Osteoporosis (ah-stee-o-por-O-sis), which literally means “porous bones,” is a disease that occurs when there is loss of bone density, which increases the likelihood of a bone fracture from even a minor fall or bump.
Bone is living tissue. There are two general types of bone tissue: cortical and spongy. Cortical bone is dense and compact and generally forms the outer layer of bones. Spongy, or cancellous, bone generally forms the inner layer. Spongy bone is mesh-like and contains bone marrow * within its meshwork. Osteoporosis is more common in bones with a large percentage of spongy bone. These include the vertebrae (bones of the spine), the hips, and the wrists. These bones are more fragile and are especially prone to fracture when they have been affected by osteoporosis.
Because bone is living tissue, old bone is constantly being broken down (bone resorption) and new bone is constantly being deposited (bone formation). Until late adolescence, bone mass and density increase because more bone is formed than is resorbed. When people are in their mid-20s to their mid-30s, their bones are at their maximum mass and strength. After that, more bone is resorbed than is formed, and bone mass and strength are gradually lost. Osteoporosis develops gradually over time, although rates vary among individuals.
Although individuals of either sex and of any ethnic background can develop osteoporosis, it is especially common among white and Asian women over age 50, and small, slender women are at greater risk. Many people do not become aware that they have osteoporosis until they fracture (break) a bone. Typically, in those who have osteoporosis, the fracture is the result of a simple fall that would not have caused a fracture in a young adult. These fractures can occur in any bone, but the most common locations are the hip, spine, and wrist. Hip fractures are the most serious, and around 24 percent of persons over 50 die in the year following such a break. Over half (57%) of fractures resulting in hospitalization occur in persons age 65 and over, including 90 percent of hip fractures, 65 percent of pelvic fractures, and 56 percent of spinal fractures.
Breaks in the hip and spine are of special concern because they usually require hospitalization and major surgery. Because many people with osteoporosis-related fractures are elderly, the fractures often lead to other serious consequences, including permanent disability and even death. Recovery from a hip fracture is slow, which means that only about 15 percent of people who have fractured a hip are able to walk across a room unaided six months later. Total recovery may be impossible. Thirty-three percent of persons suffering a hip fracture are either totally dependent on others or in a nursing home a year after the break.
The two main types of osteoporosis are primary or secondary. Primary osteoporosis is part of the aging process and is not associated with any other disease process. Secondary osteoporosis is a result of another disease, treatment, or abnormality. There is a third, rare type of osteoporosis called idiopathic * osteoporosis. With this type of osteoporosis, the cause of the condition is unknown.
Primary osteoporosis is associated with aging. It is the most common form of the disease, accounting for about 95 percent of osteoporosis in women and at least 80 percent in men. In women, primary osteoporosis is often referred to as “postmenopausal osteoporosis” because it results from the accelerated bone loss that occurs in women during and after menopause * . After menopause, ovaries produce very little estrogen, a hormone that helps to maintain bone mass.
Several factors influence whether a person develops primary osteoporosis. These include:
Secondary osteoporosis is osteoporosis that results from another underlying medical condition or is the result of taking medication. Secondary osteoporosis can have many causes. Confinement to a wheelchair or bed can cause the bones to lose mass and density. This effect also has been observed in astronauts who have undergone prolonged periods of weightlessness in space, as it is impossible to get proper exercise when there is no gravity. Cancer, certain blood and autoimmune disorders * , some endocrine * diseases, and some liver and digestive diseases can also lead to secondary osteoporosis. Mental illnesses may also be a cause. Depression has been linked to lower bone density, potentially because of certain medications used to treat the condition. Eating disorders such as anorexia nervosa * and bulimia * can also lead to osteoporosis.
Osteoporosis does not always produce obvious symptoms. Often, an older person first learns of his or her condition after breaking a bone in a fall, when an x-ray reveals decreased bone density. Although falls are the most common cause of fractures, the thinning vertebrae in a person with osteoporosis may actually collapse under the weight of the upper body. Called compression fractures, these fractures can cause severe pain, usually in the mid or lower back. Chronic, or long-lasting, pain may develop after several such fractures have occurred. Another potential symptom is the gradual loss of inches of height, and the upper back may curve forward, creating a hunchback appearance.
If a doctor suspects the presence of osteoporosis, he or she will take a complete medical history, conduct a physical examination, and order x-rays, as well as blood and urine tests, in an effort to rule out other diseases that can cause loss of bone mass. The only sure way to confirm a diagnosis of osteoporosis is to measure bone density. A standard x-ray may reveal that the bones are less dense than normal, but osteoporosis is usually advanced by the time it is evident on an x-ray.
The most common test to confirm osteoporosis is a bone density scan known as dual-energy x-ray absorptiometry (DXA). Bone density scanning is painless and exposes the patient to only a small amount of radiation—about 1/50th of a chest x-ray. Typically, only a few bones are evaluated in this test, most often in the hip and spine. After the scan is complete, the person's bone density is compared against the bone density measurements of a population of healthy young adults to see how widely the measurements differ. The greater the difference, the more severe the degree of osteoporosis.
In some instances, a blood test and bone biopsy (removal of a tiny sample of bone for examination) may be used to rule out the possibility of osteomalacia (ah-stee-o-ma-LAY-she-a), which is a closely related condition, known as rickets when it affects children. Osteomalacia usually results from a lack of vitamin D.
Osteoporosis cannot be cured, but it can be treated. Treatment is usually multisided and is aimed primarily at stopping or slowing bone loss.
The lifestyle changes that help slow bone loss are beneficial to people of all ages, including the elderly, in whom there is going to be at least some measure of osteoporosis. Exercise, especially weight-bearing exercise or strength training, is important to the maintenance of bone strength. Even frail individuals with chronic health problems can exercise with weights under the supervision of a physical therapist or health professional familiar with the American College of Sports Medicine's strength-training guidelines for older people. Exercise that improves flexibility and balance can also improve coordination and help to prevent falls and fractures.
Although recent studies have presented some conflicting evidence, in general it is thought that a diet that includes enough calcium and vitamin D may help to slow osteoporosis. Calcium is the main mineral in bones, and very few people get enough of it in their diet. Most experts recommend 1,000 milligrams (mg) of calcium per day for women 50 and younger and 1,200 mg for those 51 and older. For men, 1,000 mg is recommended daily for those 70 and younger and 1,200 mg for those 71 and older. Foods are the best source for this important mineral. Low-fat milk, cheese, and yogurt have the highest amounts. Other foods that are high in calcium are green leafy vegetables, tofu, shellfish, Brazil nuts, sardines, and almonds.
People who do not get enough calcium from food may need to take calcium supplements. Calcium supplements vary in calcium content and absorbability. Calcium carbonate is the most common and least expensive calcium supplement. Calcium tablets of 500 or 600 mg can be taken once or twice daily, depending on how much calcium is being supplied by the person's normal diet. In addition to calcium, it is recommended that people over 50 get 800 to 1,000 international units (IU) of vitamin D3 daily. Vitamin D helps the body absorb calcium in the digestive tract. Too much vitamin D can be toxic, however, so care must be taken with supplements.
Other lifestyle choices include not smoking and not drinking alcohol. Older people should assess their homes for hazards that might cause falls. This might include removing small, loose rugs; installing grab bars in showers; improving lighting on stairs; marking the final stair with reflective tape; avoiding loose, floppy footwear; and placing often-used kitchen supplies where they can be reached without climbing on a stool or chair.
In the past, women often received estrogen (ES-tro-jen)/progesterone (pro-JES-the-ron) hormone replacement therapy (HRT) to ease the symptoms of menopause. Because HRT artificially increased the amount of estrogen in the body, it had the added effect of slowing or preventing bone loss. But large studies have shown that HRT can also increase the risks of heart disease and breast cancer. Because of this, HRT is being used sparingly and only for a short time to prevent osteoporosis.
Several drugs belonging to a group called bisphosphonates have been approved in the United States for treatment and/or prevention of osteoporosis. These drugs have been shown to increase bone density in the spine and hips. Some are approved exclusively for use in women, whereas others can also be taken by men. Drugs in this category include alendronate, ibandronate, and risedronate. Another drug, calcitonin, is produced by the thyroid gland and suppresses bone resorption; it is approved for the treatment of osteoporosis. Raloxifene has effects on bone similar to those of estrogen and is used in the treatment of osteoporosis. Teriparatide, a form of human parathyroid hormone, has been shown to actually stimulate bone growth. Patients should discuss with their doctor the risks and benefits of these drugs based on their individual situation.
The best time to take steps to promote bone growth (and make osteoporosis less likely in later years) is during the childhood and teen years. This is particularly true for young women who have small frames as well as close relatives with osteoporosis. For young people, just as for the elderly, getting plenty of regular exercise is important, as is getting enough calcium and Vitamin D in the diet. It is estimated that more than 70 percent of children and teenagers fail to consume adequate amounts of calcium. The aim is to achieve full bone density in the skeleton by the time individuals have reached their early 20s.
Not smoking and not drinking alcohol (or drinking in moderation, for adults) are important. Fad diets that promise rapid weight loss need to be avoided. While exercise, particularly supervised weight training, is important in the prevention of osteoporosis, extreme exercise, especially when combined with dieting and weight loss, can stop menstrual periods and reduce estrogen levels in young women. This decreased estrogen can cause significant bone loss.
See also Aging • Anorexia Nervosa • Broken Bones (Fractures) • Bulmina Nervosa and Binge Eating Disorder • Eating Disorders: Overview • Menopause • Rickets • Thyroid Disease
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* bone marrow is the soft tissue inside bones where blood cells are made.
* idiopathic (id-e-o-PA-thik) means arising from an unknown cause.
* menopause (MEN-o-pawz) is the end of menstruation.
* genes (JEENS) are the chemical structures composed of deoxyribonucleic acid (DNA) that help determine a person's body structure and physical characteristics such as hair and eye color. Inherited from a person's parents, genes are contained in the chromosomes found in the body's cells.
* autoimmune disorder is a disorder that occurs when the body's immune system accidentally attacks and destroys healthy body tissue.
* endocrine (EN-do-krin) refers to a group of glands, such as the thyroid, adrenal, and pituitary glands, and the hormones they produce. The endocrine glands secrete their hormones into the bloodstream, and the hormones travel to the cells that have receptors for them. Certain hormones have effects on mood and sometimes cause emotional swings.
* anorexia nervosa (an-o-REKse-a ner-VO-sa) is an emotional disorder characterized by dread of gaining weight, leading to selfstarvation and dangerous loss of weight and malnutrition.
* bulimia (bu-LEE-me-a) is an eating disorder in which a person has episodes of out-of-control overeating, or binges, and then tries to make up for them by making themselves vomit, by taking laxatives, or by exercising to excess to avoid gaining weight.