TRENTON, N.J. (AP) — Millions of people struggle to get enough sleep — and to stay alert the next day.

Lots of apps, fitness trackers, smartwatches and even mattress motion sensors claim they can diagnose or treat sleep problems. But sleep disorder doctors say there's little evidence consumer gadgets actually improve sleep.

"The technology can help describe the problem," such as waking repeatedly or too early, said Dr. Douglas Kirsch, president of the American Academy of Sleep Medicine. "It does not tell you what the cause is" or how to fix it.

Experts say such products have some value: They make people focus on and try to improve their sleep.

AMERICA'S SLEEP PROBLEM

According to the U.S. Centers for Disease Control and Prevention, about one-third of adults and two-thirds of high school students report regularly getting less than the recommended amount of nightly sleep — seven hours for adults and eight to 10 hours for teens.

"The average person in America does not spend enough time trying to actually sleep," Kirsch said.

Regularly getting too little rest doesn't just cause fatigue. It can increase risk of accidents, run down your immune system and lead to heart attack, high blood pressure, stroke, diabetes, obesity, reduced sex drive and other problems.

NO-TECH STRATEGIES

Many people simply stay up too late, and doctors say going to bed earlier is a good place to start if you're having trouble sleeping.

Block excess noise and light with ear plugs and heavy curtains.

"Make your bedroom a cave ... a quiet, comfortable, cool, dark place," Kirsch advises.

Stick to a consistent sleep schedule, even on weekends, and start winding down your activity an hour before bedtime.

Stop using computer, phone and TV screens well before then and keep them out of your bedroom. Turn your clock's face away from you and try an old technology: Read a book to induce drowsiness.

Good health practices also help. Don't smoke, limit alcohol, stop all caffeine by noon or 1 p.m. and get regular exercise, but well before bedtime. Also, try to avoid dozing off while watching TV in the evening.

FREE/LOW-COST TECH SOLUTIONS

Sleep doctors believe the blue light emitted by smartphones and other screens can keep people up.

One easy fix: Use the phone's display settings to switch from blue light to warmer yellow light in the evening.

For people who spend lots of time on screens late at night, there's evidence that so-called blue-blocker glasses can help, said Dr. Daniel Barone, associate medical director at the Weill Cornell Center for Sleep Medicine in New York. They can be found for less than $20 and filter out the stimulating blue light.

Data also show white noise can improve sleep, said Barone, co-author of the book "Let's Talk about Sleep." White noise machines start at around $20, and there are apps you can get for free or a few dollars.

Meditation tapes and apps benefit many people by helping them relax before bedtime.

Kirsch said there's data validating cognitive behavioral therapy, a range of strategies to train yourself to sleep better. Those include relaxation techniques, getting back up for a while if you can't fall asleep, even a paradoxical approach — going to bed and trying to stay awake.

Sleep clinics offer such programs, but there also are apps that can teach such techniques. The Department of Veterans Affairs developed a free one called CBT-i Coach .

WHEN TO SEE A DOCTOR

If those measures don't help, ask your doctor to check for health problems that could be disturbing your sleep. Those include many common conditions: acid reflux, allergies, anxiety, depression, medication side effects, pain, sleep apnea and snoring. In some people, evaluation by a sleep clinic may be necessary.

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Follow Linda A. Johnson at https://twitter.com/LindaJ_onPharma