Background: Non-motor symptoms are common in Parkinson's disease (PD) and some, including hyposmia, constipation, and REM sleep behavior disorder, often precede the clinical diagnosis.
Objective: To assess the relation between combinations of non-motor features and presence of PD among women.
Methods: A nested case-control study was conducted among women in the Nurses' Health Study. Women were eligible if they responded to screening questions for constipation and probable REM sleep behavior disorder (pRBD) on a 2012 questionnaire and were under age 85 on January 1, 2012. 87 women with confirmed PD and 14,170 women without PD agreed to participate and completed in 2015 the Brief Smell Identification Test to assess hyposmia, as well as a questionnaire to assess parkinsonism and other non-motor PD features, including depressive symptoms, excessive daytime sleepiness, impaired color vision, and body pain.
Results: In age-adjusted logistic models, each non-motor feature was significantly associated with PD, and the odds of PD increased exponentially with the number of features. Women with constipation, pRBD, and hyposmia had an age-adjusted OR for PD of 211 (95% CI 84.2-529) compared to women with none of these features. The odds of having PD rose further with the presence of additional non-motor signs. Comparing women with at least 6 of the 7 features assessed in this study to women with one or none, the age-adjusted OR for PD was 356 (95% CI 113-1126).
Conclusion: Results suggest that these non-motor features could be useful in discriminating PD patients from controls in women, and since they often appear during the prodromal period of PD, their combinations may prove useful for identifying populations at high risk of developing PD.
Keywords: Parkinson’s disease; REM sleep behavior disorder; hyposmia.