Parkinson disease and risk of mortality - A prospective comorbidity-matched cohort study

Objective: To evaluate the association between Parkinson disease (PD) and mortality after adjustment for comorbidities. Methods: We conducted a matched cohort analysis among 22,071 participants in the Physicians' Health Study. Five hundred sixty incident PD cases were identified by self-report. We used a modified Charlson Comorbidity Index to calculate a comorbidity score. Each PD case was matched by age to a comparator who was alive and had an identical comorbidity score at the time of PD diagnosis of the case. Both cohorts were followed for all-cause mortality. We used proportional hazards models to calculate hazard ratios (HRs) for mortality. Results: A total of 330 participants died over a median follow-up of 5.8 years, 200 (35.7%) in the PD group and 130 (23.2%) in the reference group. After adjustment for smoking and age at PD onset, the HR for mortality was 2.32 (95% CI 1.85-2.92). The mortality risk remained significant with increasing age at onset, even in those aged >= 80 years (HR = 2.10; 95% CI 1.44-3.00). The increased risk was apparent for short PD duration (<2 years) and remained stable with increasing duration. We found no different risk of mortality associated with PD according to smoking status. Conclusions: In this large prospective cohort of men and after matching on comorbidities, we found that Parkinson disease patients had an increased risk of all-cause mortality. Mortality was increased regardless of disease duration, did not diminish with increasing age at onset, and was not influenced by smoking status.