Using data from two population-based birth cohorts, Danielle Belgrave and colleagues examine the evidence for atopic march in developmental profiles for allergic disorders. Please see later in the article for the Editors' Summary
Background Studies have shown an inverse association of pet ownership with allergy but inconclusive findings for asthma. Objective To investigate whether pet ownership during pregnancy and childhood was associated with asthma and atopy at age 7 years in a UK population-based birth cohort. Methods Data from the Avon Longitudinal Study of Parents and Children (ALSPAC) were used to investigate associations of pet ownership at six time-points from pregnancy to age 7 years with asthma, atopy (grass, house-dust mite, and cat skin prick test) and atopic versus non-atopic asthma at age 7 years using logistic regression models adjusted for child's sex, maternal history of asthma/atopy, maternal smoking during pregnancy and family adversity. Results 3,768 children had complete data on pet ownership, asthma and atopy. Compared with non-ownership, continuous ownership of any pet (before and after age 3 years) was associated with 52% lower odds of atopic asthma (odds ratio [OR] 0.48, 95% CI 0.34–0.68). Pet ownership tended to be associated with increased risk of non-atopic asthma, particularly rabbits (OR 1.61, 1.04–2.51) and rodents (OR 1.86, 1.15–3.01), comparing continuous versus non-ownership. Pet ownership was consistently associated with lower odds of sensitization to grass, house-dust mite and cat allergens, but rodent ownership was associated with higher odds of sensitization to rodent allergen. Differential effects of pet ownership on atopic versus non-atopic asthma were evident for all pet types. Conclusions Pet ownership during pregnancy and childhood in this birth cohort was consistently associated with a reduced risk of aeroallergen sensitization and atopic asthma at age 7 years, but tended to be associated (particularly for rabbits and rodents) with an increased risk of non-atopic asthma. Clinical relevance The opposing effects on atopy versus non-atopic asthma might be considered by parents when they are deciding whether to acquire a pet.
Background Latent class analysis (LCA) has been used extensively to identify (latent) phenotypes of childhood wheezing. However, the number and trajectory of discovered phenotypes differed substantially between studies. Objective We sought to investigate sources of variability affecting the classification of phenotypes, identify key time points for data collection to understand wheeze heterogeneity, and ascertain the association of childhood wheeze phenotypes with asthma and lung function in adulthood. Methods We used LCA to derive wheeze phenotypes among 3167 participants in the ALSPAC cohort who had complete information on current wheeze recorded at 14 time points from birth to age 16½ years. We examined the effects of sample size and data collection age and intervals on the results and identified time points. We examined the associations of derived phenotypes with asthma and lung function at age 23 to 24 years. Results A relatively large sample size (>2000) underestimated the number of phenotypes under some conditions (eg, number of time points <11). Increasing the number of data points resulted in an increase in the optimal number of phenotypes, but an identical number of randomly selected follow-up points led to different solutions. A variable selection algorithm identified 8 informative time points (months 18, 42, 57, 81, 91, 140, 157, and 166). The proportion of asthmatic patients at age 23 to 24 years differed between phenotypes, whereas lung function was lower among persistent wheezers. Conclusions Sample size, frequency, and timing of data collection have a major influence on the number and type of wheeze phenotypes identified by using LCA in longitudinal data.
The current air quality limit values for airborne pollutants in the UK are low by historical standards and are at levels that are believed not to harm health. We assess whether this view is correct. We examine the relationship between common sources of airborne pollution and population mortality for England. We use data at local authority level for 1998-2005 to examine whether current levels of airborne pollution, as measured by annual mean concentrations of carbon monoxide, nitrogen dioxide, particulate matter less than 10 microm in diameter (PM(10)) and ozone, are associated with excess deaths. We examine all-cause mortality and deaths from specific cardiovascular and respiratory causes that are known to be exacerbated by air pollution. The panel nature of our data allows us to control for any unobserved time-invariant associations at local authority level between high levels of air pollution and poor population health and for common time trends. We estimate multi-pollutant models to allow for the fact that three of the pollutants are closely correlated. We find that higher levels of PM(10) and ozone are associated with higher mortality rates, and the effect sizes are considerably larger than previously estimated from the primarily time series studies for England.
conceived the study idea and design. J.G. and D.F. provided input on exposure modelling. M.B. and R.G. provided input on the methodology for analysing the data. Y.C. and A.L.H. did the main data analyses and wrote the manuscript. M.Z. provided input on the profile regression analysis. All authors (i) provided substantial contributions to the conception or design of the work, or the acquisition, analysis, or interpretation of data for the work,(ii) revised the manuscript for important intellectual content, (iii) approved the final version, and (iv) agreed to be accountable for all aspects of the work. The corresponding author had full access to all the data in the study and had final responsibility for the decision to submit for publication.
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