RESEARCH PAPERS

Effect of household passive smoking exposure on the risk of ischaemic heart disease in never-smoke female patients in Hong Kong

D Ding^1,2, J Wing-Hong Fung¹, Q Zhang¹, G Wai-Kwok Yip¹, C-K Chan³, C-M Yu¹

¹ Division of Cardiology, Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong
² Huashan Hospital, Fudan University, Shanghai, China
³ Department of Medicine, Alice Ho Miu Ling Nethersole Hospital, Hong Kong

^{Correspondence to} Professor C-M Yu, Institute of Vascular Medicine, Division of Cardiology, Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong; cmyu{at}cuhk.edu.hk

Objective: To investigate the relation between household passive smoking exposure and risk of ischaemic heart disease (IHD) among never-smoke female patients by a retrospective case-control analysis.

Methods: This study recruited 314 patients with IHD who had never smoked and 319 controls who were admitted for other reasons in the same hospital during the same period. Subjects were interviewed about their exposure to household passive smoking. The dose metrics of passive smoking exposure were evaluated by using "pack years" and "hour years", which indicated the cumulative amount and duration of exposure. The ORs and 95% CIs were computed by unconditional logistic regression, adjusted for other risk factors.

Results: Subjects with passive smoking exposure were associated with higher risk of IHD (OR 1.51, 95% CI 1.01 to 2.27, p = 0.043) when compared to non-exposed subjects. Subjects exposed to an average of 1 pack of cigarette per day had an OR of 1.69 (95% CI 1.07 to 2.68, p = 0.025). The OR was 1.52 for those exposed for 5 years (95% CI 1.01 to 2.29, p = 0.043) and was 1.82 for those exposed 4 h per day (95% CI 1.05 to 3.15, p = 0.032). Similarly, the risk of IHD increased with cumulative exposure duration, with an OR of 1.53 (95% CI 1.01 to 2.32, p = 0.043) at the exposure level 5 pack years, and an OR of 1.61 (95% CI 1.03 to 2.52, p = 0.037) at the exposure level 20 hour years. There was a significant dose-response association between the exposure measures and risk of IHD (p<0.01 for trend).

Conclusion: Our data suggested an increased risk of IHD from passive household smoking in female never-smoke subjects, and demonstrated a dose-response association.

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