Background: Sleep disorders are highly prevalent among patients with Parkinson's disease (PD). Chronic medication with L-dopa may be one of the factors that contributes to poor sleep quality. The aim of this study was to assess the effects of long term use of L-dopa on objective and subjective measures of sleep quality in PD patients.
Methods: Twenty-seven PD patients (mean age 62.5 ± 8.6 years, mean disease duration 7.3 ± 5.9 years, 11 females) underwent nocturnal polysomnography. Their sleep was rated subjectively using the Parkinson's disease sleep scale (PDSS), and their disease severity was assessed using the unified Parkinson's disease severity scale (UPDRS) standard questionnaire. Doses of L-dopa and other medications were correlated with parameters of sleep quality. The polysomnographic recordings were compared with those from 24 age- and gender-matched normal controls.
Results: The patients showed decreased total sleep time (TST) and sleep efficiency (SE), prolonged sleep onset and REM sleep latency and wake after sleep onset (WASO). Parts I-III of the UPDRS scores correlated with TST, SE and WASO but not with PDSS scores. L-dopa dosage and part IV of the UPDRS correlated with PDSS scores but not with polysomnographic parameters.
Conclusions: Higher doses of chronically administered L-dopa correlated with lower sleep quality according to the subjective measures but not according to the polysomnographic parameters, which were related to the severity of PD symptoms. The low sleep quality according to the subjective measurements may result from complications of therapy at high doses of L-dopa.