For the millions of people worldwide with osteoporosis, one tumble can break a hip, and a hug can crack a rib. Drugs can stop bones from thinning, but can't rebuild them. Now four studies suggest that drugs widely prescribed for lowering cholesterol unexpectedly appear to strengthen bone and prevent fractures.
Like a work crew repairing an aging street, the body normally maintains bones by digging holes, then refilling them with fresh material. Osteoporosis occurs when the body breaks down bone faster than it can replace it. Osteoporosis drugs as well as estrogen replacement therapy slow bone loss by blocking cells called osteoclasts, which dig the holes. But none of these drugs stimulates the cells, called osteoblasts, that fill in the holes.
In a surprising finding last December, a team led by endocrinologist Greg Mundy of the biotech company OsteoScreen and the University of Texas Health Science Center in San Antonio showed that statins--cholesterol-lowering drugs taken by more than 12 million people in the United States alone--dramatically boosted new bone growth in mice and rats (Science, 3 December 1999, p. 1946). But no one knew whether they would work in humans.
Now two studies reported in the 28 June issue of the Journal of the American Medical Association (JAMA) and two in the 24 June issue of The Lancet suggest that statins do build bones in people. In the largest JAMA study, a team led by Herschel Jick of Boston University School of Medicine compared the medical records of 3940 British patients older than 50 who had suffered fractures with 23,379 who had not. After adjusting for other factors that affect bone strength, they found that people who took statin were 45% less likely to have suffered fractures. Three other studies had similar results.
Statins seem to boost bone density significantly, a team led by rheumatologist Tim Spector of St. Thomas' Hospital in London reports in JAMA. After excluding the effects of hormone replacement therapy, age, height, and weight, the researchers found that the bones of women who took statins had 8% more mass than the bones of those who didn't.
"These are really quite striking reductions in fractures," says endocrinologist Conrad Johnston of Indiana University School of Medicine in Indianapolis. But he cautions that it's too soon for doctors to prescribe statins to treat osteoporosis. Proving that the drugs really strengthen human bones and prevent fractures will require clinical trials, he says, in which patients are randomly assigned to take statins or placebos.