Ozone Exposure, Outdoor Physical Activity, and Incident Type 2 Diabetes in the SALSA Cohort of Older Mexican Americans

BACKGROUND: Type 2 diabetes is a leading contributor to the global burden of morbidity and mortality. Ozone ([Formula: see text]) exposure has previously been linked to diabetes. OBJECTIVE: We studied the impact of [Formula: see text] exposure on incident diabetes risk in elderly Mexican Americans and investigated whether outdoor physical activity modifies the association. METHODS: We selected 1,090 Mexican American participants from the Sacramento Area Latino Study on Aging conducted from 1998 to 2007. Ambient [Formula: see text] exposure levels were modeled with a land-use regression built with saturation monitoring data collected at 49 sites across the Sacramento metropolitan area. Using Cox proportional hazard models, we estimated the risk of developing incident diabetes based on average [Formula: see text] exposure modeled for 5-y prior to incident diabetes diagnosis or last follow-up. Further, we estimated outdoor leisure-time physical activity at baseline and investigated whether higher vs. lower levels modified the association between [Formula: see text] exposure and diabetes. RESULTS: In total, 186 incident diabetes cases were identified during 10-y follow-up. Higher levels of physical activity were negatively associated with incident diabetes [[Formula: see text] (95% CI: 0.43, 0.95)]. The estimated HRs for incident diabetes was 1.13 (95% CI: 1.00, 1.28) per 10-ppb increment of 5-y average [Formula: see text] exposure; also, this association was stronger among those physically active outdoors [[Formula: see text] (95% CI: 1.21, 1.90)], and close to null for those reporting lower levels of outdoor activity [[Formula: see text] (95% CI: 0.90, 1.20), [Formula: see text]]. CONCLUSIONS: Our findings suggest that ambient [Formula: see text] exposure contributes to the development of type 2 diabetes, particularly among those with higher levels of leisure-time outdoor physical activity. Policies and strategies are needed to reduce [Formula: see text] exposure to guarantee that the health benefits of physical activity are not diminished by higher levels of [Formula: see text] pollution in susceptible populations such as older Hispanics. https://doi.org/10.1289/EHP8620