Commentary: Jumping the gun or asleep at the switch: is there a middle ground?

Non-communicable diseases (NCD) are now widely recognized as constituting a majority share of global mortality, accounting for 65% of all deaths. An estimated 43% of all deaths in low-income countries and 75% of deaths in lower-middle-income countries can be attributed to non-communicable conditions. In this context, it has been hypothesized that NCD may no longer be confined to only the most affluent populations in lowand middle-income countries (LMIC). Instead, even populations with lower socioeconomic status (SES) within LMIC may be experiencing increasing risk for NCD or NCD risk factors. Support for this hypothesis has been documented in a number of LMIC. In this issue of IJE, Subramanian and colleagues challenge the idea that NCD are disproportionately represented among populations with low SES in India. The authors focus specifically on cardiovascular risk factors, disease and mortality. They provide a summary of the literature and a critical appraisal of the discourse around NCD in India. They conclude that, contrary to what has been hypothesized, cardiovascular risk factors (with the exception of tobacco use/smoking) are less prevalent among the lowest SES populations in India as compared with the highest. Subramanian et al. argue that, despite the lack of empirical evidence, previous interpretations of results from India display a strong bias toward portraying results as congruent with the hypothesis that the burden of NCD is shifting toward the socioeconomically disadvantaged. Finally, they conclude that, beyond being problematic to the scientific community, these biased interpretations and the associated advocacy for NCD prevention/treatment might have unintended negative consequences for the most vulnerable populations in India. Subramanian et al. summarize the results of 53 studies reporting 353 associations between SES and cardiovascular risk factors, disease or mortality. They find that in a majority of studies, five of seven cardiovascular risk factors (obesity, diabetes, adverse lipid profile, hypertension and physical inactivity) were clearly more prevalent among populations with high SES compared with low. Only two cardiovascular risk factors (smoking/tobacco use and low fruit and vegetable intake) were clearly more prevalent among populations with low SES compared with high. Results for cardiovascular disease were more equivocal, with 52% of the 21 associations reporting higher disease prevalence among the higher SES groups (vs lower). Only two studies examined cardiovascular mortality. There are several points that should be noted while interpreting these results. First, a stated goal of the paper is to determine whether NCD have increased among populations with low SES, as a means of judging the legitimacy of claims of such. However, this review only specifically evaluates whether populations with low SES had a relatively higher risk or prevalence for each outcome than populations with high SES. NCD may pose a substantial disease burden for populations with low SES even if the prevalence is still lower than that in high SES populations. For instance, the prevalence of overweight/obesity among women in Mumbai is 25% for those living in slums and 30% for those living in non-slums. This would suggest a substantial burden of overweight/ obesity among women who live in slums, even though overweight/obesity is more prevalent among women who do not live in slums. This review also does not answer the question of whether NCDs have increased over time among lower SES populations in India. The authors pooled data collected over the span of 40 years (1969–2009), the very time period during which changes in the distribution of disease would be expected to occur. The resultant summary does not directly address the current state of associations between SES and cardiovascular risk factors or disease, nor does it address the extent to which cardiovascular risk factors or disease have changed over time. We might be fairly confident that for five out of seven cardiovascular risk factors, Published by Oxford University Press on behalf of the International Epidemiological Association