Dementia often a consequence of Parkinson's

NEW YORK (Reuters Health) - Dementia is a part of Parkinson's disease for most patients and reduces survival, researchers from Norway report, and the likelihood of developing dementia increases with age.

Of 233 Parkinson's disease patients, 140 (60 percent) developed dementia by the end of a 12-year follow up period, Dr. Dag Aarsland, of Stavanger University Hospital, and colleagues report in the journal Neurology.

At the age of 70, a man with Parkinson's disease who develops dementia would be expected to live 8.0 more years, they point out. Of these 8.0 years, 5.0 would be dementia-free and 3.0 would be with dementia.

For a 70-year old woman with Parkinson's disease, the life expectancy would be 11.0 years. Of these years, 7.2 years would be expected to be dementia-free and 3.8 would be with dementia.

However, for a Parkinson's disease patient who already has dementia at 70 years of age, the researchers estimate that the life expectancy would be substantially reduced to 4.2 years for men and 5.7 years for women.

The cumulative incidence of dementia also steadily increases with age and duration of Parkinson's disease, they note. Conditional on survival, the cumulative incidence of dementia in Parkinson's disease patients increases to between 80 percent and 90 percent by the age of 90 years.

"Our findings underline the importance of cognitive impairment in addition to the motor symptoms of the disease," Aarsland's team concludes.

SOURCE: Neurology, March 25, 2008.