The effect of alcohol strength on alcohol consumption: findings from a randomised controlled cross-over pilot trial

Reducing the alcohol content of drinks has the potential to reduce alcohol consumption. The aims of this study are to (1) test the feasibility of a randomised controlled trial (RCT) to assess the effect of alcohol strength on alcohol consumption within licensed premises in the United Kingdom (UK), and to (2) provide data to estimate key parameters for a RCT.

This study is a double-blind randomised controlled cross-over pilot trial based within four licensed premises in the UK. Participants (n = 36) purchased and consumed ad libitum a 3.5% lager and a 4.8% lager during two separate study sessions. Descriptive statistics reported the efficacy and efficiency of the study processes, and the rates of licensed premises recruitment, and participant recruitment and attrition. Mean and the 95% confidence interval (CI) compared alcohol consumption between conditions. The mean, standard deviation (SD) and CI of UK units of alcohol consumed were used to calculate a sample size for a RCT. Responses to participant questionnaires and duration of participation in study sessions between conditions were analysed.

Components of the study protocol were effective and efficient. The venue recruitment rate was less than anticipated. The participant recruitment rate was greater than anticipated. The rate of attrition was 23% and varied by less than 1% according to the arm of the trial. There was a reduction of alcohol consumed under the intervention conditions. Estimated mean difference, and 95% CI (UK units): - 3.76 (- 5.01 to - 2.52). The sample size required for a RCT is 53. Participants did not find one lager more pleasant in taste: (on a scale of one to 10) - 0.95 (- 2.11 to 0.21). Participants found the reduced-strength lager less enjoyable: (on a scale of one to 10) - 1.44 (- 2.64 to - 0.24) and they perceived themselves to be less intoxicated after consuming it: (on a scale of one to 10) - 1.00 (- 1.61 to - 0.40).

A RCT is feasible with minor alterations to the study protocol and scoping work to establish different brands of alcohol that are more alike and more enjoyable than the products used in the pilot trial.

Registered in the American Economic Association (AEA) Randomised Controlled Trial (RCT) Registry as of 16 June 2017. Unique identifying number: AEARCTR-0002266 .