The growth and development of cohort studies.

Cohort studies are special forms of longitudinal studies that have long been accepted as the primary designs to acquire information on the interaction between the environment and health and the subsequent aetiology and progression of disease. Richard Doll, Regius Professor of Medicine at Oxford University from 1969-1979, was the 20th century's pre-eminent epidemiologist in the UK. He used cohort studies to establish the relationship between smoking and health (primarily cancer) in the 1960s at a time when over 80% of British males smoked. However, the development of cohorts as a means of studying health and wellbeing across the lifespan is rooted in research on tuberculosis in Europe and America in the 1920s and 1930s. Cohort studies were recognised as the primary research design for the study of human growth and development between and during the wars in the USA. Their natural legacy as longitudinal studies emerged in Europe after WWII through a series of growth studies coordinated by the Centre Internationale de L'Enfance in Paris from the 1960s onwards. The failure of two nationally representative birth cohort studies in the USA and UK between 2010 and 2015 has highlighted the previous success of smaller birth cohorts and the advantages gained from standardised methods of measurement and assessment that allow amalgamation and metanalysis of different datasets.