Fighting a Silent Thief
Start early to protect your bones from osteoporosis

Alice Fisher

Maureen Dunn is grateful to the man who tried to steal her purse on a warm evening in Paris back in 1995. She was sitting in an outdoor café with her husband when the thief made off with her handbag. In hot pursuit, the Toronto woman was knocked to the ground and broke her wrist. Then 58 and a healthy and dedicated long-distance runner, Dunn was shocked to learn when she returned to Canada (recovered purse in hand) that she had osteoporosis, or brittle bone disease.

The robbery was a turning point for her: she decided to become an advocate for bone health. Today, she volunteers at Osteoporosis Canada and tries to get young people concerned about bone health. “You’ve got to catch potential problems while you’re still a kid,” she says.

Dunn is certainly not alone. She’s among the one in four postmenopausal Canadian women diagnosed with osteoporosis, a disorder characterized by thinning bones. Osteoporosis can result in the disfiguring spine curvature known as “dowager’s hump” and fractures—particularly in the hip, spine and wrist—sometimes incurred in something as ordinary as playing the piano, opening a window or shovelling snow.

The disease also affects one in eight men over age 50. Altogether, about 1.4 million Canadians are currently living with osteoporosis. Owing to the decline in estrogen levels during and after menopause, women start experiencing forearm fractures in their 50s, spinal fractures in their 60s and hip fractures in their 70s. Men tend to get the same fractures 10 years later in each category.

Hip fractures are among the most common consequences of this skeletal disease. In 1993, Canada reported about 25,000 hip fractures, three-quarters of which were related to osteoporosis. And these fractures can be deadly. One in five women dies following hip surgery. For men, the risk of dying after hip surgery is even worse at one in four. “We don’t fully understand the sex difference,” says bone specialist Dr. Aliya Khan, a professor of medicine at McMaster University in Hamilton, Ont. “It could be that men have more heart or lung disease and are less able to tolerate a major fracture and surgery.”

These deaths generally occur in the six months immediately following a fracture, when patients are bedridden for prolonged periods, says Khan. “They get blood clots in their legs, which travel to their lungs and kill them.”

The annual costs of treating such fractures are staggering. Osteoporosis Canada reports that the bill totals $1.3 billion each year for medical care alone. And it warns that with our aging population, annual costs could soar to $32.5 billion by 2018 if we fail to develop more effective prevention and treatment strategies.

Osteoporosis is not an inevitable consequence of aging, but you can bring it on by lifestyle choices: a low-calcium, low-calorie, high-sodium diet or being sedentary, smoking and drinking alcohol or caffeine to excess. These habits can prevent the development of healthy bones when you’re young and hasten bone loss when you’re older.

Dunn, who since her Paris fall has taken calcium and vitamin D supplements and a prescription drug to prevent bone loss and further fractures, wishes she had implemented her own prevention strategies earlier. “I hated milk as a child,” she recalls with a wince. But she should have taken supplements or dietary alternatives to calcium-rich dairy products.

Like her, many kids today are not getting enough bone-building calcium during those important years from late childhood to the early 20s, when the human skeleton is reaching its peak bone mass. One of the problems, says Khan, is that children are reaching for soft drinks full of bone-depleting phosphorus and caffeine, which increase calcium loss through the kidneys.

Khan worries, too, that today’s youngsters are not getting enough physical activity, another essential element in creating a strong, dense skeleton. And she’s concerned about adolescent girls with eating disorders such as anorexia nervosa who literally starve themselves and as a consequence cease menstruating. “When they stop having periods, they don’t have estrogen in the crucial bone-forming years of the teens,” she says. For adolescent girls, normally functioning ovaries are essential for bone formation.

A woman’s peak bone mass remains relatively stable until the age of 35 or so, when it starts to drop off at the rate of approximately 1% per year until menopause. After the loss of estrogen at menopause, bone loss can accelerate to an annual rate of 5% to 10% for up to 10 years. The estrogen in birth control pills can help protect bones during the reproductive years, especially for women who have irrregular periods. After menopause, hormone replacement therapy (HRT) may protect the bones, although prolonged use increases the risk of blood clots, heart attack, stroke and breast cancer.

Treatments

Once you’ve been diagnosed with osteoporosis, you’ll likely receive a treatment that either prevents further bone loss or helps build new bone. Bisphosphonates fall into the first group, helping to slow bone loss by killing off bone-destroying cells called osteoclasts (see primer). “We see significant improvements in bone density with these drugs, and that reduces fractures of the spine, hip and forearm by about half,“ says Khan. Fosavance, a recent variation of the bisphosphonate alendronate (Fosamax), combines the basic drug with vitamin D in a single tablet.

At Laval University in Quebec City, rheumatologist Dr. Jacques Brown is excited about zoledronic acid (Zometa), a new bisphosphonate given once a year in 15-minute infusions. “It interferes with the bone-destroying cells to produce a prolonged effect,” he says. It should be available in Canada within the next two years.

Ibandronate, a bisphosphonate marketed in the U.S. as Boniva, is not available in Canada. “It has not proved as effective as Fosamax in preventing hip fractures,” Khan says.

SERMs (selective estrogen receptor modulators) are another class of bone-preserving drugs. These agents bind to estrogen receptors in bone to provide the positive protective effects of estrogen but, unlike HRT, they do not pose risks of stroke, blood clots or heart attack. SERMs are proving to be an excellent agent for protecting breast and uterine health. A recent study showed that the SERM raloxifene (Evista) equalled the anti-estrogen drug tamoxifen in preventing breast cancer in vulnerable women, reducing the risk by half. A new series of drugs in this class is set to appear on the market within two years.

Calcitonin, a hormone taken in a nasal spray, slows down the bone-eroding osteoclasts (see primer, p. 40) and allows the osteoblasts to build bone more effectively.

Anabolic agents, such as parathyroid hormone and its analogues, actually build bone. The newest one, teriparatide (Forteo), is causing a stir in medical circles. Injected every day over 18 months, it can thicken bone and in some cases restore the skeleton to normal. Several other anabolic agents will come on stream within two years. The drawback is price. Forteo, for example, costs about 10 times as much as a bisphosphonate. But price aside, anabolic agents would be the first-line treatment. “The best approach is to use a bone-forming agent for 18 months, then maintain the gains with bisphosphonates, SERMs or other drugs,” Brown says.

Strontium, a metallic element occurring naturally in soil, has both bone-protecting and bone-building properties. It should be available in Canada early next year.

With new treatments on the way and growing public awareness about prevention, this silent thief—just like the Parisian crook who grabbed Dunn’s purse—may soon be stopped in its tracks.

For more details, call 1 800 463 6842 or go to www.osteoporosis.ca.

Bone Primer

Far from being an inert monolith, your skeleton is composed of dynamic living tissue with a regular cycle of turnover. Bone is made up of cells, blood vessels and calcium compounds, which together create the porous, mineralized structure that makes up your body’s complex scaffolding. Bone has a hollow core containing the bone marrow that makes most of your blood cells.

• Cortical bone

Almost 80% of your skeleton consists of cortical bone in the form of a protective outer shell (cortex means “tree bark” in Latin). Cortical bone is predominant in the limbs and contributes to the skeleton’s strength.

• Trabecular bone

This type of bone makes up most of the skull, ribs and spine. It helps to maintain the skeleton’s shape and also plays a role in certain metabolic functions.

• Bone remodelling

Both cortical and trabecular bone contain bone marrow, and both undergo a constant two-part process of renewal and remodelling. In this, old bone is broken down and replaced with new tissue. In a young, healthy person, the turnover is repeated every three to four months but slows down with age. It involves three groups of cells.

• Osteoclasts
  These are a kind of wrecking crew that excavates weak and crumbling areas in the skeleton and removes old bone.

• Osteoblasts
  These are the renovation guys that fill in the resulting crevices with material that is calcified to form new bone.

• Osteocytes
  These are responsible for maintaining existing bone.

• Sex hormone receptors

When activated, estrogen receptors on the surface of bone cells increase the hormone’s availability to the skeleton, thereby inhibiting bone destruction and fostering bone formation. The male hormone testosterone has a similar effect.

Know the Risks

Osteoporosis is sometimes called the “silent thief” because, as in Dunn’s case, it may not have any symptoms until a bone suddenly snaps. That’s why it is so important to be aware of your risk factors.

Risk factors you CANNOT change

• Age

Risk rises at about age 50 and sharply increases after 65.

• Sex

Women are more susceptible to osteoporosis and fractures than men because they have much lower bone-mineral density.

• Irregular menstruation

A past history of irregular or no periods and early eating disorders can mean a weakened skeleton. 

• Family history

If someone in your immediate family has or had osteoporosis, you’re more likely to get it, too.

• Race

Caucasians have a slightly increased risk.

• Height

Taller people are more likely to fracture bones because their longer bones offer larger potential breakage areas.

• Diseases

Parkinson’s patients have decreased mobility and are at greater risk of falls and fractures. Celiac disease, an intestinal condition of impaired nutrient absorption, is linked to weak bones.

• Fracture after age 40

This signals a possible existing problem and more problems to come with age.

• Drugs

Prolonged use of corticosteroids such as prednisone can decrease the absorption of calcium by the intestines and hasten its excretion by the kidneys. Diuretics, anticonvulsants and the blood thinner heparin can also deplete calcium.

Risk factors you CAN change

• Weight

People weighing less than 127 pounds lack the load-bearing and bone-strengthening benefits of carrying more pounds.

• Calcium deficiency

This mineral is the essential building block of bone (see requirements).

• Vitamin D deficiency

The bioactive form of this vitamin, made in the kidneys, signals the intestines to absorb more calcium from food or supplements, thus increasing bone-mineral density. Older people may need a supplement (see requirements).

• Being sedentary

The weight-bearing activity of walking is the best bone-preserving exercise. Strength-training exercises may help by increasing the load on the skeleton, triggering it to increase mass in order to spread the load around.

• Smoking

Tobacco smoke interferes with bone deposition.

• Alcohol, caffeine and phosphoric acid

Consumed in excess, these promote calcium excretion via the kidneys.

Calcium and Vitamin D

Minimum Daily Requirements

Calcium

• Children (age 4 to 8): 800 milligrams (mg)
• Children (age 9 to18): 1,300 mg
• Pregnant and lactating women: 1,200 mg
• Men and women under age 50: 1,000 mg
• Men and women over age 50: 1,500 mg

Vitamin D

• Children (age 4 to 8): 400 International Units (IU)
• Children (age 9 to 18): 400 IU
• Pregnant and lactating women: 400 IU
• Men and women under age 50: 400 IU
• Men and women over age 50: 800 IU

Bone Angels

U.S. researchers are studying estren, an agent in a new class of drugs called ANGELS (activators of non-genomic estrogen-like signalling). They’ve found that estren protects bone mass in male and female mice just as well as estrogen and testosterone do. But because ANGELS separate bone-boosting properties from reproductive effects, they do not cause the potentially harmful changes in reproductive organs that sex hormone therapy can.—Diana Swift