The impact of air temperature and humidity on Children's blood pressure mediated by Lipids: A prospective cohort study

Objectives: Few studies illustrate the mechanism between air temperature and blood pressure (BP) in childhood. This study aims to investigate the associations between air temperature, humidity exposure, and BP trajectories in children and adolescents, and explore the potential mediating roles of lipid profiles in these relationships. Methods: This prospective cohort study included 5,971 children with 10,800 person-times measurements at baseline from the Chongqing Health Cohort, with evaluations conducted in 2014-2015 (baseline) and follow-ups in 2016 (urban areas) and 2019 (urban and rural areas). Multilevel mixed-effects models were used to analyse the impacts of air temperature and humidity on BP levels and the incidence of elevated BP, while accounting for potential confounders. Mediation analyses were performed to evaluate the mediating effects of lipid profiles, including low-density lipoprotein (LDL), total cholesterol (TC), and specific lipid species. Results: After adjusting for covariates, higher air temperature quartiles were associated with both decreased BP levels and elevated BP risk (RR: 0.83; 95 % CIs: 0.78, 0.89; P = 0.028). Conversely, higher humidity quartiles exhibited a U-shaped relationship with BP levels. Greater variability in air temperature was linked to increase BP levels. The cumulative effects of air temperature exposure on BP were significant from pregnancy to age 10, with females exhibiting larger effects (beta:-3.291, 95 % CIs: -4.242,-2.340, P < 0.001). LDL and TC partially mediated the associations between air temperature and BP levels, particularly in males. Specific lipid species, including SM (d21:1), LPC (17:0), and PC (O-36:3), also exhibited significant mediating effects. Conclusions: This study provides novel insights into the intricate interplay between air temperature, humidity, lipid metabolism, and blood pressure regulation in children. Lower average temperatures and extreme humidity levels were associated with increased risks of elevated BP, potentially mediated by lipid profiles. Early interventions targeting air temperature exposure and lipid metabolism could mitigate hypertension risk, promoting improved cardiovascular outcomes in children.