Estimation of Parkinson’s disease survival in Israeli men and women, using health maintenance organization pharmacy data in a unique approach

Abstract

The aim of this work was to estimate in an incident cohort of pharmacy-based PD patients the survival of men and women accounting for age at treatment initiation and to compare their gender-specific survival with that of the general Israeli population. A population-based cohort of 4,848 incident pharmacy-based PD cases with definite/probable/possible certainty was previously identified using a drug-tracer approach for 1999-2008. Survival analysis was performed for two time scales: survival after treatment initiation (disease duration), and life-time survival (life expectancy). Kaplan-Meier curves and Cox regressions were used to compare survival across gender. Gender-specific SMRs were calculated from national rates and were compared using Poisson regression. During the follow-up from first purchase of any anti-parkinsonian drug (mean 4.0 ± 2.6 years, range 2 months-10 years), 1,266 (26 %) of the cases died. Younger age at first anti-parkinsonian drug purchase and female gender were associated with increased survival after treatment initiation (HR = 1.089, 95 % CI 1.080-1.098 for 1-year age increase; HR = 0.716, 95 % CI 0.640-0.800, females vs. males). Life-time survival increased with older age at first anti-parkinsonian drug purchase and female gender (HR = 0.759, 95 % CI 0.746-0.771 for 1-year age increase; HR = 0.694, 95 % CI 0.621-0.776, females vs. males). Sensitivity analysis on a sub-cohort of definite cases (n = 2501) yielded similar results. In comparison to the general Israeli population, mortality among pharmacy-based PD patients was significantly increased (SMR(men) = 1.69, 95 % CI 1.57-1.81, SMR(women) = 1.49, 95 % CI 1.37-1.62), differently between genders (p < 0.01). Female gender was associated with longer, perhaps more benign disease course, and longer life expectancy. Earlier age at anti-parkinsonian drug initiation increased disease duration, but was associated with shorter life expectancy.