Table 1:

Cross-sectional Descriptive Studies evaluating the use of caffeinated products in the military population

First Author (Year)	Data Source/Study population	Goals	Measurement/Scales	Findings
Schmidt et al(2008)	A random sample of active-duty members (N=377)	To determine the prevalence of energy – drink and Supplement Usage	Online Survey	*About 61% used ED usage with *30% or more had ≥1 drink per week,5% reported daily consumption *ED users were more likely to endorse increased mental alertness (77.3%), and better physical endurance (35.2%). *ED users were more likely to complain of difficulty falling asleep (30.9%), and difficulty staying asleep (10.9%)
Boos et al (2011)	Voluntary British military personnel attending a health promotion fair while in Afghanistan (n=87)	To assess whether previous studies done on use of dietary supplements such as caffeine were still applicable	Questionnaire on dietary and exercise supplements, as well as duration of use and sources of these supplements.	*46% of the respondents consumed caffeinated drinks per day *37.9% of participants drank 6 or more caffeinated drinks a day
Stephens et al(2013) (Stephens et al., 2014)	A random sample of US military personnel (N=586)	To assess the prevalence and effects of ED and energy shot use	30-item electronic questionnaire on ED and caffeine intake use	*≥53% consumed an ED in the past month *≥19% had ≥1 energy shot in the past month *19% consumed a beverage where ED mixed was mixed with alcohol in the past month *Younger respondents (18-29 years) were more likely to use ≥1 ED drinking per week *The most common reasons for use were to improve mental alertness (61%), mental (29%) and physical (20%) endurance. *The common side effects to use were an increased pulse rate or palpitations, restlessness, and difficulty sleeping.
Knapnik et al (2016)	A random Sample of Navy and Marine Corps Personnel (N=1,708)	To examine the characteristics associated with caffeine consumption	Self-reported questionnaire	*87% reported using caffeinated products ≥1 time/week, *their mean ± SE daily caffeine use was 226 ± 5 mg *men consumed more caffeine than women (242 ± 7 mg/day versus 183 ± 8 mg/day) *Reported sleep duration was inversely associated with caffeine consumption.
Knapnik et al (2016)	Active-duty Air Force personnel from 10 US and 2 overseas installations (2010-2011, N=1,787)	To examine prevalence, daily consumption, and related characteristics of caffeine use in Air Force personnel.	Self-reported survey	*84% consumed caffeinated products ≥1 time/week. *Mean± SE of caffeine consumption was 212 ± 9 mg/day (224 ± 11 mg/day for men, 180 ± 12 mg/day for women). *Caffeine use was associated with older age, non-Blacks, and lower sleep duration. *ED use was associated with male gender, younger age, and decreased sleep duration.
Attipoe et al (2018)	A convenience sample of US military members (N=1,706)	To describe the prevalence of ED or Energy Shot (ES) use, and their related side-effects	An online as well as paper based self-reported survey	*50% reported ED/ES use ≥ once a month *33% used ED/ES in combination with alcohol *Young, male, enlisted service personnel were more likely to use ED/ES than others *Army personnel were more likely to use ED or ED with alcohol, than other branches. * Their reasons for ED or ES for reasons for use were to, “boost energy” (77%), and “enhance mental alertness” (52% and 57%). *13% reported adverse effects from their use. *Reasons for cessation of use were price (8%), bad taste (3% and 6%), upset stomach (2% and 3%), and inability to boost energy (2% and 4%).
Kullen et al (2019)	A convenience sample of Australian Army personnel (n=667)	To examine prevalence and type of dietary supplements (DS) used, including caffeine	Questionnaire on dietary supplements and reasons for use	* Caffeine was the most commonly used DS used daily (48.4%). *The most common reasons for use were “to provide energy” and “performance”

Legend: ED = Energy Drinks; ES= Energy Shorts; US = United States; DS = Dietary Supplements; SE = Standard Error; All studies are cross-sectional.