Even light to moderate drinking linked to alcohol-related cancers

1. In women who drank light to moderate amounts of alcohol, there was an increased incidence of alcohol-related cancers; an effect that was driven mainly an increased risk for breast cancer.

2. Men who were light to moderate alcohol drinkers did not have an increased risk of alcohol-related cancers when controlling for smoking behavior.

3. There was a slight increase in overall cancer risk for men and women who were light to moderate alcohol drinkers, although this effect was non-significant.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Recent studies have demonstrated benefits of light to moderate alcohol consumption in improving the outcomes of congestive heart failure, diabetes, and coronary artery disease and even reducing all-cause mortality. However, before its virtues can be extolled, public health organizations need to weigh the benefits against the possible risks of alcohol consumption. One such drawback is an increase in the risk of cancer. This study used data from two large prospective cohorts to evaluate the relationship between the quantity and frequency of alcohol consumption and the risk of cancer.

In order to compare data across the cohorts, this study defined light to moderate alcohol consumption as ranging between 0.1 and 14.9 g/day. For reference, a single serving of 4 ounces of red wine contains approximately 11 g of alcohol. The study then compared individuals who consumed light to moderate amounts of alcohol to those who either abstained from alcohol or were heavy drinkers. Compared to abstainers, men and women who drank light to moderate amounts of alcohol had a slight, but statistically non-significant increase in all cancers. There was no difference in increased risk by the type of alcoholic beverage consumed. Increased frequency of consumption, and heavy episodic drinking were associated with an increase in cancer risk. Women who drank light to moderate amounts of alcohol had a significantly increased risk of alcohol-related cancer (though not all cancers) that was driven mostly by a greater risk of breast cancer.

This study, along with others before it, found that smoking was a significant confounder in the analysis between alcohol consumption and cancer risk. The authors were able to control for the effect of smoking, and analyzed men and women who had never smoked independently from those who had. Limitations of this study included utilization of self-reported questionnaires to assess alcohol consumption, and potential residual confounding. However, this study is unique in the fact that it was able to provide associations between cancer risk and alcohol consumption independent of smoking at different levels and frequencies.

Click to read the study in the BMJ

Click to read an accompanying editorial in the BMJ

Relevant Reading: Carcinogenicity of alcoholic beverages

In-Depth [prospective cohort]: This grouped prospective cohort study utilized data from the Nurse’s Health Study and Health Professionals Follow-up Study to quantify the risk of different levels of alcohol consumption on overall cancer risk. Overall, 88,084 women and 47,881 men were followed for more than 3 million person-years. In all, 26,840 incident cancers were diagnosed. Median alcohol consumption in the cohort for women and men were 1.8 g/day and 5.6 g/day respectively. Light consumption was defined as 0.1 – 4.9 g/day, while moderate consumption was defined as 5 – 14.9 g/day. Compared with abstainers, men who drank alcohol had a relative risk of all cancer of 1.03 for light consumption (CI₉₅ 0.96 – 1.11) and 1.05 for moderate drinkers (CI₉₅ 0.97 – 1.12). For women, relative risks were 1.02 (CI₉₅ 0.98 – 1.06) and 1.04 (CI₉₅ 1.00 – 1.09) for light and moderate consumption respectively. However, the study also analyzed the effect of alcohol consumption on those cancers known to be associated with alcohol consumption, including colorectal, breast, oral, pharyngeal, laryngeal, liver, and esophageal cancer.  For men, this risk was increased, but non-significantly, in those with light to moderate consumption of alcohol independent of smoking. This increase was led by colorectal cancer. In women however, moderate alcohol consumption was associated with an increased relative risk of cancer of 1.13 (CI₉₅ 1.06 – 1.20), that was led primarily by an increased incidence of breast cancer.

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