Is It Really Dementia?

Maybe it’s something else.

That’s what you tell yourself, isn’t it, when an older person begins to lose her memory, repeat herself, see things that aren’t there, lose her way on streets she’s traveled for decades? Maybe it’s not dementia.

And sometimes, thankfully, it is indeed some other problem, something that mimics the cognitive destruction of Alzheimer’s disease or another dementia — but, unlike them, is fixable.

“It probably happens more often than people realize,” said Dr. P. Murali Doraiswamy, a neuroscientist at Duke University Medical Center. But, he added, it doesn’t happen nearly as often as family members hope.

Several confounding cases have appeared at Duke: A woman who appeared to have Alzheimer’s actually was suffering the effects of alcoholism. Another patient’s symptoms resulted not from dementia but from chronic depression.

Dr. Doraiswamy estimates that when doctors suspect Alzheimer’s, they’re right 50 to 60 percent of the time. (The accuracy of Alzheimer’s diagnoses, even in specialized medical centers, is more haphazard than you would hope.)

Perhaps another 25 percent of patients actually have other types of dementia, like Lewy body or frontotemporal — scarcely happy news, but because these diseases have different trajectories and can be exacerbated by the wrong drugs, the distinction matters.

The remaining 15 to 25 percent “usually have conditions that can be reversed or at least improved,” Dr. Doraiswamy said.

In trying to tell the difference — not a job for amateurs — one key consideration is age, said Dr. Ronald C. Petersen, director of the Mayo Clinic’s Alzheimer’s center.

Dementia is highly age-related, he pointed out. In a 50-year-old, memory problems might very well have some other cause. But “the likelihood that a 75-year-old’s becoming forgetful over six to 12 to 18 months is due to something treatable and fixable is low,” Dr. Petersen said. “But not zero.”

Which points to another key question: speed of onset. Dementia tends to develop slowly; family members often realize, in retrospect, that an older person has shown subtle cognitive decline for years.

When a person’s mental state changes suddenly over a few days or weeks, however, “that’s not the usual picture of a degenerative disease,” Dr. Petersen said. “That means looking for something else.”

The list of other causes for dementia-like symptoms runs surprisingly long. Among the leading culprits, Dr. Doraiswamy said, are depression and anxiety. Like dementia, they can interfere with the ability to concentrate and remember.

He looks next for thyroid deficiency. “Thyroid problems are very prevalent, and thyroid has a huge effect on the brain at every age,” he said. Usually, “this can be relatively easily tested for and relatively easily fixed” with daily medication.

Vitamin deficiencies probably qualify as the most hoped-for scenario. Cognitive problems caused by lack of vitamin B1 (thiamine) or B12 are reversible with pills or injections.

Heavy drinking also causes memory loss. “If you stop drinking, if it’s not too late, the brain can repair itself,” Dr. Doraiswamy said. After years of alcoholism, “you may not be able to repair the damage, but you can keep it from getting worse.”

Sleep disorders, and in particular sleep apnea, can take a cognitive toll on older people. “Their cognitive function may become slower, with poor attention and concentration,” Dr. Petersen said. When patients with apnea use a C.P.A.P. machine, “they come back the next year markedly improved.”

Sleeping pills — you knew this was coming — and a variety of other drugs, especially in combination, frequently cause dementia-like symptoms, too.

“There’s a long list, several hundred drugs, both prescription and over the counter, that can impair memory,” Dr. Doraiswamy said. He rattled off a bunch: medications for nausea and urinary incontinence, older antihistamines like Benadryl, cardiac drugs, painkillers, certain antidepressants and anti-anxiety medications — yes, including benzodiazepines. Selectively deprescribing may help clear a patient’s head.

There’s more. Head injuries that lead to the blot clots called subdural hematomas. High blood pressure. Diabetes. Infections. A condition called normal pressure hydrocephalus. Delirium that develops during hospitalization.

Plus, older people can have any of these problems along with actual dementia. Treating the other causes may at least slow, though not stop, cognitive decline.

So it makes sense, Dr. Petersen said, to tell patients and families — many already terrified of dementia — that other causes exist. “We shouldn’t just dismiss them,” he said. “We scan the brain, do blood tests. We look for these other conditions. That’s common and not inappropriate.”

On the other hand, “I want to be realistic,” he said. “I do it softly at first, but I introduce the notion that we might not find something else.”

Because even though the list of other possibilities is long, so are the odds against restoring a patient to normal functioning. When it looks like dementia, sadly, most of the time it is.