There is compelling evidence that heavy alcohol drinking is related to increased risk of several cancer types, but the relationship of light–moderate drinking is less clear. We explored the role of inferred underreporting among light–moderate drinkers on the association between alcohol intake and cancer risk.
In a cohort of 127,176 persons, we studied risk of any cancer, a composite of five alcohol-associated cancer types, and female breast cancer. Alcohol intake was reported at baseline health examinations, and 14,880 persons were subsequently diagnosed with cancer. Cox proportional hazard models were controlled for seven covariates. Based on other computer-stored information about alcohol habits, we stratified subjects into 18.4 % (23,363) suspected of underreporting, 46.5 % (59,173) not suspected of underreporting, and 35.1 % (44,640) of unsure underreporting status.
Persons reporting light–moderate drinking had increased cancer risk in this cohort. For example, the hazard ratios (95 % confidence intervals) for risk of any cancer were 1.10 (1.04–1.17) at <1 drink per day and 1.15 (1.08–1.23) at 1–2 drinks per day. Increased risk of cancer was concentrated in the stratum suspected of underreporting. For example, among persons reporting 1–2 drinks per day risk of any cancer was 1.33 (1.21–1.45) among those suspected of underreporting, 0.98 (0.87–1.09) among those not suspected, and 1.20 (1.10–1.31) among those of unsure status. These disparities were similar for the alcohol-related composite and for breast cancer.
We conclude that the apparent increased risk of cancer among light–moderate drinkers may be substantially due to underreporting of intake.