Recent figures published by the Health and Social Care Information Centre show that alcohol related deaths rose 4% in a year. This was described as ‘shocking’ by local councils. However as with all statistics, we need to look behind the numbers before we panic too much. First, how many people died due to alcohol consumption? The total was 6,830, according to the report. Is this a lot? We have no way of knowing without checking the total number of deaths, which turns out to be 501,424 in England and Wales over the same time period. Admittedly the inclusion of Wales increases the population by just under six percent, but adjusting for this I calculate that the number of deaths due to alcohol was around 1.45% of the total, which makes me a touch less worried than I was before. However the death rate due to alcohol is rising, so obviously we should be worried. Maybe not. In fact it may even be a good thing.
Let me explain. During the war, the Americans were worried about the number of their planes that were being shot down. They could add extra armour plating, but although this gave extra protection, it also increased the weight of the planes and slowed them down, making them even more vulnerable to enemy fire, so they decided to add some armour in the areas where it would be most effective. They examined planes that had returned from missions to see which parts had the most bullet holes and found the following. The engines had 1.11 bullet holes per square foot, the fuselage 1.73, the fuel system 1.55 and the rest of the plane 1.8. Clearly, the best place to put the extra armour was in the place with the greatest need, and they consulted top mathematician Abraham Wald. They didn’t get the answer they were expecting. He told them to put the extra armour on the engines. His reasoning, backed up by a lot of complicated looking maths was that the planes that had been hit on the engines had less chance of coming back, whilst the higher number of hits on the rest of the plane showed that these areas were less critical. In maths this is known as survivorship bias, and once you recognise it, it crops up every- where.
Going back to the death statistics, it seems clear that the health service is making progress in helping people to survive diseases that not long ago were deadly. What if there are more people dying of alcohol related diseases because they are no longer dying of smallpox, scurvy, polio or a whole range of other maladies which would once have proved fatal? It could be considered a positive result that more people are surviving long enough to succumb to afflictions that mainly affect older people. After all, we will all die someday and if one cause of death declines, another must increase.
However before we all go out and celebrate with a few pints, there is also another statistical pitfall to beware. This is confirmation bias, which leads people to be more likely to accept evidence which confirms their point of view. ‘Global warming is nonsense because one measuring station in the Himalayas was calibrated wrongly’. If you want reasons to show alcohol is harmful you will find them, likewise if you want evidence that it is safe. In the end, question everything. Look at who pays for studies, who publishes them and what their motivations are. It won’t prevent you being fooled, but it might make it a bit more difficult.