THERMOREGULATORY RESPONSES OF OLD MEN TO GRADUAL CHANGES IN AMBIENT-TEMPERATURE

1. Thermoregulatory responses to gradual rise and fall in the ambient temperature (T-a) were compared between 8 old (68-78 years) and 8 youn ger (20-25 years) male subjects. 2. Starting at T-a of 31.5 degrees C (r.h. 40%), T-a was raised to 39.5 degrees C, then lowered to 21.5 deg rees C, and raised back to 31.5 degrees C at a constant rate of 0.3 de grees C/min. 3. Noticeable differences in responses between the age gr oups were as follows: decline of sweating rate and reduction of acral blood flow during room cooling were retarded in the aged group, with w ider variations among individuals, compared with those in the younger group; the tympanic and oesophageal temperatures fell considerably dur ing cooling in the elderly group, failing to return to the level at st art during the rewarming of the room, in contrast to the younger group . 4. Such sluggish responses may be attributed largely to reduced cuta neous thermal perception with advancing age.