[Study on influence of air temperature on daily chronic obstructive pulmonary disease mortality in Ningbo]

Objective: To study the influence of daily air temperature on daily chronic obstructive pulmonary disease (COPD) mortality in residents in Ningbo. Methods: A time-series analysis using distributional lag non-linear model (DLNM) was conducted to estimate the attributable numbers and fraction of average air temperature on the daily COPD mortality in Ningbo from 2011 to 2016, by controlling the long-term time trend, day of week, air pollutants and other weather variables. Results: A reverse J-shape relationship was found between the average air temperature and COPD mortality, and the minimum-mortality temperature (MMT) was 25.5 ℃. The relative risks of extreme low and extreme high air temperature over lag 0-14 d were 2.767 (95%CI: 1.950-3.928) and 1.197 (95%CI: 1.021-1.404). In total, 31.62% (95%CI: 23.05%-38.89%) of COPD mortality (4 963 cases, 95%CI: 3 469-6 027) was attributable to non-MMT exposure, More attributable deaths were due to low air temperature, with a fraction of 30.41% corresponding to 4 772 deaths, compared with 1.22% and 192 deaths due to high air temperature. Low air temperature and high temperature were more likely to influence the mortality in females and those aged ≥65 years, but the influence was not significant in people aged <65 years. Conclusion: Both high and low air temperature were associated with an increased risk of COPD mortality in residents in Ningbo, especially during cold season, related measures on disease prevention should be taken to protect vulnerable population to reduce the risk of COPD mortality.