Non-Linear Association between Exposure to Ambient Temperature and Children’s Hand-Foot-and-Mouth Disease in Beijing, China

BACKGROUND Hand, foot and mouth disease (HFMD) was listed as a notifiable communicable disease in 2008 and is an emerging public health problem in China, especially for children. However, few data are available on the risk assessment of the potential reasons for HFMD in Beijing. This study examined the association of temperature with the incidence of children's HFMD in Beijing at the daily scale for the first time. METHODS A newly developed case-crossover design with a distributed lag nonlinear model (DLNM) was used to assess the delayed and cumulative associations of daily temperature with gender- and age-specific HFMD in Beijing, China, during 2010-2012. Relative humidity, day of the week, public holiday, season and long-term trends were controlled in the model. RESULTS Among the total of 113,475 cases, the ratio between males and females was 1.52:1. HFMD was more prevalent in May-July. The temperature-HFMD relationships were non-linear in most age groups except for children aged 6-15 years, with a peak at 25.0~27.5°C. The high-temperature risks were greater, appeared earlier and lasted longer than the low-temperature risks. The relative risks for female children and those aged 6-15 years were higher than those among other groups. CONCLUSION Rising temperatures increased the incidence of children's HFMD, with the largest association at 25.0~27.5°C. Females and children aged 6-15 years were more vulnerable to changes in temperature with regard to the transmission of HFMD than males and other age groups, respectively. Further studies are warranted to confirm these findings in other populations.