Age differences in autonomic variables during sleep.

Relationships of autonomic variables and sleep were assessed in men and women at two age levels (18 to 23 and 57 to 71 years) to check for alleged associations between physiological arousal and age-related sleep disturbance. Heart rate, although relatively high at the upper age level, was unrelated to sleep measures. For the most part, underarousal rather than hyperarousal characterized older sleepers. Women's body temperature declined significantly with age. Vasoconstrictions, which were more frequent in young adults, showed some association with better sleep. The earlier the overnight temperature nadir, the more wakefulness after sleep onset. Together with other studies, this suggests that an age-related phase advance in the temperature rhythm disrupts sleep. These results are at odds with the view that sympathetic hyperactivity associated with elevated plasma norepinephrine causes age-related sleep disturbance.