Morbidity Risk of Infectious Gastroenteritis Attributable to Cold and Heat Temperatures: An Analysis of National Surveillance Data in Japan (2000-2019).

Introduction Climate change is a decisive factor affecting human health. While many epidemiological studies have investigated the acute impacts of ambient temperature on mortality and morbidity, the global burden of infectious gastroenteritis linked to temperature changes remains largely unexplored. Therefore, we aimed to examine the exposure-response associations between ambient temperature and infectious gastroenteritis incidence throughout Japan and quantify the temperature-related morbidity burden. Methods Weekly time-series data from 2000 to 2019, encompassing meteorological factors and infectious gastroenteritis cases, were collected from all 47 Japanese prefectures. A two-stage time-series design was employed. In the first stage, quasi-Poisson regression models combined with distributed lag non-linear models were used for each prefecture. In the second stage, a multivariate meta-analysis was conducted to derive national estimates. The attributable fractions were determined for both low and high temperatures, categorized as temperatures below or above the minimum risk temperature, respectively. Results The analysis included 19,571,939 infectious gastroenteritis cases. The exposure-response association between temperature and infectious gastroenteritis cases was non-linear, exhibiting an approximate M-shaped relationship. Overall, 51.7% (95% empirical confidence interval (eCI): 42.6, 58.4) of infectious gastroenteritis cases were attributable to non-optimal temperatures in Japan. The attributable fraction to low temperatures was 47.6% (95% eCI: 38.5, 54.2), whereas that of high temperatures was 4.1% (95% eCI: 2.4, 5.5). Conclusion The majority of the temperature-related infectious gastroenteritis burden in Japan was attributable to lower temperatures. Our findings indicate that public health strategies aimed at mitigating the burden of infectious gastroenteritis should take temperature levels into account.