Abstract
BACKGROUND: Despite the adverse effects of ambient fine particulate matter (PM(2.5)) on type 2 diabetes and the beneficial role of physical activity (PA), the influence of PM(2.5) on the relationship between PA and type 2 diabetes remains unclear. METHODS: In this prospective study with 71,689 participants, PA was assessed by a questionnaire and was categorized into quartiles for volume and three groups for intensity. Long-term PM(2.5) exposure was calculated using 1-km resolution satellite-based PM(2.5) estimates. PM(2.5) exposure and PA's effect on type 2 diabetes were assessed by cohort-stratified Cox proportional hazards models, individually and in combination. RESULTS: In 488,166 person-years of follow-up, 5487 incident type 2 diabetes cases were observed. The association between PA and type 2 diabetes was modified by PM(2.5). Compared with the lowest quartile of PA volume, the highest quartile was associated with reduced type 2 diabetes risk in low PM(2.5) stratification (≤65.02 µg/m(3)) other than in high PM(2.5) stratification (>65.02 µg/m(3)), with the hazard ratio (HR) of 0.75 (95% confidence interval [CI]: 0.66-0.85) and 1.10 (95% CI: 0.99-1.22), respectively. Similar results were observed for PA intensity. High PM(2.5) exposure combined with the highest PA levels increased the risk of type 2 diabetes the most (HR = 1.79, 95% CI: 1.59-2.01 for PA volume; HR = 1.82, 95% CI: 1.64-2.02 for PA intensity). CONCLUSION: PA could reduce type 2 diabetes risk in low-pollution areas, but high PM(2.5) exposure may weaken or even reverse the protective effects of PA. Safety and health benefits of PA should be thoroughly assessed for long-term polluted residents.