Educational Status and Cardiovascular Risk Profile in Indians
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Educational status and cardiovascular risk profile in Indians K. Srinath Reddy*†‡, Dorairaj Prabhakaran†, Panniyammakal Jeemon†, K. R. Thankappan§, Prashant Joshi¶, Vivek Chaturvedi†, Lakshmy Ramakrishnan†, and Farooque Ahmedʈ *Public Health Foundation of India and †Department of Cardiology, All India Institute of Medical Sciences, New Delhi 110029, India; §Achutha Menon Centre for Health Sciences and Studies, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala 695011, India; ¶Department of Medicine, Government Medical College Nagpur, Nagpur, Maharashtra 440033, India; and ʈKhajabandanawaz Institute of Medical Sciences, Gulberga, Karnataka 585106, India Edited by Barry R. Bloom, Harvard School of Public Health, Boston, MA, and approved July 9, 2007 (received for review February 1, 2007) The inverse graded relationship of education and risk factors of to an indirect relationship has been predicted to occur as the coronary heart disease (CHD) has been reported from Western epidemic advances. Even two decades ago, McKeigue and Sevak populations. To examine whether risk factors of CHD are predicted (12, 13) predicted that an inverse association between SES and by level of education and influenced by the level of urbanization CHD will finally emerge among South Asians, based on several studies carried out among migrant South Asians in the United ؍ in Indian industrial populations, a cross-sectional survey (n 19,973; response rate, 87.6%) was carried out among employees Kingdom during that period. Later, Bhopal et al. (14) observed and their family members in 10 medium-to-large industries in this relationship in South Asian migrants and most clearly in highly urban, urban, and periurban regions of India. Information migrant Indians. on behavioral, clinical, and biochemical risk factors of CHD was Studies in India over the past half century have revealed a obtained through standardized instruments, and educational sta- similar trend toward a progressive reversal of the social gradient tus was assessed in terms of the highest educational level attained. for CHD. Although studies conducted from the 1960s to the Data from 19,969 individuals were used for analysis. Tobacco use early 1990s suggested a direct relationship between income and and hypertension were significantly more prevalent in the low- CHD risk, studies conducted in the last decade have reported an (56.6% and 33.8%, respectively) compared with the high- inverse relationship between education and/or income with education group (12.5% and 22.7%, respectively; P < 0.001). prevalent or incident CHD (15–20). A large case-control study MEDICAL SCIENCES However, dyslipidemia prevalence was significantly higher in the conducted by us (20) revealed that the risk of developing high-education group (27.1% as compared with 16.9% in the myocardial infarction was two times higher in those with the lowest-education group; P < 0.01). When stratified by the level of lowest when compared with the highest level of education. urbanization, industrial populations located in highly urbanized Studies of CHD risk factors in Indians have revealed variable centers were observed to have an inverse graded relationship (i.e., associations with SES, reporting an inverse graded relationship higher-education groups had lower prevalence) for tobacco use, of education with tobacco consumption and hypertension, with SCIENCE hypertension, diabetes, and overweight, whereas in less-urban- no clear relationship identified for other risk factors (21, 22). SUSTAINABILITY ized locations, we found such a relationship only for tobacco use It is likely that the relationship between cardiovascular disease and hypertension. This study indicates the growing vulnerability of risk factors and SES in Indian population groups is influenced lower socioeconomic groups to CHD. Preventive strategies to by the stage of health transition. At the midpoint of health reduce major CHD risk factors should focus on effectively address- transition, an urbanized population would reveal a reversal of the ing these social disparities. social gradient (the presence of a graded inverse relationship of SES with CHD risk factors), whereas in a relatively rural coronary heart disease ͉ socioeconomic status population group, the relationship of SES and CHD risk factors would still show a direct relationship. Because different regions ecause cardiovascular disease has become the leading cause of India are at different stages of epidemiological transition, we Bof mortality worldwide, coronary heart disease (CHD) is hypothesize that (i) the relationship of CHD risk factors with now contributing to large and rising burdens of death and SES will vary depending on the level of urbanization; and (ii) the disability in many developing countries (1). The relationship of pattern of reversal in social gradient for CHD risk factors, in socioeconomic status (SES) and CHD has varied across different Indian population groups, will be different from that presently populations, when concurrently studied, and within each popu- observed in Western societies. To test these hypotheses, we lation, when studied over time (2). In populations where the analyzed data of individuals who participated in the multicenter CHD epidemic has matured over several decades, it has been sentinel surveillance for CHD risk factors in Indian industrial observed that the epidemic of CHD appears to emerge first in workers and their families (23). Of the several measures of SES, higher socioeconomic groups and declines first in the same educational attainment has been reported to be a valid and easily groups (3, 4). Studies conducted in developed countries over the measurable indicator of SES and considered suitable for social past three decades provide convincing evidence of an inverse relationship between SES and CHD (5–9). Additionally, the This paper is part of a special series on Sustainable Health. See the related editorial on page lowest socioeconomic group is reported to have increased prev- 15969 and accompanying articles on pages 16038, 16044, and 16194. alence of subclinical CHD compared with those in the highest Author contributions: K.S.R. and D.P. designed research; P. Jeemon, K.R.T., P. Joshi, V.C., socioeconomic group (10, 11). However, when multiple coun- L.R., and F.A. performed research; K.S.R., D.P., and P. Jeemon analyzed data; and K.S.R., tries are compared, the relationship is quite variable, depending D.P., and P. Jeemon wrote the paper. on the level of health transition in each country. It has been The authors declare no conflict of interest. suggested that studies of CHD risk factors in heterogeneous This article is a PNAS Direct Submission. populations of developing countries may help us understand the Abbreviations: CHD, coronary heart disease; SES, socioeconomic status; ES, educational multifactorial nature of CHD causation (2). status. In India, a large developing country, the relationship of SES ‡To whom correspondence should be addressed. E-mail: [email protected]. to CHD has not been clear, although an evolution from a direct © 2007 by The National Academy of Sciences of the USA www.pnas.org͞cgi͞doi͞10.1073͞pnas.0700933104 PNAS ͉ October 9, 2007 ͉ vol. 104 ͉ no. 41 ͉ 16263–16268 Downloaded by guest on September 30, 2021 Table 1. General characteristics of study population Men Women ES I ES II ES III ES IV ES I ES II ES III ES IV (n ϭ 1,611) (n ϭ 2,607) (n ϭ 5,820) (n ϭ 1,859) (n ϭ 960) (n ϭ 1,635) (n ϭ 2,832) (n ϭ 2,645) Age group, % 20–29 25.7 27.7 23.0 17.2 39.0 40.6 27.6 15.0 30–39 26.9 22.2 19.8 22.5 30.3 25.8 27.0 20.2 40–49 27.2 26.9 31.9 22.9 22.6 26.5 30.9 28.8 50–59 19.1 22.0 22.9 21.0 7.5 6.7 11.2 21.0 60–69 1.1 1.2 2.4 16.3 0.6 0.5 3.2 14.9 Age, mean years Ϯ SD 38.6 Ϯ 10.9 38.9 Ϯ 11.5 40.7 Ϯ 11.2 44.0 Ϯ 13.3 34.3 Ϯ 9.7 34.0 Ϯ 10.3 37.8 Ϯ 11.1 44.1 Ϯ 12.7 Occupation, % High end 84.7 60.1 19.5 1.7 67.8 52.1 14.6 0.5 Middle end 14.9 39.1 74.4 35.4 12.0 19.4 35.8 8.4 Low end/ 0.4 0.8 6.1 62.9 20.2 28.5 49.6 91.1 Unemployed ES, educational status. ES I, graduates plus; ES II, above secondary school and up to graduation; ES III, above primary level up to secondary school; ES IV, no formal education and up to primary level. ranking across many populations at different stages of develop- postgraduates. The remaining 21.2% were either college grad- ment (2). The present study reports the associations of educa- uates or had studied beyond the secondary-school level. tional status with different CHD risk factors in several Indian The age group and occupational status of the study group industrial population groups at different levels of urbanization. across different educational group are presented in Table 1. The low-educational-status group was significantly older compared Results with the high-educational-status group. As expected, the job Demographic Data. A total of 19,973 individuals consented to position occupied by the individuals was commensurate with participate in our study in the age group of 20–69 years. The their level of education. response rate was 87.6%. Data from 19,969 individuals were used for analysis, because the database did not capture the Prevalence of CHD Risk Factors Stratified by Education. The mean educational status of four individuals. The general characteris- levels of major CHD risk factors across various educational tics of the study population are published elsewhere (23).