A study in Tobacco Control concludes that banning smoking in public places has not driven smokers to increase smoking at home, as some critics of the legislation had warned. The study was widely reported in the British press, the Mirror headlining its story “Ban cuts cig use at home”.

But the results are not quite as clear-cut as the press coverage might imply. The authors compared the prevalence of smoking restrictions in the home in four European countries – Ireland, France, Germany and the Netherlands - before and after the introduction of public smoking bans in those countries. As a control they used data from the UK dating from the period (winter 2005-06 to winter 2006-07) before the ban was imposed here.

Home smoking bans increased in all five countries during the periods studied, but, say the authors, by more in the countries that had imposed public smoking bans than in the UK, which had yet to do so.

The increase in such bans was largely driven by smokers who had given up the habit. Since that was true of all five countries, they all saw increases in such bans – by 17 per cent in France, 22 per cent in the UK, 25 per cent in Ireland, 28 per cent in the Netherlands and 37 per cent in Germany.

At face value, these figures do not seem to justify the conclusions drawn, because the UK saw an increase in bans that, given the uncertainties, is not much different from the rest. And the authors do indeed acknowledge that the difference only reached statistical significance in the comparison between Germany and the UK.

In reaching even this modest conclusion, they do not seem to have taken into account that the “before and after” measures in the UK were only a year apart while those in Germany were two years apart. So the UK showed an increase of 22 per cent in full home smoking bans in a single year, and Germany an increase of 37 per cent in two years. Since the prevalence of home bans is determined by secular reduction in the number of smokers, the time periods over which such changes are measured make a big difference.

If we include bans that involve particular rooms as well as the entire home (partial bans), then the UK and Ireland are the only countries to show an increase in “full plus partial” bans over the periods studied, at least among those who declared themselves smokers at the first survey.  

The authors conclude: “Our finding strongly support the premise that smoke-free legislation does not lead to more smoking in smokers’ homes”. But it might be more accurate to say that in the periods studied, all five countries showed an increased tendency for people to ban or discourage smoking in their homes, whether or not a public ban was in force. The similarities between the five countries were far greater than the differences.