Cohort profile: the Hertfordshire cohort study.

1234 be related to low birth weight in these men and women, and to low weight at 1 year among the men.3 This was the first study based on individual (rather than ecological) level data to demonstrate such relationships. Having studied mortality, the next stage was to explore the relationship between the early environment and a range of morbidity outcomes in surviving members of the cohort. Detailed physiological investigations of men and women born in Hertfordshire between 1920 and 30 and still living there in the early 1990s were conducted. These studies ranged in size from 224 to 468 men, and 189 to 306 women. Small size at birth and during infancy was shown to be associated with increased risk of developing coronary heart disease and type II diabetes mellitus,4,5 the metabolic syndrome and insulin resistance,6 osteoporosis7 and sarcopenia8 in later life. These studies led to the ‘developmental origins’ hypothesis which states that the nourishment a baby receives from its mother during pregnancy, and its nutrition and illnesses in infancy and early childhood, determine its susceptibility to disease in later life.