Use of non-steroidal anti-inflammatory drugs and risk of Parkinson's disease: nested case-control study

Objective To evaluate the relation between Parkinson's disease and prior use of non-steroidal anti-inflammatory drugs (NSAIDs) in a large cohort of men. Design Case-control analysis nested in the Physicians' Health Study. Participants 22 007 male physicians aged 40-84 years without indications for or contraindications to regular NSAID use and free of Parkinson's disease at baseline. Cases and controls were matched by age alone or by age and scores for confounders (comorbidity and indicators of NSAID use). Up to five controls were matched to each of 616 cases by age and 565 cases by age and confounder scores. Setting United States. Main outcome measures Odds of having been exposed to prior non-aspirin NSAID or aspirin use by participants with Parkinson's disease and by their controls in each case-control set. Results Participants who had ever used non-aspirin NSAIDs had an increased risk of Parkinson's disease (odds ratio 1.28 (95% CI 1.05 to 1.56) in the age matched group but not in the group also matched on confounder scores (odds ratio 1.17 (0.94 to 1.46)). There was an increased risk of Parkinson's disease in men who had 12 years of regular non-aspirin NSAID use (odds ratio 1.35 (1.07 to 1.70)), a finding that remained significant after matching for confounder scores as well (odds ratio 1.35 (1.05 to 1.75)). In contrast, the significant association of use of non-aspirin NSAIDs for >= 5 years (odds ratio 1.48 (1.05 to 2.09)) in the age matched group was entirely attenuated in the group also matched on confounder scores (1.03 (0.70 to 1.53)). There was also a suggestion that men who regularly used aspirin had an increased risk of Parkinson's disease. Positive associations between non-aspirin NSAID or aspirin and risk of Parkinson's disease tended to disappear when analyses were limited to drug use >= 5 years before the disease diagnosis. Conclusions This case-control study did not find evidence that NSAID use reduces Parkinson's disease risk. The positive associations observed between NSAID use and Parkinson's disease might have been due to confounding by indication as the use was clustered in the few years before disease diagnosis.