The association between daily temperature extremes and human biomarkers: heterogeneous effects of occupation and season

The impact of extreme temperatures on the health of individuals in different organizations remains uncertain. We employed stratified analyses to examine the impacts of summer (April–September) daily maximum temperatures and winter (October–March) daily minimum temperatures on blood pressure and lipid profiles across government staff, company employees, and researchers. We examined 209,477 physical examination records from a physical examination center in the First Affiliated Hospital of USTC from 2017 to 2021. Employing a segmented regression model within the framework of generalized linear regression (GLM), we examined the causal impact of extreme temperatures on health outcomes. Additionally, sensitivity analyses were conducted via distributed lag nonlinear models (DLNMs), with a focus on observing the long-term effects over a period of 21 days. Our findings indicate that government staff face increased health risks during extremely low temperatures, regardless of the season. Compared with participants experiencing median temperatures, government staff exposed to extremely low temperatures (below the 10th percentile, below 24 °C) in the summer presented maximum increases of 2.32 mmHg (95% CI: 1.542–3.098) in diastolic blood pressure and 6.481 mmHg (95% CI: 5.368–7.594) in systolic blood pressure. In winter, government staff exposed to temperatures below the 10th percentile (below 1 °C) demonstrated maximum increases of 0.278 mmol/L (95% CI: 0.210–0.346) in total cholesterol, 0.153 mmol/L (95% CI: 0.032–0.274) in triglycerides, and 0.077 mmol/L (95% CI: 0.192–0.134) in low-density lipoprotein. Conversely, warm winters benefit company employees, whereas researchers exhibit lower sensitivity to temperature changes in winter. The maximum temperatures in summer and minimum temperatures in winter had greater impacts on individuals. Small temperature fluctuations impact health more than large changes do. Notably, both the maximum and minimum temperatures were better predictors of health outcomes than the daily average temperature was. Blood pressure consistently displayed significant associations with temperature across all three groups, with extremely low temperatures increasing the risk and extremely high temperatures reducing it. However, the relationship between temperature and blood lipids is complex.