They started by collating the information about what GP practices across England were doing, and used this to identify practices whose prescription rate for antibiotics was in the top 20 per cent for their local area. Half of this group of over-prescribers were then sent a letter, signed by the Chief Medical Officer, with feedback about their prescription habits, together with three specific things they could immediately do to reduce the number of prescriptions they gave out. For example, doctors can give patients delayed prescriptions, which enable them to get their medication in the future, so long as their symptoms persist. Alongside these tips, the doctors were told how their performance compared with others. They were informed that ‘the great majority (80 per cent) of practices in [your local area] prescribe fewer antibiotics per head than yours’. When Michael and his team compared the subsequent behaviour of those doctors who received the feedback letters to that of those who got no such letter, they were surprised by the impact. Over a six-month period, GP practices receiving the feedback letters prescribed an estimated 73,400 fewer antibiotic items than those that didn’t.
It was exactly this kind of thinking that former US president Obama had in mind when he explained why he only wore grey or blue suits when in office. ‘I’m trying to pare down decisions’, he explained to Vanity Fair. ‘I don’t want to make decisions about what I’m eating or wearing. Because I have too many other decisions to make.’
Contrary to popular belief, there isn’t a magic number of repetitions that result in a habit forming. Some say that you need to repeat an action fifty times or for twenty-one days, but very few researchers have actually looked at this question systematically. And those that have done tend to find that there isn’t a clear-cut answer to the question. In one of the few studies to have tracked the formation of healthy habits in real-world settings, researchers studied ninety-six students who had just moved to university and were encouraged to repeat behaviours in response to consistent cues (such as ‘going for a walk after breakfast’). They found that habits formed in some of the students after eighteen days, but for some it took much longer – up to 254 days. The average was sixty-six days.