Associations between PM2.5 exposure duration and physical activity intensity on the health of hypertension in urban residents of Beijing

Hypertension is reported to be associated with air pollution and physical activity (PA), and they have different or even conflicting effects on blood pressure (BP). The study evaluated the combined effects of PM2.5 exposure duration and physical activity intensity on systolic blood pressure (SBP) and diastolic blood pressure (DBP) of hypertension. A total of 2613 patients (≥18-year-olds) at baseline who attended surveys from the China Health and Nutrition Survey (2011-2015) in Beijing were selected, as well as the PM2.5 data collected in the same period. The mixed linear effects model and multivariate analysis of variance (MANOVA) were used to explore the multiple effects of PM2.5 exposure duration and PA intensity on SBP and DBP, respectively. The correlation results indicated PM2.5 exposure duration (>15 days) occurred more significant correlations with DBP and longer PM2.5 exposures duration (>60 day) with SBP. The mixed linear effects model showed the important random terms of gender, PA levels, and BMI classification for both SBP and DBP. It also indicated the significant fixed effect from age for both SBP and DBP, and the significant fixed effects from PM2.5 and weight, as well as the interaction in DBP. The random effects of PA levels put effects on different weight people for SBP and on different age people for DBP, while the person of SBP exposed to PM2.5 environments may tend to be affected by BMI classification. The model's main effects showed PA and the interaction with gender could put significant effects on BP. The gender effects and the PA level effects were also improved by the MANOVA results. We concluded that the more PM2.5 exposure duration may lead to more significant correlation with higher BP values. The PA levels could lead to the different effects on the health showing the variations in age, gender, and BMI classification. For SBP of people who are exposed to PM2.5 environments, it may tend to be affected by BMI classification, which also may influence the DBP through weight adjusting first and then cause hypertension. The gender difference of BP may be affected by PA showing the higher PA level and the more gender difference.