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Passive smokers' fourfold CHD risk

The impact of passive smoking on the risk of developing coronary heart disease has been hugely underestimated, a 20-year landmark study has found.

Researchers said the risk was nearly four-fold higher in non-smokers with high exposure to passive smoke, such as cigarette smoking by a partner, compared with non-smokers with low exposure.

GPs should regard non-smokers who live with a smoker as a high-risk patient based on the results and should consider calling them in to assess coronary risk, experts said.

Study lead Professor Peter Whincup, professor of cardiovascular epidemiology at St George's Hospital Medical School, London, said the effect of passive smoking by someone you live with was originally thought to increase CHD risk by 30 per cent.

The study followed 2,105 non-smoking men from the British Regional Heart Study and measured levels of cotinine in their blood. Cotinine is a marker in the blood that shows how much cigarette smoke a person has been exposed to. Of these, 308 suffered a major CHD event during follow-up.

The British Regional Heart Study was funded by the Department of Health and the British Heart Foundation. It followed up 4,252 men in 1998/2000 from a cohort recruited in 1978/80.

During the first five years of follow-up, patients with the highest levels of cotinine (0.8-14ng/ml) in the blood had 3.82 times the risk of having a cardiac event compared with patients with the lowest levels (0-0.7ng/ml).

The results, presented at the Society for Social Medicine conference in Manchester earlier this year, showed after 20 years patients with the highest cotinine levels were 46-65 per cent more likely to suffer a cardiac event than patients with the lowest.

Dr Mike Kirby, a GP in Letchworth, Hertfordshire, and a member of the Primary Care Cardiovascular Society, said GPs and practice nurses could use the results to call passive smokers in for a cardiac risk assessment.

'The results are quite useful because it gives us something definite to tell the patients and in this evidence- based environment, it could be used to focus our resources,' he added.

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