Effects of alcohol use and estrogen on bone

Alcohol Research & Health,  Winter, 2001  by Russell T. Turner,  Jean D. Sibonga

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In marked contrast with men who drink, women who drink alcohol are found, as a group, to have higher bone mass compared with women who abstain. Furthermore, the apparent beneficial effects of alcohol use are more apparent in postmenopausal women than women of reproductive age, suggesting that there might be an interaction between alcohol and estrogen. Estrogen deficiency accompanying menopause leads to bone loss, which in turn predisposes women to osteoporosis later in life. Estrogen deficiency accelerates bone remodeling, which is the process by which small areas of bone are destroyed and rebuilt, and leads to an imbalance whereby bone resorption--the part of remodeling consisting of breaking down and assimilating--exceeds bone formation. Alcohol might reduce bone loss in postmenopausal women by increasing the circulating levels of estrogen. Alternatively, alcohol might slow bone loss by acting on bone cells to reduce bone remodeling. Alcohol use has a negative effect on the immature skeleton but current und erstanding suggests that small quantities of alcohol may have beneficial effects on bone in older women.

KEY WORDS: chronic AODE (effects of alcohol or other drug use, abuse, and dependence); estrogens; osteoporosis; risk factors; bone fracture; bone resorption; bone mass density; beneficial vs. adverse drug effect; biological repair; post menopause; gender differences

Bone is a living tissue that undergoes lifelong remodeling (Frost 1969), whereby local regions of the bone are destroyed and rebuilt in a systematic way (see figure). This process serves to repair microdamage caused by normal body wear and tear and is essential to maintaining strong bones. Bone is lost during the normal aging process. Osteoporosis occurs when a person has an inadequate amount of bone to provide sufficient strength to perform normal daily activities. Osteoporosis usually is caused by a chronic imbalance in the bone remodeling cycle in which bone resorption (shown in part B of the figure) is not adequately compensated for by subsequent bone formation (shown in part D of the figure).

Bone mass is not constant; it reaches a peak value in the third decade of life and then declines with age. A low peak bone mass and rapid age-related loss in bone mass predispose a person to developing osteoporosis. The onset of bone loss during middle age can precede an increased risk of fractures by as much as 2 decades, during which period the person rarely shows outward signs of any problem (i.e., is asymptomatic). For example, a woman may start to lose bone mass at age 45, experience a fracture at age 65, but have no symptoms of the bone loss during the 20 years in between. No methods currently exist to restore large amounts of bone to a depleted skeleton, although hormones that stimulate bone formation are being investigated for this purpose. Therefore, reducing the rate of bone loss that occurs with aging is the only effective way to reduce osteoporotic fractures. Two important controllable risk factors for osteoporosis are a deficiency in the hormone estrogen and heavy alcohol use. (1) This article wi ll focus on these two factors by discussing estrogen and alcohol's effects on bone remodeling and the possible influence of alcohol on the bones of estrogen-deficient women.

MEDICAL AND PUBLIC HEALTH COSTS OF MUSCULOSKELETAL DISORDERS

The true extent of musculoskeletal disorders in the general population is not widely appreciated. Musculoskeletal complaints like arthritis, back pain, and bone fractures are among the most common reasons why patients see physicians and are hospitalized. The annual direct and indirect costs of musculoskeletal disorders in the United States exceed $125 billion (Praemer et al. 1992). Direct treatment costs make up a little less than half of the economic burden; morbidity, mortality, and the value of lost productivity account for most of the remaining costs.

There are more than 6 million bone fractures in the United States per year, and roughly 5 percent of fractures do nor heal properly and require additional and often costly medical care. Only one-sixth of the fracture total is a result of osteoporosis. However, the consequences of osteoporotic fractures can be disproportionately severe. Hip fractures, for example, are especially dangerous, and two-thirds of the more than 275,000 hip fractures that occur annually in the United States are a result of osteoporosis. The common perception that a fracture is not life threatening is incorrect. One-fifth of patients with hip fractures die within 6 months of having the fracture and those who survive generally have a poor prognosis for complete recovery. Of the survivors, one-fifth will require long institutionalization and another fifth face a permanent disability often with mobility limited to a walker or wheelchair (Cooper and Melton 1996).

The prevalence of osteoporosis and the number of hip fractures are increasing at an alarming rate. For example, a recent estimate of the number of hip fractures in women worldwide was 1.2 million. This number is expected to grow to 4.5 million by the year 2050. The second half of the last century witnessed an unprecedented increase in lifespan. Longer life combined with the temporary increase in birth rate in the years immediately following the Second World War will greatly increase the number of Americans at risk for osteoporosis in the next 2 decades (Cooper and Melton 1996).