Association Between Socioeconomic Status and Self-Reported Diabetes in India: a Cross-Sectional Multilevel Analysis
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Association between socioeconomic status and self-reported diabetes in India: a cross-sectional multilevel analysis The Harvard community has made this article openly available. Please share how this access benefits you. Your story matters Citation Corsi, Daniel J, and S V Subramanian. 2012. Association between socioeconomic status and self-reported diabetes in India: a cross- sectional multilevel analysis. BMJ Open 2(4): e000895. Published Version doi:10.1136/bmjopen-2012-000895 Citable link http://nrs.harvard.edu/urn-3:HUL.InstRepos:10576035 Terms of Use This article was downloaded from Harvard University’s DASH repository, and is made available under the terms and conditions applicable to Other Posted Material, as set forth at http:// nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of- use#LAA Open Access Research Association between socioeconomic status and self-reported diabetes in India: a cross-sectional multilevel analysis Daniel J Corsi,1 S V Subramanian2 To cite: Corsi DJ, ABSTRACT ARTICLE SUMMARY Subramanian SV. Association Objectives: To quantify the association between between socioeconomic socioeconomic status (SES) and type 2 diabetes in status and self-reported Article focus India. - diabetes in India: The relationship between socioeconomic factors a cross-sectional multilevel Design: Nationally representative cross-sectional and type 2 diabetes has not been previously analysis. BMJ Open 2012;2: household survey. studied for the whole of India and across states. e000895. doi:10.1136/ Setting: Urban and rural areas across 29 states in - Our objective was to investigate associations bmjopen-2012-000895 India. between measures of SES (defined as social Participants: 168 135 survey respondents aged caste, education, household wealth) and self- < Prepublication history and 18e49 years (women) and 18e54 years (men). reported diabetes status in India. additional tables for this - In addition, we explored geographic variation in paper are available online. To Primary outcome measure: Self-reported diabetes view these files please visit status. the prevalence of diabetes between states and the journal online (http://dx. Results: Markers of SES were social caste, household local areas in India and between-state variability doi.org/10.1136/ wealth and education. The overall prevalence of self- in the SESediabetes relationship. bmjopen-2012-000895). reported diabetes was 1.5%; this increased to 1.9% Key messages and 2.5% for those with the highest levels of education - The highest socioeconomic groups appear to be Received 18 January 2012 and household wealth, respectively. In multilevel Accepted 18 June 2012 at greatest risk for diabetes in India with the logistic regression models (adjusted for age, gender, strength of the association consistent in size and religion, marital status and place of residence), This final article is available magnitude across states. education (OR 1.87 for higher education vs no for use under the terms of - There is substantial geographic heterogeneity in education) and household wealth (OR 4.04 for richest the Creative Commons the prevalence of diabetes. Attribution Non-Commercial quintile vs poorest) were positively related to self- - These findings raise important policy implica- 2.0 Licence; see reported diabetes (p<0.0001). In a fully adjusted tions for addressing the disease burdens among http://bmjopen.bmj.com model including all socioeconomic variables and body the poor versus those among the non-poor in the mass index, household wealth emerged as positive and context of India, where nearly half of the statistically significant with an OR for self-reported population is living in poverty. diabetes of 2.58 (95% credible interval (CrI): 1.99 to 3.40) for the richest quintile of household wealth Strengths and limitations of this study versus the poorest. Nationally in India, a one-quintile - The key strength of this study is the use of increase in household wealth was associated with an a large nationally representative survey to assess OR of 1.31 (95% CrI 1.20 to 1.42) for self-reported the socioeconomic and geographic patterning of diabetes. This association was consistent across diabetes across all of India. Limitations include states with the relationship found to be positive in 97% the relatively younger age of the sample and of states (28 of 29) and statistically significant in 69% assessment of diabetes status on the basis of (20 of 29 states). self-reports. Conclusions: The authors found that the highest SES 1Population Health Research groups in India appear to be at greatest risk for type 2 Institute, McMaster diabetes. This raises important policy implications for University, Hamilton, Ontario, INTRODUCTION Canada addressing the disease burdens among the poor 2Department of Society, versus those among the non-poor in the context of The prevalence of type 2 diabetes in India Human Development, and India, where >40% of the population is living in has been investigated in numerous popula- Health, Harvard School of poverty. tion-based surveys conducted across a range e Public Health, Boston, of settings since the 1970s.1 6 Despite Massachusetts, USA multiple prevalence studies, no nationally Correspondence to representative studies exist that have consid- Professor S V Subramanian; ered the association between socioeconomic [email protected] status (SES) and type 2 diabetes in India. In Corsi DJ, Subramanian SV. BMJ Open 2012;2:e000895. doi:10.1136/bmjopen-2012-000895 1 Socioeconomic status and diabetes in India a review of 15 existing studies that have reported the diabetes across states and local areas along with vari- prevalence of type 2 diabetes by SES and/or associations ability in the SESediabetes association across states. between SES and type 2 diabetes, all were found to have been based on local or regional samples and a majority METHODS e were done in urban areas46 19 (table 1). It has been Data source suggested that the prevalence of type 2 diabetes and We use data from the 3rd National Family Health Survey other cardiovascular disease risk factors may increasingly (NFHS), conducted in 29 states in India between become concentrated among low SES groups in India20 November 2005 and August 2006.36 NFHS-3 is a major and other low- and middle-income countries,21 although national health survey in India that collected informa- to date the empirical evidence from India in support of tion on a range of indicators including reproductive this hypothesis remains limited. The majority of studies health, nutritional status of adults and children, utilisa- reviewed in table 1 have provided evidence of a positive tion of healthcare services and blood testing for HIV association between SES (defined as education, house- prevalence. NFHS-3 covered all states in India, which hold wealth, social caste or a composite of two or more comprises nearly 99% of the population, but excluded markers) and diabetes among populations from selected Union Territories. The survey was designed to provide geographic regions in India61117; however, the strength estimates of key indicators (except HIV prevalence) for and consistency of this association across the whole of each state by urban and rural areas. India has not previously been assessed. Type 2 diabetes is the most common form of diabetes Survey design globally, accounting for >85% of cases.22 The incidence A uniform multistage sampling strategy was adopted in of type 2 diabetes is related to genetic and non-genetic all states, with separate sampling in urban and rural components, with the latter being greatly influenced by areas.36 37 In rural areas, a two-stage sample was carried modifiable risk factors such as obesity, diets low in fibre out using a list of villages from the 2001 census as the and high in trans fat and physical inactivity.23 24 Lifestyle sampling frame. In the first stage, a stratified sample of behaviours are strongly patterned by SES25 and may be villages was drawn with probability proportional to the mediators on the causal pathway between SES and the size of the village. In the second stage, a random selec- onset of type 2 diabetes.26 In high-income countries, the tion of households was drawn in each village from SESediabetes relationship appears to be negative, with a complete list of households complied during field visits the poor at greatest risk. For example, strong associa- carried out in each sampled village. In urban areas, tions have been observed between poverty, low educa- a similar procedure was implemented beginning with tion and type 2 diabetes among AfricaneAmerican a stratified random sample of municipal wards based on women27 28 and among White women and men in the the 2001 census. Next, one census enumeration block USA.29 Similarly, a study from Canada described an (150e200 households) was selected from within wards inversely graded SESediabetes association with an OR of using probability proportional to size. Finally, as in rural 1.9 for men (95% confidence interval (CI) 1.6 to 2.4) areas, field enumerators undertook a household listing and 2.8 (95% CI 2.2 to 3.4) for women for the lowest operation in selected blocks and a random sample of versus highest income groups.30 A recent meta-analysis households was made. In both rural and urban areas, 30 of 23 caseecontrol and cohort studies and 43 measures households were targeted for selection in each of the of SESediabetes association revealed an overall sampled units. The overall household response rate for increased risk for type 2 diabetes for low SES groups NFHS-3 was 98%.36 based on education, occupation and income.31 The All women aged 15e49 years in selected households strength of the association, however, was less consistent were invited to participate in the survey. In 22 states, in low- and middle-income countries, and few studies men aged 15e54 years in a random subsample of have been conducted in these countries.