Effect modification of the association between temperature variability and hospitalization for cardiovascular disease by comorbid diabetes mellitus: A nationwide time-stratified case-crossover analysis

AIMS:We aimed to explore the association between short-term exposure to temperature variability (TV), and cardiovascular hospitalization stratified by the presence of comorbid diabetes. METHODS:We collected data on nationwide hospitalization for cardiovascular diseases and daily weather conditions during 2011-2018 in Japan. TV was calculated as the standard deviation of daily minimum and maximum temperatures within 0-7 lag days. We applied a two-stage time-stratified case-crossover design to estimate the association between TV and cardiovascular hospitalization with and without comorbid diabetes, adjusting for temperature and relative humidity. Furthermore, specific cardiovascular disease causes, demographic characteristics, and seasons were used for stratification. RESULTS:In 3,844,910 hospitalizations for cardiovascular disease, each 1 °C increase in TV was associated with a 0.44% (95% CI: 0.22%, 0.65%) increase in the risk of cardiovascular admission. We observed a 2.07% (95% CI: 1.16%, 2.99%) and 0.61% (95% CI: -0.02%, 1.23%) increase per 1 °C in risk of heart failure admission in individuals with and those without diabetes, respectively. The higher risk among individuals with diabetes was mostly consistent in the analyses stratified by age, sex, body mass index, smoking status, and season. CONCLUSION:Comorbid diabetes may increase susceptibility to TV in relation to acute cardiovascular disease hospitalization.