percentile to less than the 95th percentile, normal or healthy weight from the 5th percentile to less than the 85th percentile, and underweight as less than the 5th percentile (CDC, 2021a). A study by Ekström and colleagues (2017) looked at BMI over time in children with and without asthma at age 2 months and at ages 1, 2, 4, 8, 12, and 16 years. Age-specific definitions for asthma were used. At ages 1 and 2 years, asthma was defined as at least three episodes of wheeze after 3 months of age and in the last 12 months, respectively, in combination with treatment with inhaled glucocorticosteroids and/or signs of suspected hyperreactivity without concurrent upper respiratory infection. At ages 4, 8, 12, and 16 years, asthma was defined as at least four episodes of wheeze in the last 12 months or at least one episode of wheeze during the same time period, in combination with occasional or regular treatment with inhaled glucocorticosteroids. Transient asthma was defined as fulfilling the definition of asthma at ages 1, 2, and/or 4 years but not Physiologic interaction of asthma and obesity Co-occurrence of asthma and obesity may be because of common disease-producing factors. These including environmental factors such as exposure to air pollutants and tobacco smoke, both in utero and as a child; a diet consisting of processed foods and saturated fatty acids; and low levels of vitamin D. Specific genes have been shown to be involved in both asthma and obesity. These include protein kinase C alpha, leptin, and beta-3 adrenergic receptor. In obese subjects who develop asthma, obesity may be the cause of airway disease. In individuals with asthma who become obese, the overweight could influence asthma severity as comorbidity. Breathing at reduced lung volumes also increases AHR, which seems to have a direct correlation with the worsening of BMI. Additionally, adipose tissue contributes to corticosteroid resistance, worsening asthma outcomes (di Palmo et al., 2021; Dixon & Nyenhuis, 2021; Dixon & Peters, 2018). It should be noted that although obesity does reduce the response to systemic corticosteroids or high-dose inhaled corticosteroids, this may be because of the fact that steroids target the immune processes that mediate allergic responses, but many obese subjects with severe asthma are nonatopic (Tashiro & Shore, 2019). Childhood obesity and asthma Zhang and colleagues (2020) followed kindergarten and first- grade students up to 10 years to examine the relationship of asthma and obesity. Nonobese children with diagnosed asthma were 37% more likely to become obese compared with children without asthma. However, the presence of obesity was not statistically significantly associated with asthma onset. These authors concluded that childhood asthma appears to increase the onset of obesity among schoolchildren, whereas the onset of obesity does not necessarily imply future asthma. The CDC (2021d) asserts that children who have obesity are more likely to develop asthma. The risk of developing obesity is nearly twofold higher at age 8 in children who suffered from asthma at 3 to 4 years of age (Contreras et al., 2018). Obese children tend to have increased asthma severity, poorer disease control, and lower quality of life. These children and adolescents also tend to have a decreased response to asthma medications, including a reduced response to inhaled corticosteroids. As a result, this group has a greater need for oral steroids and experiences more asthma exacerbations. Additionally, children hospitalized for asthma who were obese have longer lengths of stay and higher risk of mechanical ventilation. Obese children with asthma may also be more susceptible to having increased Relationship among asthma, obesity, and inactivity Understanding the relationship among asthma, obesity, and physical activity is challenging. Because exercise can trigger bronchoconstriction in persons with asthma, this might lead to reduced participation in physical activity. Conversely, some researchers have found that aerobic activity reduces asthma symptoms. A vicious cycle can ensue: Just as obesity can contribute to physical inactivity, having both obesity and asthma may further contribute to sedentary
at ages 8, 12, and 16 years. Persistent asthma was defined as fulfilling the definition of asthma at ages 1, 2, and/or 4 years and at ages 8, 12, and/or 16 years. Late-onset asthma was defined as fulfilling the definition of asthma at ages 8, 12, and/or 16 years but not at ages 1, 2, and 4 years. Transient overweight was defined as overweight at ages 2, 3, and/or 4 years but not at ages 8, 10, 12, or 16 years. Ekström and colleagues (2017) found that female children with persistent asthma had the highest BMI throughout childhood, and children without asthma had the lowest. This difference in BMI continued to increase with age. This relationship was also seen with girls with transient asthma and late-onset asthma, but it was not seen in boys. For girls, late-onset overweight was associated with late-onset asthma, and persistent overweight was associated with persistent asthma. Among boys, transient overweight was associated with transient asthma. Increasing weight gain can have profound implications on lung physiology. Restriction from upward diaphragmatic displacement occurs from fat deposits around the chest wall and abdomen, resulting in reduced total lung capacity (TLC) and low expiratory reserve volume. Obesity increases the collapsibility of peripheral airways, especially among those with late-onset asthma. The risk for AHR, which is contraction of the bronchi causing narrowing (constriction) of the bronchioles and impaired airflow, increases with BMI (Peters et al., 2018; Dixon & Nyenhuis, 2021). The observation that weight reduction with bariatric surgery improves asthma severity, control, AHR, lung function, and quality of life suggests a direct effect of obesity on asthma symptomatology. It should be noted that these improvements are seen in persons with late onset obesity-associated asthma. These same outcomes were not found for obese persons with early onset allergic disease. This suggests that the adult-onset (or late) form of asthma may be more directly caused by obesity than the early onset form, and that the early-onset form may require aggressive treatment of both the obesity and allergic inflammation (Umetsu, 2017). symptoms with exposure to indoor pollutants (Peters et al., 2018). Evidence-based practice! Obesity is a major preventable risk factor for pediatric asthma. Lang and colleagues (2018) looked at the relationship between overweight and obesity and asthma in childhood. They compared the incidence of asthma among overweight and obese children ages 2 to 17 years to children with healthy weights. Overweight was defined as a BMI in the 85th to 94th percentile; obesity was defined as a BMI equal to or greater than the 95th percentile. Healthy weight was a BMI percentile between the 25th and 64th percentiles. None of the children had an asthma diagnosis at baseline. The children were followed for an average of 4 years. The incidence for asthma was 17% greater among children who were overweight and 26% greater for children who were obese. When asthma was confirmed by spirometry, the increase rose to 29%. The researchers concluded that an estimated 23% to 27% of new asthma cases in children are directly attributable to obesity, and that in the absence of overweight and obesity, 10% of all cases of asthma could be avoided (Lang et al., 2018). behaviors and worsen asthma symptoms. Studies have shown that exercise-induced bronchospasm, measured by changes in FEV1, was more severe in children with asthma who were obese compared with those who were of normal weight (del Rio-Navarro et al., 2020). Children with poorly controlled asthma may avoid strenuous exercise (or a caregiver may restrict a child’s activities because of fear of developing asthma symptoms), so their asthma may appear to be well controlled (GINA, 2021).
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