[Lagged effects of diurnal temperature range on mortality in 66 cities in China: a time-series study]

Objective: To estimate the effect of daily diurnal temperature range (DTR) on mortality in different areas in China. Methods: A time series study using the data collected from 66 areas in China was conducted, and Meta-analysis was used to analyze the estimates of associations between DTR and daily mortality. Modifying effects of extremely low and high DTR-mortality relationship by season and socioeconomic status (SES) were also evaluated respectively. Cumulative excess risk (CER) was used as an index to evaluate the effects. Results: The information about 1 260 913 registered deaths were collected between 1 January 2006 and 31 December 2011, we found the relationship between extreme DTR and mortality was non-linear in all regions and the exposure-response curve was J-shaped. In central and south areas of China, the result indicated the obvious acute effect of extremely high DTR, and the mortality effect in central area (CER=5.1%, 95% CI: 2.4%-7.9%) was significant higher than that in south area (CER=4.5%, 95% CI: 1.7%-7.3%). Regarding to the modification of seasons, the cumulative mortality effect of DTR in cold season (CER=5.8%, 95%CI: 2.5%-9.2%) was higher than that in hot season (CER=3.1%, 95%CI: 1.1%-5.1%). Generally, deaths among the elderly (≥75 years) were associated more strongly with extremely high DTR. Conclusions: The mortality effects of extremely DTR in different areas and seasons showed different characteristics, that in central area and in cold season it was significantly stronger. After modified by season and SES, DTRs were the greatest threat to vulnerable population, especially to the elderly (≥75 years). Therefore, more attention should be paid to vulnerable groups and protection measures should be taken according to the local and seasonal conditions.