We've long known that sleep-deprived workers can be a hazard to themselves and to productive work days. Many nodding off at the job consistently reach for a popular solution -- a cup of coffee, or perhaps an energy drink.
A group of researchers in the U.K. decided to put the caffeine solution to the test and see whether it actually helps workers perform better.
It does. A large review of 13 randomized, controlled studies in the U.K. showed that caffeine consistently improved memory, attention and performance.
Caffeine was even more effective than a nap in helping people's concentration.
"We've always understood that caffeine was beneficial, but this is the first systematic review of the evidence," said Phil Edwards, a co-author of the review, published Tuesday in The Cochrane Library.
"We're interested in reducing injuries in people who have to work in the night shift," said Edwards, a senior lecturer in statistics at the London school of Hygiene and Tropical Medicine.
"We thought the use of sleep to alleviate the effects of tiredness would be what would have the most beneficial effect," he said.
Sleep experts debate whether some of our favorite quick fixes for sleep loss really help us concentrate on a daily basis. They say in some cases, what helps in the short term might hurt our concentration in the long term.
Is Caffeine Always the Answer to Sleepiness at Work?
Edwards said many of the studies only followed the concentration of workers in the few hours after the jolt of caffeine. They did not follow the workers to see how they did once the caffeine was out of their system.
"That's somewhere on the range of three to five hours depending on the individual," said Dr. Donna Arand, clinical director of the Kettering Sleep Disorder Center in Dayton, Ohio.
How much caffeine, an individual's metabolism and the amount of food you ate with the caffeine can also affect the length of time it keeps you going.
Caffeine May Take Hours to Leave Your System
Arand said studies have proven the benefits of caffeine more conclusively than any problems it causes with sleep afterwards.
"If somebody's drinking caffeine during the night shift... that's been shown to improve their performance and reduce accidents," she said. "Really, the studies have been inconsistent saying that they've been affecting sleep at all."
Arand added, "The one thing that caffeine does affect is the time it takes you to fall asleep."
But Dr. Meir Kryger of the National Sleep Foundation said he often sees people who've fallen into a sleepless cycle because of caffeine overuse. The person doesn't get enough sleep one night and so drinks caffeine during the day to get through. At bedtime the caffeine still keeps them awake, so the cycle continues.
"We see this all the time in the sleep clinic," said Kryger, director of research and education at Gaylord sleep medicine in North Haven, Connecticut.
"We know caffeine will keep you awake and alert. However, it's a two-edged sword," he said.
Other Popular Sleep Solutions: Help and Hazards
Here are other ways people try to help their sleep-wake cycle, beginning with alcohol -- which, sleep experts say, usually does more harm than good.
"You will fall asleep quicker with alcohol, but when the alcohol level drops, it actually wakes your brain up," said Kryger. "If someone snores, or if someone has a disease called sleep apnea, it will make things substantially worse."
Arand said that while alcohol sedates breathing, heart rate, and "cell firing" in the brain, the body does not return to normal levels after the alcohol is metabolized. Instead, it overshoots.
"The same is true in the opposite effect for depressants -- so you always have that undershoot and overshoot issue," said Arand. "So at two in the morning you're waking up, you're still tired, exhausted, potentially you can't fall asleep."
Even if a person doesn't wake up, Arand said alcohol has been shown to disrupt sleep patterns, leaving people less rested in the morning.
"Alcohol is probably the number one over-the-counter drink people use to help them fall asleep," said Arand.
Antihistamines and Sleep: Unwanted Side Effects?
Kryger said antihistamines, found in some over-the-counter allergy medicines, will help put people to sleep and not wake them up later -- but they create other problems.
"Indeed, they will help them fall asleep, but there will be the unwanted side effects of keeping them sleepy the next day," he cautioned.
Kryger said sometimes prescribed medications will help some people sleep, but have the opposite effect in others. Asthmatics, in particular, may run into this conundrum.
Asthma Medications Keeping You Awake?
"In people with asthma, their medication can keep them awake, or their coughing can keep them awake," said Kryger.
Antidepressants are another example of medications that could either help sleep, or hurt.
"A very large number of patients with insomnia actually have depression -- insomnia is an extremely common side effect of depression," said Kryger.
On the other hand, Kryger said antidepressants can keep people awake.
Antidepressants Keeping You Up?
"Many doctors prescribe antidepressants to help people sleep, and it turns out that many antidepressants cause restless legs syndrome in some patients," said Kryger.
According to the Restless Legs Syndrome (RLS) Foundation, the neurological condition causes a nearly irresistible urge to move your legs in bed that can keep people from falling asleep at night. RLS may also cause involuntary jerks that wake people up once they've fallen asleep.
"It's also something we quite frequently see in the sleep clinic," said Kryger.
"If someone is having chronic problems with sleep, they may need to see a sleep specialist," said Kryger. "A lot of times you need to treat something different, other than sleep problems."