Just to let you know, depending on what this survey is for...you know the phrase, "Correlation is not causation?". That. A thousand times that. Caffine could lead you to be tired. People who are tired could drink more caffeine. A certain lifestyle could naturally lead to an acceptance of energy drinks and a lack of sleep. Marketing of energy drinks could appeal to people who may be more physically fit, and mask any results. Also, as far as tiredness goes, a person who sleeps 50 hours a week may sleep a little over 7 hours a day, or they may sleep 15 hours on weekends, and 4 hours on week days, and there is a huge difference..