"We knew that coffee kept us awake. Now we know why," says researcher Robert Greene, MD, PhD, in a news release.
"If we can understand better some of the factors involved in what makes us normally fall asleep, we can start to understand what might be going wrong when we don't," says Greene, a psychiatry professor at the University of Texas Southwestern Medical Center in Dallas.
Fighting Off Sleep
Ordinarily, brain cells release adenosine when they're overworked. Brain cells have a demanding job. They have to run the body, process information, and communicate with other brain cells constantly. Sooner or later, they need a break. That's when the brain starts pumping out more adenosine.
"More and more adenosine is released and feeds back onto the cells to quiet them down," says Greene. "It's like telling them, 'You guys have worked too hard. Take it easy; refresh yourselves.'"
When caffeine thwarts adenosine, go-to-sleep signals get derailed until caffeine's effects wear off.
In the U.S., 87% adults and 76% of children consume some caffeine on a daily basis. That's up from 82% of adults and 43% of children (aged 6-17) in 1977.
Those numbers appeared in January's Journal of the American Dietetic Association, which named coffee as America's No. 1 caffeine source.
People may not realize how much caffeine they're getting, researchers reported in the Journal of the American Dietetic Association. They say caffeine must be listed as an ingredient but that Nutrition Facts labels needn't specify the amount, and that herbal caffeine sources might not be listed as an active ingredient.
A quick guide to caffeine levels:
- 8 ounces of brewed coffee: 135 milligrams
- 8 ounces of tea: 50 milligrams
- 12 ounces of Coca-Cola: 34.5 milligrams
- 12 ounces of Diet Coke: 46.5 milligrams
Sleep Problems Common
Many people have trouble falling or staying asleep, and caffeine isn't the only culprit. "Insomnia and sleep loss are very common problems," says Greene.
If you have trouble sleeping, you may want to talk to your doctor about it. Possibly, you could be referred to a sleep clinic for diagnosis.
You might also consider whether stress, illness, or medications are factors. Getting too much caffeine or alcohol and keeping irregular hours can also make sleep suffer.
Tips for Better Sleep
If medical problems aren't causing sleep trouble, these "sleep hygiene" tips might help:
- Stick to a regular bedtime schedule. Get out of bed at the same time each morning (even on weekends and holidays).
- Avoid napping during the day.
- Avoid stressful activities and vigorous exercise for two hours before going to bed.
- Before going to bed, try relaxation techniques, such as deep breathing, yoga, or meditation.
- Make sure your bedroom is dark, quiet, and cool. Use earplugs or eye shades if needed.
- Leave the bedroom if you can't sleep. Go into another room and read or do something relaxing and quiet.
- Exercise regularly.
- Avoid substances that contain caffeine (such as coffee, tea, soft drinks, or diet pills).
- Avoid alcohol and nicotine before bed.