Compare people with a specific condition (case) to other people who are otherwise similar except for that condition (control) *Retrospective*: go back and ask questions about lifestyle Ex.: association between smoking and lung cancer C OHORT S TUDY Study of a group of people over a long period of time to determine which factors may be associated with the appearance of a specific condition. The subjects do not have any particular condition at the beginning, and we want to see under what particular condition a particular condition will develop *Prospective*: to go ahead Link between Case control and Cohort studies: Control study: people have developed a particular condition (retrospective) Cohort study: at the onset, the is no indication of any problem (prospective) EPIC (European Perspective Investigation into Cancer) Study : Involving 520 000 people in 10 European countries suggests that increased intake f fruits and vegetables has a minimal effect on caner rates (But fruits and vegetables do have an effect on heart diseases) Correlation VS Causation Assignment of subjects is controlled by the investigator Interventional Controlled Study : Double blind randomized placebo-controlled study EX.: Vitamin D and calcium supplementation reduces cancer risk (randomized trial). 60% reduction in cancer incidence for people that took a blend of vitamin D and calcium find more resources at oneclass.com find more resources at oneclass.com