Apparently, decaf still contains about 25% of the normal level of caffeine. I read this in the "Why we sleep" book by Matthew Walker, but haven't double checked

Apparently, decaf still contains about 25% of the normal level of caffeine. I read this in the "Why we sleep" book by Matthew Walker, but haven't double checked. Basically, that would mean that drinking decaf is not really the same as not drinking coffee.