The potential role of dietary patterns in modifying the association between ambient PM2.5 exposure and mortality in elderly Hong Kong Chinese

The potential of dietary patterns to modify the associations between long-term ambient fine particulate matter (PM2.5) exposure and all-cause, respiratory, and circulatory mortality remains unclear. A total of 3,937 older adults (≥ 65 years) living in the community were enrolled in a prospective cohort study from 2001 to 2003 in Hong Kong. Assessment of the Diet Quality Index-International (DQI-I), Dietary Inflammatory Index (DII), the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet was carried out utilizing a 280-item food frequency questionnaire. Annual PM2.5 concentrations were estimated via land use regression models. Mortality outcomes were sourced from official death registry. Time-varying Cox proportional hazards models were applied to estimate hazard ratios (HRs) and their 95% confidence intervals (CIs). During a median of 16.8 years follow-up, 1,856 deaths were recorded. PM2.5 exposure significantly increased the risks of all-cause mortality, respiratory and circulatory mortality. The MIND diet interacted with PM2.5 exposure on all-cause (p-interaction = 0.008) and respiratory mortality (p-interaction = 0.022). Higher MIND diet scores (≥ median) attenuated the adverse PM2.5 exposure-mortality association, showing lower risks for all-cause (HR: 1.18, 95% CI: 1.06–1.32) and respiratory mortality (HR: 1.14, 95% CI: 0.91–1.41). In contrast, those with lower MIND scores (< median) had elevated mortality risks, with HRs of 1.45 (95% CI: 1.27–1.65) for all-cause mortality and 1.60 (95% CI: 1.24–2.06) for respiratory mortality. No significant interaction was observed for circulatory mortality. Besides, no interaction was found between PM2.5 exposure with DQI-I or DII in relation to mortality. Adherence to MIND diet may mitigate the detrimental effects of long-term exposure to PM2.5 on all-cause and respiratory mortality in older adults, whereas overall diet quality or an anti-inflammatory diet showed no protective effects.