摘要：Objectives. We investigated the role of infant bedding items, as part of a composite bedding environment, in the development of childhood wheezing. Methods. This prospective cohort investigation involved 863 children who participated in an infant survey in 1988 and an asthma study in Tasmania, Australia, in 1995. The derived 3 composite infant bedding categories corresponded to increasing numbers of house dust mite (HDM)–rich bedding items used. Outcomes measured included recent and frequent wheezing. Results. Composite infant bedding used was associated with recent wheezing. Effects increased at increasing levels of HDM–rich bedding items used. Effects were further enhanced by home environmental factors of bedroom heating, recent bedroom painting, and absence of bedroom carpeting. When any 2 or more of these environmental factors were present, a strong dose–response relationship was evident. Conclusions. Our results show that bedding exposures in infancy are prospectively associated with childhood wheezing and that home environmental conditions may modify this association. The reasons for the changing incidence of childhood asthma over time are unclear. The indoor environment, in particular exposure to house dust mite (HDM) allergens, is an area of concern. 1 High rates of exposure to HDM allergens are associated with increased risks of subsequent HDM sensitization, but the role of HDM exposure in asthma is less clear. 2 Bedding is a significant source of HDM allergens, with infant bedding materials such as synthetic pillows and quilts 3 and sheepskins 4 harboring high HDM concentrations. One study involving adults showed that replacing old with new bed quilts led to a more than 10-fold reduction in airborne Dermatophagoides HDM allergen levels near the face during sleep. 5 HDM allergen levels associated with bedding have been shown to be more important than bedroom floor HDM levels in determining airway responsiveness 6 and asthma severity. 7 This may explain why a prospective association between infant bedroom floor HDM levels and asthma has been found in only 1 of 3 studies of which we are aware. 8 – 10 Furthermore, increased environmental exposures to endotoxins found in bedrooms have been postulated to influence risks of asthma and allergen sensitization. 11 , 12 Difficulty in measuring indoor exposures during infancy has been 1 problem hampering research on early life influences on childhood asthma. Detailed information on the infant sleep environment has not previously been readily available, but a recent cohort of infants in Tasmania, Australia, provides such information. Earlier studies focusing on this cohort have demonstrated that infant exposures to synthetic bedding items such as pillows, quilts, and cocoons are associated with wheezing in childhood. 13 – 15 Also, sheepskin use has been associated with HDM sensitization. 16 In contrast, type of bedroom carpeting 17 or infant mattress has appeared to be less important. 16 Moreover, with regard to childhood asthma, the environmental model for infant HDM exposure may not be one of single, major independent risk factors but rather one of several environmental determinants synergistically increasing infant HDM exposures. For example, bedroom heating increases HDM levels in bedding. 18 In addition to allergen exposure, environmental air quality may also be important, with substances such as volatile organic compounds (VOCs) possibly activating, enhancing, or otherwise potentiating allergen sensitization, whereas the presence of endotoxins may affect HDM sensitization. 11 Another approach to investigating the role of infant bedding and bedroom environment in the development of asthma is one in which (1) bedding exposure measurements are further quantified by considering bedding not as a single item but as a composite of items and (2) bedding–environment interactions are assessed. We used this approach, on the basis of a theoretical model of HDM bedding loads, to investigate infant sleeping environment and subsequent wheezing by the age of 7 years in the Tasmanian infant cohort.
