Environmental risk factors for Parkinson's disease: A matched sibling pair case-control study

A matched-pair case-control study was conducted to investigate non-genetic risk factors for Parkinson's disease (PD) using full sibling pairs discordant for PD. All participants reported a negative family history of PD among primary relatives, and all cases noted PD symptom onset ≥40 years of age.; Based on the results of a pilot study, a sample of 46 pairs was calculated. The risk factors of head injury accompanied by a loss of consciousness, brain infection, pesticide use and smoking history were investigated for their potential association with PD. A reliable survey instrument was used to elicit responses from participants during face-to-face interviews.; A history of at least one incidence of head injury accompanied by a loss of consciousness elevated the risk of developing PD (OR = 5.00, p = 0.038). Having smoked ≥5 packs of cigarettes over one's lifetime lessened the risk for developing PD (OR = 0.31, p = 0.049). The risk factors of pesticide use (OR = 2.67, p = 0.23), and brain infection (OR = 2.00, p = 0.51) were not associated with PD but the small number of discordant pairs sampled inhibits conclusive interpretation of these results.; Conditional logistic regression was used to assess multivariable models. A model inclusive of all of the four risk factors was associated with PD but yielded nonstatistically significant Odds Ratios for each of the variables (Chi-Square = 9.99, p = 0.041). When smoking and head injuries were both included in the model, neither remained significant at the 0.05 level. An interaction between these two variables also was not observed. Pesticide use as well as brain infection were not contributory to one's risk for PD. Interpretation of results from the multivariable models is unclear due to the small size of the sample.; This case-control study used a matched pair design with sib-pairs discordant for PD to investigate non-genetic risk factors for PD. A larger sample with revisions to the survey instrument inclusive of more comprehensive assessments of the respective risks, as well as the recruitment of spouse and/or sex-age matched controls would enhance our understanding of the relationship between these non-genetic factors and sporadic PD.