Osteoporosis – which means "porous bone" – is a disease characterized by low bone mass and structural deterioration of bone tissue. This can cause the bones to become fragile and, as a result, increase the risk of fracture. With osteoporosis, the greatest risk of fracture involves the wrist, hip, or spine. However, virtually any bone in the body is more likely to fracture in someone who has osteoporosis.
Osteoporosis is the result of too much bone resorption and not enough bone formation, a process that is discussed in the previous section of this lesson. Both collagen and mineral are depleted in osteoporosis, which can compromise both the flexibility and hardness of bone.
Osteoporosis is a common problem in the United States. Approximately 10 million Americans are living with osteoporosis, approximately 70% to 80% of whom are women. It is responsible for more than 1.5 million fractures annually, including 300,000 hip fractures, 700,000 spine (vertebrae) fractures, 250,000 wrist fractures, and more than 300,000 fractures of other bones.
Osteoporosis is less common in men than in women for several reasons. First, men have larger skeletons, meaning that they can usually afford to lose more bone before their bone strength becomes compromised. Second, their bone loss tends to start later in life and progresses more slowly. Third, they do not experience the rapid bone loss that affects women when their estrogen production drops as a result of menopause. However, despite these differences, men are still at risk for osteoporosis.
Technically speaking, there are two different types of osteoporosis: primary and secondary (see: "What are the risk factors for osteoporosis?"). Primary osteoporosis can occur in both men and women at any age, but usually follows menopause in women and occurs later in life in men. Secondary osteoporosis can occur in people who either take medications or suffer from diseases that can cause decreased bone density.
Osteoporosis is known as a silent disease, as it does not usually cause any symptoms. Many people do not find out that they have osteoporosis until they have suffered a bone fracture.
While osteoporosis is certainly an important predictor of fracture risk, it is not the only factor to consider. Fracture risk also depends on the likelihood of a serious fall or injury, which increases with age. For example, a younger man or woman with osteoporosis – someone with greater muscle mass, strength, dexterity, and coordination – is less likely to experience a serious fall of injury than an elderly man or woman. In turn, a younger person with osteoporosis is less likely to experience a bone fracture than an older person with osteoporosis. This is very important to consider when thinking about osteoporosis in relatively young, relatively fit HIV-positive people: their risk of a serious fracture is believed to be significantly lower than that of an elderly man or women with osteoporosis.
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