Lag effect of humidex on bacillary dysentery and its regional heterogeneity in North China

  Objective   To study the association of humidex with bacillary dysentery (BD) incidence and its regional heterogeneity in North China.

  Methods   The daily BD incidence and meteorological data from January 1, 2014 through December 31, 2016 in North China were collected from Chinese Center for Disease Control and Prevention and China Meteorological Science Data Sharing Service Network. Distributed lag non-linear model was used to assess associations of average ambient temperature, relative humidity and humidex with BD incidence. Multivariate meta-analysis was employed to pool region-specific analytic estimates and then meta-regression analysis was adopted to explore modifiers of the association between humidex and BD incidence.

  Results   Approximately J-shaped relationships were observed between pooled BD risk and average ambient temperature, relative humidity and humidex. The humidex showed a promotion effect on BD incidence of the same day; the effect was the most obvious for the lag day 3 (relative risk RR = 1.07, 95% confidence interval 95% CI: 1.05 – 1.09) and lasted until the lag day 7. Taking the median humidex as a reference, the humidex of 42.4 manifested a highest promotion effect on BD incidence, with the RR of 1.96 (95% CI: 1.52 – 2.53). The effect of humidex was more obvious in city-level regions at high latitude and longitude, with high natural population growth rate but low gross domestic production per capita.

  Conclusion   The meteorological condition with high humidex may promote bacillary dysentery incidence in North China and the situation needs to be concerned in the control of the disease, especially in some vulnerable cities.