LAUSR

Background and Objectives There is increasing interest in characterizing the earliest phases of Parkinson disease (PD). However, few studies have investigated prediagnostic trajectories of cognition and function. Our objective was to describe prediagnostic cognitive and functional trajectories in PD in older women and men. Methods We studied 9,595 women and 5,795 men from 2 prospective cohort studies of community-dwelling elders followed up to 20 years. In individuals without prevalent PD, we estimated the associations of incident PD diagnosis with rates of change in cognition and function before and after diagnosis compared with healthy older adults using multivariate mixed-effects models. Results Over follow-up, 297 individuals developed incident PD. Interactions between the terms in our model and sex were statistically significant for the 3 outcomes (p < 0.001 for all), so we stratified results by sex. Compared with older men without PD, men who developed PD exhibited faster decline in global cognition (0.04 SD more annual change, p < 0.001), executive function (0.05 SD more annual change, p < 0.001), and functional status (0.06 SD more annual change, p < 0.001) in the prediagnostic period. Women who developed PD compared with women without PD displayed faster decline in executive function (0.02 SD more annual change, p = 0.006) and functional status in the prediagnostic period (0.07 SD more annual change, p < 0.001). Discussion Individuals with incident PD exhibit cognitive and functional decline during the prediagnostic phase that exceeds rates associated with normal aging. Better understanding heterogeneity in prodromal PD is essential to enable earlier diagnosis and identify impactful nonmotor symptoms in all subgroups.