Smoking hurts teen girls’ bones

High school might be a bit early to start thinking about bone loss and osteoporosis, but a new study finds that teenage girls who smoke may put themselves on a trajectory to accrue less bone mineral than those who don’t light up.

Osteoporosis is a loss of bone density that predisposes people to fractures and leaves many elderly people — particularly women — hunched over. While bones regenerate and remodel nonstop over a lifetime, the teen years are crucial to developing a strong, dense skeleton.

“This age group is when you should gain about 50 percent of your bone accrual,” says study coauthor Lorah Dorn, a developmental psychologist and pediatric nurse practitioner at Cincinnati Children’s Hospital Medical Center. Failing to build adequate bone strength in adolescence could jeopardize a young woman’s ability to fully accumulate a “bone bank” that will be needed when she someday reaches menopause and begins to lose bone mass, she says.

Dorn and her colleagues recruited 262 healthy girls ages 11 to 17. The girls answered confidential questions about their nutritional habits and lifestyles and returned for three yearly visits to undergo bone density tests. Girls who reported smoking regularly showed nearly flat rates of bone density growth in the lower vertebrae and a decline in bone density at the hips. Nonsmokers showed normal, steadily rising bone density in both regions, the authors report online December 4 in the Journal of Adolescent Health. By the time they reached age 19, daily smokers in the study had fallen a full year behind nonsmokers in bone mineral accrual, the authors note.

“These girls are on different trajectories all the way across adolescence,” Dorn says. The analysis took into account differences between smokers and nonsmokers in race, weight, calcium intake, physical activity and vitamin D level.

Kenneth Ward, a clinical-health psychologist at the University of Memphis School of Public Health in Tennessee, says he was impressed that the researchers could identify smoking as a risk factor in such a young group. The effects of smoking tend to be cumulative, and teenagers haven’t had enough time to smoke a lot. But the study shows a clear trend, he says.

The results also seem to concur with studies done in adults, Ward says. A 2001 review by Ward and colleague Robert Klesges of adults’ bone density estimated that smoking increased the risk of a vertebral fracture by 13 percent and hip fracture by 31 percent in women. The new study “is something that might encourage health care providers to ask kids about smoking,” Ward says. “It may help pediatricians to be more proactive in intervening.”

Still unclear, Ward and Dorn note, is exactly how smoking contributes to the reduced bone mineralization.