Even Light Drinking Can Increase Alcohol-related Cancer Risk

A new cohort review in BMJ suggests that even light to moderate alcoholic consumption is associated with minimally increased risk of overall cancer. Earlier studies have made the link to increased risk of cancer (particularly colorectal, female breast, oral cavity, pharynx, larynx, liver, and esophagus) for heavy consumption, but the news here is that even amounts less than 30 g/day have potential bearing on cancer risk.

“Although the relation between alcohol and cancer has been extensively studied, the role of alcohol independent of smoking has not been settled,” the researchers noted.

High alcohol drinkers are more likely to be smokers, and smoking is the major risk factor for most alcohol-related cancers. They observed that in studies that included smokers, the apparent influence of alcohol on cancer could be partly driven by its effect among smokers, and findings might not be generalizable to non-smokers, who now make up the majority of the population. Thus, the BMJ review aimed to determine the dose-response relation of alcohol and cancer among never smokers.

For men who have never smoked, risk of alcohol-related cancers is not appreciably increased for light and moderate drinking (up to two drinks per day). But for women, even those who never smoked, risk of alcohol-related cancers (mainly breast cancer) increases even within the range of up to one alcoholic drink per day.

The review looked at the Nurses’ Health Study, which includes 121,700 female nurses ages 30 to 55 at enrollment in 1976. It also included the Health Professionals Follow-up Study, which consisted of more than 50,000 male professionals ages 40 to 75 at enrollment in 1986. Participants were mailed questionnaires at enrollment and two years thereafter to collect data for demographics, lifestyle factors, medical history, and disease outcomes. In addition, they reported updates in dietary intake every four years. The follow-up rates in both cohorts were greater than 90%.

Among the key findings:

• 19,269 and 7,571 (excluding non-advanced prostate cancers) incident cancers were documented among women and men, respectively, over 3,144,853 person years.
• Compared with non-drinkers, light to moderate drinkers had relative risks of total cancer of 1.02 (95% confidence interval 0.98 to 1.06) and 1.04 (1.00 to 1.09; Ptrend=0.12) for alcohol intake of 0.1-4.9 and 5-14.9 g/day among women, respectively.
• Associations for light to moderate drinking and total cancer were similar among ever or never smokers, although alcohol consumption above moderate levels (in particular >=30 g/day) was more strongly associated with risk of total cancer among ever smokers than never smokers.
• For women, even an alcohol consumption of 5-14.9 g/day was associated with increased risk of alcohol-related cancer (relative risk 1.13 (95% confidence interval 1.06 to 1.20)), driven by breast cancer.
• More frequent and heavy episodic drinking was not further associated with risk of total cancer after adjusting for total alcohol intake.