Biological aging and sex differences in cholinergic sweating: from young adults to the elderly in their 80s and...

Aging from young to middle-aged and older adulthood modulates sweating differently across body regions, yet how biological aging from young adulthood to the 80s and beyond affects cholinergic sweating remains unclear. A total of 248 participants (143 males and 105 females) were grouped as young (≥18 + 20s), middle-aged (30s + 40s + 50s), older (60s + 70s) adults, and elderly (80s + 90s). Acetylcholine-induced sweat rate, activated sweat gland density, and sweat gland output were assessed via transdermal iontophoresis. Forearm sweat rate declined in the 30s + 40s + 50s and older in males and the 60s + 70s and older in females, compared with the ≥18 + 20s group (all P ≤ 0.006). Thigh sweat rate also declined with aging and was further reduced in the 60s + 70s and 80s + 90s compared with the 30s + 40s + 50s group in males (both P ≤ 0.035). Sweat rate did not differ between the 60s + 70s and 80s + 90s groups in either region or sex (all P ≥ 0.677). Sex differences in forearm sweat rate persisted across all age groups (all P ≤ 0.012) but diminished on the thigh in the 60s + 70s and 80s + 90s groups (both P ≥ 0.183). These changes were attributed to reductions in sweat gland output in males and combined reductions in sweat gland density and output in females. Collectively, forearm cholinergic sweating declines from the 30s + 40s + 50s to the 60s + 70s relative to young adults but shows minimal further attenuation beyond the 70s in both sexes. Thigh cholinergic sweating function is more affected by biological aging in males. We also highlight the characteristics of sweating in two participants in their 90s, providing insights into sweating function at the end of the lifespan.NEW & NOTEWORTHY The effects of biological aging and sex on cholinergic sweating across the lifespan, especially beyond 80, remain poorly understood. We demonstrate that forearm cholinergic sweating declines from the 30s to 70s compared with young adults, with minimal further attenuation beyond the 70s in both sexes. In contrast, thigh sweating is more strongly impacted by aging in males. Data from 90-yr-old participants provide valuable insights into sweating function near the end of their lifespan.