The causal association between alcohol consumption and risk of prostate cancer has been suggested, but results so far have been inconclusive. Now, a collaborative study confirms the suspicions: The more you drink, the higher your risk of prostate cancer.
The study, “Is alcohol consumption a risk factor for prostate cancer? A systematic review and meta–analysis,” published in BMC Cancer, is a result from a meta-analysis of case-control and cohort studies that accounted for drinker misclassification errors, which are common in the majority of studies assessing alcohol consumption. It shows that alcohol consumption is associated with many more prostate cancer cases than previously thought.
Alcohol is a known risk factor for several cancers, including breast cancer, and at least six types of cancers of the digestive system (oropharynx, larynx, esophagus, liver, colon and rectum). Studies also have suggested a link between alcohol consumption and increased risk of skin, pancreas and prostate cancer, but findings have been conflicting. In prostate cancer, for example, studies have reported that alcohol consumption increases risk, decreases risk, or is not associated with the development of this cancer.
The researchers believe this likely occurs, in part, because of “abstainer bias.” This term refers to a common practice in studies addressing alcohol consumption, in which researchers include former (sometimes heavy) drinkers who quit due to health problems in the same group as people who never drank alcohol. In such studies, the true effect of alcohol is likely to be masked, as former drinkers will likely have a higher incidence of alcohol-related diseases than those who never drank.
To address the effects of alcohol in prostate cancer risk without the abstainer bias, the researchers conducted a meta-analysis of case-control and cohort studies, published until December 2014, that controlled for drinker misclassification errors as well as for the quantity of alcohol consumed.
They selected 27 publications studying alcohol consumption and prostate cancer that attempted to measure the risk at different levels of consumption. Studies were then classified according to the presence or absence of two types of potential abstainer bias: Studies that included former drinkers in the abstainer reference group, and studies that included occasional drinkers in the abstainer group. Among the selected studies, 10 had both biases, six had the former drinker bias only, five had the occasional drinker bias only, and six had neither abstainer bias.
The team then controlled the results from each study for abstainer bias. Their findings showed a dose-response relationship between the amount of alcohol consumption and risk of prostate cancer among current drinkers.
Low (1.30– < 25 g/day), medium (25– < 45 g/day), high (45– < 65 g/day), and higher volume (65+ g/day) drinkers all had significantly higher risk of prostate cancer compared to the abstainer group. The average drink in the U.S. has 14 grams of alcohol, and in the U.K. it has eight grams.
Compared to abstainers, low-volume drinkers had an 8% higher risk for prostate cancer, but this risk was even higher (23%) when researchers examined only the studies that had none of the abstainer biases.
Prostate cancer is the second most common cancer in American men and the second leading cause of cancer death, preceded only by lung cancer. Indeed, the American Cancer Society estimates that more than 180,000 men will be diagnosed with prostate cancer in the U.S. in 2016 alone, and that 26,120 will die from the disease. The findings, therefore, have major public health implications, suggesting that lifestyle changes can largely reduce the incidence of prostate cancer.
“This new study contributes to the strengthening evidence that alcohol consumption is a risk factor for prostate cancer. Alcohol’s contribution to prostate cancer will need to be factored in to future estimates of the global burden of disease,” Tim Stockwell, PhD, director of the Centre for Addictions Research of BC (CARBC) at the University of Victoria, and study co-author, said in a press release.