Background The contribution of long-term ambient PM_2.5 exposure to hypertension should not be ignored. However, the conclusions of whether dietary factors play a role in regulating PM_2.5-related hypertension are still inconsistent.

Objective To explore the correlation between long-term exposure to ambient PM_2.5 and blood pressure indicators (systolic blood pressure, diastolic blood pressure, mean arterial pressure, and pulse pressure) in adults in Ningxia and a potential moderating effect of dietary factors.

Methods A set of cross-sectional survey data from March, 2013 to May, 2018 was retrieved from the China Northwest Cohort-Ningxia, and the average ambient PM_2.5 concentration in the previous three years was also collected to estimate the long-term exposure of the participants. Binary logistic regression model was used to validate the correlation between long-term exposure to ambient PM_2.5 and hypertension in Ningxia, and linear model was used to study the correlation between long-term exposure to ambient PM_2.5 and blood pressure indicators (systolic blood pressure, diastolic blood pressure, mean arterial pressure and pulse pressure), and to explore the influence of dietary factors on ambient PM_2.5-related hypertension.

Results A total of 11470 participants were included in the study, 42.2% male and 57.8% female. The three-year average ambient PM_2.5 concentration before the baseline survey was 37.0 μg·m⁻³. Each 1 μg·m⁻³ increase in ambient PM_2.5 was associated with an increased risk of hypertension (OR=1.111, 95%CI: 1.097, 1.125), and increased systolic blood pressure, diastolic blood pressure, mean arterial pressure, and pulse pressure by 0.886 (95%CI: 0.783, 0.990), 0.570 (95%CI: 0.500, 0.641), 0.676 (95%CI: 0.600, 0.751), and 0.316 (95%CI: 0.243, 0.389) mmHg, respectively. The stratified analysis showed that the OR and 95%CI of hypertension were 1.171 (1.097, 1.254), 1.117 (1.064, 1.174), and 1.160 (1.116, 1.207) respectively for each 1 μg·m⁻³ increased in PM_2.5 with low frequency of vegetable and fruit consumption and salty taste respectively. The OR and 95%CI of hypertension were decreased when the moderate and high frequency of vegetable and fruit intake and moderate and light taste applied, the values were 1.091 (1.062, 1.121) and 1.114 (1.097, 1.131), 1.105 (1.082, 1.129) and 1.111 (1.092, 1.13), 1.115 (1.090, 1.140) and 1.102 (1.083, 1.121) respectively. Compared with low frequency of vegetable and fruit intake and salty taste, the increase degree of ambient PM_2.5 related systolic blood pressure, diastolic blood pressure, mean arterial pressure and pulse pressure also decreased in middle and high frequency of vegetable and fruit intake and moderate and light taste.

Conclusion Long-term exposure to ambient PM_2.5 is significantly associated with increased risks of hypertension and blood pressure in Ningxia area. Increasing the frequency of vegetable and fruit intake and decreasing salty taste may reduce the effect of ambient PM_2.5 on hypertension and blood pressure.