Mortality in a population-based cohort of patients treated with antiparkinsonian drugs

Objectives - A number of studies have been focused on the mortality of parkinsonian patients, as compared with the rest of the population. In these studies, a mortality greater than expected on the basis of mortality of the general population has been shown. Nevertheless, just a few of these studies have investigated in detail the specific causes of death, probably as a consequence of both small cohort sizes and a short time period of observation. The aim of this study was to estimate cause-specific mortality in a cohort of patients treated with antiparkinsonian drugs. Methods - The study was performed on a wide population-based cohort of patients identified and followed-up through the computerized health databases of the Italian province of Rome (about 3,800,000 inhabitants). The follow-up lasted from January 1987 to December 1994. Standardized Mortality Ratios (SMR) were calculated for each specific cause of death, using the Rome province population as reference. Results - A cohort of 10,322 subjects, receiving antiparkinsonian drugs, were identified. There were 4328 deaths on an average follow-up of 5.7 years. This figure was 17% higher than was expected. A gradual decrease in SMR was observed in the oldest age groups. Statistically significant (95%) excesses of death were related to the nervous system (SMR=1037; 95% CI 964–1110), mental disorders (SMR=182; 95% CI 129–246), and endocrine and metabolic diseases (SMR=117; 95% CI 102–133). Lower than expected mortality was found to be caused by malignant neoplasms (SMR=56; 95% CI 51–61). Conclusions - Apart from deaths specifically related to Parkinson's disease, the main differences between our cohort of patients and the general population were related to mortality due to malignant neoplasms and mental disorders. The gradual decrease in SMR for the oldest age groups, seems to indicate a greater reduction of life expectancy for patients with early onset of symptoms. This age-related trend could explain the relatively small excess of mortality, as in our cohort the median age of patients at entry was 74 years.