DEAR DOCTOR K:

Why do so many people lose height and develop a stooped posture as they get older?

DEAR READER:

You may be surprised by the answer. In many older people, loss of height and stooped posture results from fractures of the spine.

When you think of a bone fracture, you probably picture a long bone being snapped like a twig, as with a broken arm or leg. The vertebrae (bones of the spine) are not long bones. They are more like little cubes. When they break, they are compressed, not snapped. They get crunched down. Picture the way an upturned paper cup would be flattened when stepped on. (I've put an illustration on my website, AskDoctorK.com, that compares compressed and normal vertebrae.)

When the bones of your spine lose height, you lose height. The bones of your spine hold you upright. Those bones (and other bones throughout the body) become weak and susceptible to fractures because of a bone-weakening condition known as osteoporosis.

Osteoporosis is more common in women than men. It affects all of the spine bones and many other bones. Women who have had a fracture of one spine bone have a greatly increased risk that other spine bones also will follow suit.

Though it may seem solid and unchanging, bone is continually demolished and reconstructed. Inside all of your bones, even as you read this, some cells are adding new bone and other cells are eating away at the old bone. Normally, the bone-building process is equal to the bone-destroying process, so that your bones are neither too thick nor too thin. With osteoporosis, bone reconstruction lags behind bone demolition.

Spinal fractures often occur without a traumatic cause like a fall. Even simple acts of daily life, such as bending over, coughing or lifting, can collapse a vertebra weakened by osteoporosis. A minor stress can be the "straw that breaks the camel's back."

In many cases, vertebral fractures cause little or no pain. The main clue that they have occurred is a gradual shrinkage or stooped posture. One or two compression fractures in the spine may produce only a slight loss of height. But many fractures can profoundly affect appearance, mobility and health.

As the number of fractures increases, the spine becomes progressively more distorted. The upper body is thrust down and forward. The abdominal muscles sag, and the space between the ribs and the pelvis closes. The chest wall becomes cramped; abdominal organs are compressed and pushed forward. Breathing may become difficult and digestion may be impaired. Since walking erect is difficult, a cane or walker becomes essential.

Given the serious consequences of osteoporosis, you should take steps to prevent it:

-- Get enough calcium and vitamin D through foods and, if necessary, vitamin supplements.
-- Regularly perform weight-bearing exercises.
-- Don't smoke.
-- Avoid excess alcohol.
-- If you have recently entered menopause, ask your doctor about preventive medications.

(Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.)

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