Pulmonary Function Responses To Extreme Heat Exposure In Young And Older Adults

Older adults have impaired heat dissipating capabilities which leads to greater increases in core temperature in response to the same heat exposure compared to younger adults. With rising global temperatures, older adults are at a greater risk of heat related morbidity and mortality during heat waves. Epidemiological data shows that pulmonary complications are a leading cause of heat wave-related hospitalizations in older adults with COPD. However, it is not known how extreme heat exposure effects pulmonary function in healthy older adults compared to younger adults. PURPOSE: We tested the hypothesis that older adults, but not younger adults, will have decreased pulmonary function following 3-hours of extreme heat exposure. METHODS: Young (18-39 years) and older (>65 years) adults who were otherwise healthy participated in two experimental visits. Spirometry was performed to obtain pulmonary function at baseline in a thermoneutral environment and at the end of a 3-hour extreme heat exposure in a DRY (47 °C and 15% humidity) and a HUMID (41 °C and 40% humidity) environment. RESULTS: Fifteen young (7 female; 30 ± 5 years) and fifteen older (8 female; 72 ± 5 years) adults completed all aspects of the study. In young adults forced vital capacity (FVC) was no different from baseline (4.34 ± 0.55 L) to post-heating (4.31 ± 0.62 L; p = 0.72) in the DRY condition. In contrast, FVC in the older adults was increased from baseline (3.17 ± 0.72 L) to post-heating (3.29 ± 0.65 L; p = 0.02) in the DRY condition. Forced expiratory volume in one second (FEV1) in the young and older adults increased from baseline (3.55 ± 0.47, 2.38 ± 0.60 L, respectively) to post-heating (3.70 ± 0.50, 2.51 ± 0.54 L; respectively; p = 0.003) in the DRY condition. The HUMID condition resulted in the same changes in FVC and FEV1 in both age groups. There was no significant change in respiratory rate or end tidal CO2 in young or older adults during either environmental condition. CONCLUSIONS: We did not observe reductions in pulmonary function in either group. Rather, pulmonary function was either unchanged or elevated following the 3-hour extreme heat exposure, indicative of some degree of bronchodilation. Supported by: Supported by NIH R01AG069005 (CGC)