Passive temperature lability in the elderly

Abstract

Thermoregulatory responses of nine healthy elderly [seven men and two women; mean age (SD) 73.9 (4.8) years] were compared to those of nine young adult men [26.6 (5.2) years]. They exercised on a cycle ergometer for 20 min at an intensity inducing a heart rate equivalent to 65% of their predicted maximum, and were thereafter immersed in 28 degrees C water. The exercise was conducted to elevate tympanic temperature (Tty) and initiate a steady rate of sweating. The post-exercise immersion period induced gradual cooling of Tty, and changes in Tty relative to resting levels (delta Tty) at which sweating abated and shivering commenced were defined as the delta Tty thresholds for the cessation of sweating (Tsw) and onset of shivering (Tsh), respectively. In addition to Tty, oxygen uptake (VO2; l.min-1), sweating rate (g.m-2.min-1), and forehead skin blood perfusion were also measured during the trials. The mean (SD) Tsw occurred at a significantly (P < 0.005) higher delta Tty [0.48 (0.18) degrees C] in the elderly than in the young adults [0.21 (0.06) degrees C], while the Tsh occurred at significantly (P < 0.005) lower delta Tty in the elderly [-0.64 (0.34) degrees C] than in young adults [-0.22 (0.10) degrees C]. Decreases in delta Tty below the shivering threshold were met with a significantly (P < 0.01) reduced VO2. The range of temperature lability between Tsw and Tsh, defined as the null-zone, was significantly greater in the elderly [1.12 (0.39) degrees C] than in the young adults [0.43 (0.12) degrees C], and the slope of the vasoconstrictor response in the null-zone was significantly (P < 0.001) lower in the elderly subjects. The present study demonstrates a greater passive core temperature lability in older individuals, since the effector responses of sweating and shivering were initiated at higher and lower levels of Tty, respectively. The magnitudes of the effector responses beyond the thresholds were also significantly reduced, suggesting that the elderly may be more susceptible to hypo-/hyperthermia during periods of endogenous and/or exogenous thermal stress.

Sex differences in age-related changes on peripheral warm and cold innocuous thermal sensitivity

“…Age-dependent neural degeneration observed in thermoreceptors can reduce both physiological and perceptual thermal sensitivity. Impaired cutaneous vascular function and delays in the sweating and shivering thresholds have been reported in age comparison studies [2,3,4,5,6]. Likewise, reduced thermal sensations in older adults have been reported, alongside a number of other tactile responses (touch, pressure and noxious thermal sensitivity) [7,8,9,10,11].…”

National Athletic Trainers' Association Position Statement: Exertional Heat Illnesses

“…51,158,169 The evaporation of sweat from the skin depends on the water saturation of the air and the velocity of the moving air. [170][171][172] The effectiveness of this evaporation for heat loss from the body diminishes rapidly when the relative humidity is greater than 60%. 9,20,164 Cognitive performance and associated CNS functions deteriorate when brain temperature rises.…”

Perspectives on Environmental Adaptability and Physiological Polymorphism in Thermoregulation

“…Much research has been carried out on the effects of age, physical fitness, and body composition on thermoregulatory response. Compared with young people, the range of the environmental temperature at which elderly people can maintain their core body temperature is narrow, and their thermoregulation capability is inferior (Anderson et al, 1996;Inoue et al, 1992Inoue et al, , 1998Sagawa et al, 1988). Physical training improves thermoregulation capability in hot and cold environments (Andersen, 1966;Bittel et al, 1988;Ho et al, 1997;Maeda et al, 2002Maeda et al, , 2004Maeda et al, , 2005Moriya and Nakagawa, 1990;Yoshida et al, 1998).…”