It is widely reported this week that heart attack admissions in Scotland have dropped by 17% among non-smokers this year since the smoking ban was introduced. This announcement was timed to coincide with the conference "Towards a smoke-free society", at which Scottish Government-commissioned studies evaluating the smoking ban were announced yesterday.

These results should be treated with considerable caution. Similar studies have been carried out in the US in relatively small populations, with apparently startling results, which seem to indicate the unquestionable health benefits of general smoking bans. However, in 2005, David Kunemann and Michael McFadden undertook a study with a database 1000 times larger than most famous studies ("Helena" and "Pueblo"); it demonstrated that dramatic drops in cardiac admissions did not occur in larger, more stable populations. All their figures were obtained from public records and are completely verifiable.

Statistically, it is much less likely large populations will experience unusual circumstances where ER admissions for heart attacks decline suddenly and randomly. However, if researchers sift through enough small local jurisdictions with smoking bans, it may be possible to find a few unusual circumstances in which a sharp decline in ER admissions for heart attacks has occurred at the same time a smoking ban took effect.

It is certain the agenda for this conference was clear - to extend restrictions on smoking - and that at the very least claims of a 17% drop in Scottish cardiac admissions over the past year were scarcely believable in the face of compelling evidence that such enormous drops do not occur in large population bases.

Belinda Cunnison, Convener, Freedom to Choose (Scotland), 58 Constitution Street, Leith, Edinburgh.