The ‘sick-quitter effect’: potential bias in studies on the health effects of alcohol

It’s no secret that most Aussies enjoy a drink. In fact, we come in at 10^th on the list of countries that consume the most alcohol. Perhaps because alcohol is such a big part of everyday life in Australia, we often forget alcohol is a drug – and one that significantly increases the risk of many health conditions, including various cancers.

So, what’s behind the claims that ‘moderate drinking’ is good for you?

If you follow any health websites or blogs, you’ve probably seen conflicting articles about the impact of alcohol on your health with some citing research that claims ‘moderate drinking’ may in fact offer health benefits. However, there is a potential issue in the way some of these studies back up their claims: they don’t account for the ‘sick quitter effect’.

The ‘sick quitter effect’

To investigate possible links between alcohol consumption and health outcomes, researchers often compare the health of ‘moderate drinkers’ to ‘non-drinkers’, which include people who have given up drinking. While this may seem logical, there are characteristics of the population of people who don’t drink that actually skew these comparisons.

Often, people who give up drinking do so because of health conditions, which may or may not be caused by alcohol. This means that in some studies, people that drink light-moderate amounts of alcohol are often healthier than non-drinkers. This is called the ‘sick quitter effect’. Similarly, the demographic of people who have never had a sip of alcohol sometimes have underlying health conditions that prohibit them from drinking.

In a recent study¹, our researchers set out to measure and understand the ‘sick quitter’ effect in Australia. By analysing data from the NSW 45 and Up Study, they found that a variety of health conditions appeared to prompt older adults to quit drinking. The study examined the drinking habits of participants after a diagnosis of 32 common health conditions. The findings showed that quitting drinking was strongly associated with 24 of these conditions, including various cancers, diabetes, heart disease, stroke, memory loss and depression. In fact, former drinkers in the study who changed their overall health rating from “good” to “poor” had almost 3 times the odds of quitting compared to those who considered that they had remained in good health.

The researchers also found that accounting for all 32 of the health conditions captured in the study wasn’t enough to fully explain the association between self-rated poor health and quitting drinking, meaning there are likely to be many health conditions and perhaps other factors related to self-rated health that contribute to the apparent ‘sick quitter effect’. This is a limitation of the new study.

These findings suggest that future studies assessing the impact of alcohol consumption on many types of health outcomes should be carefully designed to avoid drawing potentially inaccurate conclusions as a result of not accounting for the ‘sick-quitter effect’. For example, some studies investigating the overall impact of alcohol consumption on mortality have used very light drinkers as the point of comparison, rather than non-drinkers. A recent review of 87 studies found that when ‘occasional drinkers’ were used as the comparison group (as opposed to non-drinkers), there was no benefit of low volume alcohol consumption for risk of death². In fact, the more alcohol people consumed each day, the greater the risk of death.

So, what does this mean for you?

Always check the sources of articles touting the health benefits of alcohol and other substances that are normally regarded as bad for you. The internet has flooded the world of nutritional information with a huge variety of ‘expert advice’. From fitness forums to Instagram influencers, everyone seems to have a new secret to a healthy lifestyle. When it comes to your health, it is best to take your advice from reputable sources such as the websites of government, or non-government organisations devoted to public health. A good example is a website maintained by Cancer Council which answers community questions about cancer risk factors: iheard.com.au

The reality of alcohol and cancer risk

The evidence on alcohol and cancer risk has been reviewed by the International Agency for Research on Cancer and they have concluded that alcohol use increases the risk of cancers of the mouth, pharynx, larynx, oesophagus, liver, bowel and breast. Cancer Council recommends readers reduce their alcohol consumption to lower their risk of developing these cancers.

1. _{Sarich P, Canfell K, Banks E, Paige E , Egger S, Joshy G, Korda R, Weber M. A Prospective Study of Health Conditions Related to Alcohol Consumption Cessation Among 97,852 Drinkers Aged 45 and Over in Australia. Alcohol Clin Exp Re. 2019;43:710-721. doi:10.1111/acer.13981}
2. _{Stockwell T, Zhao J, Panwar S, Roemer A, Naimi T, Chikritzhs T. Do “Moderate” Drinkers Have Reduced Mortality Risk? A Systematic Review and Meta-Analysis of Alcohol Consumption and All-Cause Mortality. J Stud Alcohol Drugs. 2016;77(2):185-198. doi:10.15288/jsad.2016.77.185}