How much does smoking affect your bone density?

Smokers have, on average, one tenth of a standard deviation less bone mass than people who have never smoked, across all measured sites combined. At the hip, that difference rises to one third of a standard deviation. This is not a small margin: the effect is dose-dependent, meaning the more you smoke, the greater the damage. Older adults and men appear to be hit the hardest.

That loss of bone mass translates into a considerably higher risk of fractures. For a hip fracture, the estimated lifetime risk is 31% higher in women and 40% higher in men. The risk of a vertebral fracture rises by roughly 13% in women and 32% in men. A large American population study confirms this picture: people with high smoking exposure had more than twice the risk of osteoporosis, and current smokers had a 70% higher risk of osteopenia (an early stage of bone density loss) than non-smokers.

Quitting smoking helps. Former smokers have a smaller bone mass deficit than people who still smoke, indicating that bones can partially recover after quitting. Returning fully to the level of someone who has never smoked does not appear to be achievable, but the difference does become smaller.

One caveat: smoking by the mother during pregnancy does not appear to have a direct effect on the child's bone density in itself. What initially seemed like a difference disappeared once researchers accounted for the child's birth weight and body size.