Predictors of dementia in Parkinson disease: a prospective cohort study.

Objective: We investigated an array of possible markers of early dementia in Parkinson disease.

Methods: We performed a comprehensive assessment of autonomic, sleep, psychiatric, visual, olfactory, and motor manifestations in 80 patients with Parkinson disease who were dementia-free at baseline. After 4.4 years' follow-up, patients were evaluated for dementia. Predictive variables were assessed using logistic regression adjusting for disease duration, follow-up duration, age, and sex.

Results: Of 80 patients, 27 (34%) developed dementia. Patients destined to develop dementia were older and more often male (odds ratio [OR] = 3.64, p = 0.023). Those with baseline mild cognitive impairment had increased dementia risk (OR = 22.5, p < 0.001). REM sleep behavior disorder at baseline dramatically increased dementia risk (OR = 49.7, p = 0.001); however, neither daytime sleepiness nor insomnia predicted dementia. Higher baseline blood pressure increased dementia risk (OR = 1.37 per 10 mm Hg, p = 0.032). Orthostatic blood pressure drop was strongly associated with dementia risk (OR = 1.84 per 10 mm Hg, p < 0.001); having a systolic drop of >10 mm Hg increased dementia odds 7-fold (OR = 7.3, p = 0.002). Abnormal color vision increased dementia risk (OR = 3.3, p = 0.014), but olfactory dysfunction did not. Among baseline motor variables, proportion of gait involvement (OR = 1.12, p = 0.023), falls (OR = 3.02, p = 0.042), and freezing (OR = 2.63, p = 0.013), as well as the Purdue Pegboard Test (OR = 0.67, p = 0.049) and alternate tap test (OR = 0.97, p = 0.033) predicted dementia.

Conclusion: Cardiovascular autonomic dysfunction, REM sleep behavior disorder, color discrimination ability, and gait dysfunction strongly predict development of dementia in Parkinson disease.