Osteoporosis

Description

Risk Factors

Gender. An estimated 28 million adults in the U.S. have osteoporosis or are at risk for osteoporosis in the hip. Women face a much higher risk than men, although this condition is not negligible in men. Men start with higher bone density and lose calcium at a slower rate than women, which is why their risk is far lower. Nevertheless, after age 50, bone loss increases, and, according to recent studies more rapidly than previously thought. An estimated five million men have osteoporosis. Furthermore, a 2002 study predicted that by 2020, 20.5 million men will have either osteoporosis or low bone mass.

Ethnicity. Although Caucasian women face a 20% to 30% chance for osteoporosis after age 60, Asian, Hispanic, and Native American women face an equal or even higher risk. One study of Japanese and Americans suggested, however, that Japanese women experience fewer hip fractures. One explanation might be that many Japanese women are used to sitting with knees flexed and they frequently stand up from a position near the floor, thus ensuring the development of strong hip muscles and balancing skills, which help prevent falling. Most studies have been done on women, but men in the same ethnic groups may also carry a parallel, although lower, risk.

Specific Risk Factors for Estrogen Deficiency and Low Bone Density in Women

Events associated with estrogen deficiencies are the primary risk factors for osteoporosis in women.

Natural and Surgical Causes of Estrogen Deficiency.

• Menopause. Within the five years after menopause, the risk for fracture increases dramatically. Fractures occurring during this period are more likely to occur in the wrist or spine than the hip, but their occurrence is a strong predictor of later severe osteoporosis and hip fracture.
• Surgical removal of ovaries.
• Missing periods for three months or longer.
• Never giving birth.
• Paradoxically, pregnancy and nursing do not increase the risk for osteoporosis even though during those times calcium is diverted from the mother to the baby. A factor believed to be associated with reduced bone density is elevated at a constant level during nursing, but as the baby is weaned, levels of the factor decline and bone formation is restored.

Female Athlete Triad. In the small community of athletes, excessive exercise plays a major role in many cases of anorexia (and, to a lesser degree, bulimia), which in turn increases the risk for low estrogen levels and bone loss. The term "female athlete triad" in fact, is now a common and serious disorder facing young female athletes and dancers and describes the combined presence of the following problems:

• Osteoporosis.
• Amenorrhea (absence or irregular menstruation). In a 2002 study, young women with amenorrhea, particularly if they experienced a late onset of their periods, exhibited low bone mass, whether or not they exercised strenuously.
• Eating disorders. Evidence is mounting that overly restricting calories may be more important than low weight in causing menstrual problems. Studies suggest that amenorrhea occurs even in women with normal weight if they severely diet.

In one study, female athletes who consumed a high-fat diet (35% of daily calories) performed longer and with greater intensity than those with a standard athletic low-fat diet (27% of daily calories). And such a diet appeared to be more estrogen-protective.

Specific Risk Factors for Bone Density Loss in Men

Some specific risk factors in men include the following:

• Hormonal deficiencies, including both testosterone and estrogen, which occur in older men (although much more slowly than in women). Estrogen deficiencies may also a play a major role in osteoporosis in older men. It is unknown yet what normal estrogen levels are in men.
• Medical conditions that can reduce testosterone levels, such as prostate cancer treatments, testicular surgery, and mumps.
• Hypogonadism, which is a severe deficiency in the primary hormone that signals the process leading to the release of testosterone and other important reproductive hormones.

Of concern, are studies, including one in 2002, suggesting that men who have osteoporosis and suffer hip fractures are far less likely to be tested and treated for low bone density than are women. In the study, only 27% of men were being treated for osteoporosis compared to 71% of women.

Risk Factors for Bone Density Loss in Both Men and Women

Dietary Factors. Diet plays an important role in preventing and speeding up bone loss in men and women. Calcium and vitamin D deficiencies, of course, are important factors in the risk for osteoporosis. Other dietary factors may also be harmful or protective for certain people.

Calcium requires adequate vitamin D in order to be absorbed by the body. In the United States, many food sources of calcium such as milk are fortified with vitamin D.

Click the icon to see an image of the sources of calcium.

Lack of Exercise. Lack of exercise can put thinner people at risk for osteoporosis.

Being Underweight. Being underweight is a risk factor for osteoporosis in men as well as women. (Shortness, thinness, and narrow hips all increase the risk for fracture in people with low bone density.)

Lack of Sunlight. The photochemical effect of sunlight on the skin is a primary source for vitamin D. Bone formation peaks in the summer and bone breakdown increases in the winter. People who avoid sun exposure to prevent skin cancer may be at risk for vitamin D deficiency, particularly it they are elderly. (One 2000 study of three different countries confirmed a higher winter-risk for hip fractures even in countries without snowfall.)

Click the icon to see an image of the sources of vitamin D.

Smoking. Women who smoke, particularly after menopause, have a significantly greater chance of spine and hip fractures than those who dont smoke. Men who smoke also have lower bone density.

Diabetes. Diabetes changes bone quality and density and increase the risk for osteoporosis, but the effects differ depending on type:

• Type 1 diabetes is associated with a slightly reduced bone density, putting patients at risk for osteoporosis and possibly fracture.
• Type 2 diabetes, on the other hand, is associated with an increased bone density. In such cases, the bone quality itself may be impaired, since people with type 2 diabetes are still at higher risk for fractures.

Older patients with any diabetes type are at high risk for falling, which compounds the risk for fracture.

Risk Factors in Children and Adolescents

The maximum density that bones achieved during the growing years is a major factor in whether a person goes on to develop osteoporosis. Persons, usually women, who never develop peak bone mass in early life are at high risk for osteoporosis later on. Children at risk for low peak bone mass include the following:

• Children born prematurely.
• Children with anorexia nervosa (more common in girls).
• Young, highly competitive athletes.
• Children who take oral corticosteroid drugs. (Inhaled steroids, which are common in asthma treatments, appear to pose a very low risk or none at all.)
• Children with certain medical conditions, including cystic fibrosis, epilepsy, inflammatory bowel disease, and celiac disease.
• Children with delayed puberty.

Although to a large extent genetics predict bone health, exercise and good nutrition during the first three decades of life, when peak bone mass is reached, are still benign safeguards against osteoporosis (and countless other health problems).

Factors Associated with Osteoporosis

Depression. One study found an association between major depression and low bone mineral density in women. More than a third of premenopausal women who suffered from major depression had low bone density comparable to that of postmenopausal women. One explanation for this association is that depressed women have higher levels of the stress hormone cortisol, which may contribute to bone density loss.

Premature Gray Hair. One study reported that men and women whose hair turns gray in their 20s or was half gray by age 40 have an incidence of thin bones that is four times higher than those who go gray later. Smoking, which also contributes to thin bones, has been associated with premature gray hair and may help explain the connection.