Objective: To investigate baseline risk factors of insomnia symptoms after five years of follow-up, on average, in a population-based study of Parkinson’s disease (PD).

Background: Sleep problems are important and common non-motor symptoms of PD¹; insomnia is one of those and is also common in the elderly in general. Insomnia is characterized by difficulty in initiating and/or maintaining and poor quality of sleep and is strongly associated with quality of life and mortality in PD². It is significant to the quality of care in PD to study early-disease risk factors for insomnia symptoms in later phases.

Methods: This is a population-based cohort of incident PD cases assessed at three time points from 2001 to 2009 by trained interviewers and neurologists. There are only 8 population-based studies of incident PD and sleep; this is the only in the U.S and the only to have used the Medical Outcomes Sleep Scale (MOS-SS) in PD. We describe the distribution and estimate associations of baseline demographic and clinical features, per insomnia symptoms severity at last assessment, measured by the continuous score (0-100) of the Sleep Disturbance sub-scale. Bi and multivariable linear regression models were used, according to causal models proposed to explain relations of variables, instead of use of pure statistical criteria.

Results: At baseline, 360 patients were included, mean(SD) age and PD duration were: 70.4(10.2) and 2.1(1.5), 206(57.2%) were men and 321(89.2%) were using levodopa or dopamine agonist. At last follow-up, 186 completed the MOS-SS, mean(SD) disease duration and insomnia score were 7.5(2.6) and 28.4(22.4). On bivariable regressions, baseline factors significantly associated with future worse insomnia, with respective mean differences 95% CI were: lifetime average of sleep hours (-1.02,-0.39), depression score (0.14,0.32), UPDRS (0.03,0.10) and PD duration (0.0,0.46). On a multivariable model, worse baseline depression, UPDRS and longer PD duration were all significant predictors of worse insomnia symptoms later in the disease.

Conclusions: Depression and worse motor symptoms early in PD were important predictors of worse sleep after an average of 5.5 years of follow-up and could be target on interventions to improve quality of life in PD.  Alternative regression models and loss to follow-up should be considered and explored in future analyses.

References: 1-Pfeiffer RF. Non-motor symptoms in Parkinson’s disease. Park Relat Disord. 2016;22:S119-S122. doi:10.1016/j.parkreldis.2015.09.004.

2-Wu Y, Guo XY, Wei QQ, et al. Determinants of the quality of life in Parkinson’s disease: Results of a cohort study from Southwest China. J Neurol Sci. 2014;340(1-2):144-149. doi:10.1016/j.jns.2014.03.014.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/baseline-risk-factors-of-insomnia-symptoms-after-five-years-of-follow-up-a-population-based-cohort-of-incident-parkinsons-disease/