Pulmonary function responses to extreme heat exposure in younger and older adults

Older adults have both lower pulmonary function and impaired thermoregulation compared with younger adults. In addition, epidemiological evidence suggests that extreme heat exposure increases the incidence of pulmonary complications in older adults. However, the impact of extreme heat exposure on pulmonary function in healthy older and younger adults is not well described. To assess this question, spirometry was performed at baseline in a thermoneutral environment and at the end of a 3-h heat exposure in a DRY (47°C and 15% humidity) and HUMID (41°C and 40% humidity) environment. Fifteen younger (7 female; 30 ± 5 yr) and 15 older (8 female; 72 ± 5 yr) adults completed the study. In the DRY condition, the younger adults had no change in forced vital capacity (FVC) from baseline (4.34 ± 0.55 L) to end-heating (4.31 ± 0.62 L; <i>P</i> = 0.72). In contrast, FVC in the older adults was increased from baseline (3.17 ± 0.72 L) to end-heating (3.29 ± 0.65 L; <i>P</i> = 0.02) in the DRY condition. Forced expiratory volume in 1 s (FEV₁) in the younger and older adults increased similarly from baseline (3.55 ± 0.47 and 2.38 ± 0.60 L, respectively) to end-heating (3.70 ± 0.50 and 2.51 ± 0.54 L, respectively; <i>P</i> = 0.003) in the DRY condition. The HUMID condition resulted in similar changes in FVC and FEV₁ in both age groups. In summary, the younger adults had an increase in expiratory airflow following heat exposure, indicative of some degree of bronchodilation, whereas the older adults had improved airflow in addition to increased FVC that could be indicative of altered pulmonary system compliance.<b>NEW & NOTEWORTHY</b> Pulmonary function increases in younger and older adults following 3 h of extreme heat exposure to a DRY (47°C and 15% humidity) and HUMID (41°C and 40% humidity) environment. Specifically, when hydration is maintained, FEV₁ increases as a result of heat-induced bronchodilation in both younger and older adults, whereas FVC increases in only the older adults due to potential improvements in pulmonary system compliance.