Table shows the neonatal and infant characteristics of the 4630 men. Each man had on average 9.3 (SD 6.6) measurements of height and weight between birth and age 1 year, 2.9 (3.8) measurements from age 1 year to 6 years and 5.8 (3.9) measurements from age 6 to 12 years. After that age school medical examinations were less frequent. In all, 288 of the men had been admitted to hospital with coronary heart disease, of whom 42 died of the disease. A further 69 had died without admission to hospital. We therefore analysed data on 357 men with coronary heart disease. The annual death rate from the disease at ages 45 to 54 years was 1.6 per 1000.
Neonatal and infant characteristics of 4630 men born at Helsinki University Central Hospital during 1934-44
Size at birth
Table shows hazard ratios for coronary heart disease according to size at birth. The hazard ratios fell with increasing birth weight and ponderal index (birth weight(kg)/(length(m)3)). These trends were found in babies born at term or prematurely and therefore reflected low rates of intrauterine growth. Hazard ratios also fell with increasing head circumference (P=0.002, adjusted for gestation), but there were no trends with length at birth or placental weight.
Hazard ratios for coronary heart disease according to body size at birth
Size at age 1 year
Table shows that hazard ratios for coronary heart disease fell progressively with increasing weight, height, and body mass index at age 1 year. Small body size at this age predicted coronary heart disease independently of size at birth. In a simultaneous analysis the hazard ratios for coronary heart disease associated with a one standard deviation increase were 0.94 (95% confidence interval 0.83 to 1.06) for birth weight and 0.84 (0.75 to 0.94) for weight at 1 year. The corresponding figures for ponderal index at birth and body mass index at 1 year were 0.86 (0.77 to 0.97) and 0.87 (0.78 to 0.96).
Hazard ratios for coronary heart disease according to body size at one year
Figure shows the childhood growth, expressed as mean Z scores, of the men who developed coronary heart disease. The Z score for the cohort is set at zero, and a boy maintaining a steady position as large or small in relation to other boys would follow a horizontal path on the figure. Boys who later developed coronary heart disease, however, having been small at birth and during infancy, had accelerated gain in weight and body mass index thereafter. In contrast, their heights remained below average, this difference being significant at each age from 1 to 5 years. We calculated the hazard ratios for coronary heart disease associated with gain in body mass index between the ages of 1 and 12 years. A one unit increase in standard deviation score was associated with a hazard ratio of 1.20 (1.08 to 1.33; P=0.0005).
Growth of 357 boys who later developed coronary heart disease in a cohort of 4630 boys born in Helsinki
In our earlier analyses of an older cohort of men born in Helsinki, whose childhood growth was recorded only from age 7 years onwards, we found that the effects of childhood body mass index on later coronary heart disease depended on ponderal index at birth.5
In the current analysis we therefore examined the simultaneous effects of ponderal index at birth and body mass index at each age. We found significant interactions between the two variables from age 2 years onwards. Figure illustrates this. Boys who had a low ponderal index at birth increased their risk of coronary heart disease if they attained even average body mass index in childhood. In contrast, among boys with a high ponderal index there was no increased risk associated with increase in body mass index. Figure describes body mass index at age 11 years, for consistency with studies of the older cohort, but data for other ages are similar. These are shown in table , in which the cohort is divided according to ponderal index at birth, using an index of 26 as the division. This division gives similar numbers of cases of coronary heart disease in the two groups.
Hazard ratios for coronary heart disease according to ponderal index at birth and body mass index at age 11 years. Arrows indicate average values; lines join points with the same hazard ratios
Hazard ratios (95% confidence intervals) for coronary heart disease according to one standard deviation increases in body mass index during childhood
Table shows the hazard ratios for coronary heart disease associated with a standard deviation increase in body mass index at each age from 1 to 12 years. In the low ponderal index group an increase in body mass index at each age from 3 years onwards was associated with increased risk of disease, whereas in the high ponderal index group an increase in body mass index at any age was associated with reduced risk. Table illustrates these contrasting effects of body mass index at the middle of the age range. At this and all other ages the boys who could not be assigned Z scores were similar to the others in their body size at birth and in their later incidence of coronary heart disease.
Hazard ratios (95% confidence interval) for coronary heart disease according to ponderal index at birth and body mass index at age 6 years