You can't find your keys. You forgot the new neighbor's name. You don't remember why you went upstairs or what you were planning to make for dinner.

If you're in your 20s or 30s, you chalk up your mental haziness to late nights or serious partying. But when you're a little older, you worry that "brain fog" means early Alzheimer's is setting in.

Although not a recognized medical condition, brain fog is typically a term people use to describe symptoms of mental haziness. In addition to forgetfulness, symptoms that people report might range from fatigue and headaches to crankiness and lack of energy.

"Brain fog is an inability to really punch through," Mady Hornig, M.D., associate professor of epidemiology at Columbia University Medical Center in New York City, tells Prevention.

"It's a vague sense of what you're trying to retrieve, but you can't focus in on it," she says, "and the effort to harness the thought can be as draining as physical activity."

Health care providers say they've seen an uptick in the number of younger people, often baby boomers, who report mental fogginess.

"These people are in the prime of their lives, and the very thought of having dementia is causing them to panic. They are particularly fearful of Alzheimer’s, the most common form of dementia, knowing it is incurable and difficult to detect early on," writes geriatric psychiatrist Marc Agronin in the Wall Street Journal. "Everyone needs to take a deep breath."

Possible causes

woman with head down asleep on laptop Being stressed and exhausted can contribute to mental haziness. (Photo: Fulltimegipsy/Shutterstock)

So, if your fuzziness isn't a sign of impending dementia, what could the root cause be? There are plenty of possibilities.

Not enough sleep. When your body doesn't get enough rest, your brain also suffers. "Poor sleep has an adverse impact on thinking," says sleep expert Dr. Lawrence Epstein, an instructor in medicine at Harvard Medical School. "This is true whether it's due to a lack of sleep or a sleep disorder." When you don't get enough sleep, your attention and clear thinking can falter, Epstein says. Try to get seven to eight hours of sleep every night. Make your room a comfortable sleep haven without electronic devices. Establish a sleep routine by going to bed and getting up at the same time every day. If that doesn't help, see a doctor to look for underlying sleep problems.

Stress. Being stressed can take a toll on your emotions and devastate your body. Symptoms of stress can range from headaches and nausea to chest pain and aching muscles. Not surprisingly, stress can also make your mind foggy. "Stress impairs performance, physically and mentally," rheumatologist Robert Lahita, M.D., Ph.D., chairman of medicine at Newark Beth Israel Medical Center, tells Prevention. So find ways to deal with whatever is causing you anxiety. Try deep breathing or meditation, yoga or biofeedback. Run around the block or get some coloring books that help you de-stress.

Drug side effects. As we age, we tend to take more medications. Whether it's antibiotics, allergy pills or even blood pressure drugs, check the fine print about potential side effects. Often fogginess is just one of the extras that comes with your new drug. If the medication is short-term and the cloudiness is minimal, then know you'll likely be coming out of the haze soon. But if you're on the drug for the long haul, talk to your doctor. He or she may be able to switch you to a different medication.

Hormone issues. If you're a woman and your pregnant, settle in for a possible nine months of mental haziness. On the other end of the spectrum, the same thing can happen during menopause. Several studies have found a drop in performance on memory tasks right around the same time that a woman's estrogen level dips — between age 45 and 55. Based on other studies, up to 60 percent of women report memory issues as they go through menopause, Julie Dumas, an associate professor of psychiatry at the University of Vermont, told HealthDay. "There really is something going on in the brain," she said. "You're not crazy."

An overworked brain. If you are trying to do too many things at once, it's no wonder your brain gets a little fuzzy. "Processing speed and other skills of the typical brain begin to slow down in middle age," says Agronin. But no matter how old you are, multitasking takes a toll. Try concentrating on just one thing at a time and see if you get a little clarity.

Other health issues. Brain fog can be a symptom in a number of diseases including chronic fatigue syndrome, fibromyalgia, lupus and multiple sclerosis. It can also be a major part of depression. If you're experiencing cognitive issues that can't be explained away by sleep, stress or other issues, see your doctor to rule out any other possible problems.

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.