Patients with newly diagnosed Parkinson disease with a mild phenotype and normal cognition have a mortality rate equivalent to the general population, according to a new Swedish study.
However patients with even mild cognitive impairment had a 2.4 times higher rate of death than other patients.
The study of 182 patients with parkinsonism (PD) included those with atypical symptoms such as multiple system atrophy (MSA) and progressive supranuclear palsy (PSP) but excluded anyone with dementia or secondary parkinsonism.
Patients were typically in their early 70s on diagnosis and mean age of death was 82 years.
The standardized mortality ratio and expected survival in patients with PD was 1.58 and 9.6 years respectively compared to 3.32 and 6.1 years for the patients with atypical parkinsonism.
However expected survival in patients with Parkinson disease and normal cognition extended to 11.6 years compared to 8.2 years with mild cognitive impairment.
“We found that the increased mortality in PD correlated with core parkinsonism symptoms (with the notable exception of tremor) and olfactory dysfunction, independently of age,” the study said.
“There is evidence that PD is associated with lower risk of some diseases, such as many cancers, and a lower risk factor burden from tobacco smoking and arterial hypertension.”
“In PD patients with normal cognition, who have a milder disease phenotype, such differences could counterbalance mortality increases caused by neurodegeneration.”
The study also found changes in cerebrospinal fluid (CSF) – low Aβ42 and high white cells – predicted poorer survival.
“Taken together, our findings might suggest a triggered immune system, responding to the presence of abnormal, misfolded proteins in PD patients with short lifespans, possibly contributing to disease progression.”
An editorial in Neurology said the findings provided useful pointers for patient management.
“The finding of an inflammatory reaction in the CSF suggests direct secondary prophylaxis via anti-inflammatory treatment; and the finding of cognitive status as a predictor similarly suggests rehabilitative measures, not just as palliation, but potentially as prophylaxis.”