Coffee is everywhere! Many people can’t even think about starting their day until they have had their first cup. Coffee shops seem to be on every block. Not only do they provide the wake-promoting substance we crave, but they have become a place for social gatherings and business meetings, as well. Unfortunately, one reason why people must keep the coffee pot close at hand is because we are a chronically sleep-deprived nation. However, drinking all that coffee may mean even worse-quality sleep as we age.
Approximately 83% of Americans report drinking coffee,1 and caffeine is the most widely used central nervous system stimulant in the world.2 An average cup of coffee can contain anywhere between 50 and 560 mg of caffeine. The “grande” size cup of coffee contains approximately 330 mg caffeine. Other sources of caffeine include energy drinks, soft drinks, tea, and chocolate. The caffeine in coffee is absorbed quickly, and the half-life is between 3.5 and 5 hours.3 Of course, to keep the level of caffeine high, multiple cups of coffee are typically consumed in a day.
There is a reason coffee is often called “liquid energy.” The beneficial effects of drinking coffee include increased mental alertness, stamina, muscle recovery, and wakefulness. The unwanted effects, however, can include restlessness, palpitations, hypertension, insomnia, tremors, and increased urine output.4
The primary mechanism of action of caffeine is antagonism of adenosine receptors in the brain. Adenosine is a sleep promoter, increasing melatonin production in the pineal gland, a small neuroendocrine gland located in the brain. When coffee is ingested, it blocks adenosine from binding to the receptor. When a caffeine molecule keeps adenosine from binding, it promotes wakefulness.
New research has shown that coffee consumption can suppress the production of melatonin produced by the pineal gland.5 The volume of the pineal gland positively correlates with melatonin levels. A lifetime of coffee consumption, equivalent to ≥3 cups per day for 20 years, can cause a decrease in pineal volume and melatonin production. This leads to poor sleep efficiency, daytime sleepiness, and a shorter sleep time. Other sources of caffeine, such as those mentioned earlier, were not evaluated, so we may learn that any caffeinated beverage could be contributing to poor sleep.
Ask your patients about their caffeine intake, especially elderly adults who may have been lifelong coffee drinkers. Suggest decreasing their caffeine intake, especially later in the day. Warn parents about the effects of caffeine in children, as they may be exposed to caffeine in soft drinks. And remember, the next time you have had a long day, think about taking a walk or engaging in a different activity other than drinking the java juice.
- National Coffee Association of USA. NCA national coffee drinking trends report. Available at: http://www.ncausa.org/Industry-Resources/Market-Research/National-Coffee-Drinking-Trends-Report. Accessed August 14, 2018.
- Meredith SE, Juliano LM, Hughes JR, Griffiths RR. Caffeine use disorder: a comprehensive review and research agenda. J Caffeine Res. 2013;3(3):114-130.
- Heffron TM. Sleep and caffeine. American Association of Sleep Education. Available at: http://www.sleepeducation.org/news/2013/08/01/sleep-and-caffeine. Updated January 29, 2018. Accessed August 14, 2018.
- Bazalakova M, Benca Ruth M. Wake promoting medications: efficacy and adverse effects. In: Principles and Practice of Sleep Medicine, 6th ed. Philadelphia: Elsevier, 2017:462-479.
- Park J, Han JW, Lee JR, et al. Lifetime coffee consumption, pineal gland volume, and sleep quality in late life [published online July 14, 2018]. Sleep. doi.org/10.1093/sleep/zsy127