Children of parents who smoke have evidence of impaired bone health in adulthood, according to a study recently published in The Journal of Clinical Endocrinology and Metabolism.
Researchers led by Markus Juonala, MD, PhD, of the University of Turku and Division of Medicine, Turku University Hospital, and FinlandMurdoch Childrens Research Institute in Parkville, Victoria, Australia, point out that previous studies have shown that an environmental factor in osteoporosis is exposure to tobacco smoke, even secondhand smoke. However, not much is known about how childhood exposure to secondhand smoke affects bone health. “In the present study, we aimed to examine passive smoking exposure in childhood (age 3- 18 years) as a determinant of bone health at the skeletal maturity in mid-adulthood (age 31-46 years) among 1422 individuals,” the authors write.
The researchers analyzed data from 1422 individuals who had a baseline evaluation in 1980 and a follow-up 28 years later as adults in the longitudinal Cardiovascular Risk in Young Finns Study. Exposure to passive smoking was established in childhood, and the researchers controlled for active smoking in childhood and adolescence, as well as age, sex, BMI, serum 25-OH vitamin D concentration, physical activity, and parental socioeconomic position.
The researchers found that exposure to passive smoking in childhood was lower quantitative computed tomography (pQCT) derived bone sum index in adulthood, lower heel ultrasound estimated bone mineral density in adulthood, and the incidence of low-energy fractures. “Individuals with elevated cotinine levels (3-20 ng/ml) in childhood had lower bone sum index with pQCT (β±SE -0.206±0.057, P=0.0003),” the authors write. “Children whose parents smoked and had high cotinine levels (3-20 ng/ml) had significantly lower pQCT derived bone sum index compared to those with smoking parents but low cotinine levels (<3ng/ml) (β±SE -0.192±0.072, P=0.008).”
The authors write that the most plausible mechanisms in smoking-induced bone loss are increased bone resorption and decreased efficiency in absorbing calcium. Tobacco smoke affects osteoneogenesis and osseointegration in bone cell culture, and animal models have shown tobacco smoke’s myriad effects on bone health. “In the present study,” the authors write, “independent associations were seen with different indices of bone mineral density, bone mass and strength after a 28-year follow-up in both men and women, suggesting that tobacco smoke exposure may compromise the growing bone through multiple mechanisms.”
Based on these findings, the authors conclude that exposure to secondhand smoke during childhood persistently affects bone health, independent of confounding factors. “Programs aimed at avoiding exposure to tobacco smoke early in life could improve later bone health of children in risk to passive smoke exposure,” the authors write.