Asthma trajectories in early childhood: identifying modifiable factors.
BACKGROUND
There are conflicting views as to whether childhood wheezing represents several discreet entities or a single but variable disease. Classification has centered on phenotypes often derived using subjective criteria, small samples, and/or with little data for young children. This is particularly problematic as asthmatic features appear to be entrenched by age 6/7. In this paper we aim to: identify longitudinal trajectories of wheeze and other atopic symptoms in early childhood; characterize the resulting trajectories by the socio-economic background of children; and identify potentially modifiable processes in infancy correlated with these trajectories.


METHODS
The Millennium Cohort Study is a large, representative birth cohort of British children born in 2000-2002. Our analytical sample includes 11,632 children with data on key variables (wheeze in the last year; ever hay-fever and/or eczema) reported by the main carers at age 3, 5 and 7 using a validated tool, the International Study of Asthma and Allergies in Childhood module. We employ longitudinal Latent Class Analysis, a clustering methodology which identifies classes underlying the observed population heterogeneity.


RESULTS
Our model distinguished four latent trajectories: a trajectory with both low levels of wheeze and other atopic symptoms (54% of the sample); a trajectory with low levels of wheeze but high prevalence of other atopic symptoms (29%); a trajectory with high prevalence of both wheeze and other atopic symptoms (9%); and a trajectory with high levels of wheeze but low levels of other atopic symptoms (8%). These groups differed in terms of socio-economic markers and potential intervenable factors, including household damp and breastfeeding initiation.


CONCLUSIONS
Using data-driven techniques, we derived four trajectories of asthmatic symptoms in early childhood in a large, population based sample. These groups differ in terms of their socio-economic profiles. We identified correlated intervenable pathways in infancy, including household damp and breastfeeding initiation.
Institut National d'Etudes Démographiques, Paris, France.
Lidia
L
Panico
Faculty of Medicine, University of Southampton, Southampton, United Kingdom.
Beth
B
Stuart
International Centre for Lifecourse Studies, Department for Epidemiology and Population Health, University College London, London, United Kingdom.
Mel
M
Bartley
International Centre for Lifecourse Studies, Department for Epidemiology and Population Health, University College London, London, United Kingdom.
Yvonne
Y
Kelly
D001249:Asthma / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology; D001942:Breast Feeding; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D015331:Cohort Studies; D004739:England / Q000453:epidemiology; D005260:Female; D006798:Housing; D006801:Humans; D007223:Infant; D008137:Longitudinal Studies; D008297:Male; D015233:Models, Statistical; D010641:Phenotype; D015995:Prevalence; D012135:Respiratory Sounds; D012307:Risk Factors; D012923:Social Class