Circadian temperature variation in healthy aged and in Alzheimer's disease.

Circadian temperature variation was monitored in healthy older adults and in health-, age-, and sex-matched Alzheimer's dementia patients. Oral and rectal temperatures were analyzed for mean level, amplitude, and phase using cosinor analyses. Mean 24-hour temperature level was not altered by dementia. A significant sex effect, however, was observed among dementia patients with women exceeding men in mean 24-hour temperatures and across daytime time periods. Cosinor-derived phase and amplitude measures were unaffected by dementia or by sex. This indicates that the primary neuronal degeneration characteristic of Alzheimer's disease in its early stages does not disable the neural pathway(s) controlling circadian temperature regulation. Some impairment in temperature homeostatic regulation may be present, however, because a greater intrasubject temperature variability was observed in Alzheimer men than in control men.