But what does this 13% actually mean? What is it 13% of? In 2009/10 there were 5,837 admissions to hospital due to dog attacks. In 2011/12 the number was 6,580. That's an increase in 13 % or 743 cases. Is this a big problem for the NHS or society in general? In order to work that out we need to know the number of hospital admissions. In 2009/10 there were 6,430,372. This means that dog attacks represent 1 in 10,000 admissions. So a 13% increase is an increase from 0.0118% to 0.103%. This means that we are dealing with very small numbers which are unlikely to be of much clinical significance.
The same caution needs to be applied to other hospital statistics. Take for example the current debate about weekend working in the NHS. This has been fuelled by studies indicating that the risk of dying is greater if you are admitted to hospital at the weekend compared to a weekday. This is shown in a recent study which reported that the 30 day mortality was 16% greater if you are admitted at the weekend. But what does this mean? Is it for every 100 deaths during the week there are 116 at the weekend. We need to analyse the data further. 14.2 million people were admitted to hospital in 2009/10 and 187,337 died. This means that 1.3% of people admitted died. The rate of death if you were admitted at the weekend was 16% higher, in other words about 0.21%. This means that the chance of dying within 30 days of admission is 0.21% higher if you are admitted at the weekend compared to a weekday. Alternatively there is a 98% chance of survival if admitted on a weekday compared to a 97.68% chance if admitted at the weekend. Is this clinically significant? I would welcome your comments.