I thought I knew my way around coffee, especially after spending time in Bogota, Florence and other spots. According to leading sleep expert Matthew Walker, though, decaf will have you just as wired as regular coffee. In fact, you could end up having a harder time settling down after your decaf fix.

In his best-seller Why We Sleep, the TED speaker shares one particularly surprising fact:

Decaffeinated coffee has 15 - 30 percent of the caffeine of regular coffee.

Wonder why you're humbly drinking decaf and still having a hard time sleeping? This could very well be the answer.

Might as well drink caffeinated coffee

As Walker points out in his book, the problem comes down to math. To your body, three cups of decaf could very well equal one cup of regular. You can expect the same caffeinated effects, too, from hyperness to sleep loss, for many hours. Walker says caffeine lasts in our systems for at least eight hours.

We may be prone to drink more coffee, too, if we don't believe we'll have a caffeine hangover or crash, making it more likely for us to have enough decaf to cause the very effects we think we're avoiding. It's similar to drinkers having way more diet soda because they believe, unlike regular soda, it is completely free of health side effects.

If you are offered an after-dinner coffee and decide to play it safe with a few cups of decaf, then it may be wiser just to have one real cup of joe.

This could solve your sleep puzzle

I've been fortunate enough to be a lifelong solid sleeper, but I know many people who have had a hard time getting to sleep or staying asleep once they go down. Drinking regular coffee, soft drinks and even black tea have always been the first thing eliminated from their habits. But decaf? It has never been a discussion.

When I saw Walker speak at TED last year, three insomnia recommendations stood out:

  • Get out of bed when you can't sleep
  • Put the phone away
  • Be consistent

We can throw "Avoid the decaf" on the list now, too.