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Passive smoking and risk of coronary heart disease and stroke: prospective study with cotinine measurement

Peter H Whincup ¹, Julie A Gilg ¹, Jonathan R Emberson ², Martin J Jarvis ³, Colin Feyerabend ⁴, Andrew Bryant ⁴, Mary Walker ², Derek G Cook ¹

¹ Department of Community Health Sciences, St George's Hospital Medical School, London SW17 0RE
² Department of Primary Care and Population Sciences, Royal Free Campus, Royal Free and University College Medical School, London NW3 2PF
³ Cancer Research UK Health Behaviour Research Unit, Department of Epidemiology and Public Health, Royal Free and University College Medical School, London WC1E 6BT
⁴ Medical Toxicology Unit, New Cross Hospital, London SE14 5ER

British Medical Journal [06/30/04]

Objective To examine the associations between a biomarker of overall passive exposure to tobacco smoke (serum cotinine concentration) and risk of coronary heart disease and stroke.

Design Prospective population based study in general practice (the British regional heart study).

Participants 4729 men in 18 towns who provided baseline blood samples (for cotinine assay) and a detailed smoking history in 1978-80.

Main outcome measure Major coronary heart disease and stroke events (fatal and non-fatal) during 20 years of follow up.

Results 2105 men who said they did not smoke and who had cotinine concentrations <14.1 ng/ml were divided into four equal sized groups on the basis of cotinine concentrations. Relative hazards (95% confidence intervals) for coronary heart disease in the second (0.8-1.4 ng/ml), third (1.5-2.7 ng/ml), and fourth (2.8-14.0 ng/ml) quarters of cotinine concentration compared with the first (0.7 ng/ml) were 1.45 (1.01 to 2.08), 1.49 (1.03 to 2.14), and 1.57 (1.08 to 2.28), respectively, after adjustment for established risk factors for coronary heart disease. Hazard ratios (for cotinine 0.8-14.0 v 0.7 ng/ml) were particularly increased during the first (3.73, 1.32 to 10.58) and second five year follow up periods (1.95, 1.09 to 3.48) compared with later periods. There was no consistent association between cotinine concentration and risk of stroke.

Conclusion Studies based on reports of smoking in a partner alone seem to underestimate the risks of exposure to passive smoking. Further prospective studies relating biomarkers of passive smoking to risk of coronary heart disease are needed.