Objective: To determine how growth during infancy and childhood modifies the increased risk of coronary heart disease associated with small body size at birth.
Design: Longitudinal study.
Setting: Helsinki, Finland.
Subjects: 4630 men who were born in the Helsinki University Hospital during 1934-44 and who attended child welfare clinics in the city. Each man had on average 18.0 (SD 9.5) measurements of height and weight between birth and age 12 years.
Main outcome measures: Hospital admission or death from coronary heart disease.
Results: Low birth weight and low ponderal index (birth weight/length(3)) were associated with increased risk of coronary heart disease. Low height, weight, and body mass index (weight/height(2)) at age 1 year also increased the risk. Hazard ratios fell progressively from 1.83 (95% confidence interval 1.28 to 2.60) in men whose body mass index at age 1 year was below 16 kg/m(2) to 1.00 in those whose body mass index was >19 (P for trend=0.0004). After age 1 year, rapid gain in weight and body mass index increased the risk of coronary heart disease. This effect was confined, however, to men with a ponderal index <26 at birth. In these men the hazard ratio associated with a one unit increase in standard deviation score for body mass index between ages 1 and 12 years was 1.27 (1.10 to 1.47; P=0.001).
Conclusion: Irrespective of size at birth, low weight gain during infancy is associated with increased risk of coronary heart disease. After age 1 year, rapid weight gain is associated with further increase in risk, but only among boys who were thin at birth. In these boys the adverse effects of rapid weight gain on later coronary heart disease are already apparent at age 3 years. Improvements in fetal, infant, and child growth could lead to substantial reductions in the incidence of coronary heart disease.