Tuesday, 25 October 2016

Who's to blame - journals or journalists?

In the age of 24 hour news, all the dead tree press have left are embargoed studies from journals - and, boy, do they like to make the most of them. Two front page stories caught my eye today. Both are largely rubbish. The question is who is at fault: the journalists or the journals?

First, this from the Guardian...

Women now drink as much alcohol as men, global study finds

Women have caught up with men in the amount of alcohol they drink and are doing increasing amounts of damage to their health as a result, according to a global study that looked at the consumption habits of four million people over a period of over a century.

The change is partly the result of successful marketing campaigns and the creation of sweeter products aimed at young women or girls, as well as cuts in price, say health campaigners.

These claims are not borne out by the Office for National Statistics which has consistently found that men are the bigger drinkers. In the most recent drinking survey, conducted in 2014, the ONS found:

Men were more likely than women to drink alcohol, as well as consuming higher amounts. In the week previous to the survey, 64% of men had drunk alcohol, with over half (52%) drinking more than 4.67 units on their heaviest drinking day. In comparison, 53% of women had drunk alcohol in the previous week, with only 37% of those drinking more than 4.67 units on the heaviest day. Men were 3 times more likely to have drunk over 14 units on their heaviest drinking day, 12% of men compared with 4% of women.

If that's the situation in Britain, it seems unlikely that women are out-drinking men in some of the less socially progressive in the world, but let's see what the study - published in BMJ Open - says:

Among those born in the early 1900s, males were 2.2 (95% CI 1.9 to 2.5) times more likely than females to consume alcohol, 3.0 (95% CI 1.5 to 6.0) times more likely to drink alcohol in ways suggestive of problematic use and 3.6 (95% CI 0.4 to 30.3) times more likely to experience alcohol-related harms. Among cohorts born in the late 1900s, males were 1.1 (95% CI 1.1 to 1.2) times more likely than females to consume alcohol, 1.2 (95% CI 1.1 to 1.4) times more likely to drink alcohol in ways suggestive of problematic use and 1.3 (95% CI 1.2 to 1.3) times more likely to experience alcohol-related harms.

As you can see, the authors make the infuriating mistake of using '1900s' to describe the twentieth century rather than the first decade of the twentieth century. (This is not pedantry. If this common error becomes universal, historians will have no way of describing the first decade of a century.) Assuming that by 'late 1900s' they mean 1980-1999 rather than 1907-09, the study shows that the gap between male and female drinking rates has narrowed, but has not reached parity. Men are 20 per cent more likely to drink heavily and are 30 per cent more likely to experience alcohol-related harms. The whole premise of the Guardian front page story is therefore incorrect.

The study - actually an evidence review - doesn't show the actual rates of consumption, nor does it show trends for either sex. It focuses only on the gap. As the authors acknowledge...

It is important to note that the sex ratio metric used in the current study provides information on the relative prevalence of alcohol use or related harms in males versus females. This metric does not empirically determine whether observed changes in the sex ratio are being driven by increases or decreases in male or female prevalence

However, they say that in most instances rates of drinking have risen among women. That has certainly been the case in Britain but it is also the case that drinking amongst men has fallen sharply since 1900 (and has fallen amongst both sexes since 2004). It would be possible for the gap to narrow even if both sexes drank less.

The authors do not discuss the reasons for the narrowing of the gender gap other than to mention greater equality in the labour market, but this does not prevent the Guardian from inviting the usual neo-prohibitionist talking heads from Alcohol Concern and the Institute for Alcohol Studies to spout off about marketing and the 'need' for health warnings on drinks.

You can't blame the journal for this shoddy reporting. The study is not misleading and the press release repeatedly stated that women were 'catching up', but had not caught up, with men. The press release also said that the study did not 'address whether alcohol use is falling among men or rising among women' and that the authors 'did not set out to explain the reasons behind their observed findings'.

Verdict: Bad journalism

Meanwhile, the Times led with this story...

On its face, this is a crazy idea. Doctors have very little time with patients as it is without weighing everybody who comes in to see them. Most people are not obese and you don't need to weigh somebody to tell if they are fat. Moreover, the claim that heart disease would be cut by 23 per cent and diabetes would be cut by 17 per cent if doctors sent their patients off to Weight Watchers to lose two pounds seems deeply implausible.

The study in question was published in the Lancet. It's a randomised experiment in a real world setting in which GPs said something along the following line to obese patients:

'While you’re here, I just wanted to talk about your weight. You know the best way to lose weight is to go to [Slimming World or Rosemary Conley] and that’s available free on the NHS?'

The doctors didn't weigh the patients - only obese people were selected for the study - and so the intervention only took around 30 seconds.

The take-home message from the study is that the vast majority of obese people do not mind doctors raising the issue of their weight, and most of them appreciate the offer of help. Those who were offered help lost a bit more weight than those who didn't (1.4 kg on average).

The predictions about heart disease and diabetes are contained in the study, but the figures are relative to a counter-factual of future obesity rates. As regular readers know, 'public health' forecasts of future obesity rates are worthless and so are these.

While some of the basic facts in the Times story are correct, the headline claim that 'patients should be weighed during routine GP appointments' is not being made by anybody, as far as I can see - not in the study and not in the press release. The BBC has a somewhat more accurate report of the study here.

Verdict: Mostly bad journalism

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