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Osteoporosis is a chronic, progressive skeletal disorder in which the architecture of bone deteriorates and bone mass decreases. This results in fragile, weakened bones that fracture easily, even in the absence of trauma. Many factors contribute to the development of osteoporosis.
Bone is living material. The normal, ongoing metabolism of bone involves a delicate balance between bone formation (osteogenesis) and bone resorption (osteolysis). When more bone is resorbed than is formed, the density of the bone decreases. The bone material that remains is biochemically normal, but overall the bone is weakened and more brittle because of decreased bone mass. This increases the risk of fractures.
Peak bone mass in both men and women occurs in their early twenties followed by a period of about 20 years during which rates of bone formation and resorption are approximately equal. Beginning around age forty, there is a gradual net loss of bone. When women enter menopause, bone loss accelerates rapidly for 5 to 7 years, after which loss continues but at a slower rate. Although men also lose bone mass as they age, this loss tends to begin later in life than it does for women.
Most cases of osteoporosis in both men and women are primary (Weppner). There are three distinct types of primary osteoporosis: Type I osteoporosis, Type II (or involutional) osteoporosis, and osteoporosis of unknown cause (idiopathic). Type I osteoporosis occurs in postmenopausal women as a result of estrogen withdrawal effect or in men with testosterone deficiency, and tends to be associated with fractures in the forearm near the wrist (distal forearm) and in the vertebrae (Weppner). Type II osteoporosis is associated with normal aging processes in both men and women older than age 70. It tends to be associated with hip and pelvic fractures (Weppner). Idiopathic osteoporosis can affect children and young adults as well as older individuals. Although usually systemic, osteoporosis may be regional in certain specific circumstances. For example, when there is no weight bearing on a lower extremity for 6 to 12 weeks, “disuse” osteoporosis may occur.
Secondary osteoporosis is caused by an underlying disease process such as endocrine disorders (e.g., diabetes, thyroid problems), kidney disease, certain hereditary disorders, nutritional deficiencies (e.g., calcium, vitamin D), intestinal absorption problems, certain types of inflammatory arthritis, and some blood disorders. Secondary osteoporosis can also be caused by long-term use of some medications (e.g., steroids, chemotherapy, transplant drugs, certain medications to prevent seizures, certain hormonal treatments, lithium, heparin, overuse of aluminum-containing antacids). Other things that can contribute to development of osteoporosis include heavy alcohol consumption, tobacco use, inactivity, and immobilization (disuse). There is also evidence of a genetic component(s) that increases the risk of developing osteoporosis.
Falls, especially among older individuals, are a risk factor for osteoporosis-related fractures. Falls frequently are the result of poor balance, dizziness resulting from a sudden movement or changes in position (orthostatic hypotension), weak leg muscles, effects of sedative medications, poor vision or hearing, and confusion (cognitive impairment) (Jacobs-Kosmin).
Risk: Age is a major risk factor. After 40 years of age, the risk for osteoporosis increases five-fold for each decade of life (Weppner). Type I osteoporosis generally affects people between 50 and 70 years of age, while Type II osteoporosis generally occurs in people 70 years of age or older. Secondary osteoporosis affects men and women equally and can occur at any age. Osteoporosis is more common in individuals of European and Asian ancestry. Low body weight and low body mass index (BMI) are also known risk factors. Incidence and Prevalence: Osteoporosis is the most common metabolic bone disease (Slovik). About 34 million people in the US have low bone density of the hip, putting them at risk for developing osteoporosis (Jacobs-Kosmin). Another 25 million people in the US already have osteoporosis. The disorder is responsible for approximately 1.5 million fractures annually (Weppner), including approximately 700,000 vertebral fractures, 300,000 hip fractures, and 250,000 wrist fractures (Slovik). Institutional care, mortality, and other costs related to osteoporotic fractures are estimated to exceed $10 billion annually in the US. Approximately 200 million people worldwide or 1 in every 8 men and 1 in every 3 women are affected by osteoporosis (Jacobs-Kosmin). |