Developing persistent mild cognitive impairment soon after being diagnosed with Parkinson’s disease significantly increased the risk of subsequent dementia, according to a cohort study that examined the natural history of mild cognitive impairment in 178 patients over 5 years.
After the researchers controlled for age, sex, and education, patients who had persistent mild cognitive impairment (MCI) by 1 year after their Parkinson’s disease (PD) diagnosis had a 16.6-fold greater odds of subsequent dementia, compared with those who were cognitively normal (95% confidence interval, 5.1-54.7; P less than .001). Notably, early MCI significantly predicted dementia even if patients reverted to normal cognition with dopaminergic treatment, reported Kenn F. Pedersen, MD, PhD, of the Norwegian Centre for Movement Disorders at Stavanger (Norway) University Hospital, and his associates. “Early PD-MCI, regardless of persistence or reversion to normal cognition, has prognostic value for predicting dementia in patients with PD,” they concluded.
Their population-based study included white patients from Norway with a confirmed diagnosis of incident PD. Patients repeatedly underwent the Mini-Mental State Examination and a battery of tests of verbal memory, attention, executive functioning, and visuospatial skills ( Neurology. 2017 Jan 20. doi: 10.1212/WNL.0000000000003634 ).
At baseline, 20% of patients had MCI. Among those who did not, cumulative incidence rates of MCI were 10% at year 1, 23% at year 3, and 29% by the end of the study after 5 years of follow-up. In all, 59% of patients with persistent MCI by year 1 developed dementia, compared with 7% of patients who retained normal cognition at 1 year. About one in four patients with MCI reverted to normal cognition by the end of the study, but they still faced a 10.7-fold greater odds of dementia at the 5-year follow-up, compared with cognitively normal patients (95% CI, 1.5-78.5; P = .02).
The Research Council of Norway, the Western Norway Regional Health Authority, and the Norwegian Parkinson’s Disease Association funded the study. Dr. Pedersen had no disclosures. One coauthor reported serving on advisory boards for Lundbeck and GlaxoSmithKline and receiving payment for lecturing from Orion Pharma and GlaxoSmithKline.