Evidence from the Million Women Study has demonstrated that there is an association between the amount of alcohol a woman drinks and her risk of developing several types of cancer. The study, conducted by researchers at Oxford Population Health’s Cancer Epidemiology Unit, is published in BMC Cancer.
Previous studies have demonstrated that drinking alcohol is associated with increased risk of certain cancers and decreased risk of some other cancers. Few of these studies have provided evidence to show whether or not alcohol-associated risks for specific cancers are affected by smoking, body mass index, or taking menopausal hormone therapy (commonly known as HRT). Much of this evidence has also been retrospective and subject to recall bias, whereby there may be differences in reporting of behaviours such as drinking alcohol or smoking between those who develop cancer and those who do not.
The researchers analysed data from 795,121 post-menopausal participants in the Million Women Study, who reported consuming an average of 6.7 alcoholic drinks per week. Their health records were then followed up over an average of 17 years to identify how many cases of cancer were diagnosed during this time. The participants were grouped into four categories according to the total number of alcoholic drinks (one glass of wine, half a pint of beer/lager/cider, or one measure of spirits) they said they consumed per week when they joined the study: 1-2, 3-6, 7-14, and >15 drinks per week.
The study excluded women who reported drinking one or fewer alcoholic drinks per week because some of these women are likely to have stopped drinking alcohol due to poor health and their reported alcohol consumption at joining may not be representative of their lifelong average intake. Most of the participants reported a low to moderate level of alcohol consumption, with 92% drinking less than the current UK recommended limit of 14 drinks per week.
Key findings:
- During the 17 years of follow up, 140,203 cases of cancer were diagnosed in the study participants;
- There was strong evidence for an association between alcohol intake and upper aerodigestive cancers (oesophageal squamous cell carcinoma, oral cavity, pharynx, and larynx), with a 38% increased risk per 1 drink per day increase in alcohol consumption;
- There were significant interactions between alcohol and smoking for aerodigestive cancers with a 66% increased risk per 1 drink per day increase in consumption in women who drank alcohol and smoked, but only a 12% increased risk per 1 drink per day increase in consumption in women who drank alcohol but had never smoked. There were no significant interactions between alcohol and smoking for any of the other types of cancer;
- The majority of the alcohol-related excess risk of aerodigestive cancers was in heavy smokers, with some excess risk in light smokers and past smokers, and very little excess risk in never smokers;
- Body mass index and menopausal hormone therapy did not significantly modify any associations between alcohol intake and cancer risk;
- There was also evidence for more moderate positive associations between alcohol intake and risk of breast, colorectal, and pancreatic cancer;
- Moderate alcohol intake was associated with a decreased risk of thyroid cancer, renal cell carcinoma, non-Hodgkin’s lymphoma and multiple myeloma.
Associate Professor Sarah Floud, lead author of the study, said ‘These findings provide robust evidence that greater alcohol intake, even within relatively moderate ranges, increases the risk of many common cancers. In addition, most of the increased risk of aerodigestive cancers associated with higher alcohol consumption is confined to smokers, suggesting that alcohol intake at these levels primarily acts by exacerbating the effect of smoking.’
The researchers note that while they were only able to study the effect of alcohol and its interactions in women, there is no reason to expect that the findings would not be broadly generalisable to men.