Recente onderzoeken als de Helena, Saskatoon en Pueblo studies, die zwaar onder kritiek staan van experts als Dr. Siegel, beweren steevast weer dat er een sterk verband is tussen het aantal gevallen van hartaanvallen en het invoeren van rookverboden: door het invoeren van rookverboden zouden de aantallen drastisch dalen, beweren deze radicale anti-rokenonderzoekers.
Een nieuw onderzoek door Dr Saverio Stranges (Warwick Medical School, Coventry, UK) spreekt (tot de eigen verbazing van de onderzoeker) dit soort geluiden tegen. In zijn onderzoek analyseerde hij op een geheel nieuwe en betrouwbaarder manier de effecten van levenslange blootstelling aan omgevingsrook op de hoeveelheid hartaanvallen (Myocardial Infarcts, MI) die optraden. Zijn cijfers laten geen enkel verband zien.
Hoewel de onderzoeker geschokt is door zijn eigen resultaten zijn wij niet verbaasd. Al eerder toonden Dr. Enstrom en Dr. Kabatt in een van de grootste onderzoeken op dit gebied ooit, hetzelfde aan. Dat kwam hun op grote kritiek van hun ideologisch georiënteerde anti-rokencollega’s te staan. Deze beide onderzoekers hebben nu duidelijk, uit onverwachte hoek, steun gekregen voor hun conclusies.
Secondhand-smoke exposure over the course of a lifetime is not significantly associated with an increased risk of MI, according to the surprising results of a new study . Investigators point out, however, that exposure to secondhand smoke among nonsmokers has declined significantly in recent years, with less exposure in the workplace and public places as well as at home, and this declining exposure is likely the reason that secondhand smoke may not be as important a risk factor as previously believed.
“Exposure to secondhand smoke is declining, and this is a positive development,” lead investigator Dr Saverio Stranges (Warwick Medical School, Coventry, UK) told heartwire. If an individual quits smoking, depending on the duration of active smoking time, their coronary heart disease risk declines, and this risk reversal is likely the same reason for the lack of association with secondhand smoke and risk of myocardial infarction, he said. “In terms of coronary heart disease, this study can be viewed positively in light of the smoking bans that have occurred in the US, as these people have not been as exposed to secondhand smoke in recent years and consequently their cumulative lifetime risk is null.”
The results of the study are published in the October 9, 2006 issue of the Archives of Internal Medicine.
Risk reversal due to public smoking bans?
Speaking with heartwire, Stranges said that during the past two decades several published studies have reported on the relationship between coronary heart disease and exposure to secondhand smoke. In addition to these studies, as well as the biological plausibility, reviews from meta-analyses indicate that exposure to secondhand smoke is associated with a 25% to 30% increased risk of coronary heart disease among never-smokers. Stranges expressed dissatisfaction, however, with previous research, as difficulties in assessing exposure have been difficult, with researchers relying on proxy measures of exposure, such as spousal smoking status or cotinine levels, a nicotine metabolite with a relatively short half-life.
In this most recent study, Stranges and colleagues sought to assess exposure to secondhand smoke from different sources over a lifetime, allowing the group to test the association between lifetime cumulative exposure to secondhand smoke and risk of MI among nonsmokers. Using data from a population-based, case-control study of residents aged 35 to 70 years in New York State, 1541 never-smokers, of whom 284 were discharged alive after MI and 1257 who served as controls, were included in the analysis. Collecting data between 1995 and 2001, study subjects were asked to report their exposure to secondhand smoke at home, at work, and in public settings from childhood to their present age to form a cumulative lifetime exposure measure.
After adjustment for covariates, secondhand smoke exposure was not significantly associated with the risk of myocardial infarction, although there was a trend toward an increased risk (odds ratio 1.19; 95% CI 0.78-1.82). Data also revealed evidence of declining trends in the prevalence of secondhand-smoke exposure for both men and women and from all three settings, with declining exposure strongest at work and at home.
“The findings may be surprising if we expect exposure to secondhand smoke to be related to coronary disease, especially in light of previous studies showing strong associations between exposure and coronary risk,” said Stranges. He pointed out, however, that some studies have shown exposure to secondhand smoke to be associated with a 40% increased risk of coronary heart disease, a number he considers too high. “Aside from ideological positions on this issue, we need to be careful in both directions. Clearly, I don’t think the association is as large as that. We found a point estimate of 1.19, something that is quite consistent with what we expected, and this increased risk was even higher in men, although not significant.”
Dave Kuneman, Research Director van de Smokersclub, over de ‘verklaring’ door Dr. Stranges:
“I would not accept dr strange’s explanation of why they found a lower, and statistically insignificant effect. he claimed it is because nonsmokers are exposed less today, than years ago. however, this was a case controlled study. he identified nonsmokers who were still exposed to lots of ETS for his study. Therefore, they were still looking at data representing the exposure which was common years ago.
if anything, the lower exposure in the control group, should have magnified the effect in the group still exposed, since all these studies simply look for the ratio between the exposed, and nonexposed.”