A large Chinese cohort study suggests that sleep patterns, especially short sleep and poor sleep quality, may help identify people at higher risk of Parkinson’s disease before clinical diagnosis.
Study: Sleep and Parkinson’s disease: a population-based study from the CHARLS cohort. Image Credit: Lightspring / Shutterstock
In a recent study published as an Article in Press in the journal npj Parkinson’s Disease, researchers investigated the association between sleep and the risk of Parkinson’s disease (PD).
PD is the second-most prevalent neurodegenerative disease after Alzheimer’s disease (AD) and predominantly affects older adults. Besides motor symptoms, patients with PD often experience non-motor symptoms, including sleep disorders that affect up to 75% of patients. The severity and prevalence of sleep disorders increase with age. Nevertheless, research on the multidimensional impact of sleep disorders in PD patients remains limited.
About the Study
In the present study, researchers examined the association between sleep and the risk of PD. The 2020 dataset of the China Health and Retirement Longitudinal Study (CHARLS) was used for a cross-sectional analysis, excluding individuals with missing information on PD, demographics, agricultural work, or sleep. In a cohort analysis, CHARLS participants from the 2011, 2013, 2015, and 2020 cycles were included.
The cohort analysis excluded individuals with memory-related diseases at baseline, including PD, and those without data on sleep, agricultural work, demographics, and these diseases. Sleep indicators, including sleep duration, self-reported sleep quality, and nap duration, were assessed using the Health Status (III) module of the CHARLS. Information on sociodemographic and health-related covariates was also collected.
Covariates included age, sex, marital status, residence, smoking status, alcohol intake, nap duration, and engagement in agricultural work. Educational attainment was excluded from the 2020 adjusted analysis due to high missingness, although education was reported in the cohort baseline table. Group comparisons were performed using the chi-square test. The association of sleep duration and sleep quality with PD was assessed using logistic regression models. Furthermore, a least absolute shrinkage and selection operator (LASSO) regression was performed to identify the sleep indicators most strongly associated with PD.
A restricted cubic spline (RCS) analysis was conducted to evaluate the nature of the association. Subgroup analyses were performed by age, sex, marital status, residence, alcohol intake habits, and farming activity. Further, PD incidence rates were calculated, and group differences in these rates were assessed. Finally, the predictive performance of sleep indicators for PD was determined using logistic regression models for sleep quality, sleep duration, and both.
Findings
The cross-sectional analysis included 16,403 CHARLS participants. Most participants were females (53.1%), cohabitants (76.9%), non-smokers (61.2%), and non-drinkers (63.4%). Overall, 275 individuals were classified as having PD based on CHARLS questionnaire-derived information, of which only 1.8% reported sleeping more than nine hours, while 54.2% slept four to seven hours. Further, 40.7% of participants classified as having PD reported poor sleep rarely or none of the time, whereas 24.4% reported poor sleep most of the time.
Among non-PD subjects, most individuals slept four to seven hours (59.3%), and only 3.5% slept longer than nine hours. Logistic regression analysis showed that PD risk had a lower, non-significant point estimate in individuals with over nine hours of sleep compared to those with seven to nine hours of sleep (reference). PD risk was comparable between those with four to seven hours of sleep and the reference group, but significantly higher in those with ≤ four hours of sleep.
Among the sleep measures assessed, sleep duration and sleep quality were most strongly associated with PD. Age and sex also emerged as relevant exposure factors in the model. RCS analysis showed a significant linear relationship between sleep duration and PD risk in people aged ≤ 60 years, but a non-linear relationship in those aged over 60 years. The cohort analysis included 8,624 participants, grouped into four categories (Q1–Q4) based on sleep quality and duration. Most of these participants (89.3%) were aged 60 years or older.
The Q1 group included participants with sleep duration ≤ the mean but without self-reported sleep problems; Q2 included individuals with sleep duration greater than the mean but without self-reported sleep problems; Q3 included subjects with sleep duration ≤ the mean and self-reported sleep problems; and Q4 included those with sleep duration greater than the mean and self-reported sleep problems. In this cohort, 97 PD cases were recorded at an incidence rate of 1.12%.
The lowest PD incidence was observed in the Q1 group, and the highest in the Q3 group. A significant difference in PD incidence was observed only between groups Q1 and Q3. Among participants with sleep disorders, PD incidence was higher in those aged ≤ 60 years than in those aged over 60 years, while sex-specific patterns varied by sleep status and duration. The sleep duration model achieved an area under the receiver operating characteristic curve (AUROC) of 0.59 for predicting PD, whereas the sleep quality model had an AUROC of 0.62. Incorporating both sleep quality and duration into a single model increased the AUROC to 0.64, although overall predictive performance remained modest. The combined model was significantly better than sleep duration alone, but not sleep quality alone.
Conclusions
In sum, both sleep duration and sleep quality showed significant associations with PD risk. Sleep duration was negatively associated with PD risk, with longer sleep being associated with a lower PD risk in people aged ≤ 60 years. In contrast, a U-shaped relationship was observed between sleep duration and PD risk in those aged 60 years or older, with the highest risk at 5.2 hours of sleep. However, the findings were observational and cannot establish causality. PD status was inferred from questionnaire items rather than confirmed clinical records, sleep measures were self-reported, and the Chinese middle-aged and older adult cohort may limit generalizability. Overall, sleep assessment and management could be a promising target for strategies aimed at early risk stratification and preventive sleep health management in PD.
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