Who Has Osteoporosis?

It is estimated that 25 million people in the United States have significant bone loss, 8 million of them severe enough to meet the definition of osteoporosis. Most of those who have this disease are women. Although I have never seen good epidemiological studies, according to many authors those most at risk appear to be white women.

What is the Result of Osteoporosis?

There are an estimated 1.5 million bone fractures per year resulting from bone loss. These are most likely vertebral compression fractures - about 650,000 - during which the cylindrical body of the backbone compresses down, causing pain and disability.

Next are the most devastating hip fractures - about 250,000 per year. Forearm fractures and those of other sites are also common. These fractures are seen with little or no trauma - in fact, we often wonder whether or not the patient "fell and broke her hip" or actually "broke her hip and fell" - the patient frequently thinks she "must have tripped over the rug" - but it's a rug which she has been walking over for ten years! The mere act of stepping was enough to break her hip.

Likelyhood of a Fracture

The odds of an American woman getting a hip fracture at some time in her life appears to be about 18%, a vertebral body fracture about 16%.

Consequences of a Fracture

The most devastating consequence of a hip fracture is loss of mobility. This sets up the patient for potential rapid deterioration - it is estimated that half of those who have a hip fracture are deceased or in a nursing home within a year of the event. The financial cost to our society of these fractures is astronomical. There are clearly compelling reasons to prevent them whenever possible.

What Causes Osteoporosis?

Bone Turnover

The matrix of bone is constantly being turned over - bone is broken down and the minerals released into the body, and new bone is being made. Cells called osteoclasts break down the bone and cells called osteoblasts build new bone. Different factors effect each, and a difference in the rates of rebuilding and tearing-down of bone results in bone growth or bone loss.

Images courtesy of Merck, Inc.

Risk Factors:

Increasing risk:

1. Older age.
2. Caucasian race.
3. Lighter weight (for hip especially).
4. Younger age at menopause.
5. Low estrogen conditions when younger (very athletic, thin, few menstrual periods)
6. Alcohol use.
7. Tobacco use.
8. Family history of osteoporosis.
9. Corticosteroid (cortisone) use.
10. Thyroid replacement - especially if too high.
11. Anticonvulsant medications.
12. Malabsorption problems.
13. Lack of exercise.
14. Dietary deficiencies, excess protein?

What is Your Risk?

Diet

The issue of diet is very controversial. It is fairly well understood that a low intake of Calcium and Vitamin D can predispose to osteoporosis. It is probably useful, especially for those at higher risk, to get at least 1200mg of calcium per day, and at least 500mcg of Vitamin D. Some have proposed that our high-protein diet is partly responsible for this disease. Many cultures which have a low-protein diet have a low-incidence of osteoporosis. It has been shown that consumption of excess protein results in larger urinary losses of calcium. Calcium supplements are often recommended for those at risk - review the page on calcium supplements and dietary calcium.

Evaluating Osteoporosis

Bone density is measured in relationship to the average bone density of a pre-menopausal woman, expressed in terms of standard deviation units. Normal bone density is that between +1 and -1 SD of young women. Osteopenia is defined as bone density between -1 and -2.5 SD of that of a young woman. Osteoporosis is defined as bone density lower than -2.5 SD of that of a young woman.

Predictive Value of Bone Density

Every decrease of spinal bone density of 1 SD increases spine fracture risk by two. Every decrease of hip bone density of 1 SD triples hip fracture risk.

Estrogen

Estrogen decreases bone breakdown, or resorption. Estrogen replacement therapy after menopause has been shown to increase bone density 2 to 3% and to slow the progression of osteoporosis. Spine and hip fracture rates for women who receive post-menopausal estrogen supplements is shown to be about half that of those who do not. Women who have had lowered estrogen levels earlier in life - either through early menopause (natural or due to removal of the ovaries) and those who are thin and athletic and have missed periods have a higher risk. Young athletic women who have missed periods are now being put on birth-control pills to give them sufficient estrogen to maintain bone mass.

Other risks and benefits of estrogen

Estrogen also helps in the treatment of menopausal symptoms, and has been shown to significantly lower the risk of heart disease.  It may also lower the risk of colon cancer and delay the development of Alzheimer's disease.  The risks include increased rate of breast cancer and cancer of the uterus. The later has been shown to be greatly reduced by balancing the estrogens with progesterone.

Newer Treatments for Osteoporosis

Calcitonin, a hormone which decreases bone resorption, has been available for a number of years. The difficulty is that it must be given as an injection daily for six months. It is about $8 per shot, and not covered by Medicare. It has been shown to increase bone density in the spine, and even to decrease pain associated with spinal osteoporosis, but it is unclear to what extent it improves bone density in the hip. It is now available as a once-a-day nose spray - "Miacalcin" - which is equally effective but may cause nasal irritation.

Alendronate - "Fosamax" is a drug in the class called biphosphonates which also decreases bone resorption. It has been shown to increase bone density in both the spine and hip, and to decrease fractures over three years. Although it is a safe medication, it tends to cause potentially severe acid reflux into the esophagus. It is also not absorbed with food in the stomach. Therefore, the requirements for taking it are to take it with a large glass of water on an empty stomach first thing in the morning, not to eat for 30 minutes, and NOT to lay back down after taking it..

There are other experimental treatments, and ones that may work but have not been studied to a great extent. For example, diuretics such as hydrochlorothiazide, used for hypertension, have long been used to help prevent calcium-containing kidney stones in those at risk by reducing calcium excretion in the urine. It is unknown whether or not this would have a benefit in treating osteoporosis, but if these medications are included in a list of potential medications being considered for treating high blood pressure in a woman at risk for osteoporosis, it might make sense to use them.

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