Sleep disturbances in drug naive Parkinson's disease (PD) patients and effect of levodopa on sleep

Context: Parkinson's disease (PD) is associated with sleep disturbances, attributed to the neurodegenerative process and therapeutic drugs. Studies have found levodopa to increase wakefulness in some patients while increasing sleepiness in others. Aims: To confirm sleep disturbances in drug naive PD patients and understand the impact of levodopa on their sleep. Materials and Methods: Twenty-three drug naive PD patients and 31 age-gender matched controls were compared using the Parkinson's Disease Sleep Scale (PDSS) and Epworth Sleepiness Scale (ESS). A polysomnogram objectively compared sleep quality. Of the 23 patients, the 12 initiated on levodopa were reassessed subjectively and through polysomnography after 2 months of therapy. Statistical Analysis: Data was expressed as mean +/- standard deviation, median, and range. Continuous variables were analyzed by Student's T test for normally distributed data and Mann-Whitney U test for skewed data. Discrete variables were compared by Chi Square tests (Pearson Chi square Test or Fisher's Exact Test). Wilcoxon signed ranks test was applied in the analysis of paired data pre-and post-levodopa. A P value < 0.05 was considered as statistically significant. Statistical analysis of the data was done using the Statistical Package for the Social Sciences (SPSS) version 12. Results: Drug naive PD patients had lower PDSS scores than controls. The sleep architecture changes observed on polysomnogram were reduced NREM Stage III and REM sleep and increased sleep latency and wake after sleep onset time. Following levodopa, improved sleep efficiency with reduced sleep latency and wake after sleep onset time was noted, coupled with improved PDSS scores. However, NREM Stage III and REM sleep duration did not increase. Discussion: PD patients take longer to fall asleep and have difficulty in sleep maintenance. Sleep maintenance is affected by nocturia, REM behavioral disorder, nocturnal cramps, akinesia, and tremors, as observed in PDSS scores. Levodopa improves sleep efficiency by improving motor scores without altering sleep architecture. Conclusions: Poor sleep quality and sleep architecture changes occur secondary to the neurodegenerative process in PD patients. Though levodopa improves sleep quality by reducing rigidity and tremor, it does not reverse sleep architecture changes.