Objective: To examine the development of tracking of serum cholesterol concentration from birth to childhood.
Design: In a longitudinal study of healthy children, concentrations of total serum cholesterol and triglyceride were determined at birth (n = 193); at 2 (n = 192), 4 (n = 192), 6 (n = 190), 7.5 (n = 118), 9 (n = 188), and 12 months (n = 196); and at 5 years of age (n = 162). Concentrations of cholesterol--very-low-density lipoprotein, low-density lipoprotein, high-density lipoprotein-2 (HDL2), and HDL3--were determined at 2, 6, 9, and 12 months (n = 36) and at 5 years (n = 162).
Results: The correlation coefficients of total cholesterol levels during the first year of life with the level at 5 years of age were as follows: at birth .04, at 2 months .36 (P < .001), at 4 months .26 (P < .001), at 6 months .28 (P < .001), at 7.5 months .25 (P < .001), at 9 months .35 (P < .001), and at 12 months .48 (P < .001). The correlation for exclusively breast-fed children between 6 months and 5 years of age was r = .37, P < .001, while that for children receiving partially breast milk, formula, or solid foods was r = .12, P = not significant (NS), and between 9 months and 5 years r = .38, P < .01, and r = .28, P < .05, respectively. The correlation coefficients of the lipoprotein levels between ages 12 months and 5 years were as follows: low-density lipoprotein cholesterol .58 (P < .001), total HDL cholesterol .30 (P < .05), HDL2 cholesterol .34 (P < .05), HDL3 cholesterol .17 (P = NS), very-low-density lipoprotein cholesterol .24 (P = NS), total triglyceride .37 (P < .05), and triglyceride-very-low-density lipoprotein .37 (P < .05). Of the children whose total serum cholesterol level was above the 90th percentile at birth, or at 2, 4, 6, 7.5, 9, or 12 months, 6%, 35%, 29%, 30%, 31%, 33%, and 45%, respectively, were above the 90th percentile at 5 years of age. In retrospect, 45% of the children whose serum cholesterol level was above the 90th percentile at 5 years were above the 90th percentile at the age of 12 months and 80% were in the highest quartile.
Conclusions: The results indicate that tracking of serum cholesterol concentration during the first year of life is stronger when examining children who are receiving a relatively homogenous diet, such as exclusive breast-feeding, and weaker as children are weaned to formula and solid foods. After the weaning process is completed, children's relative serum cholesterol levels have become established and the tracking of serum cholesterol is of the same magnitude as for older children and adolescents.