Published: Oct. 17, 2006
Updated: June 2, 2010
Osteoporosis, the lightening and weakening of the skeleton due to years or decades of bone loss, often causes no symptoms at all -- until bones become so thin and porous that they fracture at the slightest impact. These fractures can lead to a vicious cycle of increased fragility and additional fractures that may -- like the straw breaking the proverbial camel's back -- prove disfiguring, debilitating, or even fatal.
"Twenty to 30 percent of people who suffer hip fractures die within a year, usually because fracture makes other health problems even worse," says Thomas Weber, MD, director of Duke's Clinical Bone Laboratory. "Among those who survive, half are disabled."
Yet general awareness of the dangers of osteoporosis is relatively low. Research has found that women are usually more worried about relatively rare gynecological cancers, even though osteoporosis is far more widespread and associated with many more fatalities. Many people also believe that the visible signs of osteoporosis, such as height loss and curvature of the spine, are just "part of getting old."
They aren't. Though the risk for osteoporosis increases with advancing years, it's not a natural part of aging, but a disease caused by a shift in the metabolic processes that control bone loss and regeneration.
Like other living tissue, bone is constantly being replenished. In the process known as bone resorption, cells on the bone surface dissolve bone, creating small cavities -- in bone formation, the cavities receive new bone tissue, building and strengthening the skeleton. In children and young adults, new bone is added faster than old bone is removed, so that bones become heavier, denser, and larger until about age 30, when the cycle begins to reverse.
Menopause is a time of especially rapid bone loss -- smoking, excessive alcohol use, and a sedentary lifestyle also contribute to bone thinning. So can certain medications, including steroids, anti-seizure drugs, some cancer therapies, and even excessive amounts of common drugs such as thyroid hormone and aluminum-containing antacids.
The classic "poster child" for osteoporosis risk would be a slender, post-menopausal woman of Caucasian or Asian descent with a family history of bone fractures. But she is by no means alone. The disease can strike at any age. Obese people are not immune. And while women are four times more likely than men to develop osteoporosis, men also suffer from it -- as do African-Americans and people of other ethnic origins.
Today, 10 million Americans have osteoporosis and 34 million more have dangerously low bone mass. One out of every two women and one in four men over 50 will have an osteoporosis-related fracture in his or her lifetime.
While you can't change your age or sex, osteoporosis is a disease in which, to a large extent, you truly are what you eat. A well-rounded exercise program that includes both aerobic and weight-bearing components is also critical to keep osteoporosis at bay.
Ideally, these lifestyle choices should begin not in middle or advanced age, but in youth. "You really need to load your skeleton early in life," says Duke geriatrician Kenneth Lyles, MD, "because that's when you build the bone mass you'll be working from as you age. If you eat junk food and grow up as a couch potato, you may not achieve your full genetic potential -- and you'll move into your later years with less of a skeletal safety margin."
Getting appropriate screenings is another key to keeping bones healthy. At Duke, orthopaedic and sports medicine surgeons work closely with specialists in endocrinology and geriatrics to identify patients at risk for the disease.
According to Weber, a simple ultrasound test of heel-bone density, known as a peripheral screening, can offer a quick indicator of whether bone loss is under way. "While peripheral screening is not a definitive diagnostic test," he says, "it can lead people who didn't realize they were at risk to get a more in-depth evaluation."
That in-depth evaluation is provided by a central bone mineral density scan. Painless, non-invasive, and safe, the technology uses a weak x-ray to evaluate the density of bones in the spinal column, hip, or wrist. "Sometimes, we even spot fractures that the patient is unaware of," Weber says. Like many physicians, he and Lyles believe that most people with risk factors such as advanced age, low body weight, or a family history of fractures should be tested.
Should osteoporosis be diagnosed, even a calcium-rich diet and regular exercise may need to be augmented with one of the medications now widely available to help preserve or rebuild bone mass. Most of these drugs are known as anti-resorptives because they reduce the rate of bone dissolution, often making it possible to regain some lost bone density over time.
Lyles and several Duke colleagues recently published results showing that once yearly zoledronic acid given as a 15-minute intravenous (IV) infusion significantly reduces the risk of low-trauma fractures in older men and women who have had a recent hip fracture. A special form of parathyroid hormone recently approved by the FDA helps fight osteoporosis not by slowing bone dissolution, but by directly enhancing bone formation.
Though hormone replacement therapy (HRT) has proven clearly beneficial in reducing the risk of osteoporosis, millions of women abandoned the regimen after results of the Women's Health Initiative study linked HRT use to a heightened risk for heart disease, stroke, and cancer. According to Lyles, the results of this sudden, widespread withdrawal from HRT could be disastrous.
"Less than 10 percent of women who have stopped HRT in the past year are getting appropriate evaluation or treatment for osteoporosis," he says. "This is a huge issue, because there's evidence to suggest that the bone loss that occurs after HRT is stopped is even more rapid than during the natural process of menopause."
Yet another sobering fact about osteoporosis is how subtle the damage it causes can be. "The medical literature says that about two-thirds of spinal fractures don't come to medical attention," says Lyles. "Either they cause no symptoms, or the discomfort they cause is chalked up to the aches and pains of aging." Osteoporotic fractures usually heal in two or three months, but -- in addition to weakening the body if unrecognized and untreated -- sometimes cause persistent pain.
An emerging, FDA-approved procedure called a vertebroplasty, which is offered by interventional radiologists at Duke, can be helpful. A tiny, carefully controlled stream of a special cement is injected into a fracture, lowering nerve stimulation and reducing pain.
Vertebroplasty is most typically recommended for people who have severe, persistent pain lasting more than three months after a fracture. Duke also offers a procedure called a kyphoplasty, which helps realign vertebrae damaged by compression fractures and can sometimes restore lost height.
Of course, it's better to avoid fractures entirely than cope with their effects. But even if you didn't eat enough dairy products in your formative years, there's no point in crying over spilled milk. "You have to go forward from where you are now," says Lyles. "So get informed about your bone density issues. That will give you the tools to help prevent fractures -- and hang on to what you've got."