Dimensions of respiratory symptoms in preschool children: population-based birth cohort study.
BACKGROUND
A focus on distinctive collections of symptoms may be more informative of the probability of respiratory disease than individual and possibly transient phenotypes. However, such collections or components of overall symptomatology need to be valid, and their relationship established with the known risk factors and physiologic measures.


OBJECTIVE
To analyze detailed parentally reported respiratory symptoms by principal components analysis and derive symptom components; to examine the relationship of such components with measures of lung physiology and atopy.


METHODS
An unselected, population-based birth cohort (n = 946).


RESULTS
Interviewer-administered questionnaires, lung function (specific airway resistance [sRaw]), airway reactivity (dry air challenge), and atopic status were obtained at ages 3 and 5 years; principal components analysis and multivariate analysis of variance were used to analyze the data. The four-component solution (wheeze, cough, colds, chronic symptoms) explained 53.2% of the variance in symptoms at age 3, and the five-component solution (wheeze, wheeze with irritants, wheeze with allergens, cough, chest congestion) explained 49.8% of variance at age 5. The multivariate analysis revealed novel relationships between symptoms, risk factors for asthma, and measures of lung function. At age 3, sRaw and the interaction between maternal asthma and child's atopy were not only related to wheeze but also independently to the cough component. At age 5, overall wheeze and allergic wheeze were related to lung function and airway reactivity; child's atopy was only related to symptoms when considered as a continuous trait.


CONCLUSIONS
Our analysis supports the need to move beyond the presence or absence of individual symptoms. Syndromes of coexisting symptoms more likely reflect underlying pathophysiologic processes.
Smith
Jaclyn A
JA
1Respiratory Research Group, University of Manchester, Manchester M23 9LT, UK. jacky.smith@manchester.ac.uk
Drake
Richard
R
Simpson
Angela
A
Woodcock
Ashley
A
Pickles
Andrew
A
Custovic
Adnan
A
D001249:Asthma / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology; D002675:Child, Preschool; D003371:Cough; D004739:England / Q000453:epidemiology; D006306:Health Surveys; D006801:Humans; D008487:Medical History Taking; D015999:Multivariate Analysis; D010641:Phenotype; D025341:Principal Component Analysis; D011446:Prospective Studies; D015203:Reproducibility of Results; D012129:Respiratory Function Tests; D012135:Respiratory Sounds; D012307:Risk Factors; D012882:Skin Tests; D011795:Surveys and Questionnaires