It’s an annual ritual: Every December, I and my oldest New York City friends—all six of us in our fifties and sixties—gather to exchange gifts. This year, the shutterbug among us also passed out something extra: photos of the wedding shower of our pal Susan, taken 21 years ago at my apartment. Everyone reminisced about how much fun we’d had and the pictures bore that out. Yet I remembered nothing about the shower—least of all that I had been the hostess. That worried me. How could I have forgotten such a major event? Was this a sign that my brain was going soft?

It was not. “There is a normal loss of memory as we age,” notes Lisa Ravdin, PhD, Associate Professor of Neuropsychology at New York Presbyterian Hospital. “Some people have very good memories and others don’t. It’s not necessarily a cause for concern.”

In fact, we aren’t programmed to have total recall. “Most of the things we learn, our brains are really wired to forget,” says Gayatri Devi, M.D., Director of New York Memory and Healthy Aging Services and Clinical Associate Professor at NYU School of Medicine. “We can’t remember everything, or we’d be a mess! If you ask people about the same incident, everyone will remember it differently. Some people will remember something better than others, and it doesn’t mean anything. We all have different textures to our memories.”

It’s not a function of our gender either. Both men and women typically start to notice memory changes in their sixties—with one notable exception. “As women go through menopause, their estrogen levels plummet,” notes Dr. Devi. “I see women who are scared that they have Alzheimer’s, but they’re just perimenopausal. I’ve done a study of women going through menopause, and the incidence of memory loss is about 80 percent—but usually it’s temporary. You get your memory back, but it’s very scary when it happens.”

Dr. Devi recalls such a scenario with a 48-year-old woman who was the president of an accounting firm. “She couldn’t keep her books straight, and she began to feel as if she was going insane,” says Dr. Devi. “She often couldn’t find the right words to explain a situation to a client, and she thought she sounded incoherent. It turned out her problem was related to hormone loss. Once we replaced her hormones, her condition was cured.” 

Hormones aside, a host of other factors can affect memory. “There could be a systemic illness, or chronic pain, or a sensory change that affects hearing or sight, or a new medication,” notes Dr. Ravdin. Adds Dr. Devi, “A serious fall or fracture or significant head injuries would put you at high risk for cognitive problems.”

Sleep disturbance is also a big issue. “Sleep is important for consolidating memory,” says Dr. Devi. Dr. Ravdin agrees. “If you’re tired, you’re not functioning at your best. You’re not able to take in as much information, and that information won’t be remembered as well.”

What should set off alarm bells? “When you have a sudden change in your thinking ability—a rapid onset of change in speech or attention or arousal—you should seek medical attention right away,” says Dr. Ravdin. “A change in your ability to function independently, to carry out key activities of daily living, should also cause concern. If you forget to take your keys, forget medication, forget an appointment, that’s not necessarily a problem. But when there’s a pattern of behavior—somebody repeatedly forgetting to go to a doctor’s appointment or forgetting important events like birthdays and anniversaries—you should pay attention.”

And yes, there are ways to hone your cognitive skills. To sharpen your memory, keep your brain active: Like your body, your mind needs exercise. “Computer games are good,” says Dr. Devi, “but, frankly, going out and socializing or running a mile will probably get you up and going more.” Above all, do things that give you pleasure. Says Dr. Ravdin, “People ask me if they should do crossword puzzles to keep their brains alert, and I say only if you like them. Do something you enjoy so you’ll stick with it—and challenge yourself. Build your brain power.”