The aim of this study is to develop information about the acute and residual effects of a new product being targeted to young adults. Using a double placebo-controlled 2 X 2 factorial model study design, we will compare the acute and residual effects on driving impairment of caffeinated alcohol, non-caffeinated alcohol, caffeinated placebo, and non-caffeinated placebo. Under the alcohol conditions, participants will receive sufficient alcoholic beverage to attain a blood alcohol concentration (BAC) of .12 g%. Participants will be 144 undergraduate and graduate students, and recent college graduates.

Caffeinated alcoholic beverages target young adults with the promise that the caffeine will counteract the sedating effects of alcohol and thus let the consumer remain alert and active longer, while continuing to drink. It is likely that in the minds of some young people, this promise also translates into the idea that mixing caffeine with alcohol allows one to drive more safely than would be possible after having consumed an equivalent amount of non-caffeinated alcoholic beverage. These are dangerous assumptions because (1) alertness may not indicate the absence of impairment under intoxication and (2) next-day impairment from the residual effects of heavy drinking may be exacerbated by mixing caffeine and alcohol. We will compare the acute and residual effects of caffeinated and non-caffeinated beer in terms of a highly relevant outcome - the ability to drive safely.

The long-term objectives of this program of research are to investigate factors that predict or contribute to performance decrements after alcohol ingestion, with a focus on behaviors most relevant to public health, such as driving. The primary specific aims of the proposed work are:

AIM 1: To compare the acute effects of caffeinated alcohol, non-caffeinated alcohol, caffeinated placebo, and non-caffeinated placebo on driving-related impairment, as measured by performance on a driving simulator and the Psychomotor Vigilance Test (PVT), a test of sustained attention/reaction time. We hypothesize that caffeinated beverage will result in less impaired simulated driving ability and better PVT performance acutely, compared to non-caffeinated beverage, but that performance on these measures following both caffeinated and non-caffeinated beverage be impaired relative to placebo beverages.

AIM 2: To compare the residual effects of caffeinated alcohol, non-caffeinated alcohol, caffeinated placebo, and non-caffeinated placebo on next-day driving-related impairment, as measured by a driving simulator and the PVT. We hypothesize that caffeinated beverage will result in greater impairment in next-day simulated driving and attention/reaction time, relative to non-caffeinated beverage, and that performance following both caffeinated and non-caffeinated alcoholic beverages will be impaired relative to corresponding placebo beverages.

AIM 3: To compare the acute effects of caffeinated alcohol, non-caffeinated alcohol, caffeinated placebo, and non-caffeinated placebo on self-rated ability to drive, as measured by a self assessment of ability-to-drive questionnaire, and estimate of blood alcohol concentration (BAC). We hypothesize that caffeinated alcoholic beverages will result in greater confidence in ability to drive and lower estimates of BAC, compared to non-caffeinated alcoholic beverages, but that for both alcoholic beverages, confidence in driving ability will be lower and estimates of BAC will be greater, relative to placebos.

AIM 4: To compare the residual effects of caffeinated alcohol, non-caffeinated alcohol, caffeinated placebo, and non-caffeinated placebo on self-rated ability to drive. We hypothesize that caffeinated alcoholic beverage will result in lower confidence in ability to drive and higher estimates of BAC, compared to non-caffeinated alcoholic beverage, but that for both alcoholic beverages, confidence in driving ability will be lower and estimates of BAC will be greater, relative to placebo.

Inclusion Criteria:

• College students, graduate students, or recent graduates
• Between the ages of 21 and 30 years inclusive (as verified by valid drivers license)
• Who, if a student, reports good academic standing
• Have not been diagnosed with a sleep disorder
• Are not daily smokers
• At least occasionally in the past month, consume five drinks (for men) or more (four or more if female [based on Flannery et al 2002]) during a single drinking episode
• Have a valid drivers license, so as to include only people who know how to drive.

Exclusion Criteria:

• Scores of 5 or more on a screening measure for alcoholism (the short version of the Michigan Alcohol Screening Test [SMAST])
• A history of counseling or treatment for chronic substance abuse by self-report
• Daily smoker (to mitigate confounding of caffeine by nicotine withdrawal, or acute nicotine administration, smokers will be excluded from participation)
• Current use of medications that affect the sleep/wake cycle or daytime alertness or that are contraindicated for alcohol
• Presence of a health condition that contraindicates alcohol
• Diagnosis of a sleep disorder (sleep apnea, narcolepsy, periodic limb movement, restless legs syndrome, circadian rhythm disorder, and insomnia)
• Use of recreational drugs (e.g., marijuana) while participating in the study
• Working overnight shifts
• Female and pregnant, nursing, or not using reliable birth control
• Participants who have traveled across two or more time zones in the last month will be rescheduled for later participation (minimum of 1 month from time-zone travel)
• On average consume greater than 4 cups of coffee per day (>400 mg/day)
• Participants who report ever getting motion sick during screening or become motion sick after practicing on the driving simulator during Session 1.
• Weigh more than 230 Lbs.

We compared participants across groups by age and sex.

3 years

Difficulties with the driver simulator resulted in invalid data for 6 participants so their results were not included in the lane position deviation results. Inaccurate caffeine doses resulted in exclusion of 12 participants from the trial.