Background: Metabolic syndrome has been called a "small baby syndrome," but other analyses suggest that postnatal growth is more important than birthweight, or that large babies are also at risk. The aim of this analysis was to examine whether there was a relationship between both low and high birthweight and metabolic syndrome, using multiple definitions of metabolic syndrome, and to determine whether this relationship varied by body size across the life course.
Methods: Data from the Bogalusa Heart Study, a study of cardiovascular disease in children and young adults, were linked to birth certificate data. Metabolic syndrome was defined by the National Cholesterol Education Program, the International Diabetes Foundation, and the World Health Organization (WHO) definition. Small-for-gestational-age (SGA) was defined as birthweight <10(th) percentile by sex for gestational age and large-for-gestational-age (LGA) as birthweight >90(th) percentile. Birthweight-for-gestational-age was also examined as a continuous predictor. Chi-squared tests and logistic regression were used to examine the relationship between birth size and metabolic syndrome.
Results: Higher birthweight-for-gestational-age was associated with a reduced risk of metabolic syndrome, especially by the WHO definition. After adjustment for body mass index (BMI), categorized birthweight was associated with metabolic syndrome, with the protective associations with LGA being stronger than the positive associations with SGA. Among the individual components of metabolic syndrome, higher waist circumference was associated with both SGA and LGA after BMI was controlled for. Effects of SGA and BMI at any age were largely independent rather than interactive.
Conclusions: SGA is associated with some, but not all, components of metabolic syndrome. The relationship between SGA and metabolic syndrome is partially confounded by later BMI.