Backgrounder: Heavier Alcohol Use Predicts Prostate Cancer
Prostate cancer rates: Prostate cancer is a highly prevalent form of cancer in Australia, Canada and the US, and its incidence is increasing in many other countries. It is the most common cancer among Canadian men: on average, every week 475 Canadian men will be diagnosed with prostate cancer and 83 Canadian men will die of it. In Australia one in nine men will develop the disease in their lifetime, and in the US it is the second leading cause of cancer death among men. Diagnosis rates in Europe are starting to catch up with the US and Canada.
Causes of prostate cancer: There has been scientific mystery surrounding the disease. It is known that the rates differ across nations and men moving to another country tend to take on the rate of their adoptive country. This alone suggests that environmental factors play a role in the disease. Except for age, race and family history, there is no consistent evidence for other factors (such as diet, smoking, exercise) to understand what factors might contribute to this serious form of cancer and how men might actively prevent it. The findings have been mixed or highly inconsistent for the role of alcohol in prostate cancer such that it is often concluded that alcohol use plays no role at all in its incidence.
This new study: This international study reports that when all 35 available epidemiological studies assessing level of alcohol use and prostate cancer incidence are analyzed together, heavier drinkers (14 or more drinks a week) are about 20 per cent more likely to develop prostate cancer than abstainers or light drinkers. All studies published in or before 2006 were included and were global in scope. The study also examined differences among the identified studies that might have contributed to the past confusion regarding drinking and prostate cancer incidence. Among the differences, the closer the proximity of the measurement of drinking to diagnosis, the more likely there was a significant association between drinking and prostate cancer.
Where to now? The study team suggests that future studies utilize multiple measurements because both the drinking habits and health status of men are rapidly changing with increasing age, making it difficult to ascertain the relationship between drinking and disease outcome. Of considerable importance is the fact that many men with the disease are never diagnosed. This means findings from studies that do not determine if their control groups have the disease may be in serious doubt. The NDRI study tested for the degree to which the available studies made efforts to be sure that their control or comparison groups did not have prostate cancer. Even among studies attempting to ascertain if these men had the disease, the positive association between alcohol use and prostate cancer remained. This finding gave the study team more confidence that the association between alcohol use and prostate cancer is valid.
What about protective effects? There is irony to the study findings. Much research has suggested that if middle aged and older men use alcohol at the rate of about 14 drinks a week this may prevent coronary heart disease, although recent evidence has suggested that the preventative power of alcohol may have been overstated. In contrast, the new study finds that it is at about the same levels of drinking that alcohol use contributes to the incidence of prostate cancer. Taken together these findings emphasize the value for men to drink moderately.