Kitty Ng

The effects of body weight on airway calibre

Increased wheeze and asthma diagnosis in obesity may be due to reduced lung volume with subsequent airway narrowing. Asthma (wheeze and airway hyperresponsiveness), functional residual capacity (FRC) and airway conductance (Gaw) were measured in 276 randomly selected subjects aged 28–30 yrs. Data were initially adjusted for smoking and asthma before examining relationships between weight and FRC (after adjustment for height), and between body mass index (BMI = weight·height−2) and Gaw (after adjustment for FRC) by multiple linear regression, separately for females and males. For males and females, BMI (±95% confidence interval) was 27.0±4.6 kg·m−2 and 25.6±6.0 kg·m−2 respectively, Gaw was 0.64±0.04 L·s−1·cmH2O−1 and 0.57±0.03 L·s−1·cmH2O−1, and FRC was 85.3±3.4 and 84.0±2.9% of predicted. Weight correlated independently with FRC in males and females. BMI correlated independently and inversely with Gaw in males, but only weakly in females. In conclusion, obesity is associated with reduced lung volume, which is linked with airway narrowing. However, in males, airway narrowing is greater than that due to reduced lung volume alone. The mechanisms causing airway narrowing and sex differences in obesity are unknown.

Repeatability of peak nasal inspiratory flow measurements and utility for assessing the severity of rhinitis

Background:  The measurement of peak nasal inspiratory flow (PNIF) provides a simple, cheap, fast and readily available tool for determining the extent of nasal airway patency. However, there are questions regarding its repeatability when used to assess the degree of nasal obstruction in large populations. Therefore, this study aimed to evaluate the repeatability of PNIF measurements and to assess their association with the signs and symptoms of rhinitis.

Effects of gas and other fume emitting heaters on the development of asthma during childhood.

Background: Several studies have shown adverse effects of gas cookers and heaters on respiratory health. The long term effects of early life exposure to these appliances are not known. This study investigated the effect of exposure to fume emitting heaters, currently and during the first year of life, on the risk of asthma outcomes. Methods: A cross sectional study of schoolchildren (n = 627) aged 8–11 years was conducted in Belmont, Australia. Information on symptoms and heating types was collected by parent completed questionnaire. Atopy was assessed by skin prick tests and airway hyperresponsiveness (AHR) was assessed by histamine challenge test. Results: There was no association between the current use of fume emitting heaters and any of the asthma outcomes. However, having been exposed to fume emitting heaters during the first year of life was associated with an increased risk of having AHR (relative risk (RR) 1.47, 95% confidence interval (CI) 1.06 to 2.03), recent wheeze (RR 1.44, 95% CI 1.11 to 1.86), and recent wheeze + AHR (RR 2.08, 95% CI 1.31 to 3.31). Conclusion: If confirmed in other settings, this finding would require a review of the range of heating types that are appropriate for use in households in which young children live.

Weighted Road Density and Allergic Disease in Children at High Risk of Developing Asthma

Background Evidence for an association between traffic-related air pollution and allergic disease is inconsistent, possibly because the adverse effects may be limited to susceptible subgroups and these have not been identified. This study examined children in the Childhood Asthma Prevention Study (CAPS), potentially susceptible to air pollution effects because of a family history of asthma. Methods We examined cross-sectional associations at age eight years between road density within 75 m and 50 m of home address weighted by road type (traffic density), as a proxy for traffic-related air pollution, on the following allergic and respiratory outcomes: skin prick tests (SPTs), total and specific serum IgE, pre- and post-bronchodilator lung function, airway hyperresponsiveness, exhaled NO, and reported asthma and rhinitis. Results Weighted road density was positively associated with allergic sensitisation and allergic rhinitis. Adjusted relative risk (RR) for house dust mite (HDM) positive SPT was 1.25 (95% CI: 1.06–1.48), for detectable house dust mite-specific IgE was 1.19 (95% CI: 1.01–1.41) and for allergic rhinitis was 1.30 (95% CI: 1.03–1.63) per 100 m local road or 33.3 m motorway within 50 m of home. Associations were also seen with small decrements of peak and mid-expiratory flows and increased risk of asthma, current wheeze and rhinitis in atopic children. Conclusion Associations between road density and allergic disease were found in a potentially susceptible subgroup of children at high risk of developing atopy and asthma.