Early growth and coronary heart disease in later life: longitudinal study.

Abstract

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.sup.2] to 1.00 in those whose body mass index was [is greater than] 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 [is less than] 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 1'2 years was 1.27 (1.10 to 1.47; P = 0.001).

Conclusion Irrespective of size at birth, low weight gain during intancy 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 eft&ts of rapid weight gain on later coronary heart disease are already apparent at age 3 years, hnprovements in fetal, inthnt, and child growth could lead to substantial reductions in the incidence of coronary heart disease.

Introduction

Low birth weight is associated with increased rates of coronary heart disease in later life.[1-8] This is thought to be a consequence of persisting physiological and metabolic changes that accompany slow growth in utero.[9] Among men in Hertibrdshire, where both birth weight and weight at age 1 year were recorded routinely, low weight at 1 year added to the increased risk of coronary heart disease associated with low birth weight.[1] This association between low weight gain in infancy and later coronary heart disease has not been explored in other studies. We report here on associations between early growth and coronary heart disease in a cohort of 4630 men born in Helsinki during 1934-44, for whom serial measurements of height and weight from birth to age 12 years were recorded in obstetric, child welfare, and school health records.

Methods

We studied a sample of men who were born at Helsinki University Central Hospital during 1934-44 and who attended child welfare clinics in the city of Helsinki and were still resident in Finland in 1971. Details of the birth records kept at the hospital have been described.[10] Attendance at child welfare clinics in Helsinki was voluntary. Clinic records include serial measurements of height and weight.

We identified 5502 men who had birth and child welfare records. Of these, 4630 (84%) were alive and living in Finland in 1971, when a unique identification number was allocated to each member of the Finnish population; 3544 of these men went to school in Helsinki and had school health records. Details of school health records have been described.[5] They include measurements of height and weight recorded at periodic medical examinations from age 6 years onwards.

Using the personal identification number, we identified all hospital admissions and deaths among the men during 1971-97. All hospital admissions in Finland are recorded in the national hospital discharge register. All deaths are recorded in the national mortality register. Causes of hospital admissions or deaths were recorded according to ICD-8 (international classification of diseases, eighth revision) until 1986; thereafter ICD-9 was used until 1995 and ICD-10 until 1997. The first three digits from the cause of admission or death were used to identify the occurrence of coronary heart disease (ICD-8 and ICD-9 codes 410-414, ICD- 10 code 121-125).

We obtained ethical approval for the study from …