Association of White Matter Hyperintensities With Pathology and Progression of Parkinsonism in Aging

IMPORTANCE Progressive parkinsonism is common in older adults without a diagnosis of Parkinson disease and is associated with adverse health outcomes, but its pathologic basis is controversial. OBJECTIVE To examine if the burden of cerebral white matter hyperintensity (WMH), a common manifestation of cerebrovascular disease pathologies, is associated with the rate of progressive parkinsonism. DESIGN, SETTING, AND PARTICIPANTS This community-based cohort study included participants recruited in 3 ongoing cohorts that began enrollment in 1994, 1997, and 2004. Prior to death, participants were observed for a mean of 7.5 years, with annual clinical assessments. From 4427 participants enrolled in the 3 cohorts, 2134 died. Postmortem autopsy was performed in 1725 decedents, and 598 also had ex vivo brain magnetic resonance imaging. Participants were excluded if they were missing any of the 9 postmortem pathology indices (n = 22) or repeated parkinsonism assessment (n = 41) or had received a clinical diagnosis of Parkinson disease at any point before or during the study (n = 19). Data were analyzed from April 2020 to August 2021. EXPOSURES WMH burden was assessed using a modified Fazekas rating scale. MAIN OUTCOMES AND MEASURES Parkinsonism was assessed annually using 26 items of a modified motor portion of the Unified Parkinson's Disease Rating Scale. A summary score was developed from the item scores, with higher scores indicating more severe parkinsonism. RESULTS Of 516 included decedents, 364 (70.5%) were female, and the mean (SD) age at death was 90.2 (6.4) years. Higher WMH was associated with faster progressive parkinsonism (estimate, 0.024; SE, 0.008; P = .002). The attenuation of this association was greater when controlling for indices of cerebrovascular disease pathologies than when controlling for neurodegenerative pathologies (cerebrovascular disease: estimate, 0.019; SE, 0.008; P = .02; neurodegenerative: estimate, 0.022; SE, 0.008; P = .003), but both remained significant. CONCLUSIONS AND RELEVANCE In this cohort study, higher levels of both WMH and indices of cerebrovascular disease pathologies in aging brains were associated with more rapid progressive parkinsonism. Further studies are needed to determine if in vivo brain imaging of older adults for evidence of WMH and aggressive medical treatment of vascular risk factors and diseases can reduce the occurrence or severity of late-life parkinsonism.