Age-related thermoregulatory differences during core cooling in humans

Steven M. Frank, Srinivasa N. Raja, Christian Bulcao, David S. Goldstein

Research output: Contribution to journalArticlepeer-review

Abstract

The current study assessed sympathetic neuronal and vasomotor responses, total body oxygen consumption, and sensory thermal perception to identify thermoregulatory differences in younger and older human subjects during core cooling. Cold fluid (40 ml/kg, 4°C) was given intravenously over 30 min to decrease core temperature (Tc) in eight younger (age 18-23) and eight older (age 55-71) individuals. Compared with younger subjects, the older subjects had significantly lower Tc thresholds for vasoconstriction (35.5 ± 0.3 vs. 36.2 ± 0.2°C, P = 0.03), heat production (35.2 ± 0.4 vs. 35.9 ± 0.1°C, P = 0.04), and plasma norepinephrine (NE) responses (35.0 vs. 36.0°C, P < 0.05). Despite a lower Tc nadir during cooling, the maximum intensities of the vaso-constriction (P = 0.03) and heat production (P = 0.006) responses were less in the older compared with the younger subjects, whereas subjective thermal comfort scores were similar. Plasma NE concentrations increased fourfold in the younger but only twofold in the older subjects at maximal Tc cooling. The vasomotor response for a given change in plasma NE concentration was decreased in the older group (P = 0.01). In summary, aging is associated with 1) a decreased Tc threshold and maximum response intensity for vasoconstriction, total body oxygen consumption, and NE release, 2) decreased vasomotor responsiveness to NE, and 3) decreased subjective sensory thermal perception.

Original languageEnglish (US)
Pages (from-to)R349-R354
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume279
Issue number1 48-1
DOIs
StatePublished - 2000

Keywords

  • Epinephrine
  • Heat production
  • Norepinephrine regulation
  • Temperature vasoconstriction

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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