Cohort studies.
Cohort studies generally provide more definitive evidence regarding causality than do other types of observational epidemiologic studies, but the high cost usually associated with them limits their use to special situations. Retrospective cohort studies and combined cohort/case-control studies are suggested as modifications of the traditional prospective cohort study which retain certain of their advantages but which are considerably less expensive.
D001172:Arthritis, Rheumatoid / Q000209:etiology*; D003430:Cross-Sectional Studies; D004812:Epidemiologic Methods; D006801:Humans; D009765:Obesity / Q000150:complications; D010003:Osteoarthritis / Q000209:etiology*; D011336:Probability; D011446:Prospective Studies; D012107:Research Design; D012189:Retrospective Studies; D012306:Risk