Alcoholic liver disease is a relatively rare condition that overwhelmingly affects very heavy drinkers. It would be surprising, to say the least, if ‘very low levels’ of drinking caused it.
And yet the media’s coverage of this study accurately reflected the claims made by its authors. They claim to have shown that ‘consumption of alcohol early in life is associated with an increased risk of developing severe liver disease in men’. They say that ‘men consuming as little as one to five grams [less than one unit] of alcohol per day had an increased risk of severe liver disease compared to abstainers, indicating that the increased risk of severe liver disease might be present even at very low doses of alcohol.’ Moreover, they declare – in the abstract of the study – that: ‘Current guidelines for safe alcohol intake in men might have to be revised.’
How did they arrive at these remarkable conclusions? First, they dug up some old documents from the Swedish army dating back to 1969-70 when conscription was still in force. These documents contain survey data from conscripts aged between 18 and 20, including estimates of how much they drank.
This gave the researchers the baseline figures for alcohol consumption. The men were then ‘followed for a mean period of 37.8 years’ to see what happened to them. This is a rather grand way of saying that the researchers looked at Sweden’s National Patient Register to see how many had developed alcoholic liver disease by 2009.
Of the 43,296 individuals who had provided drinking estimates in 1969/70, 383 had developed severe liver disease (0.9 per cent). When the researchers looked at their alcohol consumption, they found that those who drank the most were the most at risk and those who did not drink at all were the least at risk. Fair enough but, more surprisingly, they also found that those who only drank one or two units a day were at increased risk.
The authors describe these findings as ‘borderline statistical [sic] significant’. In fact, they are nowhere near being statistically significant, but we’ll leave that to one side. The more interesting question is this. In the 39 years between the men being recruited to the army and their medical records being examined, how often do you think the researchers asked them how much they drank?
Every six months? Once a year? Once every five years?
How about never? Because that’s how often they kept abreast of what these men were drinking. Not once. They have no idea how much their subjects’ drinking behaviour changed in the intervening years. All they know is that the people who were teetotal in 1970 were less likely to develop liver disease than the people who were drinkers in 1970. Hold the front page!
In no way does this study show, or even imply, that drinking at low levels causes liver cirrhosis. The authors’ suggestion that their study shows that ‘recommendations for safe alcohol consumption regarding the risk for development of severe liver disease in men might be set too high’ is an absurd non-sequitur.
Quite obviously, the men in this study did not continue drinking at the same level as their 19 year old selves for the rest of their lives. Some of the teetotallers became heavy drinkers (we know this because eleven of them developed alcoholic liver disease), some of the heavy drinkers became teetotallers, and some of the light drinkers became heavy drinkers. It is not drinking at ‘very low levels early in life’ that causes the damage. It is drinking at very high levels later in life. Without knowing anything about what these men were drinking after 1970, the study tells us precisely zero about the relationship between alcohol and liver disease, nor does it inform the discussion about what a ‘safe level’ of drinking is.
Why are journals publishing this pointless rubbish? Judging by the lead author’s comments to the press, the aim is not to tell us anything useful, but to put pressure on the Swedish government to follow the UK in lowering the drinking guidelines.
It would be strangely fitting if the Swedes lower their drinking guidelines based on junk science which claims that alcoholic liver disease is a threat to light drinkers. As the e-mails released under the Freedom of Information Act show, it was only by making this scientifically illiterate assumption that the UK’s Chief Medical Officer was able to lower the guidelines in 2016.“If these results lead to lowering the cut-off levels for a ‘safe’ consumption of alcohol in men, and if men adhere to recommendations, we may see a reduced incidence of alcoholic liver disease in the future,” Dr Hagström said.
We can expect more studies of this kind in the next few years. The anti-drink lobby will not be happy until the official drinking guidelines are zero and they will go to any lengths to achieve it.
[Cross-posted at Spectator Health]
No comments:
Post a Comment