CIRCADIAN LOCOMOTOR-ACTIVITY AND CORE-BODY TEMPERATURE RHYTHMS IN ALZHEIMERS-DISEASE

Sleep-wake cycle disturbances suggest that circadian rhythms may be di srupted in patients with Alzheimer's disease (AD). In this study, we e xamined the circadian rhythms of core-body temperature and locomotor a ctivity in 28 patients with probable AD and 10 healthy controls. AD pa tients had higher percent nocturnal activity than controls, correspond ing to the clinical picture of fragmented sleep. The amplitude of the activity cycle in the AD patients was lower than that of controls and the acrophase of this cycle in AD patients was 4.5 h later. There was no difference in the amplitude of the core-body temperature circadian rhythm, but AD patients had delayed temperature acrophases. A subgroup of AD patients with large mean time differences between the acrophase s of their activity and temperature cycles had lower temperature ampli tudes and greater activity during the night. These findings suggest th at a subgroup of AD patients with impaired endogenous pacemaker functi on may have a diminished capacity to synchronize the rhythm of core-bo dy temperature with the circadian cycle of rest-activity. This circadi an rhythm dysfunction may partly explain the fragmented nocturnal slee p exhibited by these patients.