Study Reveals Key Predictors of Dementia Risk in Patients With Parkinson Disease

The increased risk of dementia among people with Parkinson disease (PD), with substantial variability influenced by age, sex, and education is highlighted in a recent study published in Neurology.

Researchers used data from the Parkinson’s Progression Markers Initiative (PPMI) and a University of Pennsylvania (Penn) cohort to reexamine long-term dementia rates among patients with PD—a critical factor as cognitive decline is a common, often severe, nonmotor symptom of PD. Up to 80% of patients with PD develop dementia, significantly impacting quality of life and disease management.

“Unfortunately, treatment of PD cognitive impairment lags treatment of motor symptoms,” wrote Julia Gallagher, Department of Neurology, University of Pennsylvania in Philadelphia, Pennsylvania, and coauthors. “To optimize clinical management, better understand progression to dementia, and spur treatment development, accurate estimates of long-term dementia rates are needed.”

The PPMI cohort followed 417 participants with newly diagnosed PD, with an average disease duration of 0.6 years at enrollment, while the Penn cohort tracked 389 patients with more established PD, averaging 6.3 years since diagnosis. Over the entire follow-up period in PPMI, 8.5% of patients were diagnosed with dementia based on clinical criteria. Using additional assessments, such as the Montreal Cognitive Assessment (MoCA) and the Movement Disorder Society’s Unified Parkinson’s Disease Rating Scale (MDS-UPDRS), dementia rates increased slightly, with approximately 11% of patients classified as having dementia.

The Penn cohort showed higher dementia rates, likely reflecting the longer disease duration at baseline, with 47.3% developing dementia over the study period. Older age at disease onset was linked to faster cognitive decline: Patients diagnosed with PD after age 70 had a median time to dementia of 9.2 years, whereas those diagnosed before age 56 had an estimated 19.4 years.

The analysis also pointed to educational attainment and sex as predictors of dementia risk. Among participants with less than 13 years of education, the median time to dementia was significantly shorter at 11.6 years compared with 15.2 years for those with higher education levels. Males showed a higher likelihood of cognitive decline than females, with median times to dementia of 13.3 years for males and 19.4 years for females.

“These results provide updated, and more hopeful, estimates of long-term dementia risk in PD, suggesting a longer window to intervene to prevent or delay cognitive decline,” concluded the study authors.

Reference

Gallagher J, Gochanour C, Caspell-Garcia C, et al. Long-term dementia risk in Parkinson disease. Neurology. 2024;103(5):e209699. doi:10.1212/WNL.0000000000209699