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Cathy Hope hit fatigue in her mid-50s. Even after her usual eight hours of sleep, every morning she awoke exhausted, and after a year, she was out of breath simply walking.

At 5 feet and 98 pounds, Hope didn’t fit the standard picture of a sleep apnea patient: An obese man with a rattling snore who falls asleep in office meetings. “I didn’t snore and I didn’t have problems with sleepiness,” Hope said. Still, an imaginative doctor sleuthed it out and after several months of treatment, her energy had completely returned.

Are you tired all the time, fuzzy-headed, or can’t imagine life getting any better? It’s easy to attribute symptoms like these to menopause or depression. But speak to your doctor about a sleep apnea evaluation, since your sleep may be contributing to the problem.

In an Australian study, for example, of 293 sleep apnea patients, 213 had clinically significant symptoms of depression—nearly 73 percent. Many were happier after their sleep apnea was treated.

Other research has found that sleep apnea can affect your memory and ability to focus, symptoms that can drag down your mood as well.

The jury is still out on whether treating sleep apnea improves mood. But if you do have this sleep problem, it's not something to ignore, and your depression may be a symptom.

Who Gets Sleep Apnea?

As you get older, your risk of sleep apnea increases. Between the ages of 50 and 70, more than 43 percent of U.S. men have sleep apnea, and almost 28 percent of women, according to one study. Other research found that more than half of Black men and women had sleep apnea in midlife.

But you can also have sleep apnea in your 30s and 40s, especially if you carry extra pounds.

What Is Sleep Apnea?

Sleep apnea is a breathing problem. Your brain may fail to send correct signals to the breathing muscles (also called central sleep apnea), or, more often, the airway collapses or is blocked because of fat or abnormalities in the throat and nasal passages (known as obstructive sleep apnea). When your breathing pauses or becomes shallow, you’re pushed out of deep sleep.

Although patients don’t wake up, they end up sleep-deprived and become more vulnerable to cognitive dysfunction, depression, diabetes, stroke, high blood pressure, heart failure, and car accidents from sleepiness at the wheel. A night of oxygen deprivation continues to affect you throughout the day, research suggests, which explains why Hope felt so breathless.

In serious cases, untreated sleep apnea can damage brain function permanently. So this isn’t a health issue you can ignore.

What You Can Do

To diagnose the problem, you may be able to take a test at home, attaching sensors to yourself that monitor your breathing while you sleep (you’ll be told how either by video or a phone call). Home tests are prone to false negatives, however, so if you feel that sleep apnea is likely in your case, and your home test is negative, ask for a test in a lab where you’ll sleep overnight.

If you do have frequent episodes of interrupted breathing, there are several steps you can take.

You can get more exercise, lose weight, and stay away from alcohol. In one study, exercise cut the severity of sleep apnea by up to a third, even in people who didn’t lose weight.

Some people need to sleep on their side rather than on their back. Over-the-counter nasal sprays, or products that keep your nostrils open, may help snoring and mild sleep apnea.

You may benefit from sleeping with a mandibular advancement device—a device you put in your mouth to keep your lower jaw slightly forward. Some people in severe cases get surgery.

The most effective remedy is a CPAP machine—CPAP stands for Continuous Positive Airway Pressure—which comes with a mask. The mask may cover both your mouth and nose or just your nose. The machine will blow air into the mask, which will reach your throat to keep the airway open.

You may have heard that people don’t like these machines. However, some research suggests that 75 percent of patients were using their machines at least five nights a week.

So how confident can you be that using a CPAP will boost your mood? In the Australian study, the results were dramatic: Some 40 patients who had been harboring thoughts of suicide before the treatment were no longer struggling with those demons after sleeping with a CPAP for three months.

A study of more than 300 women in Spain diagnosed with moderate to several obstructive sleep apnea also showed a boost in mood after three months on a CPAP. A small study in Taiwan, mainly of men, concluded that CPAP improved mood as long as six months later, although surgery did not.

It’s possible that some or all of the mood boost from CPAP comes because patients expect to feel better. However, if you feel better, you might not care if you're experiencing a placebo effect. Feeling better is the goal.

In a metaanalysis of 31 relevant reports, researchers concluded that too many studies didn’t meet the highest standards. Overall, anxious and depressed CPAP patients did have improved mood after treatment, yet they didn’t do reliably better than people who were fitted with dental appliances or fake CPAP machines.

That said, CPAP seemed more clearly beneficial in people who were more severely depressed.

Similarly, the evidence that sleeping with a CPAP machine will protect your brain function is a bit mixed. It may be most helpful if you start young and use the machine for a long time,

If you do receive a CPAP, commit yourself to using the machine regularly. Skipping nights, taking it off during the night, or stopping altogether could affect your health more than you think.