Thin Bones

By Peter Galvin, MD

Osteoporosis is a disorder of decreased bone density that increases the risk of fractures, especially after a fall. Throughout life, our bones undergo a continual process of being broken down and rebuilt. With aging, the rate of bone breakdown begins to overtake the rate of bone building, which can lead to low bone mineral density and, eventually, osteoporosis and increased fracture risk. Hip fractures in particular are associated with disability, chronic pain, decreased quality of life, and death.

For women, decreased estrogen levels during and after menopause increase bone breakdown. As a result, postmenopausal women have a greater risk of osteoporosis compared with men and premenopausal women. Other risk factors for osteoporosis include cigarette smoking, high alcohol consumption, low body weight, long term steroid use, a history of fractures, stroke, diabetes treated with insulin, and a history of hip fractures in a parent.

Several risk assessment tools can be used to estimate the risk of osteoporosis. The most commonly used screening test is a type of imaging that measures bone mineral density, called dual-energy x-ray absorptiometry (DEXA or DXA). Most of these tests look at the “central” bones of the body, including the hip and spine. Sometimes DXA is performed on peripheral bones like the forearm or heel. Ultrasound can also be used on peripheral bones but does not directly measure bone mineral density.The term screening means looking for a condition or illness in individuals who do not have specific concerns or symptoms related to that illness. The pros of screening for osteoporosis are earlier diagnosis and treatment, which decreases the risk of future fractures. Because low bone density is asymptomatic, individuals may not know they have osteoporosis until a fracture occurs. There is significant evidence that DXA tests are accurate in diagnosing osteoporosis and that treating osteoporosis is effective in preventing fractures. The cons of screening are minimal, if any, as DXA is safe and noninvasive.

The U.S. Preventive Services Task Force (www.uspreventiveservicestaskforce.org) recommends screening for osteoporosis in women 65 years or older and also recommends screening for postmenopausal women younger that 65 years who are at increased risk for osteoporosis (see risk factors above). For men, there is not enough information available for the USPSTF to make a recommendation.

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