Size at birth and resilience to effects of poor living conditions in adult life: longitudinal study.

To determine whether men who grew slowly in utero or during infancy are more vulnerable to the later effects of poor living conditions on coronary heart disease. Follow up study of men for whom there were data on body size at birth and growth and social class during childhood, educational level, and social class and income in adult life. Helsinki, Finland. 3676 men who were born during 1934-44, attended child welfare clinics in Helsinki, were still resident in Finland in 1971, and for whom data from the 1980 census were available. Hospital admission for or death from coronary heart disease. Men who had low social class or low household income in adult life had increased rates of coronary heart disease. The hazard ratio among men with the lowest annual income (<8400 pound sterling) was 1.71 (95% confidence interval 1.18 to 2.48) compared with 1.00 in men with incomes above 15, 700 pound sterling. These effects were stronger in men who were thin at birth (ponderal index <26 kg/m(3)): hazard ratio 2.58 (1.45 to 4.60) for men with lowest annual income. Among the men who were thin at birth the effects of low social class were greater in those who had accelerated weight gain between ages 1 and 12 years. Low social class in childhood further increased risk of disease, partly because it was associated with poor growth during infancy. Low educational attainment was associated with increased risk, and low income had no effect once this was taken into account. Men who grow slowly in utero remain biologically different to other men. They are more vulnerable to the effects of low socioeconomic status and low income on coronary heart disease.