The reduced bone mineral density that leads to osteoporosis, resulting in bones becoming increasingly brittle and at risk of fracture, is normally associated with women approaching menopause. However, new research shows that it begins much, much earlier than that.
The Bone Mineral Density in Childhood Study is an ongoing multicenter study in the USA examining bone development in healthy children and teenagers of both sexes and various ethnic groups. This is only a small scale study, involving 78 girls and 84 boys who had just entered puberty and follows their progress until they reach sexual maturity.
“Puberty has a significant role in bone development,” explained Dr. Vincente Gilsanz, lead researcher, “During this time, bones lengthen and increase in density. At the end of puberty the epiphyseal plates close, terminating the ability of the bones to lengthen. When this occurs, the teenager has reached their maximum adult height and peak bone mass. We found that early puberty was associated with greater bone mass while later puberty resulted in less.”
They also found that the actual length of puberty did not affect bone density.
Adolescents with short stature sometimes undergo medical intervention to delay puberty in an effort to achieve greater height. This study indicates that prolonging the growth period by delaying puberty may have unexpected consequences in later life.
The 2000 National Institutes of Health Consensus Development Conference on Osteoporosis Prevention, Diagnosis, and Therapy identified bone mineral deposition during adolescence as a critical determinant of osteoporosis risk later in life. The care of patients with osteoporosis is difficult, and most therapies increase bone density by small amounts yet require long periods of treatment. In contrast, during puberty large increases in bone density occur over a short period of time.
Given that the rate of decline of bone mass in adulthood is approximately 1% to 2% each year, a 10% to 20% increase in bone density resulting from a natural early puberty corresponds to an additional 10 to 20 years of protection against the normal age-related decline in bone strength.
In a family with a history of osteoporosis, this is an additional factor to bear in mind when looking at preventive action.