The Medical Minute: National Osteoporosis Awareness Month

By John Messmer

Chances are mothers received flowers, dinner or other gifts this Mother's Day from loving children who want only the best for them. When dinner is past and the flowers have wilted, we should ask our mothers, wives and sisters what they are doing to protect their bones. They could be at risk for osteoporosis.

Bones are made of calcium deposited into a protein scaffold. Osteoporosis results when the calcium content of bones, referred to as “bone mass,” drops low enough for a risk of fracture. Osteopenia is the term for bones with abnormally low amounts of calcium but not low enough to be osteoporosis. Our bones are the framework to which our muscles attach and if they are weak, they can break, sometimes without any significant trauma.

While broken bones can often be repaired, having a broken hip increases the risk of death by 10-20 percent and is associated with a high risk of another fracture in the next year. About 25 percent of those who sustain a hip fracture require long term nursing home placement, and 40 percent never regain their prior level of independence. Fractures of the vertebrae can lead to kyphosis or "dowager's hump," which, in addition to being uncomfortable, can compromise heart and lung function. It is estimated that osteoporosis-related fractures cost us more than $17 billion annually. That could double or triple by 2040 with the increasing age of our population.

Osteoporosis is common. Among women over 50, it is estimated to be present in 20 percent of non-Hispanic Caucasians and Asians, 10 percent of Hispanics and 5 percent of non-Hispanic blacks, and osteopenia in 52, 49 and 35 percent of these groups, respectively. (Men with osteoporosis are fewer and typically older.) It does not happen suddenly, however. About 90 percent of a woman's bone mass is present by age 18. She gives up calcium for each baby she has, and by age 35 she begins to lose calcium faster than she replaces it. After menopause the rate of loss accelerates. Since it does not cause any symptoms until a break occurs, it is not possible to "feel" osteoporosis.

Bone mass can be measured by a bone density test, commonly through a dual-energy X-ray absorptiometry or DEXA scan. A DEXA is a special X-ray exam of the spine, hip and sometimes the forearm, performed without special preparation and taking only a few minutes. The DEXA machine analyzes the amount of calcium in the bone and compares that to the amount that should be there at her age (the Z-score) and to the amount a healthy young woman would have (the T-score). If the T-score is less than -1.0, it means osteopenia; less than -2.5 means osteoporosis.

Fortunately, osteoporosis and osteopenia are preventable and treatable before damage occurs. Everyone needs enough calcium in their diets to build bone tissue. The main sources of calcium are dairy products, but meat, fish and many green vegetables have a little. Everyone needs at least 800 mg of calcium daily; those at higher risk for osteoporosis need 1,200 mg. Milk and yogurt have about 350 mg in 8 ounce and cheese has about 200 mg per ounce. Calcium fortified foods and calcium supplements can provide this essential mineral for those who cannot or will not consume dairy products.

Vitamin D is necessary to absorb and store calcium. Since the 1930s, vitamin D fortified milk has been the norm, with each cup of milk supplying 100 IU of vitamin D. Children and adults up to age 50 need a minimum of 200 IU daily and adults over 50 should have 400 IU. Some authorities are recommending even more, although more than 1,000 IU daily may be excessive. Oily fish like salmon, cod, tuna, sardines and mackerel can supply 200-400 IU per 3 ounce serving.

Another source is sunlight, which induces the production of vitamin D in the skin. It is possible for most people to meet their vitamin D needs through sun exposure, with some caveats. Ultraviolet B (UVB) light, which is not responsible for sunburn, converts vitamin D precursors in the skin into vitamin D. The more sunlight available, the more likely a person can get enough vitamin D from the sun. Above 42 degrees north latitude, roughly a line from the northern California border to Boston, the sun is not bright enough from November to February to meet vitamin D needs. Farther north, the low-light season is longer. Cloud cover, time of day, smog and sunscreen reduce UVB, and UVB does not penetrate glass.

Despite these limits, depending on the season and cloud cover, only 5-30 minutes of exposure to the face and arms without sunscreen twice a week between 10 a.m and 3 p.m. will produce enough vitamin D. That amount of sunlight is unlikely to increase the risk of skin cancer, wrinkles or sunburn in all but the most sensitive fair-skinned people. Darker skin absorbs less UVB so exposure times need to be longer, but the risk of sun damage is less in darker skin.

Smoking and more than three alcoholic drinks per day take calcium out of bones. Exercise, particularly weight-bearing and strengthening exercises, encourages stronger bones and also reduces the chance of falling. This includes walking, jogging, stairs, weightlifting, Tai-Chi, dancing and so on.

If osteoporosis is present, treatment is available. The need for calcium and vitamin D remains, but there are various medications that can reverse osteoporosis. Each medication has pros and cons so it’s best to work out treatment with one’s physician.

One class of osteoporosis medication, the bisphosphonates, has received some bad press coverage recently due to its association with osteonecrosis of the jaw. Patients should understand that this very rare complication is highly unlikely except in cancer patients receiving the intravenous version of the medication to treat complications of the cancer and who develop an infection in the bone of the jaw. Other than these patients, the danger from osteoporosis far exceeds the exceedingly rare complication of osteonecrosis.

Let’s encourage America's women (and older men) to think about their bone health by exercising, getting enough calcium and vitamin D and discussing a screening for osteoporosis with their physicians. What better Mother's Day gift could there be than a future free of disability from a pathologic fracture?

For more information on osteoporosis, go to www.niams.nih.gov/Health_Info/Bone/Osteoporosis/default.asp or www.nof.org on the Web.

John Messmer is associate professor of family and community medicine at Penn State College of Medicine and a staff physician at Penn State Hershey Medical Center.
 

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Last Updated March 19, 2009