Debating Shield <i>et al</i>.'s perspectives on how to formulate alcohol drinking guidelines

It is premature to make recommendations on new national alcohol guidelines before the evidence of improved uptake is developed. Acute harms follow from bunched drinking or heavy episodic drinking patterns, so daily limits as well as weekly limits are desirable. Shield et al. [1] present an important debate piece undergirding the recently adopted Canadian drinking guidelines. It is valuable to have provided the main rationales for four propositions that the expert panel developed in updating Canada's low-risk drinking guidelines (LRDGs) that are now being implemented in Canada's 2023 Guidance on Alcohol and Health. Two of the propositions are relatively non-controversial: (1) as an indicator of health loss; (2) use of years of life lost (YLL), for which there is higher quality data than disability-adjusted life years (DALYs); and (3) use of a weighted composite risk function versus a cause-specific approach. As regards point (2), a life-course approach without age-specific guidelines, I have some additional concerns, specifically how aging populations might opt for moderate risk if they did not already have cancer (figure 3), given this group often has interacting medications, and younger groups, who might have greater risks from heavy episodic drinking. However, I want to focus primarily on point (4), the risk-zones approach that, in the authors' conclusions, becomes a recommendation. The authors note this is a new LRDG strategy that has not been empirically tested; they provide some examples of similar gradations. One, the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition degree of severity of alcohol use disorder (AUD) [2], is not too apt, being aimed at clinicians assessing severity rather than public messaging per se. Although the innovative presentation of risk zones does offer potential to reach individuals with higher levels of drinking and possibly influence them to move down the risk spectrum, it seems premature to make a recommendation for this strategy until there has been opportunity to empirically test, perhaps by a randomized controlled trial or quasi-experiment like the Yukon warning labels study [3], whether the Canadian public actually benefits from this approach. In general, we do not know how effective this innovation will be (contrasted to other LRDG frameworks). The decision to take this approach in Canada seems fine, but I believe recommending it more broadly is premature before marshalling evidence that it works and for whom it is most effective. An additional point regards drinking patterns. The expert panel, by emphasizing average weekly alcohol consumption, implicitly decided that the way alcohol is consumed is less important to health risk. I believe evidence is sufficient that the pattern of drinking, especially bunched into one or two occasions rather than spaced drinking through the week, possibly with meals, affects health outcomes [4, 5]. This may be so even for liver cirrhosis, where chronic drinking dominates, but acute episodes may affect important pathways [6]. Authors note that 21% of Canadians have a heavy episodic drinking pattern and tend to drink outside of meals [1]. It is possible that those now classed in the moderate risk category, with five or six drinks per week, would actually be at high risk for acute harms if they drank this amount in one sitting (not too unlikely); Knupfer [7] identified the myth of the steady drinker years ago, but this remains true; drinking patterns are highly predictive, for example, of AUD [8]. Additionally, a 2015 United States (US) national alcohol survey adjusting for numerous covariates showed that three to four drinks in any day, versus abstention, was associated with higher family and financial harms due to a partner or family member's drinking [9]. Many people obtain their alcohol volume by heavy drinking episodes. The US LRDGs reflect this by separate thresholds for daily drinking and for weekly drinking [10, 11]. Although Shield et al. [1] pay some attention to drinking pattern in the discourse, the decision to not include this in the Canadian LRDGs is not much discussed, and implicitly this reflects a volume-only view of risk. I suspect the expert group may have felt there was insufficient empirical evidence for the role of the pattern, by which the volume was obtained, but with this point I disagree, and at least in the United States, likely also in Canada, multiple important outcomes are associated with exceeding the weekly/daily combined guideline [12]. It may be that having decided on the risk zone framework, introducing daily and weekly amounts was just viewed as “a bridge too far.” A test of both these objectively complex message alternatives is overdue. Funded by National Institute on Alcohol Abuse and Alcoholism (NIAAA) grant P50 AA005595. Opinions are those of the author and do not represent official positions of NIAAA and the National Institutes of Health. T.K.G. has had support from the National Alcohol Beverage Control Association and is a volunteer Member of the Board of Directors of Alcohol Justice. He is a consultant to the University of North Carolina's R01 on alcohol warning labels.

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