(HealthDay News) – Mild cognitive impairment (MCI) at the time of a diagnosis of Parkinson’s disease (PD) predicts a highly increased risk for early dementia, according to a study published online March 25 in JAMA Neurology.

Kenn Freddy Pedersen, MD, PhD, from the Norwegian Centre for Movement Disorders at Stavanger University Hospital, and colleagues conducted a prospective, longitudinal study in which 182 patients with incident PD were monitored for three years. At baseline, one year, and three years, serial neuropsychological tests of attention, executive function, verbal memory, and visuospatial skills were given.

The researchers found that, over the study period, significantly more patients with MCI at baseline than those without MCI progressed to dementia (10 of 37 [27%] vs. 1 of 145 [0.7%]). Eight of 37 (21.6%) with MCI at baseline reverted to normal cognition during follow-up. Similar results were seen for those having MCI at the one-year visit, including rates of progression to dementia (10 of 36 patients [27.8%]) and reversion rate to normal cognition (7 of 36 [19.4%]). Among the 22 patients with persistent MCI at baseline and at the one-year visit, 10 (45.5%) developed dementia and only two (9.1%) reverted to normal cognition by the study’s end.

“Repeated neuropsychological testing increases the prognostic accuracy of MCI with respect to early dementia development in PD,” the authors write.

Several authors disclosed financial ties to the pharmaceutical industry.

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