Circadian and sleep disturbances are common behavioural and psychological symptoms of dementia; circadian rhythm-related molecules may be altered in dementia patients. This study investigated the expression of the period 1 clock gene product (PER1), which is involved in circadian rhythms, and inducible nitric oxide synthase (iNOS), thought to generate nitric oxide, important in rapid eye movement (REM) sleep regulation. Specifically, we investigated the difference in expression of these two genes between patients with cognitive impairment and controls. We studied iNOS and PER1 mRNA expression using real-time polymerase chain reaction in peripheral leukocytes during REM sleep, non-REM sleep and wake stages in patients with Alzheimer's disease (AD, n = 5), patients with mild cognitive impairment (MCI, n = 8) and controls (n = 9) during polysomnography examination. Expression of iNOS significantly increased during REM sleep in AD patients compared to MCI patients and controls. There were no significant differences in PER1 expression between the three groups, but an increase in PER1 expression during the wake stage was observed for all participants. Increased expression of iNOS during REM sleep of patients with AD might be a compensation mechanism for maintaining REM sleep. However, the precise role of nocturnal expression of iNOS in patients with AD requires further investigation.
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