Comparisons of blood and urinary responses to cold exposures in young and older men and women.

Minimally dressed men and women between 20 and 72 years old rested for 2 hr in 28, 20, 15, and 10 degrees C room temperatures (Ta). Older women maintained core temperatures during all exposures, partially due to rapid increases in metabolism. Regardless of Ta, blood glucose levels were higher in older than younger women during the first hour of the exposures (p less than .05). Free fatty acid levels in older women were double those of others (p less than .001). Epinephrine levels were 25% higher in men than women (p less than .05). Cortisol levels were 30% higher in younger than older adults, regardless of sex (p less than .01). All measurements, and norepinephrine, were elevated in all groups during the 10 degrees C exposure. Rapid increases in metabolism in older women during cold exposure may have been facilitated by substrate availability. This advantage may have resulted from greater utilization of cortisol and epinephrine, increased catecholamine sensitivity, or hormonal changes consequent to menopause.