Headlines
As reported by the New Haven Register, July 1, 2008.
Depleting the Bone
By Abe Katz
Connecticut women are at a higher risk for osteoporosis than other women in the continental United States, according to a study by the U.S. Centers for Disease Control and Prevention.
Only post-menopausal women in Hawaii were found to be more prone to the bone-depleting disease, according to the study, conducted at Johns Hopkins University and the Maryland Department of Public Health.
About 10 million Americans older than 50 have osteoporosis. Another 34 million are at risk, and 1.5 million experience broken bones related to osteoporosis, according to the U.S. surgeon general.
While the study suggests that Connecticut women be screened for bone loss and take other measures, there is no test to determine whether “thinner” bone is necessarily weaker than regular bone, said Dr. Lawrence G. Raisz, director of the University of Connecticut Health Center’s Center for Osteoporosis.
Raisz helped write a 2004 study of osteoporosis by the U.S. Department of Health and Human Services. This research suggests that by 2020 half of all Americans over 50 will be at risk for bone fractures because of osteoporosis or low bone mass.
The Maryland scientists analyzed weight and age statistics of 62,822 post-menopausal women to estimate each state’s risk.
About 11.5 percent of Connecticut’s older women are at high risk for osteoporosis, researchers calculated. Only Hawaii, at 14 percent, showed more risk.
Louisiana’s elderly women are at a 5.4 percent risk.
“Osteoporosis is usually undetected until a bone breaks, so it’s hard to say how many people indeed have it,” said Dr. Jo-Anne Smith, clinical director of UConn’s center for osteoporosis.
“It’s not realistic for everyone in Connecticut to go for a bone density test, but this study, at the very least, suggests a way to get a sense of how prevalent osteoporosis may be in our population,” Smith said.
The study’s authors based their calculations of risk on the woman’s weight and age, rather than using bone mass density, as in previous government studies.
The main advantage of the Osteoporosis Self-assessment Tool Index is its ease of use and low expense, the authors wrote.
Raisz said Connecticut women may be at higher risk because as a population they are older, thinner than average, and probably receive less vitamin D because Connecticut is at a fairly high latitude.
Vitamin D is important because it reduces bone loss. Vitamin D, which the body makes in response to sunlight, interferes with a protein necessary to make osteoclasts, the cells that remove calcium from bone.
Bone-removing osteoclasts work much faster than bone-building osteoblasts, resulting in osteoporosis.
Other states may not have the same combination of age and weight. Also, blacks have a lower rate of osteoporosis than whites.
Men of the same age have half to one-quarter the risk of osteoporosis as women, largely because men have higher levels of the protective hormone testosterone.
Estrogen defends women until they reach menopause, at which point estrogen levels drop significantly.
Currently, bone density tests are used to assess a person’s risk of a fracture aggravated by calcium-depleted bones.
However, the microscopic structure of bones is not the same in all cases of osteoporosis, Raisz said.
In some people, remaining bone forms a thin plate structure. In others, the bone becomes more like a sponge, with many of the arches disconnected, he said.
Generally, the plate structure is stronger than the sponge, meaning that some people with higher, “spongy” bone density may be at a higher risk of fracture than individuals with a lower density platelike configuration, Raisz said.
Fractures among the elderly are often a life-altering or life-ending event.
About 20 percent of senior citizens who suffer a hip fracture die within a year, the department of health and human services calculated.
Hip fractures also account for 300,000 hospitalizations a year, at a cost of about $18 billion annually in the United States.
The Department of Health and Human Services recommends that every person over 50 receive recommended amounts of calcium and vitamin D; remain physically active with at least 30 minutes of exercise a day; and take steps to prevent falls, such as moving objects that might cause tripping, improving lighting and taking vision and balance tests.
These steps could cut the risk of fractures by half, Raisz said. Early detection of bone loss is also important, he said.
The density of bones is now measured in a process called dual energy X-ray absorptiometry, or DXA. During this painless and brief test, certain bones, usually in the lower spine or hips, are exposed to two wavelengths of X-rays. One is more sensitive to minerals and the other to soft tissue.
Using computers, the “soft-tissue x-ray” can be removed, leaving an image of minerals.
The test is usually summarized as two scores, the T score and Z score. The T score indicates bone loss, while the Z score shows how the patient compares to others of her age.
The only difficulty, Raisz said, is that sometimes the same bone of the same density can be weaker because of the underlying structure.
Eventually, magnetic resonance imaging or micro computerized tomography, (micro CT) may yield more revealing results, he said. Both offer greater resolution. The micro CT, in particular, can make images of samples smaller than a tenth of a diameter of a human hair.
“Right now, this is a research tool. Five years from now, it will be in clinical use,” Raisz said.
Meanwhile, fewer women are choosing hormone replacement therapy, which would help protect against bone loss. Much of the reluctance is based on a controversial 2002 Women’s Health Initiative Study that found hormone replacement therapy increased the risk of heart disease and other health problems, Raisz said.
That leaves bisphosphonate drugs, which retain bone by binding to
sites to which bone-removing osteoclast cells would otherwise
attach.
Another drug, teriparatide, is a synthetic parathyroid hormone that
stimulates bone formation.
“Osteoporosis is a disease of civilization and aging,” Raisz said. “There is no population anywhere that doesn’t have osteoporosis.”