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Caffeine's Impact on Sleep

Caffeine is the most popular drug in the world. There's a 90% chance you consume some form of caffeine pretty much every day, and most likely you get your caffeine from coffee. However, you have many choices available to you if you're seeking caffeine, which is also found in soft drinks, chocolate and tea.

In the United States, adults consume an average of about 200 mg of caffeine daily. In some countries, consumption is much higher. For instance, in England, where tea is the caffeine delivery drink of choice, the average consumption of caffeine is about double that of the United States.

Most people, of course, don't really know how much caffeine they're consuming. That's in part because the caffeine content of a cup of coffee can vary dramatically depending on the type of coffee bean used and how the coffee is prepared. Because the U.S. Food and Drug Administration considers caffeine safe, it's not regulated. But caffeine still has a powerful effect on the body, especially when it comes to sleep.

How Caffeine Affects the Body

Caffeine is a stimulant that enhances physical performance, improves endurance and boosts the powers of concentration. In the body, it blocks the receptors for adenosine, an organic compound that promotes sleepiness. Because caffeine doesn't allow your body to receive adenosine, it keeps you from becoming sleepy.

Caffeine affects the body quickly, reaching its peak influence on the blood within 30 to 60 minutes after you've drunk your coffee or cola. Within three to five hours, half the caffeine you ingested has been eliminated from the body — but the remaining half can stick with you for a long time.

The amount of caffeine you ingest determines its effects on your body. At a normal dose of 60 to 200 mg, you're likely to experience increased alertness. However, if you take in high doses of caffeine — in the range of 500 to 600 mg or the equivalent of six or more cups of coffee — your body starts to react as it would to a low-dose amphetamine. High doses of caffeine can result in the following results:

  • Headaches
  • Irritability
  • Increased heart rate
  • Insomnia
  • Excessive urination
  • Nausea
  • Dizziness
  • Increased breathing rate
  • Nervousness or anxiety
  • Diarrhea
  • Muscle tremors

Several studies indicate that the body becomes physically dependent on caffeine. You can test for dependence by eliminating caffeine from your diet. If you experience signs of withdrawal, such as headache or fatigue, your body has become dependent on caffeine to stay alert. Understandably, this type of dependence can have a drastic effect on your sleep

How Caffeine Affects Sleep

One of the most significant side effects of caffeine is sleep deprivation. Because it's a stimulant, caffeine makes it hard to fall asleep, and it also disrupts the functioning of your body's circadian rhythms. In addition, caffeine can disrupt your deep sleep, which is needed to restore your brain each night.

The effects of sleep deprivation caused by caffeine last far longer than just through the night of lost sleep. Some researchers call this effect the coffee cycle. Too much caffeine consumption on Monday can cause not only loss of sleep on Monday night but decreased performance during the day on Tuesday. Many people compensate for their diminished performance by ingesting more caffeine on Tuesday — and the problem then rolls over to Wednesday, and on into the future.

Sleep deprivation results in decreased cognitive function across the board. Losing as little as 90 minutes of sleep can reduce alertness the next day by 33%. The specific results of sleep deprivation include:

  • Slowed cognitive response
  • Increased risk-taking
  • Decreased vigilance
  • Ethical misbehavior
  • Disrupted planning capability
  • Decreased alertness
  • Altered leadership style
  • Decreased creativity
  • Lapses of attention
  • Loss of productivity
  • Increased number of work-related accidents
  • Decreased ability to interpret others' facial expressions
  • Increased negative emotional responses

Many people are aware that ingesting caffeine at bedtime is a bad idea. Studies show, however, that caffeine intake as much as six hours before bedtime can have a drastic effect on sleep, reducing sleep time by an average of one hour. People may not notice this effect, however. They're likely to notice the effect of caffeine on their sleep if they drink it up to four hours before going to bed — but that six-hour effect is still present, decreasing their performance the next day, even if they're not aware of it. In other words, you think you're fine, and your coffee intake isn't affecting you — but it is.

Of course, different people metabolize caffeine at different rates, with older adults taking longer to process caffeine — which means its effects last longer. Because the effects of caffeine vary so greatly, most researchers agree that stopping caffeine intake at least six hours before bedtime is the best solution.

If you realize that caffeine is affecting your sleep, you're likely to want to do something about it. However, since caffeine is a drug, withdrawal comes at a cost to your body. When people stop caffeine suddenly, they're likely to suffer from headaches, reduced motor function, bad moods, increased anxiety and, not surprisingly, sleepiness.

Tips for Healthy Caffeine Use

If you love a good cup of coffee in the morning or after meals but aren't getting the sound sleep you need at night, there are a few guidelines you should follow to keep your caffeine intake at moderate levels.

  1. Avoid caffeine completely in the evening, and try to stay away from it in the late afternoon as well. Remember, today's caffeine can negatively affect your performance tomorrow, even if you don't think it's having an effect.
  2. Avoid pure powdered caffeine and high-caffeine energy boosters.
  3. Keep to a regular schedule where your bedtime, wake time and caffeine intake are concerned, and don't disrupt this schedule on weekends.
  4. Avoid exercise and eating close to bedtime — and stay away from late-night nibbling on chocolate, which also contains caffeine.
  5. Limit your caffeine consumption during the day to no more than 400 mg (about three cups of coffee).
  6. Avoid caffeine, especially at high levels, if you have high blood pressure or heart conditions. Pregnant and nursing women should also avoid caffeine.

By limiting and monitoring caffeine intake during the day, you can still enjoy a fine cup of coffee or a tasty chocolate treat without experiencing a negative effect on your nighttime sleep.

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