The effect of diurnal temperature range on mortality in Kerman, Iran

Abstract

Diurnal temperature range (DTR) is one of the climate indicators likely to be related to human health. The purpose of this study was to investigate the relation between mortality and DTR in Kerman, Iran. The DLNM (Distributed Lag Non-linear Model)with a quas/i-Poisson regression model was used to evaluate the effect of DTR on mortality in age and sex groups by controlling the confounding variables (long-term trend of daily mortality, effect of day of the week, holidays, mean temperature, humidity, and air pollution). Since DTR effects on mortality may vary in cold and warm seasons, separate analyses were conducted for cold and warm seasons. DTR showed a non-linear relation with mortality. Mortality increased at the 90th percentile of DTR (CRR = 1.16, 95% CI 1.00–1.34), in lag 0–21 and at the 10th percentile of DTR in lag 0–13 (1.27, 95% CI 1.06–1.52), and lag 0–21 1.35 (95% CI 1.06–1.71). Increased mortality was more observed in the > 60 age group and in men. High levels of DTR after long lags (13 days) in the cold season were associated with increasing mortality. High and low diurnal temperature range may be a risk factor for mortality, especially in the men and elderly.