Epidemiological studies have identified thermotaxic decline in the elderly, with lower temperatures than the general population by 0.36-0.54°F. Researchers consider the lower temperatures to be due to a diminished thermoregulatory discrimination sensitivity to environmental temperature oscillations. Every 1.8°F reduction in temperature from 98.6° Fahrenheit is known to effect a decrease in laminar cerebral blood flow (CBF) by approximately 6%-7%. This reduction in CBF, however, is not without significant central nervous system effects. Correlations between CBF and performance on tests of language, memory, attention, figure copying, judgment, and similarity discrimination have been described.
We have recently attempted to identify thermoregulatory changes occurring in a cognitively impaired population. We examined 39 subjects randomly selected from a clinical database (Statistical Analysis System) based upon NINCDS criteria for Alzheimer's dementia, probable and possible subtypes. Exclusion criteria included indications of abnormal endocrine or immune indices, histories of head trauma, cerebrovascular accidents, substance abuse, or current use of medications known to affect thermoregulation.