Is Caffeine Affecting Your Sleep?

On any given night, millions of Americans have trouble sleeping.  On any given afternoon, millions of Americans struggle to stay alert.  It’s no wonder that over 48 million sleeping aid prescriptions were written in 2006. Nor is it any wonder that caffeine has become the second largest commodity (next to oil, in dollar amounts) traded in the world. 

Our population is increasingly reaching for medications and stimulants to battle its sleep problems, often simultaneously:  pharmaceuticals for the insomnia, and caffeine for the daytime fatigue.  Unfortunately, neither solution can replace the recuperative and restorative powers of natural sleep.  Both can alter nature’s elaborate sleep architecture, the quality and the optimum proportion of deep and light sleep, as well as the amount of REM, or dream sleep.

Health care practitioners should pay special attention to their patient’s sleep quality and co-manage any sleep difficulties.  This could dramatically affect treatment outcomes of primary concern.  Patients should certainly report any sleep problems to their provider!

Insomnia is a self-reported condition, a complaint of the inability to fall asleep or stay asleep, or of waking unrefreshed with excessive daytime fatigue. According to the National Institutes of Health, 30-40% of adults report some symptoms of insomnia within a given year; 10 – 15 percent reports that it is a chronic condition. In some instances, insomnia is primary, or not directly associated with any other health issue. For others, the insomnia is secondary, a symptom of another health issue or a byproduct of another medical condition (or of the medications used to treat that condition.)  In most of these cases, the sleep problem can be managed once the root cause is identified.  The same can be said for the 90 or so clearly identified and defined sleep disorders, such as obstructive sleep apnea, or restless legs syndrome.

For millions, however, insomnia is “self-inflicted”. It is simply the result of poor lifestyle factors—violations of the conditions and practices that promote quality sleep, collectively known as sleep hygiene.  Proper sleep hygiene allows the powerful mechanisms that regulate the human sleep-wake cycle to function as designed.  Obviously, high noise levels, bright lights and excessive temperatures are conditions that interfere with sleep.  Less obvious are the influences that diet and exercise exert on sleep patterns.  One of particular magnitude is caffeine intake.

In addition to coffee, tea and colas, caffeine can be found in energy drinks, over the counter pain medicines and chocolate.  In moderation, caffeine can be tolerated and can contribute to a healthy lifestyle.  In excess, especially late in the day, it can substantially alter sleep quality by interfering with a key component of sleep: the homeostatic process.

Sleep homeostasis is the process by which the body establishes a steady state of physiological balance and readiness.  From the moment of morning wakefulness, the homeostatic drive for sleep accumulates until it reaches its maximum late in the evening, establishing enough pressure for sleep to sustain about 8 continuous hours of slumber. Although the exact neurological mechanisms aren’t fully understood, sleep most likely involves the nucleoside adenosine. Adenosine binds to receptors in the basal forebrain that control the cells that are essential for wakefulness, and turns them off, triggering sleep. Levels of adenosine rise continuously during the day as cells break down ATP (adenosine triphosphate) to generate energy. While awake and active, the body burns ATP and thus adenosine levels rise, creating the pressure for sleep.  During sleep, there is a marked decrease in cellular activity.  Less ATP is burned, hence adenosine levels fall, preparing the body for another day’s wakefulness. 

Caffeine molecules are similar in structure to adenosine and bind to the same receptors that signal the pressure for sleep, thus blocking the homeostatic sleep drive. Masking tiredness is a signature feature of caffeine.  Caffeine also prevents adenosine from dilating the brain’s blood vessels (theoretically to increase oxygen efficiency during sleep). That’s why caffeine is found in many over the counter headache pain medications, such as Anacin.  If a headache is vascular in nature, caffeine helps relieve the pain by narrowing the blood vessels.   

All of this activity caused by the caffeine also triggers the body to release epinephrine (adrenaline), another anti-sleep chemical.  Adrenaline, among other things, increases the heart rate and blood pressure, dilates the pupils, increases blood sugar levels, and increases the blood supply to the large muscle groups.

Moderate amounts of caffeine ingested in the morning are sufficiently metabolized by bedtime; they won’t have a major impact on sleep.  However, since caffeine has a 4 – 7 hour half-life, substantial amounts of the caffeine consumed later in the day will linger in the body well past the evening.  For example, a well known chain of coffee shops has a large-sized coffee product that contains over 500 mg. of caffeine (roughly five times that of an average cup of drip coffee).  If one were to drink that as a “pick me upper” at 3 p.m. to “get through the day”, half of its caffeine could still be in the body at bedtime.  In other words, a 10 p.m. bedtime could be challenged by the caffeine equivalent of two full cups of coffee!  One might be tired enough to fall asleep, but the caffeine tampers with the quality and depth of the sleep, damaging sleep’s restorative powers. 

Simply restricting caffeine intake after the noon hour could have dramatic effects on the ability to fall asleep at night and the ensuing quality of one’s sleep.  It may also negate or reduce the need for sleep aids. Nature wins, and so does the sleeper!

Click here to learn about caffeine levels in Starbucks and in your other favorite beverages. 

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