Caffeine sensitivity grows as people age

DEAR DOCTORS: I think that as I get older, I may be developing a sensitivity to caffeine. If that’s actually something that can happen, it will make me very sad. I have always loved my cup of coffee in the morning, but now I find that it makes me a bit racy. I would love to understand why.

DEAR READER: We join you, along with billions (yes, billions-with-a-b) of people throughout the world in your devotion to caffeine. Whether it’s coffee, tea or other caffeinated beverages, we humans love the lift it gives. Recent data estimate that 85% of adults in the United States consume caffeine in some form each day.

Caffeine stimulates the central nervous system. Due to its physiological effects, as well as its potential for abuse, it is considered a drug. In fact,…