Background
Few studies have examined how developing obesity in early adulthood affects the course of asthma.
Objective
We analyzed lung function and asthma impairment and risk among non-obese children with asthma, comparing those who were obese in young adulthood to those who remained non-obese.
Methods
Post-hoc analysis of 771 subjects with mild-moderate asthma who were not obese (pediatric definition, body mass index (BMI) <95th percentile) when enrolled in the Childhood Asthma Management Program at ages 5–12 years. Subjects were then followed to age ≥ 20 years. For visits at ages ≥ 20 years, spirometry values as percent predicted and recent asthma symptom scores and prednisone exposure were compared between 579 subjects who were non-obese at all visits and 151 who obese (adult definition of BMI ≥ 30 kg/m2) on at least one visit (median number of visits when obese = 4, IQR 2–7).
Results
Compared to participants who were non-obese (BMI 23.4 ± 2.6 kg/m2), those who became obese (BMI 31.5 ± 3.8 kg/m2) had significant decreases in FEV1/FVC (p<0.0003) and FEV1 (p = 0.001), without differences in FVC (p=0.15) during visits at ages ≥ 20 years. For each unit increase of BMI, FEV1 percent predicted decreased by 0.29 (p=0.0009). The relationship between BMI and lung function was not confounded by sex or BMI at baseline. Asthma impairment (symptom scores) and risk (prednisone use) did not differ between the two groups.
Conclusion
Becoming obese in early adulthood was associated with increased airway obstruction, without impact on asthma impairment or risk.
SUMMARY
Rationale
To evaluate the appropriateness of spirometric and plethysmographic reference equations in healthy young children according to ethnic origin.
Methods
Spirometry data were collated in 400 healthy children (214 Black and 186 White) aged 6 to 12 years. Of these children, 68 Black and 115 White children also undertook plethysmography. Results were expressed as percent predicted according to commonly used equations for spirometry and plethysmography.
Results
Black children had lower lung function for a given height compared to White children. The magnitude and direction of these differences varied according to specific outcome. In the studied age range (6–12yrs) the ethnic-specific Wang equations were adequate for spirometry (mean results approximating 100% predicted in both ethnic groups). By contrast, significant differences were found between observed and % predicted plethysmographic lung volumes according to published equations derived from White children: Among the Black children, FRC and TLC for were, on average, 14% and 6% lower than predicted, whereas mean RV and RV/TLC were 4% and 10% higher. Among White children, the Rosenthal equations gave the best fit, with the exception of FRC which was, on average, 9% lower than predicted.
Conclusion
Spirometry equations may suffice in Black children; however interpretation of static lung volumes in Black children is limited due to inappropriate reference equations. More appropriate plethysmographic reference equations that are applicable to all ethnic groups across the entire age range are urgently needed.
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