One of the most well-known cohort studies, the Framingham Study looked at cardiovascular disease in the town of around 30,000 inhabitants in 1948. The study involved 5,127 men and women between the ages of 30 and 62 who did not have cardiovascular disease at the beginning of the study. Participants were followed up every 2 years while the hospital in Framingham kept note of daily hospitalizations, meaning it was a prospective cohort study.