Association of daytime napping and Parkinsonian signs in Alzheimer's disease

BACKGROUND AND PURPOSE: Excessive daytime sleepiness (EDS) is reported in Alzheimer's disease (AD), with unstable sleep-wake rhythms that worsen with advancing disease stage. EDS is also very common in Parkinson's disease (PD), regardless of disease severity. The purpose of this study was to determine whether more Parkinsonian motor signs exist in AD patients with more reported daytime napping compared to AD patients without daytime napping. PATIENTS AND METHODS: AD patients ((National Institute of Neurological and Communicative Diseases and Stroke/Alzheimer's Disease and Related Disorders Association) NINCDS/ADRDA criteria) were prospectively evaluated in a dementia clinic. Parkinsonian motor signs were assessed using a modified motor Unified Parkinson's Disease Rating Scale (mmUPDRS). AD patients were grouped according to daytime napping frequency: (1) minimal napping (AD-Naps), or (2) napping at least once a day (AD+Naps). Wilcoxon rank-sum tests and chi2-tests computed differences between groups for mmUPDRS, nighttime sleep disturbances, and the Mini Mental State Examination (MMSE). Statistical significance was set at P<0.05. RESULTS: AD patients were classified as AD-Naps (n=155) or AD+Naps (n=180). Compared with AD-Naps patients, AD+Naps patients had higher total mmUPDRS scores (P<0.001), higher rigidity scores (P<0.005), and more gait impairment (P<0.001). CONCLUSION: AD patients with more reported daytime napping had more Parkinsonian motor signs, suggesting that this subgroup may have an increased propensity for sleepiness resembling PD. Longitudinal studies with objective measures are needed to determine whether causal relationships exist between sleepiness and Parkinsonism in AD.