Chronic diseases and multimorbidity patterns, their recent onset, and risk of new-onset Parkinson's disease and related functional degeneration in older adults: a prospective cohort study

Background Certain chronic diseases contribute to increased risks of Parkinson's disease (PD), but the association between time-varying multimorbidity patterns and new-onset PD remains underexplored. Methods Data were from the Survey of Health, Ageing and Retirement in Europe (SHARE) waves 5-8 conducted between January 2013 and March 2020. Eleven chronic diseases were included, with >= 2 denoting multimorbidity. Three multimorbidity patterns were further defined: somatic multimorbidity (SMM), neuropsychiatric multi -morbidity (NPM), and cardiometabolic multimorbidity (CMM). PD-related function degeneration included functional limitations, mobility limitations, depressive symptoms, and cognitive decline. Time-dependent analyses, competing -risk analyses, and mixed-effect models were utilised.Findings In this prospective cohort study, 557 developed new-onset PD during follow-ups among 64,273 participants included at baseline, as defined by participants' self-reported physician diagnoses. Participants with (vs. without) multimorbidity, SMM, NPM, and CMM were at 1.40-2.70 times higher PD risk after considering the competing role of all-cause death, which remained significant in all sensitivity analyses and were more pronounced in lower -income participants (P for interaction <0.05). Similarly, they tended to develop functional degeneration faster than those without these multimorbidity patterns (P < 0.05). Participants with recent-onset (newly diagnosed in 2015) multimorbidity patterns were at 1.45-3.72 times higher risk of PD than those never diagnosed. Interestingly, they were at comparable or even higher (though P values for >0.05) PD risk compared to participants with multimorbidity patterns diagnosed in 2013 or before. Furthermore, recent-onset (vs. prior diagnosed) NPM exhibited faster functional deterioration and cognitive decline (P for difference <0.05).Interpretation Our findings suggest that promoting early prevention of multimorbidity, especially recent-onset multimorbidity and NPM, could prevent some subsequent cases of PD and related functional degeneration among older adults. However, further studies are needed to confirm this association.