Causes of death in a community-based study of Parkinson's disease

INTRODUCTION: The aim of this community-based study of Parkinson's disease (PD) was to investigate the causes of death among PD patients over a 4-year period and to examine the quality of death certificates with regard to PD. PATIENTS AND METHODS: A total of 245 patients were diagnosed with PD on Jan 1st 1993 in a defined geographical area in Norway. This patient cohort was followed from 1993 until Dec 31st 1996. Some 84 patients died in the 4-year period of follow-up. Their death certificates were collected, and causes of death were registered. A control group with the same age and sex distribution as the decedents, from the same geographical area, were also examined for causes of death. RESULTS: We found that the deceased PD patients at baseline were older, had a higher Unified Parkinson's Disease Rating Scale (UPDRS) score and Hoehn and Yahr staging than those patients who did not die during the observation period. Twice as many PD patients (20%) as controls (9%) died from pneumonia, whereas more controls than patients died from ischemic heart disease. There was a trend towards more deaths from malignant neoplasms in the control group than among PD patients. Only 56% of the death certificates of the deceased patients had PD registered as either underlying or contributing cause of death. CONCLUSION: We found that in an unselected group of PD patients there is a significant increase in deaths from pneumonia. The low frequency of PD on deceased patients' death certificates show that research based on these certificates should be evaluated with caution.