Longitudinal course of mild parkinsonian signs in elderly people: A population-based study in Japan.

We aimed to clarify the longitudinal course of mild parkinsonian signs (MPS) and their association with dementia and functional disability by conducting a comprehensive epidemiological study, including brain MRI, and assessments of cognition, depression, and sleep, in people aged ≥65years living in Ama-cho. We diagnosed MPS and parkinsonism (PS) using a modified Unified Parkinson's Disease Rating Scale. The phase I study was conducted between 2008 and 2010 (n=729) and the phase II between 2011 and 2013 (n=436). By phase II, 8.5% of the phase I participants without PS had developed PS. In addition to older age, a lower Mini-Mental State Examination (MMSE) score, and lower body mass index, the MPS rigidity subtype was a significant independent predictor of PS onset. By phase II, 10.1% of the participants without dementia or PS at phase I had developed dementia. Older age, lower MMSE score, and the axial dysfunction and tremor MPS subtypes were significant independent predictors of dementia development. By phase II, 38.8% of participants with MPS at phase I showed no motor symptoms. Younger age and adequate sleep were significant predictors for this reversion. Periventricular and deep white matter hyperintensity Fazekas scores increased with the evolution of parkinsonian signs. MPS is therefore critically, although sometimes reversibly, associated with PS and dementia development in elderly people.