The individual and joint effects of long-term exposure to temperature and relative humidity on blood pressure: a prospective cohort study in China

BACKGROUND: The opportunity of long-term exposure to non-optimal temperature and relative humidity (RH) may increase which might contribute to elevations in blood pressure (BP). This study aimed to examine the joint effect of long-term exposure to temperature and RH on BP which help better adaption to climate change. METHODS: Data were collected from 9272 participants in global AGEing and adult health cohort study across eight provinces in China from 2007 to 2019. Annual meteorological data were treated as indicators which derived from European Centre for Medium-Range Weather Forecasts atmospheric reanalysis (ERA5). Generalized linear mixed models (GLMM) and quantile-based g-computation models were employed to estimate the individual and joint associations between long-term exposure to temperature and RH with BP. RESULTS: In joint effect analysis, we found a U-shaped pattern. The minimum blood pressure percentile (MBPP) for both systolic blood pressure (SBP) and diastolic blood pressure (DBP) was observed at a temperature of approximately 15.4 °C and RH of 72.8%. Compared to MBPP, exposure to 4.6 °C and 57.9% was associated with increases of 12.05mmHg (95%CI:11.63-12.42mmHg) and 6.67mmHg (95%CI:6.43-6.88mmHg) in SBP and DBP, respectively. Exposure to 22.5 °C and 79.2% was associated with increases of 11.75mmHg (95%CI:10.32-13.08mmHg) and 6.47mmHg (95%CI:5.65-7.25mmHg) in of SBP and DBP, respectively. People < 60 years old, female and hypertensive patients not taking antihypertensive medication were more susceptible to mixture exposure to low temperature and low RH. Additionally, the effect of dry-cold event on BP was higher than that of wet-cold, wet-hot, and dry-hot events. CONCLUSION: The associations between long-term co-exposure to temperature and RH and BP exhibited a U-shaped curve. Individuals under 60 years old, females, and hypertensive patients not taking antihypertensive medication were more susceptible to dry-cold events.