Tremendous efforts have been directed toward the identification of factors that affect the progression of Parkinson's disease, yet to date few factors have been identified. Most studies seeking to identify agents that may protect the brain have used a basic laboratory or a clinical trials approach. Surprisingly few studies have investigated the influence of demographic, environmental or genetic factors on survival in people with PD. Determining factors that influence survival in people with PD will provide direction for the development of interventions to alter the progression of PD. Leading candidates for investigation can be factors that have been found to affect the risk of getting the disease. For example, smoking has been found to result in a lower risk of Parkinson’s disease in nearly all prior studies, and it is important to assess how smoking may, or may not, affect progression of the disease. Other factors, such as male gender, caffeine intake, diet, home pesticide exposure, certain genes and family history have also been associated with the risk of developing PD. These factors have either not been studied or have been investigated in only a few studies of mortality.
In this study we will follow up with a group of 496 men and women who were newly diagnosed with PD in 1994-1995 and their matched controls. Baseline data were obtained shortly after diagnosis as part of a large NIH-funded study. As part of the data collected in that study, detailed information on clinical characteristics, smoking and alcohol use, and other risk factors was obtained as part of an in-person interview. We have conducted ongoing mortality surveillance for the cohort and propose to conduct analyses to investigate how clinical and selected environmental factors may identify subtypes of PD that are at higher or lower risk of mortality. The primary focus will be on predictors of mortality measured at diagnosis. Secondary analyses will investigate how these factors differ in predicting morality for a matched group of controls. The results of this research have the potential to provide important clues to identify PD subtypes that can result in interventions that may prolong survival in those with PD.
Dr. Van Den Eeden identified specific subtypes in patients within two years of diagnosis. These subtypes ranged from the more benign, tremor-dominant forms of PD to more malignant forms marked by the postural instability and gait disorder, or PIGD, subtype. The subtype breakdown was as follows: 2% tremor-dominant; 7% PIGD; 74% mixed.
PIGD patients had poorer survival than tremor-dominant group, as did patients with cognitive impairment. Dr. Van Den Eeden and his group are now looking at clinical factors and survival -- specifically, uric acid and lipid levels.
Results of this project were published in the journal Archives of Neurology.