Socio-environmental factors associated with heat and cold related mortality in Vadu Health and Demographic Surveillance System, western India: A population based case-crossover study

Abstract

Background: Ambient temperatures are associated with mortality, but limited research is available about groups most vulnerable to these effects in rural populations. We estimated the effects of heat and cold on daily mortality among different socio-demographic groups in the Vadu Health and Demographic Surveillance System (HDSS), western India. Method: We studied all daily deaths in the Vadu HDSS area during 2004-2013. A conditional logistics regression model in a case-crossover design was used. Separate analyses were carried out for summer (above a threshold of 31°C) and winter season temperature. Odd ratios and 95% confidence intervals were estimated for total mortality and population subgroups. Results: Temperature above 31°C was associated with total mortality (OR 1.48; CI=1.05-2.09) per °C increase in daily mean temperature. Odds ratios were higher among females (OR 1.93; CI=1.07-3.47), those with little education (OR 1.65; CI=1.00-2.75), higher socio-economic status (OR 2.18; CI= 0.99-4.79) and farmers (OR 1.70; CI=1.02-2.81). In winter, per °C decrease in temperature, OR for total mortality was 1.06 (CI=1.00-1.12) in lag 0-13 days. High risk of cold-related mortality was observed among people occupied in housework (OR=1.09; CI=1.00-1.19). Conclusion: Our study suggests that both heat and cold have an impact on mortality, and that effects differ partly by sex, education, occupation and socio-economic status. These findings might have important policy implications in preventing heat and cold effects on particularly vulnerable groups of the rural populations in low and middle-income countries with hot semi-arid climate.