During a routine checkup, a 70-year-old man comments that he is sleeping less than he once did, often waking up before dawn. His doctor assures him that this is normal at his age, and that he need not worry.

The children of a 78-year-old woman observe that their usually alert mother seems distracted and increasingly forgetful, and has no zest for things that used to please her. They consider consulting her physician but decide against it. After all, what's to be expected from a woman of 78?

Just five years ago, these approaches would have received an understanding nod from most people who care for the elderly. Now, however, gerontologists no longer view such behavior by older people as normal. Geriatric psychiatry, a new discipline designed to treat the special problems of elderly adults, has begun to give hope to situations once viewed as hopeless.

For instance, the wakefulness of the man could signal an underlying physical or mental problem. Studies show that healthy older people do not sleep less. They average eight hours of bed rest per night, with more than six hours of sleep. And the woman may be suffering from the progressive, incurable disorder known as Alzheimer's disease, which has destroyed the minds of about 2 million Americans over 65.

But there is a good chance, psychiatrists say, that both patients suffer from a condition that, once labeled, can be treated: Depression.

"A lot of people think, 'Gee, I'm old, it's normal to be depressed.' It isn't," says Dr. Gene Cohen, a psychiatrist and director of the Program on Aging for the National Institute of Mental Health. "Depression, anxiety, memory disorders, delusions and hallucinations too often are dismissed as eccentricities of old age, part of an inevitable decline. That's missing the problem. In every case there is some treatment that could improve or alleviate the situation."

Millions of active, productive older adults have proved that good health is quite normal during life's last segment. Only 5 percent of those over 65 live in hospitals or nursing homes.

The average life expectancy is about 76; for people who have reached age 65, the life expectancy increases to 15 or 20 more years.

But while people are living longer, there are signs of trouble. Only 12 percent of the population is over age 65, but 25 percent of suicides in the United States each year occur in that group.

"Clinical, treatable depression is a rampant disease among the elderly," says Dr. Nathan Billig, who runs the clinic for geriatric psychiatry at the Georgetown University Medical Center. "Old age is a time of many losses -- of mobility, of friends and family, of health, and of financial and social status. The extent to which we learn to handle losses throughout life may well determine how we deal with old age."

The Georgetown program, which began a year ago, is one of 20 such programs nationwide created in the past six years. Now, two to three new patients come into the clinic each week, usually accompanied by a family member who often also receives counseling, Billig says.

The majority of the clinic's elderly patients suffer from depression, dementia, or both. Dementia is a broad category that covers problems of memory, orientation, concentration and the ability to care for oneself on a daily basis.

Dementias fall into two categories. The first, known as primary dementia, is a group of brain diseases including Alzheimer's disease and injuries caused by multiple small strokes. For those problems there is no cure, although treating those patients for depression sometimes eases their distress. For Alzheimer's patients, who constitute 60 percent of the people with dementia, this is especially true in the disease's early stage.

Another 15 to 20 percent of persons with dementia have potentially reversible dementias, which have many causes, including disorders of the heart, thyroid or metabolism, and the side effects of medications.

The potent chemical stews of prescribed and over-the-counter medications often consumed by the elderly commonly cause complications, Billig says. A single drug may have little-known side effects that disrupt intellectual function, memory and mood. With a variety of medications, the interactions are even less predictable.

Treated for depression, some patients destined for custodial care in a nursing home improved enough to live independently. Others, resigned to the dreary stereotype of old age, are "often stunned at the improvement," Cohen says.

Treating the mental problems of the elderly is in some ways no different from treating the young. A complete medical history is essential.

"At the end of our evaluation, we have a pretty good idea if the patient has a problem that can be helped by medication or by some other form of psychotherapy," Billig says. Often, he adds, it is depression that creates complications in an otherwise treatable physical problem. Older depressed patients respond well to psychotherapy, medication or both. A careful look at the reversible dementias may suggest relatively simple remedies, such as reducing or changing medications or checking out thyroid function.

Advice is straightforward: Don't take sudden changes in behavior for granted regardless of age. If any of the following are observed, a physician should be consulted:

* A change in sleeping patterns, such as early morning wakening.

* Increase in physical symptoms that don't seem to have a physical basis.

* Lack of interest in pleasurable activities.

* Expressions of not wanting to live, or hints of suicide.

* Forgetfulness and disorientation.

For more information about the Georgetown University Hospital geriatric psychiatry out-patient service, ask your physician or call 625-6184.