Energy Drink Consumption and Its Association With Sleep Problems Among U.S. Service Members on a Combat Deployment

Afghanistan, 2010

Robin L. Toblin, PhD; Kristina Clarke-Walper, MPH; Brian C. Kok; Maurice L. Sipos, PhD; Jeffrey L. Thomas, PhD


Morbidity and Mortality Weekly Report. 2012;61(44):895-898. 

In This Article


Beverages marketed as energy drinks have become a popular form of caffeine consumption targeted at young males, with some brands containing the caffeine equivalent of 1–3 cups of coffee or cans of soda.[1] Energy drinks also include other ingredients intended to boost physical energy or mental alertness, such as herbal substances, amino acids, sugars, and sugar derivatives; however, caffeine is the main active ingredient.[1] Approximately 6% of adolescent and young adult males in U.S. civilian and military populations consume energy drinks daily.[2,3] These products generally are unregulated and can have negative side effects (e.g., caffeine intoxication, overdose, withdrawal, and poor interactions with alcohol).[1] Paradoxically, excess consumption also can increase sleep problems and daytime sleepiness, which can impair performance.[1] To determine the extent of energy drink use and the association with sleep problems and sleepiness during combat operations, Walter Reed Army Institute of Research analyzed data collected by Joint Mental Health Advisory Team 7 (J-MHAT 7) to Operation Enduring Freedom in Afghanistan in 2010. The analysis showed that 44.8% of deployed service members consumed at least one energy drink daily, with 13.9% drinking three or more a day. No differences by age or rank were found. Service members drinking three or more energy drinks a day were significantly more likely to report sleeping ≤4 hours a night on average than those consuming two drinks or fewer. Those who drank three or more drinks a day also were more likely to report sleep disruption related to stress and illness and were more likely to fall asleep during briefings or on guard duty. Service members should be educated regarding the potential adverse effects of excessive energy drink consumption on sleep and mission performance and should be encouraged to moderate their energy drink consumption in combat environments.

Mental Health Advisory Teams conduct comprehensive mental health surveillance of U.S. service members in combat environments and have administered the Deployment Well-Being Survey in Iraq during 2003–2009 and Afghanistan during 2005–2010 and 2012. The survey version used by J-MHAT 7 to collect data in Afghanistan during the summer of 2010 asked about demographic characteristics, deployment history, combat experiences, mental health, deployment stressors, family and relationship concerns, work environment, sleep difficulties and daytime sleepiness, health-care utilization, and various health behaviors, including energy drink consumption. The J-MHAT 7 survey was the first to inquire about the use of energy drinks.

In total, 1,249 service members were surveyed using a cluster sample of randomly selected U.S. Army and Marine combat platoons deployed to Afghanistan. All participants were male, because of the type of unit surveyed. Of those surveyed, 1,000 consented to have their data used for research purposes and 988 answered the following question: "How many energy drinks (e.g., Monster, Red Bull, 5-Hour Energy) do you use per day?" The six response options ranged from zero to five or more drinks per day. Service members also were asked about their use of sleep medication, average number of hours of sleep per day, concerns regarding lack of sleep, disruptions to sleep, and work impairment associated with sleepiness ( Table 1 ). The number of sleep hours was dichotomized at ≤4 hours (reported by 24.2% of the persons sampled); in comparison, 50.2% of those sampled reported sleeping ≤5 hours. For comparison across sleep outcomes, energy drink use was divided into the following categories: no drinks, one to two drinks, and three or more drinks per day. These cutoffs were chosen because previous research demonstrated that 200 mg of caffeine, the equivalent of one to two energy drinks, improved cognitive performance in a military population.[4] Prevalence rates of energy drink use are reported. Chi-square tests were used to determine significant differences between groups for sleep variables, using p<0.05 for significance. Post hoc analyses of the chi-square tests were conducted by examining discrepancies between observed and expected values for standardized residuals to produce z-scores and identify those cells contributing to the significant differences. The Sidak-Bonferroni correction was used to account for conducting multiple post hoc tests.

Service members surveyed were predominantly on active duty (93.2%), of junior enlisted rank (E1–E4; 71.2%), on their first deployment (60.8%), in the Army (75.5%), aged 18–24 years (66.6%), single (54.5%), not parents (70.9%), in the military <5 years (81.2%), and had been on this deployment <6 months at the time of the survey (54.3%). The prevalence of daily energy drink use was 44.8%; 13.9% consumed three or more per day ( Table 2 ). Of those reporting daily energy drink use, 56.6% consumed more than one energy drink per day. No associations were found between the proportion of service members reporting the number of drinks used per day (i.e., 0, 1, 2, 3, 4, or ≥5) and rank category, number of deployments, branch of service, age, marital status, or being a parent. In the same comparison, however, service members in the National Guard or Reserves were significantly more likely to use energy drinks than their active duty counterparts (p=0.002).

Service members who drank three or more energy drinks per day were more likely to report ≤4 hours of sleep on average per night (38.2%) than service members who drank one to two (18.4%) or zero (23.9%) energy drinks per day ( Table 3 ). The groups did not differ in their levels of concern regarding not getting enough sleep. Service members drinking three or more energy drinks per day were significantly more likely than the other groups to report sleep disruption on more than half the nights in the past 30 days because of stress related to combat, stress related to personal life, and illness. However, no differences were noted in sleep disruption because of the sleep environment, high operational tempo, nighttime duties, or leisure activities. Service members who drank three or more energy drinks per day also were significantly more likely to report sometimes or often falling asleep while sitting in briefings or while on guard duty, but not while riding in convoys. No differences in energy drink consumption were found related to having had an accident or making a mistake that affected the mission because of sleepiness ( Table 3 ). Despite a significant, omnibus chi-squared association, after post-hoc analyses were conducted, no differences were found in sleep medication use or receiving prescriptions for sleep medications while deployed by levels of energy drink consumption ( Table 3 ). Across sleep disruption and daytime sleepiness outcomes, service members who consumed one to two energy drinks did not differ from those not consuming energy drinks.