Drink and disease: how figures can confuse

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The annual compendium of alcohol statistics from the NHS Information Centre, published yesterday, shows that alcohol-related admissions to NHS hospitals have exceeded 1 million for the first time, reaching 1,057,000.

The increase on the 2008-09 figure (945,000) is 12 per cent, at a time when the amount of alcohol people say they drink is declining. The proportion of men drinking more than 21 units a week fell by two percentage points, from 28 to 26 per cent, and the number of women drinking more than 14 units by one percentage point, from 19 to 18 per cent, between 2008 and 2009.

Total consumption rose slightly, from an average of 1,149 ml per person per week to 1,190 ml per person as the UK emerged from the recession, but this was still below the 2007 level of 1,275 ml. Alcohol-related deaths – that is, those caused by conditions directly linked to alcohol – fell from 6,768 in 2008 to 6,584 in 2009. Much of the fall was attributable to a fall of nearly 250 in deaths from alcoholic liver disease.

So there is much to celebrate in the report. Even the minor tables, such as the ones showing the number of people aware of the daily drinking limits, are encouraging. In 2009, 75 per cent of respondents of the ONS’s Opinions Survey said they were aware of the limits, against 67 per cent in 2008. This is the highest figure ever recorded.

Yet I will wager that tomorrow’s newspapers will headline their stories “More than a million admitted to hospital as a result of drink” – or something a bit snappier conveying the same message. That’s the headline on the NHS IC’s press release, which goes on (erroneously) to quote Tim Straughan, Chief Executive of the centre, as saying: “Today’s report shows the number of people admitted to hospital each year for alcohol-related problems had tapped 1 million for the first time”.

Wrong. Why? It is the number of admissions that has topped 1 million, not the number of people. Some people are bound to have been admitted more than once, possibly repeatedly, so the number of people must be less than the number of admissions, and possibly less than a million. I bet nobody spots this mistake.

However, it’s a minor matter in the broader context. How is it that almost all the statistics related to alcohol can be moving in the right direction, yet the numbers of alcohol-related admissions keep going up at a dizzying rate?

It’s largely a function of methodology. Alcohol-related admissions are calculated in such a way that if you are unlucky enough, say, to be involved in a fire and admitted to hospital for the treatment of your burns, it will count as 0.38 of an alcohol-related admission – unless you happen to be under 15, when it won’t count at all.

If you drown, it counts as 0.34 of an alcohol-related admission – though most people unlucky enough to drown aren’t admitted to hospital. Getting chilled to the bone (accidental excessive cold) counts for 0.25 of an admission, intentional self-harm to 0.20 per cent of an admission.

These fractions apply whether or not there was any evidence you had been drinking before these disasters befell you.

Of course, much greater contributions to the total are made by conditions such as high blood pressure, which accounted for 383,900 admissions – more than a third of the total. Around a third of admissions for hypertensive diseases in men aged between 25 and 65 are attributed to alcohol, and around a fifth in women. There are far more of these admissions than there are for fires or accidents, so they contribute a huge proportion of the total.  

Note that no account is taken of the amount these people actually drink. It is reasonable to suppose that only fairly heavy drinking could do enough damage to require an admission, but in calculating these figures the assumption is made that there is no threshold below which drinking is safe. So a third of all admissions for cardiac arrhythmias, for example, are attributed to drinking, even if the sufferer happens to be a teetotaller.

The result is paradoxical. Since the majority of people are moderate drinkers, the majority of alcohol-related admissions and deaths occur in moderate drinkers. The North West Public Health Observatory, which devised the method, reported that there were far more deaths from cancer of the oesophagus in women in the lowest alcohol category (156) than there were in the highest (23).

The paradox is this. “Safe” drinking limits (21 units a week for men, 14 for women) are promoted by the Government on the basis that if you stay within them, the chances of harm befalling you are small. Yet the alcohol-related admissions and deaths statistics include far more people who are modest drinkers than who are heavy drinkers. Am I alone in thinking there is something batty about this?

 As for the increases in these admissions over recent years, the report says that the methodology, in use since 2009, “represents a substantial change in the way the impact of alcohol on hospital admissions was calculated before”. That doesn’t stop the press release making a direct comparison between the 2009 figure (1,057,000 admissions) and the 2002-03 figure (510,800).

Given the trends in alcohol consumption over that time, this abrupt a change can only be the result of a change in the method of calculation, not in the actual admissions. Not only have the diseases wholly attributable to alcohol changed, but many of the alcohol attributable fractions have, too. Year-by-year comparison is almost impossible.

But the story plays well to the current belief that alcohol is out of control. The report is bound to be widely covered tomorrow. Just don’t believe everything you read.