The majority of Parkinson’s patients will develop some form of dementia as they age, which will affect their life expectancy, according to a research team from Norway.

Researchers followed the cases of 233 Parkinson’s patients over a 12-year period to determine the rate of dementia among them. They found that, during that time, a full 60% – 140 patients in all – developed some form of dementia.

Furthermore, they found that life expectancy was significantly reduced among those with Parkinson’s who had dementia by the time they were 70, compared with those who developed it as a septuagenarian. Women tended to live a few years longer then men. The study appears in the journal Neurology.