16 Mar Type 2 diabetes does not exacerbate body heat storage in older adults during brief, extreme passive heat exposure
Poirier MP, Notley SR, Boulay P, Sigal RJ, Friesen BJ, Malcolm J, Flouris AD, Kenny GP. Type 2 diabetes does not exacerbate body heat storage in older adults during brief, extreme passive heat exposure. Temperature (Austin). 2020 Mar 16;7(3):263-269. doi: 10.1080/23328940.2020.1736760. PMID: 33123619; PMCID: PMC7575233.
Aging exacerbates hyperthermia and cardiovascular strain during passive heat exposure, but it remains unclear whether those effects worsen in older adults with type 2 diabetes (T2D). We examined these responses in unacclimatized, physically active, older individuals with (n = 13, mean ± SD age: 60 ± 8 years, HbA1c: 7.0 ± 1.0%) and without (Control, n = 30, 62 ± 6 years) well-controlled T2D during a brief, 3-h passive exposure to extreme heat (44°C, 30% relative humidity). Metabolic heat production, dry heat gain, total heat gain (metabolic heat production + dry heat gain), evaporative heat loss, body heat storage (summation of heat gain/loss), rectal and mean skin temperatures as well as heart rate were measured continuously.
No between-group differences were observed for metabolic heat production (T2D vs. Control; 53 ± 5 vs. 55 ± 7 W/m2), dry heat gain (48 ± 9 vs. 47 ± 11 W/m2), total heat gain (101 ± 10 vs. 102 ± 14 W/m2) and evaporative heat loss (83 ± 10 vs. 85 ± 12 W/m2) over the 3 h (all P > 0.05). Consequently, the changes in body heat storage (380 ± 93 vs. 358 ± 172 kJ, P = 0.67) were similar between groups. Moreover, no between-group differences in rectal and mean skin temperatures or heart rate were measured. We conclude that unacclimatized, physically active, older adults with well-controlled T2D do not experience greater hyperthermia and cardiovascular strain compared to their healthy counterparts while resting in extreme heat for a brief, 3-h period.
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