RESEARCH PAPERS

Effect of Passive Household Smoking Exposure on the Risk of Ischemic Heart Disease in Never-Smoke Female Patients in Hong Kong

Ding Ding, Jeffrey Wing-Hong Fung, Qing Zhang, Gabriel Wai-Kwok Yip, Chi-Kin Chan, Cheuk-Man Yu

The Chinese University of Hong Kong, Hong Kong

E-mail: cmyu{at}cuhk.edu.hk

Objective: To investigate the relation between household passive smoking exposure and risk of ischaemic heart disease (IHD) among female never-smoke 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 Odds ratios (OR) and 95% confidence intervals (CI) 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: 1.01-2.27, 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: 1.07-2.68, P=0.025). The OR was 1.52 for those exposed for 5 years (95% CI: 1.01-2.29, P=0.043) and was 1.82 for those exposed 4 hours per day (95% CI: 1.05-3.15, P=0.032). Similarly, the risk of IHD increased with cumulative exposure duration, with an OR of 1.53 (95%CI: 1.01-2.32, P=0.043) at the exposure level 5 pack-years, and an OR of 1.61 (95%CI: 1.03-2.52, 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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