DEAR DR. DONOHUE: I am an 80-year-old woman. I was nearly 5 feet 4 inches tall, but am now 4 feet 10 inches. One doctor suggests I take Actonel. My primary-care doctor says there is no benefit from it, if taken after 80 years of age. What is your opinion of this drug? – F.R.

ANSWER: Height loss is an inevitable consequence of aging. Partly it comes from the flattening of the disks that lie between adjacent backbones. Mostly it comes from the compression of backbones weakened by osteoporosis. The osteoporotic bones cannot support body weight, and they collapse – something called a compression fracture. At times those fractures are painful, but more often they are painless, and their evidence lies in a person’s downsizing.

Loss of height is a valid indication of osteoporosis. Women reach peak height in their 20s. Older women who have lost 2.4 inches (6 cm) in height from their peak height can be relatively certain that they have significant osteoporosis and have suffered from compression fractures, even if they have had no back pain. A height loss of as little as 0.8 inch (2 cm) within three years should raise concerns about osteoporosis.

Osteoporosis progresses most rapidly in the first six or seven years of menopause. Estrogen deprivation is its cause. However, the process continues throughout life, but at a diminished rate.

For that reason, many doctors feel that it is never too late to begin a program to combat osteoporosis. Actonel belongs to a family of drugs that are quite effective in retarding bone loss and possibly building bone. The safety and efficacy of these drugs have been demonstrated in women older than 75.

If you have no contraindication to taking the medicine, I believe you would derive benefit from doing so.

You and women your age should not forget the other measures that are effective for osteoporosis – calcium, vitamin D and exercise.

DEAR DR. DONOHUE: My daughter, age 54, has just been diagnosed with spondylolisthesis. I’ve never heard of it. Could you explain it? Her doctor says there is no cure for it. – M.H.

ANSWER: Vertebrae – backbones – are piled neatly on top of one another, like a stack of blocks. When one vertebra slips over the one below it, like one block sliding slightly over the block beneath it, that is spondylolisthesis (SPAWN-duh-low-lis-THEE-sis). It’s an unpronounceable and unfamiliar name, but it is a relatively common back problem.

Sometimes the slippage brings on pain in the lower back, the buttocks or the thighs. Sometimes it is painless and is discovered only accidentally when a back X-ray happens to be taken.

What needs to be done depends on how bad the pain is and how bad the slippage is.

Frequently, a program of back rehabilitation along with pain-relieving anti-inflammatory medicines can bring matters under control. In a few instances, a back brace might be required. In fewer instances still, surgical correction has to be made.

DEAR DR. DONOHUE: I am a frequent blood donor. Recently, when having blood work done, the technician told me that blood donors develop scar tissue, which induces blood clots. Is this true? – A.M.

ANSWER: No, that’s not usually true. I know many people who donate blood six times a year and have never suffered a single problem with scar tissue or clots.

The technician gave you bad information.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.