Are there 800 needless asthma deaths a year?

"More than 800 asthma sufferers die needlessly each year - two thirds of the annual fatality figure." - The Sun, 6 May 2014

Yesterday we voiced doubts over how the Sun and Daily Mail had interpreted figures from research into asthma deaths.

The estimate of 800 'needless' deaths from asthma is based on a misinterpretation of what a "potentially avoidable" death is, and on a comparison of two non-comparable groups. The figure is therefore not supported by the research's author.

Not all "potentially" avoidable deaths would have been avoided

The report looked at 195 people who had died of asthma. Of these deaths 130, or 67%, had at least one "potentially avoidable factor". These included aspects of their care, such as the expertise of diagnosing doctors, and of their own behaviour, such as whether they smoked.

However many of the deaths from asthma have multiple contributing factors, and the report's author told us that "some deaths will be inevitable." In fact, the report is careful to stress that it is not a study of the number of deaths that are avoidable.

The report doesn't therefore support the interpretation of the Sun and Mail that 800 asthma deaths each year are needless. While some of those 130 people may have lived longer if the potentially avoidable factors had been removed, the report doesn't speculate about how many would have, and certainly doesn't say that they all would.

The "800" deaths estimate doesn't compare like with like

The estimate was calculated by the two papers by applying the 67% figure from the report to Asthma UK's estimate that 1,200 people a year die from the condition.

But the study wasn't intended to make such an estimate, so it didn't look at a random sample of those who died from asthma.

The researchers filtered out some cases, such as where the person was 75 or over, and were unable to collect sufficient information on the medical histories of 270 people. And of the cases where there was enough information to be reviewed, an expert panel concluded that over a fifth had not died of asthma at all.

This means that the 67% figure only tells us about the presence of avoidable factors in the deaths of that particular group of 195 people, not about the total number in the UK.