Ever watch someone with sleep apnea? It’s one of the most frightening — and unforgettable — things you’ll ever see.

One minute, the sleeper is snoring away. The next, nothing.

At first, you might be thankful for the quiet — until you realize the reason for that sudden silence: they’re not breathing.

Someone with apnea can go through dozens of breathless bouts per night and never even realize it — but in this case, what you don’t know can not only hurt you… it can kill you, too.

Apnea has been linked to everything from sexual dysfunction and metabolic syndrome to diabetes and heart disease — but now, researchers have confirmed that it’s not too late for people already fighting that nightly battle.

The standard mainstream treatment for apnea is an oxygen mask called CPAP, for continuous positive airway pressure. In a new study, 86 patients with moderate to severe apnea were assigned to either the real CPAP mask or a sham treatment.

After three months, the volunteers took a one-month break… then switched places for another three months.

When they got the real CPAP, the volunteers saw drops in blood pressure and cholesterol levels — including an average dip of nearly 20 points in dangerous triglycerides — as well as better control of their blood sugar levels.

More importantly, they also lost weight — and while most of the patients were battling metabolic syndrome at the start of the study, 13 percent no longer had the condition after the three months of CPAP, according to the study in the New England Journal of Medicine.

But does all the credit go to that mask?

The researchers say they’re not sure — and I’m not either, because while CPAP can help get you through the night, the best way to beat apnea isn’t with oxygen — it’s with lifestyle changes.

And it starts with losing some weight — like the patients in this study managed to do. Studies have shown that even modest weight loss can end the apnea as well as slash your risk of diabetes and heart disease.

Lose that weight yourself, and you’ll not only look and feel better than you have in years — you’ll sleep better, too.

Sometimes, the simplest things are hardest to get — like a good night’s sleep.

If you’re up late burning the midnight oil working a job that requires you to be available around the clock, there’s not much I can do for you other than suggest a new line of work.

But if you go to bed at a reasonable hour each night only to find yourself staring at the ceiling, watching the clock and wondering what’s on TV as the minutes turn to hours, there are some simple steps you can take right now to help get to sleep quicker — and stay asleep longer.

And it starts with getting more active during the daytime.

Oregon State University researchers looked at data on more than 2,600 adult men and women in just about every age group — from 18 to 85 — who wore accelerometers to measure their daily activities for a week.

Those who got at least 150 minutes of moderate exercise or 75 minutes of more intense workouts a week had a 65 percent boost in sleep quality — and, as a result, they were less likely to report feeling tired during the day.

Not feeling tired during the day on its own would be a huge improvement for many of us — especially during those late afternoon doldrums that often lead to one more cup of coffee (or two).

But the benefits didn’t end there — the people who got more activity were better able to handle being tired: They were 45 percent less likely to report concentration problems once drowsiness set in.

And once they were in bed, they were 68 percent less likely to experience those annoying leg cramps that can keep you up at night.

Of course, the study doesn’t directly prove that more activity and exercise leads to better sleep — but it’s a connection that’s been made before.

And you don’t need to join a gym, lift weights or train for a marathon to get the benefits (which go well beyond better sleep). Everything from gardening to a brisk walk in the park counts as moderate activity — so find something you enjoy, and stick with it.

But while more activity might lead to better sleep, don’t get your exercise right before bed. In addition to an adrenaline boost that might keep you up at night, exercise can also raise the body temperature — and while you might prefer a warm bed, the best way to sleep is with a cool body.

I’m not done with sleep yet — keep reading for some great natural sleep aids.

People looking for a little help getting to sleep used to drink a glass of warm milk.

That, or maybe a little brandy.

But there’s another drink that might help you get off to dreamland quicker — and it’s not what you’d expect.

It’s tart cherry juice — and a new study finds that just two cups a day can help you sleep an average of 39 minutes longer and get a 6 percent boost in sleep efficiency.

That’s the amount of time you spend in bed actually asleep, instead of wondering when you’ll fall asleep.

Twenty volunteers were given either two cups of tart cherry juice concentrate diluted in water or two cups of ordinary fruit juice every day for a week — one in the morning, and one at night.

And along with more time asleep and better sleep efficiency, the cherry juice drinkers had dramatic bumps in melatonin levels. That’s the “sleep hormone” that some people take as a supplement — and apparently, tart cherries will work almost as well.

On the other hand, it’s probably easier — and cheaper — for most people to just add a melatonin supplement.

Whatever you do, make sure a good night’s sleep is on your agenda — because poor sleep has been linked to erectile dysfunction, hypertension, cognitive decline and even an early death.

Don’t look to sleeping pills for help — they can make matters worse, with some of the most popular meds linked to horrible side effects, including sleepers who get up and engage in bizarre behavior while still actually asleep.

Go natural instead — and if cherry juice isn’t your cup of tea, try a 2:1 ratio of calcium to magnesium in the evening. This combination can help you get to sleep quicker, and sleep better once you’re out.

In addition, a supplement of valerian root or valerian tea has also been shown to help bring about a good night’s sleep — try it about 30 minutes or so before bedtime.

Kids who miss out on sleep aren’t just groggy in school — they’re also far more likely to do all the things that give parents nightmares.

From fistfights to fighting off depression, smoking pot to sucking back sugary drinks, researchers say kids who don’t get the time they need in bed are busy doing other things… and clearly not the things you want your kids doing.

Using data from the 2007 National Youth Risk Behavior Survey, the researchers found that 69 percent of 12,100 kids between 12 and 18 years old got less than eight hours of sleep a night.

And these children — the vast majority of kids, obviously — were more likely to engage in some of the worst-of-the-worst activities: sex, booze, smoking, marijuana, and fistfights.

It didn’t stop there, either. These kids were also more likely to battle mood problems, including sadness and depression, and even entertain serious thoughts of suicide.

Next to all that, the rest of the “risky” behaviors seem downright tame: The researchers say sleepless kids are more likely to drink a sugary soda each day, get less physical activity, and spend too much time on the computer.

Maybe it’s just that kids who stay up later stay out later — and are more likely to be in situations where they’d engage in risky activities. Or maybe it’s just the fact that, at 69 percent, sleepless kids make up such a huge percentage that they’re more likely to do just about anything.

Whatever the reason, as long as you keep control over what goes on in your home, make sure to set some rules about bedtime — because even if your children aren’t out boozing, smoking pot, and having sex, a lack of sleep could have an impact on everything from their waistlines to their schoolwork.

Remember, a kid may hate the rules of the house — but those same rules will help set either a long lifetime of good habits… or a shorter span of bad ones.