Older Firefighters Are Susceptible to Age-Related Impairments in Heat Dissipation

Purpose: The aging-induced reduction inwhole-body heat loss (H-L) capacity generates concerns regarding the continued participation of older workers in occupations such as firefighting. We compared H-L and change in body heat storage (S) during intermittent exercise in warm/dry and warm/humid conditions among older male firefighters (OLDER, n = 9, age = 54.7 +/- 2.1 yr), older (age-matched) nonfirefighters (NO-NFF, n = 9, age = 52.8 +/- 1.2 yr), and young firefighters (YOUNG, n = 6, age = 26.7 +/- 0.8 yr). Methods: We measured evaporative heat loss and dry heat exchange via the Snellen whole-body direct calorimeter while participants performed four 15-min bouts of cycling at 400 W of metabolic heat production separated by 15-min recovery periods in warm/dry (35 degrees C, 20% relative humidity) and warm/humid (35 degrees C, 60% relative humidity) conditions. Results: We found no differences (P > 0.05) in H-L or cumulative S (Delta S) between OLDER and NON-FF in the warm/dry (Delta S: OLDER = 233 +/- 26 kJ, NON-FF = 270 +/- 29 kJ) or warm/humid (Delta S: OLDER = 548 +/- 24 kJ, NON-FF = 504 +/- 47 kJ) conditions. The OLDER and NON-FF had lower H-L than the YOUNG during exercise in both environmental conditions (P < 0.05). The OLDER stored 40% (P > 0.05) and 46% (P = 0.004) more heat than YOUNG in the warm/dry and warm/humid conditions, respectively. The NON-FF stored 63% (P = 0.016) and 34% (P = 0.025) more heat than the YOUNG in the dry and humid conditions, respectively. Conclusions: Older firefighters and age-matched nonfirefighters demonstrate similar H-L and S during work in the heat. Moreover, H-L is significantly reduced in older compared to younger firefighters during exercise in both warm/dry and warm/humid conditions. Consequently, older firefighters may be more susceptible to thermal injury while on duty than their younger counterparts.