Life expectancy among people with Parkinson's disease and parkinsonism is lower than the general population. Now, a study published in Neurology on November 27 suggests that certain symptoms may predict survival and the risk of mortality.
To identify predictors of mortality in Parkinson’s disease and parkinsonism, a term used for neurologic disorders that lead to movement problems similar to those of Parkinson’s, the researchers analyzed 182 patients newly diagnosed with parkinsonism of an unknown cause in Northern Sweden from January 2004 to April 2009.
Of the 182 patients, 143 had Parkinson’s disease, 18 had progressive supranuclear palsy (PSP)—a rare brain disorder that causes problems with walking, balance, and eye movements—13 had multiple system atrophy (MSA), a rare brain disorder that affects movement and balance and disrupts the function of the autonomic nervous, and four patients were unclassified. The researchers followed patients prospectively for up to 14 years.
Patients underwent neurologic, neuropsychological, neuroimaging, and lab tests, including a lumbar puncture to measure white blood cells in cerebrospinal fluid, and received standard or advanced treatments. The team assessed Parkinson’s symptoms as well as memory and thinking skills at baseline and at least once a year using standard Parkinson’s disease tests that measure both motor and non-motor symptoms and disease progression. Researchers also used a standard test to measure cognitive impairment. In addition, participants completed a questionnaire about cognition and emotional well-being.
The researchers reviewed the mortality rates in the general Swedish population to calculate the mortality rate and expected survival of participants relative to the entire population.
During the study period, 109 patients died; Of that number, 53.8 percent had Parkinson’s, 92.3 percent had MSA; and 88.9 percent had PSP. The four patients with unclassifiable parkinsonism were excluded from further analyses since they did not fulfill specific diagnostic criteria. The overall mean age at death was 82 years.
Patients with Parkinson’s who exhibited mild cognitive impairment (MCI), freezing of gait, a reduced sense of smell, elevated white blood cells in the cerebrospinal fluid, and less dopamine activity in areas of the brain involved in motor control were more likely to die earlier.
Assuming the mean age of patients at baseline was 72 years, the researchers found that people with Parkinson’s were likely to live another 9.6 years. For people with PSP or MSA, the life expectancy was only another 6.1 years. Those with PSP or MSA had a three times higher mortality rate than the general population.
Meanwhile, mortality rates for people with Parkinson’s with normal cognition at baseline did not differ significantly from the general Swedish population. Compared to this group, those with MCI at baseline were 2.4 times more likely to die during follow-up. The expected survival, after assuming the mean age at baseline was 71 years, was 8.2 years for people with Parkinson’s who also had MCI and 11.6 years for those who did not have MCI. The life expectancy of people with Parkinson’s who did not have MCI was not significantly different from the general population.
The researchers hypothesized that the higher mortality in patients with poorer cognition may be related to the pathologic process leading to cognitive dysfunction, rather than socioeconomic factors. Overall, the findings highlight the importance of diagnosing both Parkinson’s disease and mild cognitive impairment early.
