MedWire News: A meta-analysis has identified 19 risk factors that significantly impact a person's risk for Parkinson's disease (PD) and could be of potential value for clinical screening, say the authors.
The strongest among these was having a family history of PD or tremor and a history of constipation, which increased future risk, and smoking history, which decreased the risk ‑ the nature of the latter association being "still poorly understood," the authors note.
Anette Schrag (University College London, UK) and colleagues performed an extensive literature search for observational studies that assessed at least one risk factor preceding a subsequent diagnosis of PD.
They considered factors that could be determined through questionnaires or widely available blood tests, including genetic and environmental risk factors, comorbidities and medication exposures, as well as early non-motor features that may represent the earliest stages of PD.
From a total of 375 eligible studies, there were 40 individual risk factors of potential value for clinical screening, of which 19 significantly altered the risk for future PD.
The factors which were most strongly associated with a subsequent diagnosis of PD were having a first degree or any relative with PD, with odds ratios (ORs) of 3.23 and 4.45 respectively; having any relative with tremor (OR=2.74); and having a history of constipation (risk ratio [RR]=2.34).
Meanwhile, having a history of smoking actually decreased the risk for a subsequent diagnosis of PD (RR=0.44 for current smokers and 0.78 for past smokers relative to never smokers).
Other associations with a more modest impact on future PD risk included history of anxiety or depression, pesticide exposure, head injury, rural living, beta-blocker use, farming as an occupation, and well-water drinking, which increased PD risk; and coffee drinking, hypertension, nonsteroidal antiinflammatory drug use, calcium-channel blocker use, and alcohol, which decreased PD risk.
The authors however failed to find any PD risk association with diabetes mellitus, cancer, oral contraceptive pill use, surgical menopause or hormone replacement therapy use, statins, acetaminophen/paracetamol or aspirin use, tea drinking, history of general anaesthesia, or gastric ulcers.
"This report allows comparative assessment of the evidence for, and magnitude of association for, the numerous proposed risk and early disease factors of PD, and helps to understand better their contribution to the risk of PD," Schrag et al comment.
"They also provide important information for the earlier diagnosis of PD, which is often delayed by several years," the authors add.
The research is published in the Annals of Neurology.
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