Political opponents, armchair pundits and even nervous supporters are demanding that President Joe Biden undergo such testing after his dismal debate performance—even though his physician says he gets, and passes, an annual neurologic exam.

Former President Donald Trump, who’s only a few years younger, makes his own gaffes. He recently bragged about passing a 2018 cognitive test—while calling the doctor who administered it by the wrong name.

With all the concern, what can cognitive testing actually tell about a person’s brain health—and what can’t they answer? And presidents aside, does the average older adult need one?

What are cognitive tests?

They’re brief screening tools, a 10-minute series of questions to assess different brain functions. Two of the most common are called the MMSE, Mini-Mental State Exam, and the MoCA, Montreal Cognitive Assessment.

Recalling a list of five unrelated nouns or seeing how many words beginning with F you can say in a minute can assess short-term memory and language. Counting backward by 7s tests attention and concentration. Drawing a clock with the correct time is a clue to spatial awareness.

How reliable are cognitive screenings?

They don’t diagnose health problems. A bad score is just a red flag that indicates a need for further testing to see if there is a health problem and uncover what kind, said Dr. James Galvin, a neurologist at the University of Miami.

A good score usually is good news. But the highly educated especially tend to be good test-takers even if cognitive trouble is starting to brew. So if someone scores OK yet they, a family member or the doctor sees some day-to-day concern, more testing still could be warranted.

“We simply use it as a benchmark to determine our suspicion level,” Galvin said.

When and how often should cognitive screenings be done?

“A screening test is exactly a snapshot in time. So it tells you in that moment how someone does on that test,” Galvin stressed. “It doesn’t tell you how a person is functioning in their everyday life.”

Simply reporting a concern is reason enough for a primary care doctor to perform one. But it’s also supposed to be part of the annual Medicare wellness visit for those 65 and older.

Galvin wouldn’t discuss Biden or Trump because he hasn’t examined them—but said that generally it’s a good idea for seniors to get checked yearly to spot changes. It’s much like how doctors don’t assume your blood pressure’s still fine, they measure it.

How is a cognitive test different from a neurologic exam?

Cognitive screenings are “pencil and paper tests” usually handled by primary care doctors, while neurologic exams generally are performed by a specialist, Galvin said.

It’s a very detailed physical exam. Doctors watch the patient’s speech patterns and behavior, test how key nerves are functioning, check reflexes that can signal brain diseases and assess muscle tone and function.

If either kind of test signals real cognitive concerns, the next step may be more intensive neuropsychological testing—an exam that often lasts up to three hours.

After an exhaustive interview of the patient and any accompanying family members, the neuropsychologist goes through tests and tasks designed to check specific brain functions—intelligence, memory, verbal ability, problem-solving and reasoning skills, visual and auditory responses, emotion and mood. They may use puzzles, objects to rearrange, or drawing and writing tests.

Blood tests and brain scans also may be ordered. Special types of PET scans can detect Alzheimer’s hallmark amyloid plaques and tau tangles in the brain. An MRI can detect past strokes, helpful in diagnosing vascular dementia.

How can you tell if cognitive concerns are a disease or just getting older?

“Age makes us do things a lot slower,” Galvin said. “We move slower. We think slower. But we’re still moving correctly and we’re still thinking correctly—it just takes us longer.”

Examples of slower cognitive “processing” might be difficulty remembering a name, numbers or specific details under pressure—but they come back to you later.

Galvin noted that sometimes, reversible health problems mimic cognitive trouble. For example, urinary tract infections are notorious for causing sudden confusion in older people. Certain medications affect memory, as can thyroid problems, depression, even poorly controlled diabetes.

Anyone who’s worried about their memory should talk to their doctor, or seek a specialist, “who can reassure you that everything’s OK or develop a treatment plan that’s specific for you,” he said.