Short-term exposure to heat associated with lower lung function in older adults: analysis of the Lung VITAL cohort.

BACKGROUND: High temperatures are associated with respiratory symptoms, hospitalisations and mortality. Yet, the effects on lung function are not well described. The aim of this study was to determine associations of acute exposure to high temperatures with lung function in adults. METHODS: We included 1923 study participants from Lung VITamin D and OmegA-3 TriaL (VITAL) cohort, an ancillary study of VITAL, who underwent spirometry (two per participant) between 2010 and 2018. We assigned daily mean temperature, relative humidity, air pollution to geocoded participant home addresses. Forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and forced expiratory flow (FEF25-75) were obtained at baseline and 2-year follow-up across 11 US sites. We used distributed lag nonlinear models to examine potentially nonlinear associations of temperature with FEV1 and FVC in primary analyses as well as FEF25-75. Effect estimates reported as estimated mean difference in lung function for a contrast of 30°C vs 20°C. All models adjusted for age, sex, height, weight, trial intervention arm, current tobacco use, season, social vulnerability, relative humidity, PM2.5 and O3, testing site. RESULTS: Median (IQR) daily mean temperature was 13.6°C (17.4°C) for the study population. Daily exposures moderately correlated (rs-0.31 to 0.34). Cumulative short-term exposure to high temperature (lag 1-7 days) was associated with 49.96 mL (95% CI -96.32 to -3.61) lower FEV1 and 89.74 mL (95% CI -157.07 to -22.42) lower FVC compared with reference temperature (30°C vs 20°C). CONCLUSIONS: Short-term exposure to high temperatures over the preceding 7 days was associated with lower lung function in older US adults. Increases in heat exposure warrant interventions to protect older adults.