July 27, 2016
There is “strong evidence” that alcohol causes seven cancers, and other evidence indicates that it “probably” causes more, according to a new literature review published online July 21 in Addiction.
Epidemiologic evidence supports a causal association of alcohol consumption and cancers of the oropharynx, larynx, esophagus, liver, colon, rectum, and female breast, says Jennie Connor, MB, ChB, MPH, from the Department of Preventive and Social Medicine, University of Otago, in Dunegin, New Zealand.
In short, alcohol causes cancer.
This is not news, says Dr Connor. The International Agency for Research on Cancer (IARC) and other agencies have long identified alcohol consumption as being causally associated with these seven cancers.
So why did Dr Connor, who is an epidemiologist and physician, write a new review? Because she wants to “clarify the strength of the evidence” in an “accessible way.”
There is “confusion” about the statement, “Alcohol causes cancer,” explains Dr Connor.
Public and scientific discussion about alcohol and cancer has muted the truth about causality, she suggests.
“In the public and the media, statements made by the world’s experts are often given the same weight as messages from alcohol companies and their scientists. Overall messages become unclear. For these reasons, the journal [Addiction] has tagged this piece [her review] as ‘For Debate,’ ” she told Medscape Medical News.
The use of causal language in scientific and public discussions is “patchy,” she writes.
For example, articles and newspaper stories often use expressions such as “alcohol-related cancer” and “alcohol-attributable cancer”; they refer to a “link” between alcohol and cancer and to the effect of alcohol on “the risk of cancer.”
These wordings “incorporate an implicit causal association, but are easily interpreted as something less than cancer being caused by drinking,” observes Dr Connor.
“Stop drinking alcohol” is a catch phrase that could be ― but is not ― akin to “stop smoking,” she also suggests.
“Currently, alcohol’s causal role is perceived to be more complex than tobacco’s, and the solution suggested by the smoking analogy — that we should all reduce and eventually give up drinking alcohol — is widely unacceptable,” writes Dr Connor.
The newly published review “reinforces the need for the public to be made aware of the causal link between alcohol and cancer,” said Colin Shevills, from the Alcohol Health Alliance UK, in a press statement.
“Research shows that only around 1 in 10 people [in the UK] are currently aware of the alcohol-cancer link,” he said.
“People have the right to know about the impact of alcohol on their health, including its link with cancer, so that they can make informed choices about how much they drink,” added Shevills.
The lack of clarity about alcohol causing cancer, Dr Connor believes, is related to alcohol industry propaganda as well as the fact that the “epidemiological basis for causal inference is an iterative process that is never completed fully.”
Of the 36,030 (31%) current drinkers, 72% had low consumption. Over a follow-up of about 4 years, current drinking was linked to a 24% lower risk for heart attack (hazard ratio [HR], 0.76; 95% confidence interval [CI], 0.63 – 0.93), a 51% increased risk for alcohol-related cancers (mouth, esophagus, stomach, colorectal, liver, breast, ovary, and head and neck) (HR, 1.51; 95% CI, 1.22 – 1.89), and a 29% increased risk for injury (HR, 1.29; 95% CI, 1.04 – 1.61). There was no reduction in the risk for death or stroke among current drinkers.
The risk for cardiovascular disease was lower in wine drinkers than in never drinkers, and the risk for heart attack was significantly lower (HR, 0.55; 95% CI, 0.39 – 0.77).
However, the risk for cancer was 38% higher in wine drinkers than in never drinkers (HR, 1.38; 95% CI, 1.05 – 1.81), 69% higher in spirit drinkers (HR, 1.69; 95% CI, 1.26 – 2.26), and 20% higher in beer drinkers (HR, 1.20; 95% CI, 0.91 – 1.57).
“The reduction in risk of heart attack is consistent with previous literature, both concerning red wine and low alcohol consumption. However, this may be offset by increases in risk for other outcomes,” Dr Smyth pointed out.
People with high alcohol intake had a 31% increased risk for death (HR, 1.31; 95% CI, 1.04 – 1.66). Those with heavy episodic drinking had a 54% increased risk for mortality (HR, 1.54; 95% CI, 1.27 – 1.87) and a 71% increased risk for injury (HR, 1.71; 95% CI, 1.14 – 2.56).
More than three-quarters of people in high-income countries consumed alcohol, whereas only one-eighth of those in low-income countries did. However, even though low-income countries had the lowest frequency of current drinking, they also had the highest rates of current drinkers with high intake and heavy episodic drinking patterns.
In higher-income countries, risk on a composite score indicating the net association between alcohol and health outcomes was significantly lower for current drinkers than for never drinkers (HR, 0.84; 95% CI, 0.77 – 0.92). In lower-income countries, there was no reduction in composite score for current drinkers (HR, 1.07; 0.95 – 1.21; P interaction ≤ .0001).
Dr Smyth and his colleagues emphasize that people who do not drink should not be advised to start drinking because of the potential to increase consumption or to start drinking in a heavy episodic pattern.
A detailed assessment of alcohol use during follow-up is lacking in this study, Jason P. Connor, PhD, from the University of Queensland in Herston, Australia, and Wayne Hall, PhD, from King’s College London in the United Kingdom, write in an accompanying comment.
Even though outcomes on all health measures assessed were worse in former drinkers, the researchers did not collect data on how much alcohol these people drank before they abstained. In addition, relatively few adverse events occurred during the short follow-up period, which affects the study’s statistical power, they note.
Nevertheless, Drs Connor and Hall commend the researchers, noting that the value of the PURE study “will greatly increase as the number of adverse health outcomes accumulates with longer follow-up.”
“In the meantime, we should not delay action,” they write. “More than sufficient evidence is available for governments to give increased public health priority to reducing alcohol-related disease burden in low-income and middle-income countries.”
“This should be done by implementing the most effective population policies to discourage harmful drinking — namely, increasing the price of alcohol and reducing its availability, especially to younger drinkers, and preventing the alcohol industry from promotion of frequent drinking to intoxication,” they explain.
The study authors, Dr Connor, and Dr Hall have disclosed no relevant financial relationships
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