How to Live Up to Growing Down : Just when you think you’re staving off the aging process, you discover you’re getting shorter. Here’s how to stall The Shrink.

Gray hair can be colored. Flab can be fashionably dressed. Crow’s feet can be ironed out. But just when it seems there’s no symptom of aging that can’t be tamed, it can come creeping up on you. Or creeping down.

The Shrink. That gradual erosion of stature that hints (and sometimes shouts) that you are past your peak and sliding swiftly over the hill.

In the beginning, of course, it’s easy to ignore and rationalize The Shrink. The frazzled nurse measured wrong, that’s all. You’re not growing shorter, your kids and grandkids are just getting taller.

When you discover more of you is missing, there’s disbelief and anger. With every inch of height you lose, those ideal-weight charts get more hilarious. Then come the nightmares: Will you spend your golden years perched on pillows just to see over the steering wheel?

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Shrinking, the folklore goes, is a normal, can’t-fight-it fact of aging. No magic cream, no surgery, nothing but higher heels and taller hats can stem the southward spiral.

But recently, that thinking has been increasingly challenged by physicians and researchers in the field (many of them, by the way, very tall people who show every intention of staying that way).

Some shrinking with age probably is inevitable, most experts agree--but not as much as you may be blaming on birthdays alone. When height loss is so great that others start to notice, many experts now say, it could indicate an underlying problem such as osteoporosis.

While the risk of osteoporosis is partly determined by factors out of your control, many behaviors that lead to height loss--smoking, sedentary lifestyle, poor body mechanics or posture--can easily be altered.

“It is normal not to shrink,” says K. Michael Davies, a six-foot-tall researcher at the Osteoporosis Research Center at Creighton University, Omaha. It’s possible to reach the golden years, he says, at the same or about the same height as you were in your young adulthood.

The folklore about shrinking into senior citizenhood has been popularized partly, Davies says, by researchers’ habit of comparing younger women (who grew progressively taller from one generation to the next, from about 1900 to 1965) with older women, who were always shorter to begin with. Researchers who found height differences between these generations mistakenly chalked it all up to old-age shrinking.

“Yes, the older people were shorter than the younger ones--but that doesn’t necessarily mean they were shrinking,” says Davies, who spelled out his argument in a paper published recently in the Journal of Bone and Mineral Research.

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To better understand shrinking-- or the lack of it--in the later years, it helps to know there are really two types: senior shrink, and the day-in day-out shrink that happens way before you’re eligible for movie discounts.

From dawn to dusk, it’s not unusual to lose nearly a half inch in height, says Dr. Charles Prickett, a 6-foot-7 Pasadena orthopedic surgeon and USC associate clinical professor of orthopedics who also directs a spine clinic at Orthopaedic Hospital, Los Angeles.

“You’re at your tallest when you wake up,” Prickett explains. “By late afternoon and evening, you have settled.”

The fluctuation is due to normal functioning of the intervertebral disks--the fluid-filled cushions between the 33 vertebrae, the bones that make up the spine.

“People think of bone as static, but it’s dynamic,” says Dr. Mauro “Stretch” Giordani, a 5-foot-7 Pasadena orthopedic surgeon (who claims he must stand on a crate in the operating room when working with his partner, Prickett).

With daily activity, fluid diffuses from the disks into the vertebral bodies, the building blocks of the spine, Giordani and Prickett explain. With less fluid, the disks provide less cushion. And you become shorter. When you lie down, fluid moves back into the disks, explaining why you’re back at full height by morning.

Few people notice these daily fluctuations.

“But if you’re going out for basketball,” Prickett advises, “get measured in the morning. If you’re about to be drafted, make an afternoon appointment.”

It follows that youngsters stretching to meet the height requirement for certain amusement park rides should line up early.

Over the years, the amount of fluid decreases. Cushioning decreases. You get the rest of the picture. Stay in good health, and this settling effect will have a negligible effect on your height, many experts concur.

But other factors--some under our control, others not--can take their toll on height.

“Truck drivers, for instance, are bouncing up and down all day,” Prickett says. That’s very tough on the spine.

Those who sit for long periods also put more stress and strain on the spine and its cushions. Diabetics are especially prone to loss of disk resiliency.

Smokers do their bones no favors. Smoking reduces circulation within the small blood vessels that deliver oxygen-rich blood to the bones, Giordani explains. The diminished blood supply, in turn, hinders the ongoing process of bone restoration and healing. Calcium stores decline.

Poor posture can also exaggerate The Shrink, although with practice it can be corrected.

“Older people are known to slump,” says Dr. Loren Lipson, 5-foot-8 chief of the division of geriatric medicine at USC. “This slump on average can take off 1.5 inches,” he estimates.

Parents, in particular, are known to contort their spines into previously unimaginable shapes when they teach their children how to ride a bike without training wheels or some similar feat.

By far, though, the biggest height robber with age is osteoporosis, a disease marked by low bone mass and deterioration of the bone tissue. This in turn leads to fractures of the hip, wrist and spine, deformities such as stooped posture or a dowager’s hump--and a decrease in height.

While half of all women in the United States will be afflicted with osteoporosis, according to the National Osteoporosis Foundation, men aren’t immune. By age 75, a third of men have the disorder, too, according to foundation estimates.

Height loss due to osteoporosis often becomes noticeable around age 50 in women and 60 or 65 in men, says Dr. Charles Sharp, a 6-foot-4 Pasadena endocrinologist specializing in metabolic bone disorders and a USC clinical associate professor of medicine.

Certain people are at much higher risk of getting osteoporosis. Among risk factors: menopause before age 45, low calcium intake, cigarette smoking, excessive drinking and inactivity. Whites and Asians are at higher risk than other ethnic groups; thin people have higher risk than heavier people.

How much height can osteoporosis take?

“I have seen women lose two or three inches over 15 or 20 years,” Sharp says. “I’ve even seen women who have lost six inches.”

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While you can’t control some risk factors for height loss, there are some ways to reduce the odds that you’ll someday shop for clothes alongside Dr. Ruth. Among the experts’ suggestions:

* Don’t smoke.

* Do engage regularly in weight-bearing exercise, but don’t become a fanatic, says Prickett, who contends overdoing is as bad as doing nothing. Moderate walking, swimming and stationary cycling are the best for maintaining bone health, he says.

In a recent study conducted at Texas A&M; University, post-menopausal women who exercised on stationary bikes three times for 30 minutes a week built bone mass by 3.5% in their lumbar spines, found researcher Susan Bloomfield, while sedentary women lost 2.4% of their bone mass during the same eight-month study. Water aerobics and resistance training with light weights are also good choices, says Sharp.

* Take vitamins and minerals. Pay special attention to calcium, copper, zinc and manganese--all important for bone maintenance. Teen-agers and young adults should build as much bone mass as possible before age 30, when it peaks.

* Those at high risk for osteoporosis might consider a bone-density test, which can predict the chances of fracture and differentiate spinal osteoporosis from other spine problems.

* Women experiencing menopause, when bone mass decreases, should discuss with their doctor whether they’re good candidates for estrogen replacement therapy, which can help maintain bone.

If height loss at any age seems sudden or extreme, it could signal an abnormality such as disk disease leading to scoliosis (an abnormal spine curvature) or compression fractures, Prickett says. If you have lost a half inch or more before your mid-40s, it bears checking with a physician, Sharp suggests.

If clean living, a sense of humor or finding shorter friends don’t ease The Shrink, there is another possible--though temporary--option: join the space program.

Astronauts, whatever their original height, tend to grow in space. Astronaut Richard Hieb was 6-foot-3 when he blasted off on the recent Columbia shuttle mission but soon added an inch, a NASA spokesman says.

The good news (at least for Hieb, who was close to NASA’S maximum of 6-foot-4): height returns to normal back on Earth.