.75e2.01) plus others Others 0.80 (0.69e0.94) None Ref d Urban vs rural 0.97 (0.82e1.14) Self-rated household income levels Very high 0.44 (0.15e1.33) Relatively high 1.47 (0.97e2.24) Average 1.35 (1.14e1.60) Relatively poor 1.07 (0.89e1.29) Poor Ref d Dyslipidemia Chronic lung disease Chronic liver disease Chronic heart disease Chronic kidney disease Chronic digestive disease Memory-related disease Arthritis Hypertension Diabetes Stroke Cancer
P
95% CI
P
.0097 0.99 (0.99e1.00) .0787 0.93 (0.81e1.06)
.0705 .2624
.5523 1.29 (0.90e1.84) 1.34 (0.94e1.93)
.5909
1.23 1.18 1.15 Ref
(0.85e1.77) (0.82e1.68) (0.79e1.69) d
.0090 1.00 (0.81e1.23) 1.18 (0.75e1.85) 0.81 (0.69e0.95) Ref .6673 0.97 (0.82e1.15) .0002 0.31 1.17 1.13 0.97 Ref 1.40 1.43 1.62 1.63 1.81 1.73 1.53 1.86 0.91 1.38 2.66 1.55
.0450
.7335
(0.09e1.13) (0.77e1.77) (0.96e1.33) (0.81e1.15)
.0527
(1.15e1.70) (1.21e1.68) (1.29e2.03) (1.41e1.89) (1.52e2.17) (1.53e1.96) (0.99e2.36) (1.64e2.11) (0.8e1.04) (1.05e1.82) (1.97e3.58) (1.01e2.37)
.0008 <.0001 <.0001 <.0001 <.0001 <.0001 .0531 <.0001 .1683 .0222 <.0001 .0429
Note: bold font indicates statistical significance (P < .05). CI, confidence interval; OR, odds ratio.
the full model, self-reported dyslipidemia, lung disease, liver disease, cardiovascular disease, kidney disease, digestive disease, diabetes, stroke and cancer were significant; and self-rated household income levels and having memory-related conditions were borderline significant. Discussion In the first ever study on TCM prevalence among the middle-aged and older Chinese population, we estimated that the overall prevalence of using TCM was 19.3% in this population. TCM use did not differ between genders or living areas; however, it increased with selfrated household income levels and age. TCM had a U-shape distribution by education levels. The prevalence of TCM was much higher among those with chronic conditions. Participants with stroke, chronic kidney disease and cardiovascular diseases had the highest proportion of using TCM to treat their conditions. Among participants with chronic conditions, TCM was significantly associated with age, self-rated household income levels, and sources of individual income. However, when further controlling for chronic conditions, only sources of individual income were significantly associated with TCM use. Approximately one-fifth of China’s middle-aged and older adults used TCM. This translates into approximately 95.6 million middleaged and older Chinese adults who used TCM based on China’s population size in 2014.10 The current study provides the first estimates of TCM prevalence in this population. TCM is an important part of China’s
health care system.3 Such information will aid in the appropriate allocation of health care resources at the national level in China. The information can also act as an important baseline, and subsequent national surveys are recommended to track the time trends of TCM prevalence. Patients with stroke, kidney disease, and cardiovascular disease had the highest prevalence of using TCM for the treatment of their conditions. For stroke, the prevalence of TCM use was as high as more than 40%. Further, the 3 conditions were also significantly associated with TCM use after controlling for demographic and socioeconomic factors. Considering the large population size of middle-aged and older patients in China, their preferences of TCM for the treatment of these chronic conditions indicate that TCM may be particularly effective for these conditions. Future studies evaluating the effect of TCM on these conditions are warranted. In addition, such information may aid in treatment selection for patients outside of China. In the multivariate analysis of socioeconomic variables among people with chronic conditions, the prevalence of TCM did not differ by gender, education level, and living areas. This indicates that TCM was widely accepted and used among the middle-aged and older Chinese population. Age and self-rated household income levels were significantly associated with TCM use. However, when further controlling for chronic conditions, these variables were no longer significant. This indicates that the use of TCM among people with chronic disease was mainly driven by chronic conditions. TCM service is provided in most of the hospitals and clinics in China and the price of these services is usually much lower than conventional medicine.6 So it is understandable that the use of TCM was only driven by patients’ need, the treatment of chronic conditions. The current study has strengths. First, the study was a large nationwide representative survey, and the generalization of the current study is high. Therefore, the findings of this current study can be generalized to all the middle-aged and older Chinese adults. Second, data collection in the CHARLS had stringent quality assurance and quality control measures. GPS matching, data checking, recording and checking interviews, and calling back participants were implemented at every stage of the study to ensure data validity and reliability. Our study also has weakness. The chronic conditions were self-reported by the participants. So the diagnosis of chronic conditions may be underestimated, which may affect the prevalence estimates of TCM among patients with chronic conditions. However, previous studies showed that self-reports of many chronic conditions as those included in the current analysis were sufficiently sensitive and valid, particularly for well-known and defined chronic diseases, such as diabetes, stroke, hypertension, angina pectoris, myocardial infarction, and obstructive pulmonary disease.11e14 So the prevalence estimates among people with chronic conditions may be only slightly over- or underestimated. Further, there was no detailed information on TCM use in the questionnaires; hence, we cannot estimate the prevalence of each specific type of TCM. Finally, the response rate among urban areas was lower than that in rural areas. So the prevalence estimate in urban areas may not be as accurate as that in rural areas. However, similar to response rate (72.6%) of the 2011e2012 National Health and Nutrition Examination Survey (NHANES),15 the response rate in the urban residents of CHARLS is still higher than most survey response rates in previous studies, in which the response rates were generally approximately 53%.16 More importantly, we also presented the prevalence estimation by rural and urban areas, so that such information would be valuable to policy makers in health resource distribution. Conclusion Approximately one-fifth of the middle-aged and older Chinese adults used TCM and only approximately 4% used non-TCM complementary medicine. The prevalence of TCM was higher among people
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with chronic conditions. Participants with stroke, chronic kidney diseases, and cardiovascular diseases had the highest proportion of using TCM to treat their conditions. Finally, the use of TCM among people with chronic conditions was mainly driven by their chronic diseases. Acknowledgment We thank the Peking University National Center for Economic Research for providing the CHARLS data. Supplementary Data Supplementary data related to this article can be found online at http://dx.doi.org/10.1016/j.jamda.2015.07.011. References 1. National Center for Complementary and Alternative Medicine. Traditional chinese medicine: An introduction, 2013. Available from: http://nccam.nih. gov/health/whatiscam/chinesemed.htm. Accessed August 21, 2015. 2. National Center for Complementary and Alternative Medicine. What is cam? 2014. Available from: http://nccam.nih.gov/health. Accessed August 21, 2015. 3. Hesketh T, Zhu WX. Health in China. Traditional Chinese medicine: One country, two systems. BMJ 1997;315:115e117. 4. United Nations. World population ageing 1950e2050, 2009, 2014. Available from: http://www.un.org/esa/population/publications/worldageing19502050/. Accessed August 21, 2015.
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5. Zhao W. Challenges and strategies of treating chronic diseases using traditional Chinese medicine. China News of TCM:2014. Available from: http://cntcm.39kf. com/shtml/2125-b-17.shtml; 2004. Accessed August 21, 2015. 6. Jiang M, Zhang C, Cao H, et al. The role of Chinese medicine in the treatment of chronic diseases in China. Planta Med 2011;77:873e881. 7. Ng TP, Tan CH, Kua EH. The use of Chinese herbal medicines and their correlates in Chinese older adults: The Singapore Chinese Longitudinal Aging Study. Age Ageing 2004;33:135e142. 8. Zhao Y, Hu Y, Smith JP, et al. Cohort profile: The China Health and Retirement Longitudinal Study (CHARLS). Int J Epidemiol 2014;43:61e68. 9. Zhao Y, Strauss J, Yang G, et al. China health and retirement longitudinal study - 2011e2012 national baseline users’ guide. Beijing: Peking University; 2013. 10. United States Census Bureau. Mid-year population by five year age groups and sex custom region - China, 2014. Available from: http://www.census.gov/population/ international/data/idb/region.php?N¼%20Results%20&T¼10&A¼separate&RT¼0& Y¼2014&R¼-1&C¼CH. Accessed August 21, 2015. 11. Haapanen N, Miilunpalo S, Pasanen M, et al. Agreement between questionnaire data and medical records of chronic diseases in middle-aged and elderly Finnish men and women. Am J Epidemiol 1997;145:762e769. 12. Engstad T, Bonaa KH, Viitanen M. Validity of self-reported stroke: The Tromso study. Stroke 2000;31:1602e1607. 13. Van Eenwyk J, Bensley L, Ossiander EM, Krueger K. Comparison of examination-based and self-reported risk factors for cardiovascular disease, Washington state, 2006e2007. Prev Chronic Dis 2012;9:E117. 14. Barr RG, Herbstman J, Speizer FE, Camargo CA Jr. Validation of self-reported chronic obstructive pulmonary disease in a cohort study of nurses. Am J Epidemiol 2002;155:965e971. 15. National Center for Health Statistics. NHANES: Response rates and population totals: 2011e2012 response rates, 2013. Available from: http://www.cdc.gov/ nchs/nhanes/response_rates_cps.htm. Accessed August 21, 2015. 16. Baruch Y, Hotom BC. Survey response rate levels and trends in organizational research. Human Relations 2008;61:1139e1160.
JAMDA journal homepage: www.jamda.com
Original Study
The Prevalence and Determinants of Using Traditional Chinese Medicine Among Middle-aged and Older Chinese Adults: Results From the China Health and Retirement Longitudinal Study Tingting Liu RN, PhD a, Xiang Li BM b, Zhi-Yong Zou MD, PhD c, Changwei Li MD, PhD, MPH b, * a b c
Nell Hodgson Woodruff School of Nursing, Emory University, Atlanta, GA Department of Epidemiology, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA Institute of Child and Adolescent Health, School of Public Health, Peking University, Beijing, China
a b s t r a c t Keywords: Traditional Chinese medicine prevalence determinants chronic diseases
Background: Although traditional Chinese medicine (TCM) is known as an integrative part of China’s health care system, little is known on the prevalence and determinants of using TCM among the middleaged and older Chinese population, especially among those with chronic conditions. Methods: The nationwide survey data of 17,708 Chinese adults aged 45 and older from the China Health and Retirement Longitudinal Study were used to estimate the prevalence of TCM. SAS SURVEYLOGISTIC procedure was applied to identify factors associated with using TCM. Analysis took into account the complex survey design and nonresponse rate. Results: The prevalence of using TCM was 19.3% (95% CI 18.4%e20.1%) among the overall participants and 24.5% (95% CI 23.4%e25.5%) among those with self-reported chronic conditions. Participants with stroke, cardiovascular disease, and chronic kidney diseases were the most frequent users of TCM to treat their conditions. Age, individual income, and family income were associated with TCM use; however, when further controlling for chronic diseases, these variables became nonsignificant. Besides TCM, 4.4% (3.8% e5.0%) and 4.6% (4.0%e5.2%) of the overall participants and those with chronic conditions, respectively, used other forms of complementary and alternative medicine. Conclusions: The prevalence of using TCM was high among the middle-aged and older Chinese population. The use of TCM was mainly driven by chronic conditions. The main conditions that patients used TCM to treat were stroke, cardiovascular disease, and chronic kidney disease. Ó 2015 AMDA e The Society for Post-Acute and Long-Term Care Medicine.
Traditional Chinese medicine (TCM) originated in ancient China and has evolved over 2500 years.1 TCM encompasses a wealth of documented therapeutic resources, mainly including Chinese herb medicine, acupuncture, moxibustion, Chinese massage, cupping, and guasha.1 TCM is considered as a subset of complementary and alternative medicine in the West.2 However, in China, TCM is an integral component of the health care system, where it is practiced side by side with conventional medicine in most hospitals and clinics.3 TCM is also considered as an affordable medical service and is particularly popular among low-income and middle-aged and older Chinese adults. It is projected that the proportion of adults aged 60 years and older will
The authors declare no conflicts of interest. * Address correspondence to Changwei Li, MD, PhD, MPH, Department of Epidemiology, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA 70112. E-mail address: [email protected] (C. Li). http://dx.doi.org/10.1016/j.jamda.2015.07.011 1525-8610/Ó 2015 AMDA e The Society for Post-Acute and Long-Term Care Medicine.
increase from 10% in 2000 to approximately 30% in 2050.4 As China’s population ages rapidly, the trend and prevalence of TCM use among the middle-aged and older population will provide significant information in health care planning and health policy development. However, there are no data on TCM prevalence in China. In addition, TCM is perceived to be effective in treating and managing chronic conditions,5,6 and patients frequently turn to TCM whenever conventional medicine fails to provide anticipated relief in China.7 Considering the large population base and long history of TCM in China, the patterns of TCM use among patients with different chronic conditions would provide valuable information for patients outside China. However, such information was never available. Therefore, the aims of the current study were to estimate the prevalence of TCM use among the middle-aged and older Chinese population and among those with chronic conditions, respectively, using nationwide representative survey data from the China Health and Retirement Longitudinal Study (CHARLS). We further aimed to
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T. Liu et al. / JAMDA 16 (2015) 1002.e1e1002.e5
identify factors that are associated with TCM use among people with chronic conditions. Methods Study Population The CHARLS is a representative national survey of Chinese adults aged 45 years or older.8 It was designed to obtain detailed information regarding the dynamics of retirement and how it interacts with health, health insurance, and economic well-being.8 The CHARLS provides comprehensive and detailed information on demographics, health status, physical measures, employment history, pension insurance, retirement, income, and expenditures and assets.8 The comprehensive and multifaceted dataset provided by the CHARLS allows us to estimate the prevalence of TCM among different demographic and socioeconomic groups and to identify the patterns of and factors associated with TCM among people with chronic diseases. The CHARLS baseline survey was conducted in 28 provinces across the country from May 2011 to March 2012. The subjects of the CHARLS were selected using a 4-stage, stratified, cluster sampling method.8 The primary sampling units (PSU) in the CHARLS were administrative villages (cun) in rural areas and neighborhoods (shequ) in urban areas. In the first stage, all counties in China were sorted by regions as defined by the National Bureau of Statistics of China, rural and urban types, and per capita gross domestic products levels. Population sizes and cumulative population sizes were then listed for the sorted counties. A random number r between 0 and 1 was generated, and sampling interval n was calculated as the total population divided by the prespecified targeted number of counties of 150. The first county was selected as the first county that the cumulative population size exceeded the product of the random number r and the sampling interval n. The second county was the first county that the cumulative population size exceeded the sum of r*n plus n. In this manner, 150 counties were selected. And the 150th county was selected as the first county that the cumulative population size exceeded r*nþ149n. In the second stage, 3 PSUs were selected in each county with the probabilities proportional to their population sizes. A total of 450 PSUs located in 150 counties were sampled in this stage. In the third stage, all the households in each selected PSU were first outlined using the CHARLS-GIS software (Beijing, China), which was designed specifically for the CHARLS. Then, a random sample of 24 households was selected among all households with residents aged 45 years or older within each PSU. Finally, for a selected household, one random resident aged 45 years or older was selected as a participant of the survey. If the spouse of the selected resident was aged 45 years or older, the spouse was also included in the survey. The response rate among eligible households was 80.51%. The response rate was higher among rural households than urban households (94.15% vs 68.63%, respectively). The baseline survey was implemented as a face-to-face household interview by trained interviewers. If the participant could not answer questions in the interview, an adult offspring of the participant would be selected as the representative of the participant to answer questions in the interview. Overall, a total of 17,708 individuals within 10,257 households were interviewed in the baseline survey. All the participants were included in the current analysis. The current study was a secondary analysis of the open-access dataset of the CHARLS. The original CHARLS was approved by the Ethical Review Committee of Peking University, and all participants signed informed consent at the time of participation. Definitions and Measures of TCM TCM includes Chinese herbal medicines, acupuncture, moxibustion, Chinese massage, cupping, and guasha. Respondents were
defined as using TCM service if they circled TCM as one of the treatment options to the questions: “Are you now using any of the following treatments to treat or control your disease?” “In your recent visit to a health care provider in the last month, what kind of treatment did you receive?” “During the hospitalization in the past year, what kind of treatment did you receive?” and “How did you treat yourself during the past month?” Covariates All covariates were collected using questionnaires. Demographic variables included age, gender, and living areas (rural vs urban). Socioeconomic status was assessed by income and educational levels. Age was categorized into 6 groups. The first 5 groups have an interval of 5 years, and the last group was defined as 70 years or older. Income variables included self-rated household income levels and sources of individual income. Self-rated household income levels included “very high,” “relatively high,” “average,” “relatively poor,” and “poor.” Sources of individual income included “wage and bonus,” “wage and bonus plus others,” “others,” and “none.” Education was measured as “illiterate,” “less than elementary school,” “elementary school,” “middle school,” “high school,” and “above vocational school.” Health status and functioning were assessed based on self-reports of a number of specific chronic health conditions, including hypertension; dyslipidemia; diabetes; cancer (excluding minor skin cancers); chronic lung diseases (except for tumors or cancer); liver diseases (except for fatty liver; tumors; or cancer); cardiovascular diseases (heart attack; coronary heart disease; angina; congestive heart failure; or other heart problems); stroke; kidney disease (except for cancer or tumor); stomach or other gastrointestinal diseases (except for tumor or cancer); emotional, nervous, or psychiatric problems; memory-related diseases; arthritis; and asthma. Statistical Analysis Continuous variables were reported as mean (SD), and categorical variables were presented as percentages. The prevalence of TCM was estimated taking into account the complex survey design and nonresponse rate.9 SAS PROC SURVEYFREQ procedure was used to estimate TCM prevalence according to different demographic and socioeconomic status among the overall middle-aged and older Chinese population and among those with chronic conditions, respectively. We further estimated the prevalence of TCM that was used specifically for the treatment of each chronic condition. SAS PROC SURVEYLOGISTIC procedure was used to identify significant demographic and socioeconomic predictors of using TCM among participants with chronic conditions, including age, gender, living areas, education, and income. We also evaluated the impact of chronic conditions on the association between demographic and socioeconomic predictors and TCM use by adding all the chronic conditions in the model. Two-sided P values are provided, and P less than .05 was considered significant. All the analyses were performed using SAS version 9.3 (SAS Institute Inc., Cary, NC). Results A total of 17,708 CHARLS participants were included in the current analysis. The characteristics of the participants are shown in Table 1. Among all the participants, 47.62% were male, 66.45% lived in rural areas, 55.94% had no individual income, only 25.61% were illiterate, most of the participants rated their household income level as average or below, and approximately two-thirds of the participants had at least 1 chronic condition.
T. Liu et al. / JAMDA 16 (2015) 1002.e1e1002.e5 Table 1 Characteristics of the Participants, n ¼ 17,708 % Gender Male Female Living areas Rural residents Urban residents Self-rated household income levels Very high Relatively high Average Relatively poor Poor Individual income types Wage and bonus Wage and bonus plus others Others None Age groups 45e50 50e55 55e60 60e65 65e70 70 Education Illiterate Less than elementary school Elementary school Middle school High school Above vocational school Having at least 1 chronic condition
Table 2 The Prevalence of Using Traditional Chinese Medicine Among the Overall Middleaged and Older Chinese Population (n ¼ 17,708) and Those With Chronic Conditions (n ¼ 11,807) by Demographic and Social Economic Status
47.62 52.38 66.45 33.55 0.23 3.05 53.20 31.76 11.77 17.45 3.11 23.50 55.94 21.39 14.84 19.65 15.31 9.93 18.88 25.61 16.65 21.31 21.17 8.61 6.65 65.54
Using TCM Among the Overall Participants As shown in Table 2, a total of 19.3% of the participants used TCM. TCM use did not differ between genders or living areas; however, its use increased with self-rated household income levels and age. People with low or high education levels had higher proportions of TCM use compared with those with middle school education. Approximately 4.4% of the participants used other forms of complementary and alternative medicine (CAM). Detailed information on the distribution of these non-TCM CAM is presented in supplementary Table S1. Using TCM Among Participants With Chronic Conditions The distribution of TCM use among participants with chronic conditions is also shown in Table 2. The prevalence of TCM was much higher than that in the overall participants (24.5% vs 19.3%, respectively). The prevalence increased with age, but did not differ by living areas and education levels. In addition, female patients and patients with lower self-rated household income levels were more likely to use TCM. The distribution of using non-TCM CAM is shown in supplementary Table S2. TCM Used by People With Different Chronic Conditions The prevalence of TCM used for the treatment of chronic conditions is shown in Table 3. Patients with stroke, chronic kidney disease, and cardiovascular disease were the most frequent users of TCM to treat their conditions. On the other hand, patients with memoryrelated disease, diabetes, or hypertension were least likely to use TCM to treat their disease; however, the prevalence of TCM was still above 11%.
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Overall Participants
Participants With Chronic Conditions
Prevalence (95% CI), %
Prevalence (95% CI), %
Overall 19.3 (18.4e20.1) Gender Male 18.6 (17.3e19.9) Female 19.9 (18.8e21.1) Age groups 45e50 14.8 (12.8e16.9) 50e55 15.8 (14.1e17.5) 55e60 19.6 (17.4e21.8) 60e65 21.5 (19.6e23.3) 65e70 23.1 (20.2e26.1) 70 23.8 (21.6e26.0) Living areas Rural residents 18.8 (18.0e19.5) Urban residents 19.8 (17.7e21.9) Self-rated household income levels Very high 12.6 (1.0e24.2) Relatively high 17.6 (12.8e22.3) Average 17.4 (16.3e18.6) Relatively poor 21.8 (20.1e23.5) Poor 24.3 (21.6e27.1) Individual income types Wage and bonus 13.0 (11.4e14.6) Wage and bonus 18.1 (9.8e26.4) plus others Others 24.4 (22.3e26.5) None 18.9 (17.9e19.9) Education Illiterate 20.2 (18.8e21.6) Less than elementary 19.8 (18.0e21.6) school Elementary school 19.2 (17.2e21.2) Middle school 16.9 (15.1e18.7) High school 18.2 (14.9e21.5) Above vocational 23.8 (18.4e29.2) school
P
P
24.5 (23.4e25.5) .1208
<.0001
.3393
23.0 (21.5e24.4) 25.8 (24.2e27.4)
.0098
20.2 22.9 24.0 26.0 26.4 27.2
.001
(17.7e22.6) (20.4e25.3) (21.3e26.6) (23.7e28.4) (22.8e30.1) (24.7e29.7)
24.5 (23.5e25.5) 24.2 (21.6e26.7)
.7915
<.0001
16.7 21.0 23.0 25.7 29.5
(0e34.9) (14.3e27.7) (21.5e24.5) (23.7e27.6) (26.0e33.0)
.0019
<.0001
19.4 (16.8e22.1) 20.3 (12.6e27.9)
.0008
27.3 (24.8e29.8) 24.5 (23.3e25.8) .032
26.3 (24.4e28.1) 25.5 (23.1e27.9) 24.8 22.2 22.1 23.1
.1377
(22.0e27.6) (19.9e24.6) (18.5e25.7) (18.4e27.7)
CI, confidence interval.
Factors Associated With TCM Use Among People With Chronic Conditions The multivariate logistic regression results are shown in Table 4. Age, sources of individual income, and self-rated household income levels were significant predictors of TCM use among patients with chronic conditions. However, when further controlling for chronic diseases, only sources of individual income remained significant. In
Table 3 The Prevalence of Using TCM Specifically for the Treatment of Chronic Conditions (n ¼ 11,807) Prevalence (95% CI), % Stroke Kidney disease Heart disease Cancer Chronic digestive disease Lung disease Liver disease Arthritis Dyslipidemia Memory-related disease Diabetes Hypertension CI, confidence interval.
40.5 24.4 23.2 21.0 20.0 19.4 19.3 19.1 14.1 13.1 11.9 11.1
(34.5e46.4) (21.1e27.8) (20.5e26.0) (13.7e28.3) (18.4e21.5) (16.4e22.3) (15.6e22.9) (17.8e20.4) (11.0e17.3) (8.9e17.4) (9.4e14.4) (9.6e12.6)
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Table 4 The Effects of Socioeconomic Status and Chronic Conditions on the Use of Traditional Chinese Medicine Variables
Model 1, n ¼ 10,852
Model 2, n ¼ 10,819
OR
OR
95% CI
Per 1 year increase in age 0.99 (0.98e1.00) Female vs. male 0.89 (0.78e1.01) Education Illiterate 1.38 (0.98e1.92) Less than elementary 1.30 (0.92e1.83) school Elementary school 1.26 (0.88e1.81) Middle school 1.26 (0.89e1.79) High school 1.24 (0.85e1.81) Above vocational Ref d school Individual income sources Wage and bonus 1.12 (0.91e1.37) Wage and bonus 1.22 (0.75e2.01) plus others Others 0.80 (0.69e0.94) None Ref d Urban vs rural 0.97 (0.82e1.14) Self-rated household income levels Very high 0.44 (0.15e1.33) Relatively high 1.47 (0.97e2.24) Average 1.35 (1.14e1.60) Relatively poor 1.07 (0.89e1.29) Poor Ref d Dyslipidemia Chronic lung disease Chronic liver disease Chronic heart disease Chronic kidney disease Chronic digestive disease Memory-related disease Arthritis Hypertension Diabetes Stroke Cancer
P
95% CI
P
.0097 0.99 (0.99e1.00) .0787 0.93 (0.81e1.06)
.0705 .2624
.5523 1.29 (0.90e1.84) 1.34 (0.94e1.93)
.5909
1.23 1.18 1.15 Ref
(0.85e1.77) (0.82e1.68) (0.79e1.69) d
.0090 1.00 (0.81e1.23) 1.18 (0.75e1.85) 0.81 (0.69e0.95) Ref .6673 0.97 (0.82e1.15) .0002 0.31 1.17 1.13 0.97 Ref 1.40 1.43 1.62 1.63 1.81 1.73 1.53 1.86 0.91 1.38 2.66 1.55
.0450
.7335
(0.09e1.13) (0.77e1.77) (0.96e1.33) (0.81e1.15)
.0527
(1.15e1.70) (1.21e1.68) (1.29e2.03) (1.41e1.89) (1.52e2.17) (1.53e1.96) (0.99e2.36) (1.64e2.11) (0.8e1.04) (1.05e1.82) (1.97e3.58) (1.01e2.37)
.0008 <.0001 <.0001 <.0001 <.0001 <.0001 .0531 <.0001 .1683 .0222 <.0001 .0429
Note: bold font indicates statistical significance (P < .05). CI, confidence interval; OR, odds ratio.
the full model, self-reported dyslipidemia, lung disease, liver disease, cardiovascular disease, kidney disease, digestive disease, diabetes, stroke and cancer were significant; and self-rated household income levels and having memory-related conditions were borderline significant. Discussion In the first ever study on TCM prevalence among the middle-aged and older Chinese population, we estimated that the overall prevalence of using TCM was 19.3% in this population. TCM use did not differ between genders or living areas; however, it increased with selfrated household income levels and age. TCM had a U-shape distribution by education levels. The prevalence of TCM was much higher among those with chronic conditions. Participants with stroke, chronic kidney disease and cardiovascular diseases had the highest proportion of using TCM to treat their conditions. Among participants with chronic conditions, TCM was significantly associated with age, self-rated household income levels, and sources of individual income. However, when further controlling for chronic conditions, only sources of individual income were significantly associated with TCM use. Approximately one-fifth of China’s middle-aged and older adults used TCM. This translates into approximately 95.6 million middleaged and older Chinese adults who used TCM based on China’s population size in 2014.10 The current study provides the first estimates of TCM prevalence in this population. TCM is an important part of China’s
health care system.3 Such information will aid in the appropriate allocation of health care resources at the national level in China. The information can also act as an important baseline, and subsequent national surveys are recommended to track the time trends of TCM prevalence. Patients with stroke, kidney disease, and cardiovascular disease had the highest prevalence of using TCM for the treatment of their conditions. For stroke, the prevalence of TCM use was as high as more than 40%. Further, the 3 conditions were also significantly associated with TCM use after controlling for demographic and socioeconomic factors. Considering the large population size of middle-aged and older patients in China, their preferences of TCM for the treatment of these chronic conditions indicate that TCM may be particularly effective for these conditions. Future studies evaluating the effect of TCM on these conditions are warranted. In addition, such information may aid in treatment selection for patients outside of China. In the multivariate analysis of socioeconomic variables among people with chronic conditions, the prevalence of TCM did not differ by gender, education level, and living areas. This indicates that TCM was widely accepted and used among the middle-aged and older Chinese population. Age and self-rated household income levels were significantly associated with TCM use. However, when further controlling for chronic conditions, these variables were no longer significant. This indicates that the use of TCM among people with chronic disease was mainly driven by chronic conditions. TCM service is provided in most of the hospitals and clinics in China and the price of these services is usually much lower than conventional medicine.6 So it is understandable that the use of TCM was only driven by patients’ need, the treatment of chronic conditions. The current study has strengths. First, the study was a large nationwide representative survey, and the generalization of the current study is high. Therefore, the findings of this current study can be generalized to all the middle-aged and older Chinese adults. Second, data collection in the CHARLS had stringent quality assurance and quality control measures. GPS matching, data checking, recording and checking interviews, and calling back participants were implemented at every stage of the study to ensure data validity and reliability. Our study also has weakness. The chronic conditions were self-reported by the participants. So the diagnosis of chronic conditions may be underestimated, which may affect the prevalence estimates of TCM among patients with chronic conditions. However, previous studies showed that self-reports of many chronic conditions as those included in the current analysis were sufficiently sensitive and valid, particularly for well-known and defined chronic diseases, such as diabetes, stroke, hypertension, angina pectoris, myocardial infarction, and obstructive pulmonary disease.11e14 So the prevalence estimates among people with chronic conditions may be only slightly over- or underestimated. Further, there was no detailed information on TCM use in the questionnaires; hence, we cannot estimate the prevalence of each specific type of TCM. Finally, the response rate among urban areas was lower than that in rural areas. So the prevalence estimate in urban areas may not be as accurate as that in rural areas. However, similar to response rate (72.6%) of the 2011e2012 National Health and Nutrition Examination Survey (NHANES),15 the response rate in the urban residents of CHARLS is still higher than most survey response rates in previous studies, in which the response rates were generally approximately 53%.16 More importantly, we also presented the prevalence estimation by rural and urban areas, so that such information would be valuable to policy makers in health resource distribution. Conclusion Approximately one-fifth of the middle-aged and older Chinese adults used TCM and only approximately 4% used non-TCM complementary medicine. The prevalence of TCM was higher among people
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with chronic conditions. Participants with stroke, chronic kidney diseases, and cardiovascular diseases had the highest proportion of using TCM to treat their conditions. Finally, the use of TCM among people with chronic conditions was mainly driven by their chronic diseases. Acknowledgment We thank the Peking University National Center for Economic Research for providing the CHARLS data. Supplementary Data Supplementary data related to this article can be found online at http://dx.doi.org/10.1016/j.jamda.2015.07.011. References 1. National Center for Complementary and Alternative Medicine. Traditional chinese medicine: An introduction, 2013. Available from: http://nccam.nih. gov/health/whatiscam/chinesemed.htm. Accessed August 21, 2015. 2. National Center for Complementary and Alternative Medicine. What is cam? 2014. Available from: http://nccam.nih.gov/health. Accessed August 21, 2015. 3. Hesketh T, Zhu WX. Health in China. Traditional Chinese medicine: One country, two systems. BMJ 1997;315:115e117. 4. United Nations. World population ageing 1950e2050, 2009, 2014. Available from: http://www.un.org/esa/population/publications/worldageing19502050/. Accessed August 21, 2015.
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5. Zhao W. Challenges and strategies of treating chronic diseases using traditional Chinese medicine. China News of TCM:2014. Available from: http://cntcm.39kf. com/shtml/2125-b-17.shtml; 2004. Accessed August 21, 2015. 6. Jiang M, Zhang C, Cao H, et al. The role of Chinese medicine in the treatment of chronic diseases in China. Planta Med 2011;77:873e881. 7. Ng TP, Tan CH, Kua EH. The use of Chinese herbal medicines and their correlates in Chinese older adults: The Singapore Chinese Longitudinal Aging Study. Age Ageing 2004;33:135e142. 8. Zhao Y, Hu Y, Smith JP, et al. Cohort profile: The China Health and Retirement Longitudinal Study (CHARLS). Int J Epidemiol 2014;43:61e68. 9. Zhao Y, Strauss J, Yang G, et al. China health and retirement longitudinal study - 2011e2012 national baseline users’ guide. Beijing: Peking University; 2013. 10. United States Census Bureau. Mid-year population by five year age groups and sex custom region - China, 2014. Available from: http://www.census.gov/population/ international/data/idb/region.php?N¼%20Results%20&T¼10&A¼separate&RT¼0& Y¼2014&R¼-1&C¼CH. Accessed August 21, 2015. 11. Haapanen N, Miilunpalo S, Pasanen M, et al. Agreement between questionnaire data and medical records of chronic diseases in middle-aged and elderly Finnish men and women. Am J Epidemiol 1997;145:762e769. 12. Engstad T, Bonaa KH, Viitanen M. Validity of self-reported stroke: The Tromso study. Stroke 2000;31:1602e1607. 13. Van Eenwyk J, Bensley L, Ossiander EM, Krueger K. Comparison of examination-based and self-reported risk factors for cardiovascular disease, Washington state, 2006e2007. Prev Chronic Dis 2012;9:E117. 14. Barr RG, Herbstman J, Speizer FE, Camargo CA Jr. Validation of self-reported chronic obstructive pulmonary disease in a cohort study of nurses. Am J Epidemiol 2002;155:965e971. 15. National Center for Health Statistics. NHANES: Response rates and population totals: 2011e2012 response rates, 2013. Available from: http://www.cdc.gov/ nchs/nhanes/response_rates_cps.htm. Accessed August 21, 2015. 16. Baruch Y, Hotom BC. Survey response rate levels and trends in organizational research. Human Relations 2008;61:1139e1160.