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New Discoveries Address Osteoporosis Risk

May 5, 2010

Two separate research studies add to our growing knowledge about preventing osteoporosis, the disease responsible for bone thinning that leads to fractures. Work done by a team of international researchers has identified 20 genes associated with osteoporosis and bone weakness, including 13 genes never previously associated with the disease. Osteoporosis reduces bone mineral density (BMD) and disrupts the microarchitecture of bone tissue, making bones more fragile and subject to fracture. The disease affects an estimated two million Canadians and 75 million people in the USA, Europe and Japan. Osteoporosis is a highly heritable trait, but this marks the largest international effort to conclusively identify genes linked to the often-devastating bone disorder. The study's co-first author is Dr. J. Brent Richards of the Lady Davis Institute for Medical Research at the Jewish General Hospital in Montreal, who collaborated with more than 30 co-authors worldwide. Their results were published recently in the journal Nature Genetics. The researchers reviewed data collected from nearly 20,000 individuals in five recent international genetic studies. "Osteoporosis hip fractures alone cost $2.4 billion dollars per year in Canada in direct care," said Dr. Richards, a genetics researcher at the Lady Davis Institute and an assistant professor at McGill University's Faculty of Medicine. "Hip fractures are a common and costly condition which has a 50 percent mortality rate at two years, worse than some cancers." Though it occurs in people of all ethnic groups, the lion's share of the osteoporosis burden falls on post-menopausal women of European and Asian descent. According to the International Osteoporosis Foundation (IOF), one in three women over the age of 50 will experience osteoporotic fractures, as will one in five men. By 2050 the worldwide incidence of hip fracture is projected to increase by 310 percent in men and 240 percent in women. "We were able to look across the whole human genome to try to identify which genes—of all the genes that we inherit—that seem to be responsible for osteoporosis," Dr. Richards explained. "Not only did we find 13 entirely new genes, we also demonstrated that some of these genes were related not just to bone density, but also to fracture risk itself." Richards is optimistic that these results will bring practical benefits to patients. "In order to better treat any condition, we need to know what causes it," he said. "We knew that one of the strongest factors in osteoporosis was genetic, but we didn't have a clear picture what those genetic factors were. This study affords us the opportunity to study the genetic mechanisms, which control bone strength, and to intervene to prevent peoples' bones from getting weak. Also, if we are able to uncover more genes which influence bone strength, then we may be able to identify whole populations that require early preventive treatment."

The second study looks at the role of exercise in osteoporosis prevention. According to a study from the Sahlgrenska Academy at the University of Gothenburg in Sweden, where osteoporotic fractures affect one in two women and one in five men at some point in life. Brittle bones cause 70,000 fractures in Sweden annually, and these fractures often result in reduced function and considerable suffering for the patients concerned. Researchers found that the positive effects of exercise while growing up seem to last longer than previously believed—physical activity when young increases bone density and size, which may mean a reduced risk of osteoporosis later in life. Among 3,200 participants, the researchers studied bone density throughout the body in around 500 randomly selected 75-year-old men. Those who had done competitive sports three or more times a week at some point between the ages of 10 and 30 had higher bone density in several parts of the body than those who had not. The researchers established that there is a positive link between exercise while young and bone density and size. The connection is even stronger if account is taken of the type of sports done. "The bones respond best when you're young, and if you train and load them with your own bodyweight during these years, it has a stimulating effect on their development," says Martin Nilsson, physiotherapist and doctoral student at the Institute of Medicine. "This may be important for bone strength much later in life too, so reducing the risk of brittle bones."