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Low level second-hand smoke exposure does not increase CVD risk in elderly

Heart 2010; 96: 854–859

Exposure to second-hand smoke (SHS) at low levels does not increase the risk for coronary heart disease (CHD) and stroke among British adults aged 60 years or older, UK researchers report.


In the Heart journal, Barbara Jefferis from University College London, and colleagues comment: "The results suggest that the lower levels of cotinine prevailing in the UK in 1998–2001, even before the introduction of legislation to reduce SHS exposure in public places, were not apparently associated with any marked increase in CHD or stroke risk in older people." For the prospective study, 8512 individuals aged 60 to 79 years were enroled between 1998 and 2001. The participants’ SHS exposure, based on serum cotinine levels in fasting blood samples, was measured alongside their risk for cardiovascular disease (CVD).

After excluding patients with a history of myocardial infarction (MI) or stroke and current smokers of at least 10 cigarettes a day, 5680 individuals with no history of CVD were included in the analysis. The participants were grouped into 5374 non-smokers and 306 who smoked 1–9 cigarettes a day.

During the median follow-up of 7.8 years, there were 217 new MI cases and 176 new stroke cases.

After adjusting for age, gender, and region of residence, the risk for MI in non-smoking individuals was increased only slightly in those with higher serum cotinine levels (0.06–0.19, 0.20–0.70, and 0.71–15.00 ng/ml), compared with those with low serum cotinine levels (≤0.05 ng/ml), at 0.92-, 1.07-, and 1.09-fold (p for trend=0.69), respectively.

The findings for stroke were similar, with the risk increased a corresponding 0.82-, 0.74-, and 0.69-fold (p for trend=0.065).

Further adjustments for sociodemographic, behavioural, and CVD risk factors had little effect on the associations, the authors note.

Individuals who smoked 1–9 cigarettes a day (average cotinine level 104.57 ng/ml) did not have a significant increase in stroke risk (hazard ratio 1.03). However, MI risk was 2.14-times greater in these individuals than in non-smokers with cotinine levels ≤0.05ng/ml.
Jefferis and team conclude that, despite the lack of a notable association between the lower levels of cotinine found among the elderly UK population and MI or stroke risk, "further evidence from pooled analyses of large population studies, including people of working age, are needed to establish the associations between low level SHS exposure and coronary heart disease risk."


Read the abstract 


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