Dr. Edward Schneider of the Univ. of Southern California recently told a group of seniors that there is little scientific evidence supporting anti-aging remedies currently in vogue.

The reason certain villagers in the Soviet Union and Pakistan reportedly live some 40 years more than the average American has less to do with differences in diet, exercise and climate than with discrepancies between actual and reported ages, said Schneider.Consider the use of megavitamins: One aging theory holds that normal metabolism results in "free radicals" that not only attack cells but accumulate with age. This suggests that saturating the body with vitamins E and C, which combat these toxins, will slow aging. Nice theory, but unproven: No one has shown that free radicals increase with age.

The widespread use of collagen products also stems from an aging theory. This one asserts that collagen, the dominant protein in connective tissues, undergoes cross-linking over time, becoming rigid and eventually interfering with vital functions. While there's evidence that some cellular molecules bind together, as Schneider noted, no one dies of rigid skin.

Schneider's pet theory holds that human cells replicate only a certain number of times and thus have limited lifespans. Studies have shown that when an old cell is fused with a younger one, the new cell acts old.

QUESTION: I've been one to forget where I put my glasses or keys 10 minutes after I set them down. Now that I'm in my late 60s, I don't want others to attribute ominous significance to my absentmindedness. Are there ways to improve memory?

ANSWER: Research shows that older people retain information as well as other age groups; however, they may have difficulty incorporating new information and retrieving it. The good news is that, "With practice, you can bring your memory skills back up to snuff," says Genevieve Meyer, who teaches memory-enhancement techniques at the Senior Health and Peer Counseling Center in Santa Monica, Calif.

"Memory . . . is a process over time that involves three phases: awareness, consolidation and retrieval of information to be remembered," notes Meyer, adding that the more actively involved you are with the first two steps, the more success you'll have with the third.

She recommends using these techniques to improve memory:

- Concentrate on the information to be remembered. If your mind is on other things, you may not be paying proper attention.

- Don't panic if you forget something. Take a few deep breaths and focus on the present.

- Consolidate information by interacting with it visually and verbally. For example, repeat a new acquaintance's name and associate it with something unusual about the person, such as a physical feature.

- Use self-instruction. For example, when you turn off the coffee maker, do so with a sweeping gesture as you say out loud, "I'm turning off the coffee pot."

- Organize information. For example, write down important dates to remember. Group a seven-digit telephone number into three- and two-digit numbers. Group errands into those close to home and those at a distance.

- Organize your environment. For example, always put your keys in the same place.

- Set up a "tag" system to remember one-time events. This is comparable to tying a string around your finger. For example, place a Kleenex on the dashboard as a reminder to turn off your headlights on a foggy morning.

QUESTION: I'm a 68-year-old woman who quit smoking Nov. 17, the day of the Great American Smokeout. Two weeks later I lit up again, marking the third time in five years I've tried and failed to kick the habit. Is it worth another attempt?

ANSWER: Keep trying. You may be closer to achieving your goal than you realize. While the likelihood of permanent success is about one in five for any single attempt to stop smoking, with repeated tries the odds go up to about three in five, according to Lynn Kozlowski of the Addiction Research Foundation. Would-be non-smokers often make progress with practice because their motivation to quit increases and their coping skills improve.

Your next attempt to quit should be guided by your answers to these questions:

- What worked best in the past?

- What was unpleasant or unhelpful?

- Why did smoking resume?

Despite the proliferation of smoking-cessation programs, the ingredients for success are still speculative. A recent report from the U.S. Preventive Services Task Force concluded that reinforcement of anti-smoking messages-rather than a specific intervention-yields the best results. This suggests that programs of long duration with frequent sessions are most successful. Other experts have found that nicotine chewing gum used with a formal program aids quitting (but the long-term effects are unknown).

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(C) 1989, Washington Post Writers Group