Osteoporosis: Risk Factors

researched and written by the ProjectAWARE group, 2001

	Primary Osteoporosis
	Secondary Osteoporosis
	Fractures

Patients with decreased bone density usually have no specific abnormal physical findings. However, there are predictors that may help assess a person's risk for developing osteoporosis as well as risk for bone fracture. Fractures are a result of both trauma and decreased bone strength. Bone strength depends on both the density (quantity) of the bone and on the quality of the bone.

RISK FACTORS FOR PRIMARY OSTEOPOROSIS

Postmenopausal osteoporosis is the most common form of osteoporosis, and risks associated with low bone density are supported by good evidence, including large prospective studies. Predictors of low bone mass include:

• female gender
• increased age
• estrogen deficiency
• white race
• low weight and body mass index (BMI)
• family history of osteoporosis
• smoking
• history of prior fracture

Use of alcohol and caffeine-containing beverages is inconsistently associated with decreased bone mass. In contrast, some measures of physical function and activity have been associated with increased bone mass, including grip strength and current exercise. Late menarche, early menopause, and low endogenous estrogen levels are also associated with low bone density in several studies.³³

A study published in the September 27, 2001 New England Journal of Medicine (NEJM) has shown that inhaled glucocorticoid therapy leads to a dose-related loss of bone at the hip in premenopausal women. Inhaled glucocorticoids are the most common medications for long-term treatment of patients with asthma, and there appears to be an association between decline in bone density and the number of puffs per year of use. The study involved 109 premenopausal women 18 to 45 years of age who had asthma and no known conditions that cause bone loss.⁴⁹

RISK FACTORS FOR SECONDARY OSTEOPOROSIS

Common forms of osteoporosis unassociated with other diseases include idiopathic, postmenopausal and senile osteoporosis.

All other causes of accelerated bone loss should be ruled out before a diagnosis of osteoporosis is made. Some other factors that may cause accelerated bone loss include:²³

RISK FACTORS FOR FRACTURES

In general, the risk of a fracture will double with every decade past 50, even with the same bone density. A woman aged 55 with osteopenia has about a 2% chance per year of having a fracture, and a woman aged 75 with osteopenia has about an 8% chance per year (which is approximately the average risk for a 75-year-old woman).⁶

At menopause, it has been shown that loss of estrogen affects postural stability by slowing down brain processing speed. After menopause, the incidence of falls among women is three times that of men. It has been determined that postural stability appears to be related to risk of fracture in women with osteoporosis.⁴⁰

One study documented improved brain processing speed and postural stability in postmenopausal women on ERT. Another study compared sway velocity (an indicator of tendency to fall) in 16 postmenopausal long-term users of 17 b-estradiol and 16 postmenopausal women who had never taken estrogen. Postural stability and bone density appeared similar in both premenopausal and postmenopausal women on ERT. However, balance deteriorated significantly in postmenopausal women not on ERT.⁴⁰

The fact that ERT improves both postural stability and bone density likely explains why it has proven superior to raloxifene and alendronate in preventing nonvertebral, fall-related fractures.⁴⁰

The lifetime risk of a hip fracture depends on age and bone density. A young person with osteopenia doesn't have much risk in the next 5 years, but if no prevention is done, the lifetime risk will be about 20 or 30%. An elderly woman with osteopenia has a lifetime risk of about 10%.⁶

Estrogen replacement therapy (ERT) during and following menopause has been shown to decrease (but not prevent) the incidence of both hip and vertebral fractures by about 50%.⁹ However, once substantial loss of trabecular micro-architecture has occurred, estrogen-induced stabilization and/or increased bone density are thought less likely to reduce fracture risk.^{13, 38}

Although low bone density has been established as an important predictor of future fracture risk, the results of many studies indicate that clinical risk factors related to risk of fall also serve as important predictors of fracture. Fracture risk has been consistently associated with a history of falls, low physical function such as slow gait speed and decreased quadriceps strength, impaired cognition, impaired vision, and the presence of environmental hazards (e.g. throw rugs).³³

All postmenopausal women who present with fractures as well as younger women who have risk factors should be evaluated for the disease. Physicians should recommend bone mineral density testing for younger women at risk, and for postmenopausal women younger than 65 years who have risk factors for osteoporosis other than being postmenopausal.⁴¹

Bone mineral density testing should be recommended to all women 65 years and older regardless of additional risk factors. Bone mineral density screening should be used as an adjunct to clinical judgment only if the results would influence the choice of therapy or convince the patient to take appropriate preventive measures.⁴¹

It is interesting to note that broken hips and ‘dowager’s hump’ are virtually unknown in cultures where women's work involves daily long walks, carrying heavy burdens, and where hormone supplementation after menopause is unknown.⁴⁵

Next: Diagnostic Tests

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Updated 05/16/2010