Living with smoking grandparents and upper respiratory symptoms in children aged 3–6 years in Hong Kong

In 1992–93, a follow-up study was carried out on a cohort of children who had taken part in a survey on breast-feeding and fertility in Hong Kong in 1988–89 (T.H. Lam et al., unpublished data). The aim of the follow-up was to study the prevalence of acute and chronic respiratory illnesses and associated factors among young children in Hong Kong. One of the major factors studied was passive smoking. Since the prevalence of maternal smoking is low in Hong Kong (2.7% in our study and about 3% among mothers of primary-school children (Hedley et al., 1993)), the power of the study was not great enough to detect any significant statistical difference for maternal smoking. Therefore, we turned our focus to smoking by grandparents. Few studies of the effect of smoking by grandparents on child health can be found in the literature. Nevertheless, a case-control study on passive smoking and childhood hospitalization due to respiratory illness in Hong Kong showed an adjusted odds ratio of 2.4, which was of borderline significance (95% confidence interval, 0.98–6.1), but there was a significant linear trend for mode of exposure (Ching et al., 1995). In a study of primary-school children in Hong Kong, their respiratory symptoms were significantly associated with exposure to passive smoking from family members other than fathers, mothers and siblings ((Hedley et al., 1991). We suspected that most of these other family members were grandparents.