Environmental and genetic factors affecting bone mass. Similarity of bone density among members of healthy families.

Abstract

To evaluate the relative importance of environmental and genetic factors in the determination of bone mineral density (BMD) and to quantify the risk of low BMD in healthy young adults in relation to the BMD of their parents. Dual-energy x-ray absorptiometry study of a series of 129 nuclear families (441 subjects), including 183 children over age 15, was performed. Correlation of BMD in children with BMD in their parents was studied in a linear model, taking into account environmental factors. Logistic regression was used to quantify the relative risk of lower BMD according to the parents' BMD level. BMD was significantly correlated with weight, height, and body mass index (BMI) in all family members, and with parents' alcohol consumption and with physical activity in fathers and sons. The BMD of the children correlated with that of their parents (r = 0.27). The child's BMI, his/her father's BMD and daily calcium intake, and his/her mother's BMD, BMI, and body fat accounted for 41.4% of the variance in the child's BMD. A son had a 3.8 times higher risk of having a low BMD if his father had a low BMD, and a daughter had a 5.1 times higher risk if her mother had a low BMD. The BMD of children in healthy families was related to the BMD of their parents as well as to environmental factors, confirming the contribution of genetic inheritance in the determination of bone density in young adults, especially in girls.