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DEAR ABBY: I am in my mid-50s and look forward to traveling with my husband when he takes early retirement next year. My mother died at 82 with Alzheimer's disease, and lately, if I misplace my sunglasses or forget somebody's name, I become terrified that I'm coming down with it, too.

I have heard there are certain brain exercises people can follow to keep from losing our memories as we get older. My husband says I'm silly to worry about this now, but if there's anything I can do to protect myself from future problems, I want to get started. Any suggestions? -- WORRIED SILLY IN L.A.

DEAR WORRIED: Although a family history of Alzheimer's does increase your risk, my experts tell me that recent scientific data estimate that only one-third of what determines memory ability and long-term brain health is genetically programmed. The other two-thirds are actually dictated by things that are under our own control, such as lifestyle and personal health choices. Thus, as we age, we have far more influence over our own brain fitness and memory abilities than we ever imagined.

It is not "silly" to be concerned about getting a head start on preventing age-related memory loss. I spoke with Dr. Gary Small, director of the UCLA Center on Aging, who says it is never too early to begin protecting our brains. In his book, "The Memory Bible," Dr. Small explains that our brains actually begin to show signs of aging when we are in our early 20s. He outlines ways to protect our brain function with healthy diet, mental aerobics, memory techniques and stress reduction.

Organizations like the UCLA Center on Aging (www.aging.ucla.edu) and AARP (www.aarp.org) also provide information and programs about healthy lifestyles and ways to stave off many age-related diseases. Check them out. It may give you some much needed peace of mind.

DEAR ABBY: For the past six years, I've had a problem with my younger sister, "Robin." She "borrows" my clothes and other things from my room without asking, and then isn't smart enough to put them back. Every time I walk by Robin's room, I find another article of my clothing, shoes or jewelry on the floor. When I confront my sister in front of our parents, Mom rolls her eyes and says she's tired of my complaints. Then Dad will ask Robin point-blank if she "really did it," and she'll say, "Yes, but I was about to return it." That's it, end of story. It's happened too many times to count.

Last summer, I put a keyed lock on my door, which helped with the problem until the lock was mysteriously filled with "goop." It never worked after that. Just yesterday, I found an expensive dry-clean-only sweater of mine on Robin's floor. She had tossed it in the washer and dryer, and it was ruined. When I told Mom, she went out and bought me a new one, but just tonight I found one of my shirts on Robin's floor -– also ruined.

I'll be moving out in July to go to college, but until then, I need some advice. Please help me, Abby -- nobody else will. -- COUNTING THE MONTHS IN MASON CITY, IOWA

DEAR COUNTING THE MONTHS: Your parents have been negligent in their responsibility to your little sister. They have failed to teach her responsibility, honesty, and respect for the possessions and boundaries of others. This will come back to haunt them -– and your sister -– in the future. Please show them this column and hang on until July. Your trials are almost over.

What teens need to know about sex, drugs, AIDS and getting along with peers and parents is in "What Every Teen Should Know." To order, send a business-sized, self-addressed envelope, plus check or money order for $5 (U.S. funds) to: Dear Abby -- Teen Booklet, P.O. Box 447, Mount Morris, IL 61054-0447. (Postage is included in the price.)

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