according to a new study from Australia.
Although alcohol is a known risk factor for cancer, people generally do not expect their heavy drinking in early adulthood to affect their cancer risk many years later, lead author Harindra Jayasekara, MBBS, MD, PhD, with Cancer Council Victoria and University of Melbourne, said in an interview. But in this analysis, “we found evidence consistent with early initiation and chronic progression of carcinogenesis linked to alcohol and its toxic metabolites.”
The study, published online Feb. 19 in the International Journal of Cancer, assessed lifetime drinking trajectories and risk for alcohol-related cancer using data from 22,756 women and 15,701 men recruited to the prospective Melbourne Collaborative Cohort Study from 1990-1994. Heavy drinking was considered an average alcohol intake of at least 60 g/day, which is equivalent to the alcohol content in 6 standard drinks.
During 485,525 person-years of follow-up among women, 2,303 incident alcohol-related cancers were diagnosed, most commonly breast (64%) and colorectal cancer (31%).
During 303,218 person-years of follow-up among men, 789 alcohol-related cancers were found, most commonly colorectal cancer (83%).
The researchers identified three distinct lifetime alcohol intake trajectories for women – lifetime abstainer (39%), stable light (54%), and increasing moderate (7%) – and six for men – lifetime abstainer (14.3%), stable light (51.5%), stable moderate (20.4%), increasing heavy (6.6%), early decreasing heavy (5.1%), and late decreasing heavy (2.2%).
Almost three times more, women were lifetime abstainers (39% vs. 14% of men). And approximately the same percentage of men and women increased their alcohol consumption over time. About 7% of men were classified as increasing heavy drinkers, consuming a moderate amount of alcohol (30-59 g/day) at age 20-39 and increasing their intake markedly from age 40-49 (over 60 g/day) before reducing it by age 60-69. Among women, 7% were classified as increasing moderate, tending to consume around 20 g/day at age 20-29 and gradually increasing their alcohol intake over time to consume close to 40 g/day at age 50-59.
Among men, the early decreasing heavy group started as heavy drinkers at age 20-39 (greater than or equal to 60 g/day) and continued to cut down their intake over time until developing stable light drinking habits by age 60-69, whereas late decreasing heavy drinks continued to drink a lot until age 60-69 before cutting their intake in their 70s.
Impact on cancer risk
For men, relative to lifetime abstention, heavy drinking trajectories were associated with an increased risk for alcohol-related cancer overall.
The strongest associations were for the early decreasing heavy trajectory (hazard ratio, 1.75) and the late decreasing heavy trajectory (HR, 1.94), with the increasing heavy trajectory not far behind (HR, 1.45).
The strength of these associations did not change appreciably in analyses excluding current smokers at baseline.
Among men, the early decreasing heavy and late decreasing heavy intake trajectories were similarly associated with an increased risk for colorectal cancer (HR, 1.56 for early, and HR, 1.74 for late). The corresponding HR for the increasing heavy trajectory was 1.36.
For women, compared with lifetime abstention, the alcohol intake trajectory classified as increasing moderate (30-59 g/day) was associated with a greater risk for alcohol-related cancer overall (HR, 1.25). The strength of this association weakened slightly when current smokers were excluded.
Compared with lifetime abstention, the increasing moderate trajectory in women was similarly associated with an increased risk for breast cancer (HR, 1.30) and colorectal cancer (HR, 1.23).
The 2018 World Cancer Research Fund and American Institute for Cancer Research global cancer prevention recommendation on alcohol is to “avoid any alcohol,” study investigator Julie Bassett, PhD, MSc, with Cancer Council Victoria, said in an interview. “As much as it is important to limit alcohol intake during middle age to prevent cancer, we have shown that limiting intake during early adulthood is also important.”