People who have a later-than-average start to puberty due to their genetic makeup tend to have lower bone mineral density, especially in their lower spine, according to a study published in the Journal of Bone and Mineral Research.
This may have lifelong effects on bone health, increasing a person’s risk of osteoporosis and bone fractures later in life, because adolescence is a critical period for accruing bone.
“If an individual is genetically programmed for later puberty, we found that he or she tends to have lower bone mineral density during childhood as well as in adulthood,” said geneticist Dr Struan F. A. Grant, one of three scientists from Children’s Hospital of Philadelphia (CHOP) who co-led the study.
Scientists already knew that later puberty was linked to lower bone mineral density, and that both are risk factors for osteoporosis. This study was the first to analyse the associations between genetic determinants of puberty timing and measurements of bone mineral density, said CHOP, reporting on the research.
The study drew on data from the Bone Mineral Density in Childhood Study (BMDCS), which included bone and growth measurements during annual visits for up to seven years in over 2,000 healthy children, adolescents and young adults.
Using a tool called a “genetic risk score” (GRS), which enables collective study of a group of genetic variants in one go, the team looked for associations between genetic variants associated with later puberty in children, and bone mineral density measurements.
For both boys and girls, the GRS for later puberty was associated with lower bone mineral density in a longitudinal cohort of 933 individuals who each had up to seven assessments, and in a cross-sectional cohort of 486 individuals. The results varied according to the part of the skeleton where bone mineral density was measured, with lowest density in the lower back and hip bones.
In a separate analysis, the team found that later puberty caused lower bone mineral density in both adult men and adult women. They also detected a strong causal effect in adolescent girls, although no causal relationship was seen for adolescent boys. This may be because the number of boys in the analysis was not large enough to show a significant effect.
“Now that we are aware of the risks to lifelong bone health if someone is genetically predisposed to later puberty, we can work on strategies such as promoting weight-bearing physical activity, to optimise bone density during skeletal development,” said Dr Babette S. Zemel, another co-leader of the study.