Some memory loss is normal and natural. But some people, when they notice a slight memory lapse, fear they have Alzheimer's disease.
"The chance of developing this disease is small," says psychologist Thomas Crook, president of Memory Assessment Clinics Inc. He calls Alzheimer's "exaggerated aging. There is a quantitative difference."
According to psychiatrist Trey Sunderland, chief, geriatric psychiatry at National Institute of Mental Health, people most at risk for this severe dementia are those with several family members who got the disease in their 70s or those with one close relative who got an aggressive form in his or her 50s.
Symptoms of this disease can include an abrupt decline in memory, accompanied by the inability to express oneself verbally, by verbal repetition and by noticeable personality changes -- tearfulness, sadness, physical fighting with caretakers, wandering or delusions.
Other physical and psychological illnesses such as cardiovascular diseases, brain injuries or diseases, or depression can also impair memory. When applicants for memory studies do poorly on the initial screening tests, Dr. Crook advises them to have thorough physical and neurological examinations with specialists to uncover often treatable organic causes for their memory lapses.
Drinking and drugs often interfere with memory. Drinking more than two alcoholic drinks a day, for example, weakens a person's ability to store and retrieve facts. Women are generally more susceptible because they do not digest alcohol as well as men, so more goes to the brain.
Beware, too, of over-the-counter and prescription medicines. "Scopolamine [a drug to prevent motion sickness] even in a minute dose can impair memory in a sensitive person," says Dr. Sunderland. High blood pressure medications can also cause temporary problems. Combining certain drugs or mixing medications and alcohol can be especially harmful.
According to memory experts, everyone is susceptible to memory lapses. "There are statistical differences -- measurable in the lab -- between an 18-year-old and a 30-year-old," says Dr. Sunderland. "Although not noticeable in conversation by you and me, the ability to take in new information also declines slightly each decade after 30."
This doesn't mean that older people across the board are less sharp. On the contrary, says Dr. Crook, "a 65-year-old who has trained his brain to remember will be sharper than an untrained 25-year-old. And some people in their 90s have incredible memories."
In an experiment at the National Institute on Aging, part of the National Institutes of Health, that focused on the best performers in an older group, 15 percent to 20 percent showed no perceptible change in their memories.
Normal memory loss, by the way, does not affect intelligence. "We are actively thinking and generating new memories at all times. Even if our speed in memorizing lists of words decreases slightly with age," says Dr. Sunderland, "our knowledge base constantly expands, and our IQ remains essentially the same throughout our lives."