Multi-center study of mortality risk of cold spell in China

Abstract:

Background: Numerous epidemiological studies have shown that the variation in temperature can cause serious health risks. Cold spell, as an extreme temperature event, it’s health effect was explored in developed countries in the past century.However, the evidence cannot be simply extrapolated to developing countries, nor can it be directly used in health protection policies making in developing country. Therefore, more research is needed to explore the exposure-response relationship between cold spell and Mortality in China.

Methods: we collected the daily metrological data and mortality data in 96 counties of China from 2013 to 2017. The metrological data included: daily mean temperature, daily minimal temperature and daily mean relative humidity. The mortality data included: non-accidental mortality, circularatory mortality, and respiratory mortality. We use seven definitions of cold waves: P1D2 (“P” means percentile, “D” means consecutive days. The definition is: the daily mean temperature for more than 2 consecutive days is less than 1% of the 5-year temperature), P5D2, P5D5, P5D7, P10D2, P10D5, P10D7. Two-stage multicenter time series analysis. In the first stage, we calculated the exposure-response realtionship for each county using time series analysis. In the second stage, we meta the county level results in national (96 counties), Northern China (52 counties), and Sounthern China (44 counties).

Results: the number of cold spell in 96 counties from 2013 to 2017 was 450 for P1D2, 1850 for P5D2, 491 for P5D5, 264 for P5D7, 3179 for P10D2, 1105 for P10D5, 684 for P10D7. The definition of P5D7 had the highest ER for non-accidental mortality (3.4% (95%CI: 1.3, 5.5)), circulatory mortality (4.0% (95%CI: 1.5, 6.6)), and respiratory mortality (6.4% (95%CI: 1.8, 11.2)) in 96 counties. The ER of P5D7 for non-accidental mortality, circulatory mortality, and respiratory mortality were ((3.8% (95%CI: 0.8, 6.8)), (5.0% (95%CI: 1.5, 8.6)), and (8.2% (95%CI: 1.0, 16.0)) in Southren China.

Discussion and conclusion: With the increase of cold wave intensity, the frequency and duration of cold wave increase. The ER of the relationship between cold spell and mortality in Southern China was higher than in Northern China. More attention should be paied to the health risks of cold spell in Southern China.