Now a app could determine the best time to sip your coffee.
The software, 'Caffeine Zone', takes information on caffeine use and integrates it with information on the effects of caffeine to produce a graph of how the caffeine will affect the users 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, said.
"It's important to understand the effect that caffeine can have at these various levels," he said.
Ritter, who worked with Kuo-Chuan (Martin) Yeh, assistant professor of computer science and engineering, said that if a person drinks a cup of coffee rapidly, they will experience a spike in mental alertness, but enough of the drug can linger in the bloodstream to cause sleep problems hours later.
The researchers used peer-reviewed studies as input data to determine that caffeine drinkers with between 200 and 400 milligrams of caffeine in their blood stream are in an optimal mental alertness zone.
For sleep, the researchers set a lower threshold of 100 milligrams. Drinkers may have sleep problems if they remain above this.
They said that people who drink too much caffeine, too quickly, may face other problems. A spike of caffeine above the optimal level can cause nausea and nervousness.
According to Ritter, maintaining proper caffeine balance is important for many workers. For example, sailors on submarines must carefully watch their sleep patterns because their sleeping and waking patterns vary each day.
"If they, and others who drink coffee to stay awake, drink too much coffee on one shift, they may have trouble sleeping.
"So, the next day, they'll drink even more coffee and have even more trouble sleeping," he said.
To plot caffeine's effect with the app, drinkers type in information about how much caffeine they drank, or plan to drink, and when they plan to have a caffeinated beverage. They also can add how fast they drink the beverage.
The app can also help people determine when to modify their caffeine habits, so that they might choose to drink a decaffeinated beverage, or mix a blend of caffeinated and decaffeinated coffees.
The app is available on iTunes for free with advertisements and for purchase without ads. It only works on Apple devices-the iPhone, iPod Touch and iPad.
The study has been presented at the 2011 Augmented Cognition International Conference.