Background and purpose: While excessive daytime sleepiness can predate Parkinson's disease in late-life, its association with parkinsonian-like (P-L) symptoms in middle age are unknown. Since neurodegeneration can appear decades before a diagnosis of Parkinson's disease, identifying clinical features associated with this early progression is important. The purpose of this study was to determine the association of daytime sleepiness with P-L symptoms in a population-based sample of middle-aged Korean adults.
Methods: During 2013 and 2014, daytime sleepiness and P-L symptoms were assessed in 2,063 males and females aged 50-64 years who were participating in the Korean Genome and Epidemiology Study. The severity of daytime sleepiness was quantified by the score on the Epworth Sleepiness Scale (ESS). Self-reported P-L symptoms included nine motor disorders commonly associated with Parkinson's disease. Participants with parkinsonism and related conditions are excluded.
Results: The prevalence of excessive daytime sleepiness (ESS score >10) was 7.0%. The frequencies of P-L symptoms ranged from 0.5% (for "trouble buttoning buttons") to 18.4% (for "handwriting smaller than it once was"). After adjustment for covariates and multiple testing, the relative odds of P-L symptoms comparing the 80th and 20th percentiles of ESS scores was 1.6 (p=0.001) for "voice is softer than it once was," 2.1 (p<0.001) for "balance when walking is poor," and 1.5 (p=0.002) for "loss of facial expression." The prevalence of excessive daytime sleepiness increased from 6.3% to 19.8% when the number of symptoms increased from zero to three (p=0.004).
Conclusions: In Korean adults aged 50-64 years, daytime sleepiness is significantly associated with P-L symptoms. Whether coexisting daytime sleepiness and P-L symptoms predate extrapyramidal and other impairments in later life warrants further investigation.
Keywords: Parkinson disease; daytime sleepiness; parkinsonism; sleep disorders.
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