Exploring age and gender sensitivity to high-temperature days: impacts on respiratory, cardiovascular, and all-cause mortality in summer in Flanders

With global warming escalating and extreme weather events rising in frequency, the impact of temperature on human health, particularly mortality, has become a critical public health concern. Responses to heat exposure exhibit considerable variability among individuals, influenced by factors such as age and gender. Acknowledging and addressing these differences among population groups is essential for the effective planning of prevention measures. In this context, the present study investigates the age and gender sensitivity to heat in the region of Flanders. This study employs the distributed lag non-linear model (DLNM) to quantify the non-linear relationship between minimum and average daily temperatures and all-cause mortality, as well as cause-specific cardiovascular and respiratory mortality in Flanders over the period 2000-2019. We focus on the summer period from May 15 to September 30 to assess the impact of extreme temperatures in low-mortality months. While many studies have shown that there is an increasing impact of temperature on mortality, we explore whether the impact of heat is different across different age- and gender groups by incorporating an interaction term between the exposure–lag–response structure and the age–gender categories. Our findings show a noteworthy increase in overall mortality at elevated mean daily temperatures, with a slightly higher relative risk for females compared to males. The elderly, particularly those aged 85 and above, face the longest-lasting effects of heat, followed by the 65-84 age group. The youngest age group experiences the shortest duration of the impact. While the risk of mortality by cardiovascular disease decreases sharply after a heat day, the risk of mortality by respiratory disease remains elevated for several days following the heat exposure. The effect modification by age and gender revealed differences in heat-related mortality across age-gender groups in Flanders, highlighting the importance of considering such interactions to accurately characterize these relationships and inform targeted prevention measures.