Mortality in Parkinson's disease is not associated with the severity of early dopaminergic defect

Although there is a relationship between the extent of striatal dopaminergic defect and the severity of motor symptoms in Parkinson's disease (PD), studies investigating associations between dopamine and mortality in PD have been scarce. If a relationship were established, dopamine restoring neuroprotective treatments could be used to decrease mortality. The objective of this study was to determine whether the initial degree of hypodopaminergic defect, as measured by 6-[(18)F]fluoro-L-DOPA positron emission tomography (FDOPA-PET), can predict patient survival.

The study population included a cohort of 88 recently diagnosed and untreated patients with PD who were clinically examined and scanned with FDOPA-PET between the years 1998 and 2000. The date of exit for the survival analysis was in April 2013 with a follow-up interval of 13-15 years. The survival model included FDOPA uptake, age, sex and symptom severity as explaining factors. Death certificates of the patients were obtained, and causes of death were analyzed.

Mortality rate was 56.8%. Although higher age (p < 0.001) and greater motor symptom severity (p < 0.05) were associated with increased mortality, there was no association between survival and FDOPA uptake in any striatal subregion (p > 0.48).

Unlike age and early motor symptom severity, dopamine synthesis capacity, as measured with PET, does not predict survival in PD.