Association between infertility prevalence and exposure to heat stress

Background: The association between heat stress and infertility remains insufficiently elucidated, particularly given the paucity of studies that classify heat stress intensity according to physiological thresholds and perform sex-stratified analyses. This study examined the relationship between heat stress and infertility prevalence.
Methods: This study employed Universal Thermal Climate Index (UTCI) to examine the age-standardized prevalence rates (ASPRs) of male and female infertility across 174 countries and regions in 1990–2021. A linear mixed-effects model was applied to evaluate the associations between varying levels of heat stress and infertility prevalence in both sexes. A weighted composite score was constructed to capture the combined effects of very strong and extreme heat stress on male and female infertility.
Results: Very strong and extreme heat stress were positively associated with the ASPRs of infertility in both men and women. The weighted composite scores of very strong and extreme heat stress were likewise significantly correlated with higher ASPR values in both sexes. For each unit increase in the heat stress score, the prevalence of male and female infertility increased by 0.796 cases (95% CI: 0.493–1.102) and 0.875 cases (95% CI: 0.646–1.102) per 100,000 population, respectively. The female infertility ASPR exhibited greater sensitivity to high-intensity heat stress than that of males.
Conclusions: These findings underscore the need to integrate reproductive health protection into heat adaptation policies and provide targeted interventions and health guidance for individuals of reproductive age to mitigate the potential reproductive health impacts of heat exposure.