Background There is a lack of evidence on whether exposure to PM_2.5 and its constituents would affect the relationship between the dietary approaches to stop hypertension (DASH) and central obesity.

Objective To investigate the effect of exposure to PM_2.5 and its constituents on the correlation between the DASH dietary pattern and the prevalence of central obesity.

Methods The data were obtained from the baseline survey of the "Xinjiang Multi-Ethnic Natural Population Cohort Construction and Health Follow-Up Study" in Urumqi. A DASH score was calculated according to intake frequency of 8 food groups, and summed from intake frequency of recommended food groups scored from 1 to 5 from low to high, and intake frequency of restricted food groups scored from 1 to 5 from high to low. A higher DASH score indicates better compliance with the DASH dietary pattern. We estimated exposure using satellite-derived PM_2.5 and a chemical transport model (GEOS-Chem) for its constituents, including organic carbon (OC), black carbon (BC), sulfate (SO₄²⁻), nitrate (NO₃⁻), ammonium (NH₄⁺), and soil dust. Central obesity was defined by waist circumference: ≥90 cm for men or ≥85 cm for women according to Criteria of weight for adults (WS/T 428—2013). A logistic regression model was used to analyze the effects of the DASH dietary pattern as well as PM_2.5 and its constituents on central obesity, and a stratified analysis was used to explore the effects of PM_2.5 and its constituents on the association between the DASH dietary pattern and central obesity.

Results The study included 9 565 urban residents, aged (62.30±9.42) years, with a central obesity prevalence rate of 60.75%. After adjusting for selected confounders, the DASH score Q5 group had a 17.5% lower risk of central obesity than the Q1 group (OR=0.825, 95%CI: 0.720-0.947). PM_2.5 and its constituents OC, BC, SO₄²⁻, NH₄⁺, and soil dust were positively associated with the prevalence of central obesity, but no association was observed between constituent NO₃⁻ exposure and central obesity. The stratified analysis revealed that the prevalence of central obesity was reduced in the DASH score Q5 group in participants exposed to low concentrations of PM_2.5 and its constituents NO₃⁻, NH₄⁺, and soil dust, while the protective effect of the DASH pattern on central obesity disappeared in subjects exposed to high concentrations of PM_2.5 and its constituents NO₃⁻, NH₄⁺, and soil dust.

Conclusion Exposure to PM_2.5 and its constituents NO₃⁻, NH₄⁺, and soil dust could attenuate the protective effect of the DASH pattern on central obesity.