Is there any evidence that closing bars at 10pm will stem the spread of coronavirus?

It seems that every aspect of Covid-19 will be contested. Students of the history of public health politics will be having a strong sense of deja vu: the field is littered with heated debates that in essence are about numbers.

a group of people walking in front of a store: Photograph: Andy Rain/EPA

© Provided by The Guardian
Photograph: Andy Rain/EPA

Related: Pubs and restaurants urge PM to review 10pm curfew in England

As someone who has worked in the field of tobacco control for some 40 years, I have witnessed many such debates. First, there was the question of how risky smoking was; then the addictive nature of tobacco. There were questions over how much safer low-tar cigarettes were. Then, of course, there was the issue of the harmfulness of passive smoking. Most recently there was the claim that e-cigarettes were 95% less harmful than “normal” cigarettes.

To my mind these tobacco control dramas have had one important thing in common: a failure of some of those involved to use numbers as a way to achieve clarity. Instead vague quantification shapes a narrative. And that is exactly what we are seeing in the evolving arguments about the coronavirus.

A recent act in this pandemic drama centres on the policy of forcing bars and restaurants in England to close at 10pm. The prime minister claimed to have based this new rule on scientific evidence that much of the spread of the virus is taking place in bars late in the evening. He says that this is at least in part due to people having consumed quite a bit of alcohol by this time and so being less likely to respect social distancing rules.

This raises an important question. Does the government have a concrete estimate of the likely number of infections, hospitalisations and deaths averted by closing bars at 10pm? If so, what is the margin of error and what is the science on which it is based? Speaking personally I cannot recall the behavioural science subgroup of Sage – of which I am a participant – ever being asked about this. On a matter of such importance I would have expected advice to be sought, because the policy depends very largely on how people behave.

a crowd of people standing in front of a store: ‘Another important number is the potential loss of income for venues’: a street in Soho, central London, on 24 September.

© Photograph: Andy Rain/EPA
‘Another important number is the potential loss of income for venues’: a street in Soho, central London, on 24 September.

If behavioural scientists had been asked to provide input into an estimate of the impact of the 10pm bar closures, one source of available evidence would be the extent to which allowing bars to remain open later at night in England and Wales back in 2005 made any difference to alcohol consumption or binge drinking. This would provide at least some evidence as to what might happen if one were to now restrict licensing hours.

The answer appears to be that the impact was minimal. This may be for reasons that are not particularly informative in the current scenario. But it points to the possibility that restricting licensing hours would have a limited