Will this cup of coffee make me unable to sleep tonight?
A new smartphone app claims to be able to help answer that question by determining how the caffeine content in coffee, soda and other drinks affect a person over time.
"Many people don't understand how caffeine levels in their bloodstream go up and how they go down," Frank Ritter, professor of information sciences and technology, psychology, and computer science and engineering, at Penn State University, said in a statement. "It's important to understand the effect that caffeine can have at these various levels."
Researchers dubbed their app "Caffeine Zone." They combed studies to find that people generally get to the optimal state of mental alertness when they have between 200 and 400 milligrams of caffeine in their blood. However, for optimal sleep, people must generally have 100 milligrams of caffeine or lower in their blood.
The app, which is free for iPhone with ads or for purchase without ads, works by having the user type in how much caffeine they've consumed or plan to consume, as well as how fast they will guzzle down the beverage. They presented the app at the 2011 Augmented Cognition International Conference.
[Check out Extreme Tech's coverage to see how exactly the app works.]
But if you don't want to rely on an app to tell you when your caffeine intake may start impacting your sleep, there are general guidelines you can follow. HuffPost blogger Dr. Michael J. Breus, a clinical psychologist and board-certified sleep specialist, recommends avoiding caffeine within eight hours of bedtime.
And for people older than 40, try taking it easy on the caffeine in general because caffeine intake in older age is more apt to disrupt sleep, he said.
For the caffeine contents of some popular drinks, click through this slideshow: