Tomorrow at the World Conference on Tobacco or Health in Mumbai, researchers are scheduled to present the results of their investigation into the changes in acute coronary events in Scotland associated with the implementation of a national smoking ban.
According to the conference abstract: "Our study examined the impact of Scottish smoke-free legislation on hospital admissions for acute coronary syndrome. We collected data prospectively on all patients admitted to nine hospitals in the ten months prior to the legislation (June 05-March 06) and the same ten months following implementation (June 06-March 07). Acute coronary syndrome was defined as raised troponin following emergency admission for chest pain. ... In the 10 years prior to the study, there was a mean annual reduction of 3% (maximum 9%). ... Following the ban, ... admissions fell by 17% (14% among smokers, 19% among ex-smokers and 21% among never smokers). ... Our results suggest that smoke-free legislation is effective at reducing admissions among both non-smokers (due to reduced ETS exposure) and smokers (by encouraging them to reduce consumption or quit)."
The Rest of the Story
It will be most interesting to see whether or not the researchers present more recent national data from Scotland, which demonstrate that the declines in acute coronary events in Scotland during the first year after the smoking ban were offset by increases in those events during the second year. Thus, there was essentially no change in heart attack and angina admissions during the first two years following implementation of the smoking ban.
These data contradict the findings in the abstract and demonstrate that the conclusion in the abstract is incorrect.
The question is: will the researchers share these data, or will they only present the results of their original study, which is now outdated and whose findings have been negated?
The abstract itself is very misleading. It states that acute coronary syndrome was defined as elevated levels of cardiac troponin and that in the 10 years prior to the study there was a mean annual reduction of 3%. This is false. For the 10-year period prior to the study, there was not a mean annual reduction of 3% in acute coronary syndrome as defined by elevated levels of cardiac troponin.
In truth, for the 10-year period prior to the study, acute coronary syndrome was defined based on hospital discharge diagnosis as reported to the national health service. So the authors are comparing apples and oranges. They compare baseline annual decline in acute coronary syndrome diagnosed one way with intervention-period annual decline in the syndrome as diagnosed a completely different way.
Not only is this method invalid, but the abstract is misleading and gives a false impression of what the data actually show.
Should I hear from anyone who attends this session, I will report back on what data the researchers present (or do not present) at the conference.