Increasing body mass index from age 5 to 14 years predicts asthma among adolescents: evidence from a birth cohort study.
BACKGROUND
Obesity and asthma are common disorders, and the prevalence of both has increased in recent decades. It has been suggested that increases in the prevalence of obesity might in part explain the increase in asthma prevalence. This study aims to examine the prospective association between change in body mass index (BMI) z-score between ages 5 and 14 years and asthma symptoms at 14 years.


METHODS
Data was taken from the Mater University Study of Pregnancy and its outcomes (MUSP), a birth cohort of 7223 mothers and children started in Brisbane (Australia) in 1981. BMI was measured at age 5 and 14 years. Asthma was assessed from maternal reports of symptoms at age 5 and 14 years. In this study analyses were conducted on 2911 participants who had information on BMI and asthma at both ages.


RESULTS
BMI z-score at age 14 and the change in BMI z-score from age 5 to 14-years were positively associated with asthma symptoms at age 14 years, whereas BMI z-score at age 5 was not associated with asthma at age 14. Adjustment for a range of early-life exposures did not substantially alter these findings. The association between change in BMI z-score with asthma symptoms at 14 years appeared stronger for male subjects compared with female subjects but there was no statistical evidence for a sex difference (P=0.36).


CONCLUSIONS
Increase in BMI z-score between age 5 and 14 years is associated with increased risk of asthma symptoms in adolescence.
Mamun
A A
AA
Longitudinal Studies Unit, School of Population Health, University of Queensland, Brisbane, Australia. mamun@sph.uq.edu.au
Lawlor
D A
DA
Alati
R
R
O'Callaghan
M J
MJ
Williams
G M
GM
Najman
J M
JM
D000293:Adolescent; D017677:Age Distribution; D001249:Asthma / Q000453:epidemiology*; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D015986:Confounding Factors, Epidemiologic; D005260:Female; D006801:Humans; D008297:Male; D011247:Pregnancy; D015995:Prevalence; D011446:Prospective Studies; D011793:Queensland / Q000453:epidemiology; D017678:Sex Distribution; D012907:Smoking / Q000009:adverse effects; D012959:Socioeconomic Factors