Smoking Increases Women’s Risk of Brittle Bones, Study Finds

Women who smoke run a higher risk of developing brittle bones late in life than women who do not smoke, two Australian researchers report in the New England Journal of Medicine.

The researchers said they studied 41 pairs of female twins and uncovered fresh evidence that smoking can play a key role in the development of the brittle bones that are the hallmark of osteoporosis.

The finding “has major consequences for public health,” said the authors, John Llewelyn Hopper and Dr. Ego Seeman of the University of Melbourne.

Based on cigarette consumption and measurements of bone density, they found that if one twin smokes an extra pack of cigarettes each day for 10 years, her lower backbone will be 2% less dense and her leg bones 1% less dense than the bones of her twin.

When one twin smoked two more packs per day than the other, her backbone density was 9% less.

A 10% drop in bone density over 10 years translates into a 44% increase in the likelihood of a fracture.

Because the number of pack-a-day smokers in the United States has doubled in the last two decades, “this study suggests that by the 21st Century there will be an increase in fractures attributable to smoking,” they said.

In an editorial in the same issue, Charles Slemenda of the Indiana University School of Medicine said doctors should be telling women that when they smoke they are increasing the likelihood of brittle bones as they age.

The female hormone estrogen is known to prevent a woman’s bones from losing their strength with age. Smoking, Slemenda said, seems to make estrogen less effective. It may also have a poisonous effect on bones.

Hopper and Seeman studied twins because a person’s genetic makeup can influence the risk of developing brittle bones. When twins are compared, those genetic differences are eliminated.