Purpose: To assess the relationship between asthma, body mass index (BMI) and aerobic performance, as indicated by a shuttle test.
Methods: 20,577 participants (10,413 boys) from the SportsLinx serial cross-sectional study participated. Parental reports of asthma status and home postcode data were gathered from consent forms. Stature, sitting stature and body mass were measured and BMI, somatic maturity and indices of multiple deprivation scores (IMD) were derived. Performance on the 20 m multi-stage shuttle runs test (20mSRT) was used to estimate cardiorespiratory fitness (CRF).
Results: Asthma [F (1, 17,015) = 82.26, P < 0.01] and gender [F (1, 17,015) = 678.491, P < 0.001] significantly influenced 20mSRT. The addition of BMI, maturity and IMD to the model did not alter these significant effects. There was a significant interaction between 20mSRT and BMI [F (1, 16,723) = 132.80, P < 0.01], with a significant decrease in 20mSRT from the 50th BMI percentile upwards [t (16,699) = 36.88, P < 0.01]. Binary logistic regression revealed gender and 20mSRT to be significant predictors of asthma occurrence; BMI SDS just reached significance whilst maturity and IMD were not significant contributors to the model.
Conclusions: This study demonstrates the negative influences of low CRF and high BMI on the risk of asthma occurrence in pre-pubertal children. Furthermore, it highlights the significant influence of BMI on CRF, revealing these effects to be manifest considerably below those BMI percentiles conventionally associated with being overweight or obese.