Perceptual and Cutaneous Vasomotor Reactivity to Sudden Changes in Ambient Temperature in Older Adults

Abstract

BackgroundChanges in thermal perception often precede measureable changes in skin temperature when entering a hot or cool environment. This is believed to be due to small changes in peripheral thermoreceptor outflow, which are summed in the central nervous system causing changes in thermal perception and changes in cutaneous vasomotor tone. This is termed thermal spatial summation. Thermal perception and cutaneous vasomotor control are often impaired in older adults. However, the effect of aging on thermal spatial summation is unknown. Thus, we tested the hypothesis that thermal spatial summation is attenuated in older adults.MethodsTwelve young (24 ± 3 y, 5 females) and nine older (66 ± 4 y, 6 females) adults passively moved between a hot (40°C, 20% RH) and cool (17°C, 49% RH) room when they felt ‘too cool’ or ‘too warm’ over a 90 min period. Weighted mean skin (6 site) and intestinal temperatures, forearm skin blood flow (laser Doppler), mean arterial pressure (photoplethysmography, MAP), and thermal sensation (7‐point scale: 1=cold, 4=neutral, 7=hot) and discomfort (4‐point scale: 1=comfortable, 4=very uncomfortable) were measured immediately prior to moving and immediately after entering the new environment (25 s later). Skin blood flow was normalized to MAP and are presented as cutaneous vascular conductance (CVC), providing an of index cutaneous vasomotor tone. Data upon leaving the hot room and entering the cool room (H‐C) and vice versa (C‐H) are presented as the change from the prior environment, providing an index of thermal spatial summation. Data were averaged across 4 ± 2 movements from H‐C and from C‐H.ResultsChanges in intestinal temperature at H‐C (Young: 0.0 ± 0.1, Older: 0.0 ± 0.0°C, P=0.31) and C‐H (Young: 0.0 ± 0.1, Older: 0.0 ± 0.1°C, P=0.46) did not differ between young and older adults. Changes in mean skin temperature at H‐C (Young: 0.0 ± 0.1, Older: 0.0 ± 0.1°C, P=0.51) and C‐H (Young: 0.0 ± 0.1, Older: 0.0 ± 1.0°C, P=0.80) also did not differ between groups. At H‐C, decreases in warmth sensation did not differ between groups (Young: −1.6 ± 1.3, Older: −2.1 ± 1.0 a.u., P=0.36). However, older adults demonstrated greater increases in warmth sensation at C‐H (Young: +1.2 ± 0.8, Older: +2.4 ± 1.1 a.u., P=0.01). Improvements in thermal discomfort at H‐C (Young: −0.7 ± 0.5, Older: −1.2 ± 0.6 a.u., P=0.10) and C‐H (Young: −0.8 ± 0.3, Older: −0.6 ± 0.2 a.u., P=0.01) did not differ between groups. Changes in MAP at H‐C (Young: 8 ± 4, Older: 11 ± 5 mmHg, P=0.20) and C‐H (Young: −6 ± 4, Older: −11 ± 13 mmHg, P=0.18) were not different between groups. Changes in CVC at H‐C were attenuated in older adults (Young: −0.24 ± 0.12, Older: −0.13 ± 0.04, P=0.02), but did not differ between groups at C‐H (Young: +0.10 ± 0.07, Older: +0.11 ± 0.10, P=0.88).ConclusionsThermal spatial summation is apparent in older adults. Upon entering a cool environment, the cutaneous vasomotor response is attenuated in older adults. However, the perceptual response upon entering a hot environment is augmented in this population. These findings suggest the effect of aging on thermal spatial summation is dependent on the population of thermoreceptors activated.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.