First-born children may have a higher risk of developing high blood pressure or diabetes than their siblings, according to a new study by the University of Auckland’s Liggins Institute in New Zealand.
The study documents that first-born children have higher daytime blood pressure and are less able to absorb sugars into their bodies than their younger siblings. First-born children experienced a 21 percent drop in insulin sensitivity and a 4 mmHg increase in blood pressure.
“Although birth order alone is not a predictor of metabolic or cardiovascular disease, being the first-born child in a family can contribute to a person’s overall risk,” said Wayne Cutfield, MBChB, DCH, FRACP, of the University of Auckland.
The study involved 85 healthy children aged 4 to 11, 32 of which were first-born children. Children were selected as participants because insulin sensitivity can be affected by puberty and adult lifestyles. Researchers measured their height, weight, body composition, and fasting lipid and hormonal profiles.
Researchers speculated that the metabolic differences between first-born children and their siblings might be caused by changes in the mother’s uterus during pregnancy. After the changes occur, the mother’s body may increase nutrient flow to the fetus during subsequent pregnancies.
“Our results indicate first-born children have these risk factors, but more research is needed to determine how that translates into adult cases of diabetes, hypertension and other conditions,” Cutfield said.
The article, “First-born Children Have Reduced Insulin Sensitivity And Higher Daytime Blood Pressure Compared To Later-born Children,” appears in the March 2013 issue of The Endocrine Society’s "Journal of Clinical Endocrinology & Metabolism."