The risk of osteoporosis and its associated complications increases in women after menopause. A number of drug therapies can be employed to treat osteoporosis or prevent it in peri- and postmenopausal women at risk for its development, but the best strategy is to start early in life protecting the bone you have.

Definition

Osteoporosis is defined by the National Osteoporosis Foundation (NOF) as "a disease characterized by low bone mass and structural deterioration of bone tissue, leading to bone fragility and an increased susceptibility to fractures of the hip, spine, and wrist." Low bone mass doesn't mean the bones are smaller than normal healthy bone, only more porous. Under a microscope, normal bone is seen to be thoroughly permeated with tiny holes and interconnecting canals and tunnels--in appearance, not unlike a big sea sponge. In an osteoporotic bone, these holes and tunnels are abnormally large. A cubic inch of osteoporotic bone contains less actual bone tissue (less mass) and more air spaces than a cubic inch of normal healthy bone. We should note here that low bone mass is not osteoporosis, only a risk factor for it. We all lose bone mass as we age, but we won't all develop osteoporosis.

Statistics from the National Osteoporosis Foundation (NOF) The NOF estimates that 10 million people in this country already have osteoporosis, and 18 million or more are at risk due to low bone mass. Eighty percent of people with osteoporosis are women. Approximately half of all women and one in every eight men over 50 years of age will have an osteoporosis-related bone fracture. Each year, osteoporosis is responsible for 1.5 million fractures: 300,000 hip fractures; 700,000 vertebral (spinal) fractures; 250,000 wrist fractures; and 300,000 fractures at other sites. Hip fracture is two to three times more common among women than men, but the risk of death in the year following hip fracture for men is twice that for women. All in all, on average, 24% of hip-fracture patients die within one year their fracture.

Human bone: A work in progress?

Human bone tissue consists of a tough organic matrix that supports the deposition of inorganic calcium salts. By weight, average compact bone is about 30% organic matrix and 70% calcium salts. The high concentration of calcium salts is what makes bone so hard.

Our bones are continuously undergoing a process of remodeling, in which old tissue is replaced with new. This process involves the breakdown of old bone by cells called osteoclasts and the deposit of new tissue by the osteoblasts. The osteoclasts tunnel into bone using enzymes to digest the organic matrix and acids to dissolve the hard calcium salts; the dissolution by-products are engulfed by the osteoclasts and eventually returned to the blood stream. Yes, that's right, the body mines it's own bones for calcium.

After the debris of osteoclastic activity is removed and the newly exposed bone surfaces have been cleaned up and prepared by mononuclear cells, the osteoblasts come in and put down layer upon layer of new bone tissue, refilling the small void left by the osteoclasts until all that remains is a tiny hole to accommodate the blood vessels that supply a particular area of bone.

Bone remodeling goes on throughout life and has a number of important benefits. It allows bone strength to vary in direct proportion to the physical stress to which it is regularly subjected; bone thickens when regularly subjected to heavy loads. (This fact forms the rationale for weight-bearing exercise as a preventative measure against osteoporosis--in essence, use it or lose it.) Bone can also change shape to accommodate changes in stress that result from changes in our posture or gait after an injury or as a result of such diseases as arthritis. Further, bone has a natural tendency to become weak and brittle as it ages. Remodeling allows us to maintain normal bone strength as we ourselves age.

What happens in osteoporosis

The give and take of bone remodeling is a lifelong process, but around the age of 30 or 35, our skeletons reach a state of peak bone mass. From that point forward, all of us--male and female-- begin to lose bone mass because the activity of our osteoclasts is greater than the activity of our osteoblasts. This loss of bone mass is a natural consequence of aging and not, in and of itself, a great cause for alarm. However, some people arrive at the age of peak bone mass with comparatively little to show for their journey. And some, owing to a variety of factors, are prone to excessive osteoclastic activity that can riddle their bones with irreparable voids, weakening the bone to the point of fracture. At its worst, osteoporosis can result in bones fracturing from normal everyday stresses: a good hard sneeze may crack a rib; the weight of a large casserole dish being removed from the oven may cause a wrist to snap; the impact of a normal footfall on a stair may shatter a hip, resulting in a dangerous fall.

Risk factors

Fortunately, medical science has been able to identify a number of factors that increase a woman's risk of osteoporosis. Some experts distinguish between two types of risk factors: nonmodifiable and modifiable--a very important distinction because you can do something about the modifiable ones

Things you canchange include current cigarette smoking, body weight of less than 127 lbs, estrogen deficiency, an absence of menstrual periods for more than a year, anorexia nervosa or bulimia, calcium intake less than 400 mg/day (on average), alcohol consumption more than three drinks/day, and inadequate physical activity.

Things you cannot change include a personal history of bone fracture as an adult, a history of fracture in an adult first-degree relative, Caucasian or Asian race (although Hispanic and African American women are also at significant risk), advanced age, a history of anorexia nervosa or bulimia, female sex, dementia, and early menopause.

Diagnosis, prevention, and treatment

The status of your bones can be assessed easily and painlessly with a bone density test. Such a test can detect osteoporosis before a fracture occurs, predict your risk of future fractures, and if carried out successively over a period of several years, monitor your personal rate of bone loss. Every perimenopausal woman should have a bone density test to establish a baseline against which future test results can be compared. And it probably wouldn't be a bad idea for women with significant risk factors to be tested earlier. A 40-year-old woman whose mother developed osteoporosis, for example, or a woman who suffered from an eating disorder in her teens might save herself a lot of misery in her senior years by finding out now whether she shows evidence of excessive bone loss.