Fortunately, there are now diagnostic tools that can expose osteoporosis long before bones become dangerously fragile. These, coupled with an improved understanding of how the disease functions, have lead to new therapies and preventive strategies for tackling osteoporosis.

The term osteoporosis comes from the Latin for "porous bone." Our skeletons may seem fixed in size and shape, but they are actually living tissue that must be continuously renewed. "Your bones suffer daily wear," explains Mariluz Villa, M.D., Clinical Assistant Professor at the University of Washington School of Medicine. When damaged, the tissue is broken down by specialized bone cells called osteoclasts and replaced by others known as osteoblasts. "If you are not providing your body with enough building blocks to do the repairs," says Dr. Villa, "you can gradually lose bone over time." When bone mass and structure deteriorate too far, osteoporosis results. According to the National Osteoporosis Foundation, osteoporosis is a major health threat for more than 28 million Americans. Ten million already have the disease and 18 million more have low bone mass.

The fractures associated with osteoporosis are a critical danger. The hip, spine, wrist and ribs are most often affected, accounting for 1.5 million fractures each year. Of these, 700,000 are vertebral fractures, which occur when spinal vertebrae become so weak that they collapse, resulting in the stooped appearance often associated with the disease. Besides causing pain and discomfort, this condition, known as kyphosis, can make breathing difficult and put the spinal cord at risk for injury.

The consequences of a hip fracture can be even more serious. According to the National Osteoporosis Foundation, 24 percent of people over 50 who have hip fractures die within a year. Studies show that a woman's risk of fracturing her hip-equal to her combined risk for breast, uterine and ovarian cancer-is two to three times higher than a man's. For men, however, the risk of dying within the year is twice as high.

WHO IS AT RISK?

Women currently make up 80 percent of all osteoporosis cases. They are especially vulnerable due to the decline of blood estrogen levels after menopause. While it is best known for its role in reproduction, estrogen is now believed to inhibit osteoclasts from breaking down damaged bone. When levels decline, bone is broken down faster than it is rebuilt. During the first five years after menopause, when estrogen levels drop as much as 90 percent from the lifetime high, women can lose up to four percent of their bone mass each year.

The absence of similarly dramatic hormonal fluctuations in men makes them less vulnerable to osteoporosis. There are only two million American men with the disease, compared to eight million women, according to the National Osteoporosis Foundation. One of the reasons for this discrepancy, however, is that many doctors continue to think of osteoporosis as a women's disease. Even when there is compelling evidence, many men with osteoporosis go undiagnosed.

A similar bias contributes to the relatively low incidence of osteoporosis among minority women. However, scientists now know that, in addition to Caucasian and Asian females, other minority women are at risk. In fact, 10 percent of African-American women over 50 have osteoporosis, according to the National Osteoporosis Foundation, and 30 percent more have low bone density. "Osteoporosis does occur in African American and Latino women, and it should be something that is considered by physicians when they are taking care of all older women," says Sharon A. Brangman, MD, associate professor of medicine at Upstate Medical University in Syracuse, NY.

NEW TOOLS ARE MAKING EASIER AND EARLIER OSTEOPOROSIS DIAGNOSES POSSIBLE

Bone mass measurement or bone mineral density tests can now predict the chances of fracture, determine the rate of bone loss and monitor treatments. These are non-invasive, safe and painless procedures, which use x-rays to measure different bones. Results are compared to one of two standards, young normal-optimal strength for a similarly proportioned healthy 30-year old adult, or the expected mass of a healthy adult the same age as the patient. When a patient's bone mass falls significantly short of these standards, they are considered to have osteoporosis.

Dual Energy X-ray Absorptiometry (DXA), which measures the spine, hip or entire skeleton, provides the most precise measurements. Single Energy X-ray Absorptiometry (SXA), measures bones in the wrist or heel. Other available tests include PDXA, DPA, SPA, QCT. There is also an ultrasound technique, which uses sound waves to measure bones in the heel, shin and knee.

Getting tested for osteoporosis-especially if one is at risk-is critical. Major risk factors include being female, thin or of advanced age, or having a low- Calcium diet or a family history of the disease. Being past menopause increases the risk for women, as does a history of amenorrhea-abnormal cessation or suppression of menstruation. Among men, low levels of the hormone testosterone, often a consequence of extremely high stress, is also a risk factor. Smoking and excessive alcohol consumption are risk factors for both genders. Some drugs, such as corticosteroid and too much thyroid medication taken over long periods, may also put one at risk.

PHARMACEUTICALS PROVIDE NEW HOPE

The most popular approach for older women is hormone replacement therapy (HRT), which replaces the estrogen lost after menopause. Besides strengthening the entire skeleton, halving the risk of hip fracture and reducing the risk of spinal fraction by up to 75 percent, HRT has the added benefit of protecting against heart disease and stroke. Unfortunately, it can also cause uterine bleeding and, over time, increase the risk of breast cancer.

Such problems have motivated researchers to develop a new class of synthetic estrogens known as Selective Estrogen Receptor Modulators (SERMs). SERMs emulate the estrogen molecule with slight modifications designed to mitigate side effects. One of the first SERMs approved by the FDA for osteoporosis is raloxifene, which was introduced in 1997. Studies show that raloxifene is effective in reducing bone fractures without causing bleeding. However, it is not as effective as HRT and does not improve other symptoms associated with menopause, such as hot flashes.

Another effective treatment is alendronate, one of the newest of a class of drugs known as biphosphonates, which has been available since 1995. Alendronate has been shown to reduce spine, hip and wrist fractures by 50 percent. However, it must be taken first thing in the morning every day, on an empty stomach, with a large glass of water while seated upright, in order to avoid heartburn.

Calcitonin, a nasal spray treatment, has been shown to increase bone density in the spine, resulting in less pain and up to 40 percent fewer vertebral fractures. We do not know if calcitonin affects other bones, however.

PREVENTION IS THE BEST BET

The best way to address osteoporosis is to avoid it altogether by adopting a healthy lifestyle. And the best time to do this is in childhood. "You gain the most bone during puberty, when the body is doing a lot of growing and maturing," explains Dr. Villa. "That's why it is very critical that young people get enough calcium and vitamin D." Nevertheless, our bodies continue building bone until about age thirty, leading some experts to believe that women in their twenties can increase their bone strength by as much as 20 percent.

Calcium and vitamin D are critical to building bone strength. Adolescents and post-menopausal women should get 1,500 milligrams of calcium every day-about the equivalent of five 8-ounce glasses of milk. Men and women between the ages of 25 and 65 need at least 1,000 mg of calcium. Supplements are encouraged for anyone who cannot get enough calcium through their regular diet.

 

Vitamin D is also essential because it helps the body absorb calcium. Being outside for even a short time each day allows the body to manufacture the approximately 400 IU of vitamin D needed each day. However, studies show that nursing home patients are frequently vitamin D deficient, as they rarely get enough sunlight. Studies also show that during the winter, no amount of sunlight is adequate for people who live above the 40th parallel (the approximate latitude of New York City). This is due to the angle of the sun, which is too oblique to provide enough sunlight for the body to manufacture the vitamin. In circumstances such as these, supplements are essential.

Moderate weight bearing exercise is also important for avoiding osteoporosis. "Bone, being a live tissue, responds to the needs that the body puts on it," explains Dr. Villa. "Say at age 30 you become sedentary, there's not a lot of incentive for your bones to stay pumped up, because there's no work for them to do." Good sources of such exercise include walking, running or playing tennis.

Ignorance is osteoporosis' biggest ally. The more we learn about this disease, the less we have to fear its unexpected arrival. A healthy diet and lifestyle, coupled with screening for those at risk and carefully monitored therapy for those with positive diagnoses, can help everyone-women, men, minorities and children-better protect themselves. By talking to our doctors and following these simple steps, it is possible to make "the silent disease" truly silent.