Exercise intolerance in obese children--is it asthma?
Asthma is the most common chronic disease of childhood. It is estimated that 11.2% of the U.S. population has at some time been diagnosed with asthma, (1) and that about 5 million children across the U.S. are affected. (1) Asthma is the leading cause of school absenteeism due to chronic illness. (2) Untreated asthma may result in serious consequences, including lost school or work days, costly hospitalizations, and possibly death. Obesity (defined as body mass index > 95th percentile for age) is increasing in prevalence in children. Data from NHANES I (1971-1974) to NHANES 2003-2004 show increases in overweight among all age groups: Among preschool-aged children, aged 2-5 years, the prevalence of overweight increased from 5.0% to 13.9%; among school-aged children, aged 6-11 years, the prevalence of overweight increased from 4.0% to 18.8%; and among school-aged adolescents, aged 12-19 years, the prevalence of overweight increased from 6.1% to 17.4%. (3) Given the increasing prevalence of both asthma and obesity in childhood, it is possible that a link exists between these two conditions. The medical literature has few studies that address this question.
Gold et al examined the incidence of asthma in a longitudinal study of 9,828 children age 6 - 14 years in six US cities over a five year period. (4) Girls who were heavier at baseline were more likely to have asthma and the risk of developing asthma over the observation period increased with increasing BMI. Similarly, Castro-Rodriguez, et al found that girls who became overweight or obese between ages 6 and 11 were seven times more likely to develop new asthma between ages of 11 and 13 years. (5) A relationship between BMI at age 6 and wheezing prevalence at any age was not found. In an analysis of outcomes of childhood asthma in adolescent years, Guerra, et al found that the mean BMI was higher in a group with poorly controlled asthma (6) suggesting that obesity adversely affects asthma control. Other studies have suggested that weight reduction improves symptoms and lung function in obese adults with asthma. (6,7) Obese individuals often have exercise intolerance which is attributed to deconditioning. The present study sought to provide information on the prevalence of undiagnosed asthma in obese children who complain of shortness of breath with exercise.
Children age 6 to 18 years were eligible for the study if they had BMI > 95th percentile for age, and exercise induced shortness of breath (see figure 1). The questions outlined in figure 2 were asked, and to qualify for the study, the first two questions had to be answered affirmatively, and the last three had to be answered "no". Standard spirometry was performed at rest, with measurement of forced vital capacity (FVC), and forced exhaled volume in one second (FEV1). The reference values of Polgar (9) for pediatric patients were used, with normal values for these parameters and for the ratio of FEV1/FVC being greater than 80%. If the test was deemed abnormal, an inhaled bronchodilator (albuterol) was administered via jet nebulizer, and the test was test repeated after 10 to 15 minutes. An increase in 12% in FEV1 indicated a positive response to bronchodilator. If there was no response to bronchodilator, or if the test was deemed normal, patients were scheduled for an exercise challenge test, using a standard treadmill exercise protocol. (10) After completing the exercise protocol, spirometry was performed at 5, 10, 15, and 20 minutes, and a positive response was a drop in FEV1 > 12% from baseline for the diagnosis of exercise induced asthma to be made. If there was no drop in FEV1, the test was deemed normal, and the results were interpreted as unlikely to be asthma
The proportion of tested children with asthma was calculated by dividing the number with either an abnormal spirometry with bronchodilator response, or a positive exercise test, by the total number of subjects enrolled. No other statistical analyses were performed.
[FIGURE 1 OMITTED]
Figure 2. Screening Questionnaire 1) Do you get out of breath with exercise or physical activity? 2) Do you have to stop exercising because of difficulty catching your breath? 3) Do you have asthma? 4) Are you using any inhalers/nebulizers or other treatments for breathing problems? 5) Has anyone prescribed Albuterol or other medications for breathing problems in the last year? If you answer "yes" to questions 1 and 2 and "no" to questions 3, 4, and 5 you will be eligible for the study.
Twenty patients were entered into the study (see Table 1). Their ages ranged from 7 to 16 years, and BMI ranged from 22.1 Kg/m2 to 61.3, Kg/m2 and nine were male. Mean BMI was. 37.9 Kg/m2. Of the 19 who completed the study, nine met criteria for asthma. Four had abnormal spirometry with significant bronchodilator response, another five had normal resting spirometry but had significant drop in FEV1 at exercise testing, and the remaining nine had normal spirometry and no drop in FEV1 post exercise.
In this study, nearly half of the obese children and adolescents who become short of breath with exertion were found to have asthma. This finding suggests that many obese children are not just "deconditioned", but may actually have exercise induced bronchospasm. Although several recent studies link obesity and asthma, to our knowledge this is the first prospective study that examines the frequency of asthma in obese children. Being able to exercise is an important factor in most weight loss programs. Gym coaches and teachers also tend to attribute obese students inability to exercise as being "out of shape". Physicians and school officials alike should consider the possibility of asthma in children and adolescents who are overweight and who have difficulty exercising.
The study was limited by several factors. First, the population eligible for enrollment was a very select one, drawing from obese patients who were referred for weight management to an adolescent cardiovascular fitness program. Other obese children not referred to the program may also have asthma, at rates higher or lower than detected in our study. We also did not seek to utilize a control group of non-obese patients with dyspnea on exertion, to compare their rates of asthma to those of the obese study population.
This is a small pilot study meant to provide information on the association between dyspnea on exertion and exercise induced asthma; we did not intend to imply causality. Larger studies are needed to further support this association, as well as to evaluate possible mechanisms. Future trials are needed to evaluate whether weight loss would improve asthma in overweight children, and conversely, whether improved asthma control would foster weight loss in this population.
Another limitation is that an asthma diagnosis or any previous use of asthma medications excluded patients from entry into the study. Several patients were not offered the study because they had received bronchodilator medications recently for "bronchitis", but still do not endorse an asthma diagnosis. This may cause us to underestimate the actual rates of asthma in those obese patients. Although those in the study who demonstrated exercise induced bronchospasm were offered treatment for asthma, no follow up data was collected on the health and the success with weight loss among our study population. While it would be reasonable to assume that treatment of their asthma makes it easier to exercise, and therefore lose weight, no data are available currently to confirm this hypothesis. It is possible that exercise-induced asthma may have an exacerbating effect on the development of obesity; these children may have learned at an early age that they do not enjoy physical activity, but not be certain why. This nearly 50 percent incidence of asthma in obese children confirms previous observations demonstrating a link between obesity and asthma, although the question whether the link is causal deserves further study.
(1.) Centers for Disease Control and Prevention. Behavioral Risk Factor Surveillance System. Available on line at www.cdc.gov.brfss
(2.) U.S. Environmental Protection Agency. Information retrieved March, 2004 from www.epa.gov/asthma/introduction.html
(3.) Centers for Disease Control and Prevention, June, 2008. www.cdc.gov/nccdphp/dnpa/obesity/childhood/prevalence.htm
(4.) Gold, D.R, Damokosh, A.I., Dockery, D.W., Berkey, C.S. Body Mass Index as a Predictor of Incident Asthma in a Prospective Cohort of Children. Pediatric Pulmonology 36:514-521, 2003.
(5.) Castro-Rodriguez, J.A., Holberg, C.J., Morgan, W.J., et al. Increased Incidence of Asthmalike Symptoms in Girls Who Become Overweight or Obese during the School Years. Am J Respir Crit Care Med 163:1344-1349, 2001.
(6.) Guerra, S, Wright, A.L., Morgan, W.J, et al. Persistence of Asthma Symptoms during Adolescence; Role of Obesity Age at the Onset of Puberty. Am J Respir Crit Care Med 170:78-85, 2004.
(7.) Stenius-Aarniala, B, Poussa, T, Kvarnstrom, J, et al. Immediate and long term effects of weight reduction in obese people with asthma: randomized controlled study. BMJ 320:827-832, 2000.
(8.) Jakala, K, Stenius-Aarniala, B, Sovijarvi, A. Effects of weight loss on peak flow variability, airways obstruction, and lung volumes in obese patients with asthma. Chest 118:1315-1321, 2000.
(9.) Polgar, G, Promadhat, V. Standard values. In: Pulmonary Function Testing in children: techniques and standards. Philadelphia: W.B. Saunders, 1971. p 87-212.
(10.) ATS/ACCP Statement on Cardiopulmonary Exercise Testing. Am. J. Respir. Crit. Care Med. 167:211-277, 2003.
Robert A. Kaslovsky, MD
Pediatric Pulmonary Division Chief,
Baystate Children's Hospital,
Stephen B. Sondike, MD
Section Head, Adolescent Medicine,
WVU Physicians of Charleston and
Associate Professor of Pediatrics at
WVU Charleston Division
Stephanie Cummings, CMA
Table 1. All data subjects. Those with normal baseline spirometry are grouped together at the bottom of the table. Age/ Gender Height (cm) Weight (Kg) BMI Initial FVC 1 8/M 133 56 31.65 2.01 2 14/M 181 113 34.5 3.23 3 11/M 143 71 34.7 2.7 4 7/M 131 38 22.14 2.09 5 9/M 151.5 87.2 38.0 3.41 6 12/M 154 78.7 33.0 2.85 7 9/F 130.8 70.4 31.2 2.74 8 9/F 147 75 34.7 2.85 9 13/F 171 138 47.18 4.38 10 12/F 147 75 34.7 2.49 11 8/M 138 59 31.0 2.23 12 16/F 162.5 162 61.3 2.46 13 12/F 148 78.5 35.8 2.86 14 8/F 125 46.0 29.4 1.59 15 15/F 150.4 99.0 39.7 3.69 16 13/M 170 118 40.8 4.30 17 11/F 169 141 49.4 3.93 18 11/F 155 68.8 28.6 3.2 19 9/M 169 141 49.4 3.95 20 13/F 171.2 151.7 51.8 5.54 Post Bronchchodilator Spirometry (FEV1) Age/ Gender Initial FEV1 FVC FEV1 improvement 1 8/M 1.47 2.37 2.06 40% 2 14/M 1.54 3.63 2.42 57% 3 11/M 2.13 2.75 2.06 -3% 4 7/M 0.92 2.09 1.13 11% 5 9/M 2.38 3.40 2.46 4% 6 12/M 2.21 3.6 3.02 37% 7 9/F 2.14 2.82 2.41 12% 8 9/F 2.47 2.97 2.4 -2% 9 13/F 3.71 4.29 3.93 6% Sent directly to 10 12/F 2.06 treadmill test N/A 11 8/M 1.53 [approximately N/A equal to] 12 16/F 3.07 [approximately N/A equal to] 13 12/F 2.47 [approximately N/A equal to] 14 8/F 1.54 [approximately N/A equal to] 15 15/F 3.03 [approximately N/A equal to] 16 13/M 3.65 [approximately N/A equal to] 17 11/F 3.56 [approximately N/A equal to] 18 11/F 2.85 [approximately N/A equal to] 19 9/M 3.56 [approximately N/A equal to] 20 13/F 4.13 [approximately N/A equal to] Age/ Gender Treadmill Test Likely Asthma 1 8/M N/A Yes 2 14/M N/A Yes 3 11/M Positive Yes 4 7/M Positive Yes 5 9/M Positive Yes 6 12/M N/A Yes 7 9/F N/A Yes 8 9/F Negative No 9 13/F Refused Unknown 10 12/F Positive Yes 11 8/M Positive Yes 12 16/F Negative No 13 12/F Negative No 14 8/F Negative No 15 15/F Negative No 16 13/M Negative No 17 11/F Negative No 18 11/F Negative No 19 9/M Negative No 20 13/F Negative No