Effect of ambient temperature on hand, foot and mouth disease incidence in Weifang city: a distributed lag non-linear model analysis

  Objective  To analyze spatial and temporal distribution characteristics of hand, foot and mouth disease (HFMD) in Weifang city and to explore lag effect of ambient temperature on HFMD and populations vulnerable to the effect.

  Methods  Data on HFMD incidence and meteorological factors from 2015 through 2017 were collected for descriptive statistics. Distributed lag nonlinear model was applied to explore lag effect of ambient temperature on daily HFMD incidence and quantitative relationship between ambient temperature and HFMD incidence.

  Results  During the 3-year period in the city, totally 18 963 HFMD cases were reported and the male to female ratio of the cases was 1.58 : 1, with more cases reported between May and July in a year. An obvious lag effect of ambient temperature on HFMD incidence was observed. The highest relative risk (RR) of 1.76 (95% confidence interval: 1.26 – 2.34) of HFMD incidence was associated with lag 6-day high daily average ambient temperature of 33 ℃. Considering the influence of 50th percentile daily average ambient temperature as the reference, high daily average ambient temperature (24 ℃/29 ℃) had stronger effect on HFMD incidence than low daily average ambient temperature (– 2 ℃/4 ℃). The cumulative RR of HFMD incidence associated with ambient temperature exposure was higher among children under 5 years old than among other population groups.

  Conclusion  Ambient temperature, with obvious lag effect, is an important influencing factor of HFMD incidence in Weifang city. The lag effect of ambient temperature differs by daily average temperature and in various populations; the effect of high daily average ambient temperature is stronger than that of low temperature and children under 5 years old are more vulnerable to the influence of ambient temperature.