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expert reaction to study looking at alcohol cancer risk in cigarette equivalents

Reactions to a study published in the BMC Public Health which estimates the risk of cancer when drinking alcohol as compared with smoking.

A Before the Headlines accompanied this RoundUp.

*Background comment* Prof David Spiegelhalter, Winton Professor for the Public Understanding of Risk, University of Cambridge, said:

“If cigarette-equivalents were to be used to communicate the cancer risk of alcohol consumption, it is vital that their impact is properly evaluated to check they do not produce unreasonable concern – particularly as the overall health effect of moderate alcohol consumption is still contested.”

Prof John Britton, Director of the UK Centre for Tobacco & Alcohol Studies at the University of Nottingham, said:

“I’m not sure this study adds much that is useful.  I’m not sure many people decide whether to smoke or drink or neither or both based on how comparable the risks of the two are.  Few smokers smoke only eight cigarettes per week – and those that do have significantly increased risks of other diseases such as cardiovascular disease, compared to those who don’t smoke (or who drink one bottle of wine per week).

“This study demonstrates that in relation to cancer risk, smoking is substantially more hazardous than alcohol consumption.  Smoking is also far more hazardous than alcohol in relation to a range of other diseases.  If smokers are worried about their health, the best thing they can do is quit smoking.  People who consume alcohol should try to stick within the recommended guidelines of 14 units per week.”

Prof Jane Green, Professor of Epidemiology and Co-Director of the Cancer Epidemiology Unit, University of Oxford, said:

“It is important to view these results in context.  For both men and women in the UK, the lifetime risk of cancer is around 50%.  The authors estimate that lifetime risk is around 1% higher for men and women who drink a bottle of wine a week, or who smoke 5-10 cigarettes a week, than for those who neither smoke nor drink.  The average UK drinker reports drinking the equivalent of about a bottle and a half of wine a week, and the average smoker smokes about 10 cigarettes a day, or 70 a week.  This work confirms that for most smokers, their smoking carries much greater risks for cancer than does alcohol for most drinkers.  Moderate levels of drinking are in absolute terms particularly important for cancer risk in women, because they are associated with increased risk of breast cancer, which is very common (lifetime risk of 14%).”

Dr Minouk Schoemaker, Staff Scientist at The Institute of Cancer Research, London, who conducts research into the causes of breast cancer, said:

“The study results offer an interesting insight into the overall lifetime risk of cancer related to alcohol and smoking.  They show that drinking even moderate levels of alcohol leads to a relatively greater cancer risk in women than in men, due to the link of alcohol with breast cancer.

“The overall picture of cancer risk is enormously complex and nuanced, so it’s important to keep in mind that this new study is subject to a number of assumptions.  For example, it is difficult to disentangle the effects of alcohol and cigarette smoking entirely, and the study did not take into account the duration of smoking or time since stopping.

“There is still limited public awareness of the cancer risks of alcohol, despite the fact that drinking has been linked to common types of cancer and scientists agree that there is no ‘safe’ amount of alcohol in terms of cancer risk.  The new research underlines the importance of public health programmes to encourage people to limit their alcohol consumption.”

Dr Bob Patton, Lecturer in Clinical Psychology at the University of Surrey, with expertise in addictions research with a particular focus on harm reduction, said:

“Both tobacco and alcohol consumption are associated with a wide range of physical health complications.  In particular tobacco has long been known to cause cancer, and years of health education in the UK and beyond has resulted in this fact becoming ingrained in the consciousness of the British Public.  With regard to alcohol, while most folk understand its relationship with liver disease, it is not typically regarded as a causal factor in cancer.

“This research by Hydes and colleagues sets out to re-frame the public’s awareness of the relationships between alcohol and cancer by developing an analogy between cigarettes smoked and drinks consumed and then applying this to the risk of dying from any cancer.  They have combined data from a series of well designed studies, and re-purposed it to answer the question – how many cigarettes are in a bottle of wine.  They were cautious in their analysis, they took account of the fact that drinking and smoking in combination exacerbates the risks and they restricted their work to only focus upon cancer and not on any other physical health issue that could result in death.

“The risks are not the same for men and women.  They worked out that overall the risk of death by cancer for men drinking a bottle of wine every week, was the same as those that smoked five cigarettes a week, for women it was the equivalent of smoking ten cigarettes a week. And the risks increased disproportionately for heavier drinkers – men putting away three bottles a week equated to eight cigarettes a week, for women this jumps to twenty three cigarettes a week. The fact that alcohol consumption is linked to breast cancer may explain in part the gender differences found.

“It is likely that the findings from this simple study will have a profound effect on the way that drinkers, and in particular female drinkers, regard the risks associated with alcohol consumption; viewing alcohol drinking in the same light as cigarette smoking may well result in a decrease in consumption and its related harms.”

Prof Colin Berry, Professor Emeritus of Pathology, Queen Mary, London, said:

“The critical points are contained in the last paragraph on Page 5 of the paper; a number of assumptions made are set out here and their estimations where there are no ‘meta’ data may be   a problem.

“A different point; as the role of a number of genes influencing breast cancer incidence in the population is better known and as it becomes possible to control for these it is unwise to ignore genetic factors in estimating very small increments in risk in a population.  Do their drinkers and non-drinkers have the same genetic background?  Have they excluded all BRCA related tumours where pathogenesis may vary?  This is a trivial point but not when small changes are identified.

“Finally, the mechanism of the production of tumours in always important – and for oesophageal and breast cancer alcohol consumption can be invoked though generally at much higher levels of regular consumption.  If alcohol is regarded as a genotoxic carcinogen it is customary to ‘extrapolate backwards’ to zero in looking at risk.  However, it is the metabolites that can damage DNA and it is not clear, with the many variables that affect these, that extrapolations at low levels of exposure are sensible.”

‘A comparison of gender-linked population cancer risks between alcohol and tobacco: how many cigarettes are there in a bottle of wine?’ by Theresa J. Hydes et al. was published in BMC Public Health at 01:00 UK time on Thursday 28 March 2019.

Declared interests

Prof David Spiegelhalter: “No conflict of interest.”

Prof John Britton: “No interests to declare.”

Prof Jane Green: “No conflicts of interest.”

Dr Minouk Schoemaker: “No conflicts of interest.”

Dr Bob Paton: “No conflicts of interest to declare.”

Prof Colin Berry: “No declarations.”

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