The Modifying Effect of Age on Survival in Parkinson's Disease: A Population-Based Cohort Study

Background: To estimate the survival of a population-based cohort of Parkinson's disease (PD) patients stratified by age and sex over a 13-year period. Methods: The dynamic PD cohort included 6,622 incident PD patients who initiated anti-parkinsonian medications at age >40 years. The reference population (n = 401,498) consisted of members of a large health maintenance organization. We estimated the PD patients' death risk and sex- and age-specific standardized mortality ratio (SMR). Results: During a follow-up of 5.2 ± 3.3 years, 36% of the cohort died. Older age at first PD treatment was associated with a 55% increase in mortality (for 5-year increase, p < 0.01). More PD patients died when compared to the same age and sex reference population in all age groups, with significant results at age groups >60 years at first treatment. The age-pooled SMR was twofold (SMR for the males = 2.05, 95% CI 1.73-2.42; SMR females = 2.13, 95% CI 1.74-2.62). The highest excess death for males was 2.5-fold for those aged 60-69 years, decreasing to twofold for those in the age range 70-79 years and to 1.5-fold for those aged 80+ years. A similar trend was found among females. Conclusion: Our large-scale cohort enabled us to find an age-differential standardized death risk among PD patients, with the largest increased risk at ages 60-69 years. Comorbidities and other contributory factors warrant further investigation.