The impact of temperature extremes on mortality: a time-series study in Jinan, China

Abstract

Objective: To investigate the relationship between temperature extremes and daily number of deaths in Jinan, a temperate city in northern China.

Methods: Data ondaily number of deaths and meteorological variables over the period of 2011-2014 were collected. Cold spells or heat waves were defined as ≥3 consecutive days with mean temperature ≤5th percentile or ≥95th percentile, respectively. We applied a time-series adjusted Poisson regression to assess the effects of extreme temperature on deaths.

Results: There were 152 150 non-accidental deaths over the study period in Jinan, among which 87 607 people died of cardiovascular disease, 11 690 of respiratory disease, 33 001 of stroke and 6624 of chronic obstrutive pulmonary disease (COPD). Cold spells significantly increased the risk of deaths due to non-accidental mortality (RR 1.08, 95% CI 1.06 to 1.11), cardiovascular disease (RR 1.06, 95% CI 1.03 to 1.10), respiratory disease (RR 1.19, 95% CI 1.11 to 1.27), stroke (RR 1.11, 95% CI 1.06 to 1.17) and COPD (RR 1.27, 95% CI 1.16 to 1.38). Heat waves significantly increased the risk of deaths due to non-accidental mortality (RR 1.02, 95% CI 1.00 to 1.05), cardiovascular disease (RR 1.03, 95% CI 1.00 to 1.06) and stroke (RR 1.06, 95% CI 1.00 to 1.13). The elderly were more vulnerable during heat wave exposure; however, vulnerability to cold spell was the same for the whole population regardless of age and gender.

Conclusions: Both cold spells and heat waves have increased the risk of death in Jinan, China.

Keywords: Mortality; Poisson regression; Temperature extremes; Time series.

Figure 1

Seasonal distribution of daily number of deaths in Jinan, China. COPD, chronic obstructive pulmonary disease.

Figure 2

Comparison of the average daily number of deaths between cold spell/heat wave days and non-exposure days. COPD, chronic obstructive pulmonary disease.

Figure 3

Rate ratios of cold spells and heat waves on daily number of deaths in Jinan, China. Rate ratios were calculated as ratios between the number of deaths during the cold spell/heat wave days and the number during the non-cold spell/non-heat wave days. *p <0.05, **p <0.01. COPD, chronic obstructive pulmonary disease.