At Attention, Soldier!

February 19, 2019

Written by: Rebecca Somach


As a society, we are obsessed with caffeine and have been for a very long time. In the United States, 85% of the population has at least one caffeinated drink a day1.  Humans have been consuming caffeine for a long time, from tea drinks in the 15th and 16th centuries to coffee arriving on the scene in the 18th and 19th centuries2. We’ve been drinking this stuff for hundreds of years and are always trying to improve the world’s most commonly used addictive drug. However, while baristas and tea aficionados are looking to make your favorite brew taste better, scientists are looking to figure out how we can use caffeine to improve your concentration and attentiveness.


In the brain, caffeine works as a competitor to a neurotransmitter called adenosine, your body’s natural way of slowing down your brain and central nervous system. You can read more details about how caffeine affects adenosine in an earlier blog post here, but to put it simply, during the day, adenosine builds up in your body. When adenosine levels peak, you feel tired because the adenosine has connected with and activated receptors that signal to your brain to rest. However, caffeine is a molecule with a similar shape to adenosine. so it can also connect with those adenosine receptors. Instead of making you tired though, it prevents adenosine from connecting with the receptors, blocking its effect and causing you to feel more awake.


In April 2018, a study, was making a ‘buzz’ around the internet about caffeine consumption. The study, which can be found here, was done by researchers that were sponsored by the United States Army3. It might seem odd that the Army is interested in something as mundane as cups of coffee, but staying awake and alert after a long overnight shift could be critical to a soldier’s success. While you might think that the best way to get through a day after a sleepless night might be to have a huge cup of coffee, this study’s goal was to actually to minimize the amount of caffeine you drink while still achieving maximum wakefulness. Using people’s sleep-wake cycles, varying caffeine doses, and a task that tested attentiveness, the researchers designed an algorithm to give the optimal time and dosage that you should be taking your brew. With their calculations, they found that they could improve performance on attention tests and administer less overall caffeine by tailoring the amount and timing of caffeine consumption to the particular situation. For example, in an earlier study on caffeine and attention that required participants to have restricted sleep for five days, two doses of 200 mg of caffeine were given at the same times each day. However, the new algorithm recommended having smaller amounts of caffeine on early days and greater amounts of caffeine on later days, because people felt more tired as their lack of sleep caught up to them. The new algorithm also suggested that the participants shift some of their caffeine consumption to the end of the day, since subjects performed the worst on attention tests right before they went to bed. By combining the dosage with the scheduled sleep cycles, the algorithm predicted when the subjects would need caffeine and resulted in better performance.


Why does it matter what dose of caffeine you are getting? Most studies have found that the recommended dose of caffeine in healthy adults (400 mg/day) has few side effects4. That’s about 4 cups of coffee a day. That feels like a lot of coffee, but for anyone drinking a Starbucks Venti Coffee or a large cup from Dunkin’ Donuts, both at 20 oz, these drinks have 300-400 mg in one go5,6. While the recommended daily doses don’t show side effects in healthy individuals, some studies have linked excessive caffeine drinking to heart problems, issues with anxiety disorders and, unsurprisingly, issues with sleeping7. Hopefully by knowing your ideal caffeine drinking strategy, you can feel more awake with a smaller dose of caffeine. Instead of automatically drinking the largest cup and still feeling exhausted by lunch, you can have smaller doses and still feel perked up during your work day.


This algorithm was designed to keep people alert after sleep deprivation. So now that the Army has developed the ideal way to have caffeine, there’s no need to sleep, right? That’s not really true. While this algorithm predicts the ideal way to take in caffeine, you can’t go on avoiding sleep forever. The algorithm was designed for sleep deprivation experienced by soldiers on late night army vigils, truck drivers on long overnight drives, and nurses and doctors that are in the hospital at all hours of the night. These are extreme situations and ones that are hopefully temporary. It is important to note that the study only looks at what happens to people on the short term, and only looks at one behavioral outcome: attention. A full night of sleep does a lot of things for your body, from letting your cells rest and regrow themselves, to letting your brain process memories made while awake. As much as our world is about going non-stop, there’s no true replacement for time spent asleep. Don’t think of your sleep-time as time spent doing nothing; it is still crucial to your health and well-being. While you might be able to make it through a couple of days with the right caffeine dose, your body is still working overtime even if you don’t feel tired. So go on and dream about that next wonderful cup of coffee in the morning, after a full night’s rest of course.




  1. Mitchell D.C., Knight C.A., Hockenberry J., Teplansky R., Hartman T.J. Beverage caffeine intakes in the U.S. Food Chem. Toxicol. (2014) 63:136-42.
  2. Weinberg BA, Bealer BK. The World of Caffeine: The Science and Culture of the World’s Most Popular Drug. (2001) New York: Routledge.
  3. Vital-Lopez F., Ramakrishnan S., Doty-Thomas Balkin T.,  Reifman J., Caffeine dosing strategies to optimize alertness during sleep loss. Journal of Sleep Research (2018) 27(5):e12711.
  4. Nieber K. The impact of coffee on health. Planta Med. (2017) 83:1256–63.
  5. Nutrition Page of Dunkin’ Donuts (
  6. Nutrition Page of Starbucks (
  7. Temple, J. L., Bernard, C., Lipshultz, S. E., Czachor, J. D., Westphal, J. A., & Mestre, M. A. The Safety of Ingested Caffeine: A Comprehensive Review. Frontiers in Psychiatry (2017) 8:80.

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