Using alcohol unit-marked glasses enhances capacity to monitor intake: evidence from a mixed-method intervention trial

Aims: People tend to have poor knowledge of government guidelines for alcohol use, and lack the motivation and skills required to use them to monitor their drinking. The study aim was to determine whether using glasses marked with such guidelines would improve knowledge and attitudes, increase frequency of counting units, and lower alcohol intake. Methods: 450 adults participated in an intervention-control study with 1-month follow-up. The intervention group was encouraged to use glasses supplied by the researchers that indicated the unit content of drinks of different strengths and volumes, and stated the intake guidelines. Interviews with 13 intervention group participants focused on their experiences of using the glasses and recommendations for their use. Results: Analyses adjusted for baseline variables showed that the intervention improved: knowledge of unit-based guidelines; ability to estimate the unit content of drinks; attitudes toward the guidelines; and frequency of counting unit intake. However, there was no significant change in alcohol consumption. Interview data confirmed that the glasses provided useful information that encouraged people to think about their drinking and to discuss alcohol with other people. However, their design was not appealing to all, and their initial impact did not always persist. Conclusions: Use of unit-marked glasses led to changes in people’s use of unit-based guidelines to monitor their drinking. The qualitative data suggested that the glasses could have an impact at the individual level (on knowledge and attitudes) and at a broader level (by prompting discussion of alcohol use).