A total of 11 studies (1,020,379 patients, range 392 to 697,078) were included; one study accounted for over half the patients. Seven studies were case-control and four were cohort studies.
There appeared to be a reduced risk of developing Parkinson's disease among ibuprofen users (RR 0.76, 95% CI 0.65 to 0.89; three studies) and amongst male NSAID users (RR 0.79, 95% CI 0.69 to 0.92; four studies); no heterogeneity was present for these comparisons.
There was no reduction in risk of developing Parkinson's disease associated with NSAIDs (11 studies), high-dose or long-duration NSAID use (10 studies), NSAID use for two or more years (four studies), and amongst aspirin users (six studies).