You lay off the caffeine... get plenty of exercise... and try to go to bed and wake up at the same time every day.

When you're prone to insomnia -- as HALF of all adults over 60 are -- you know that sticking to a routine that supports sleep is crucial.

That's because night after night of lousy sleep can do much more than make you tired and cranky. It can also wreak havoc on your blood sugar, your gut, and your brain.

But if you've tried every trick in the book and STILL can't sleep, there may be one nighttime habit that's undermining you.

Now, typically we think of curling up with the newspaper or a good novel as an excellent way to get drowsy and nod off.

But according to a new study, if you're doing your bedtime reading on a smartphone or tablet, you could be setting yourself up for some serious tossing and turning.

In the study, published in Physiological Reports, researchers tracked the sleep patterns of a group of healthy folks in their 20s in a sleep lab.

For one five-night period, the participants had unrestricted access to tablets for reading -- and during another five-night period, they were only allowed to read good ol' paper-and-ink printed materials.

By the end of the study, it turned out that when the participants used tablets before bed, they were LESS sleepy at bedtime... and fell asleep on average a half hour LATER... than when they read print materials.

They were also much less alert during mornings after tablet use than they were on mornings after print reading.

That's likely because when the participants stared at the bright tablet screens, their bodies produced less melatonin than they did after staring at the printed page.

As I've shared with you before, melatonin is the "sleep hormone" that regulates your body's internal clock (a.k.a. "circadian rhythm"). It tells your body when it's time to go to sleep each night and when it's time to wake each morning.

And we know that the electronic light emitted by smartphones and tablets is a "blue" kind of light that SUPPRESSES melatonin production.

Now, as we age, our levels of melatonin naturally decline, which is why a lot of older folks have trouble getting enough shuteye.

And considering that in the study, tablet use suppressed melatonin enough to disrupt the sleep of a group of 20-somethings, just imagine how disruptive it can be for YOU!

So, it's a good idea to limit (or eliminate) your exposure to devices that emit blue light -- including TVs and LED light bulbs -- two hours before you hit the hay.

If that's not possible, you can also try wearing amber-tinted glasses that block blue light, or you could set your smartphone or tablet to "nighttime" mode.

Supplementing with melatonin... or drinking melatonin-rich tart cherry juice... can also help.