OBESITY
Asthma and obesity, together and separately, are public health conditions with increasing prevalence (Dixon & Nyenhuis, 2021). Their exact relationship, however, is not clear: Does asthma lead to obesity? Does obesity lead to asthma? Numerous studies have linked these two disorders. Research demonstrates that the higher an individual’s body mass index (BMI), the higher the risk for developing asthma. Barros and colleagues (2017) found that obesity quadrupled the risk for having asthma. Compared with lean individuals, the risk of asthma is increased almost one and a half times for adults with a BMI of 30.0 to 34.9 and two and a half times for adults with a BMI of 50 and above. In some individuals, obesity precedes asthma, and obesity is a risk factor for the later development of asthma. In other individuals, asthma precedes obesity, suggesting that asthma may be a risk factor for the development of obesity. Asthma at the age of 3 to 4 years Asthma with obesity phenotype Asthma with obesity has been identified as a specific phenotype for asthma. Because asthma encompasses several processes with distinct mechanistic pathways (endotypes) and variable clinical presentations (phenotypes), understanding the variations associated with asthma with obesity is crucial for appropriate management for the individual with obesity. Obese patients with asthma may have prominent respiratory symptoms and little eosinophilic airway inflammation, which impacts treatment options used to maintain optimal control (GINA, 2021; Kuruvilla et al., 2019). Age of onset is an important predictor of the impact for the obese asthma phenotype (Di Genova et al., 2018). Early-onset asthma occurs before age 12 years and is seen equally in both females and males. These individuals experience a severe decrease in airway function, specifically with FEV1 and forced vital capacity (FVC). Early-onset asthma is atopic in nature, with severe AHR and high asthma symptomatology. Airway inflammation with early-onset asthma is eosinophilic in nature. Conversely, late-onset asthma occurs after age 12 years and is generally more common in females. There is minimal airway obstruction, and this type of asthma is usually nonatopic. There is less AHR with few asthma symptoms. Airway inflammation is neutrophilic in nature. Both of these obese asthma phenotypes, early-onset and late-onset, are characterized by a severe asthma with more exacerbations and poorer symptom control than in lean asthmatic patients. Asthma and Obesity Prevalence Asthma and obesity prevalence are public health issues that affect the healthcare system. Prevalence rates for asthma and obesity are increasing in the United States. Over the past several decades, obesity and asthma have increased in parallel in the United States (Dixon & Nyenhuis, 2021). For the years 2017 to 2018, the US adult obesity prevalence was 42.4%, an increase of almost 12% from 1999 to 2000. During this same time period, the prevalence of severe obesity increased from 4.7% to 9.2% (Centers for Disease Control and Prevention [CDC], 2021b). For children and adolescents aged 2 to 19 years in 2017 to 2018, obesity prevalence was 19.3%, affecting nearly 14.4 million children and adolescents. Obesity prevalence increased as age increased. Obesity prevalence was 13.4% among 2- to 5-year-olds, 20.3% among 6- to 11-year-olds, and 21.2% among 12- to 19-year-olds (CDC, 2021e). Body mass index BMI is a measure of body fat based on height and weight that applies to adult men and women. A BMI between 18.5 and 24.9 kg/m 2 is considered normal weight. Overweight is defined as a BMI of 25 to 29.9 kg/m 2 , obese is a BMI of 30 kg/m 2 or higher, and underweight is a BMI of less than 18.5 kg/m 2 . BMI can be used as a screening tool but is not diagnostic of the body fatness or health of an individual. The accuracy of BMI as an indicator of body fatness appears to be higher in persons with higher levels of BMI and body fat. Although a person with a very high BMI is likely to have high body fat, a relatively high BMI can be the result of either high body fat or high lean body mass, which
is reported to increase the risk of obesity nearly twofold by age 8 (Dixon et al., 2020). However, recent evidence indicates that in adults, asthma does not affect the risk of obesity (Sun et al., 2020; Xu et al., 2019). Self-Assessment Quiz Question #4 Which of the following is correct regarding changes in the prevalence of asthma and obesity? a. Both asthma and obesity have increased. b. Asthma has decreased; obesity has increased. c. Neither asthma nor obesity has significantly changed. d. Asthma has increased; obesity has decreased Lurbet and colleagues (2019) examined data from the Behavioral Risk Factor Surveillance System from 1999 to 2016 for those 18 years and older. The researchers found a substantial increase in the prevalence of obesity among individuals with asthma over the last 2 decades. The prevalence of obesity changed from 24.7% in 1999 to 41.1% in 2016 among those with asthma. It was also found that obesity rates increased more among those with asthma when compared to those who did not have asthma. The likelihood of becoming obese increased by 36% when comparing those with asthma and those without asthma during this same time period. Analysis showed that older, African American, and Hispanic individuals with asthma had higher rates of obesity. These findings suggest that obesity is a growing problem in individuals with asthma. It should be noted, however, that although asthma is more common in obese than nonobese individuals, the respiratory symptoms associated with obesity can be mistaken for asthma symptoms. For example, many patients with obesity can present with dyspnea on exertion. Because obesity directly alters lung mechanics by affecting airway wall thickness, respiratory rate, inspiratory effort, and promoting sleep apnea, these characteristics can confound the clinical evaluation of asthma and lead to a misdiagnosis of asthma in obese individuals. These characteristics, which are similar to those of someone with asthma, can lead to a misdiagnosis of asthma in obese individuals. It is essential to confirm an asthma diagnosis with objective measures demonstrating variable expiratory airflow limitation to prevent both under- and over-diagnosis of asthma in the person with obesity (GINA, 2021; Umetsu, 2017). No areas in the United States are insulated from these statistics. According to the CDC (2021c), all US states and territories had more than 20% of adults with obesity. The Midwest (33.9%) and South (33.3%) had the highest prevalence of obesity, followed by the Northeast (29.0%), and the West (27.4%). Current asthma prevalence was higher in the Northeast (8.3%) than in the South (7.7%), West (7.7%), and Midwest (7.6%; Elfin, 2021). Prevalence rates did not differ between metropolitan and nonmetropolitan areas. These statistics highlight that both asthma and obesity are issues that need to be addressed. It is important to keep in mind that although these two factors are associated, direct causation has not been determined. This would explain why geographic areas with high obesity rates do not necessarily have the highest asthma rates. would have implications for determining health status and risks (CDC, 2020). BMI is interpreted differently for children and teens, accounting for age and sex. For children and teens, BMI is reported as a percentile based on representative data of the United States population of 2- to 19-year-olds collected between 1963 to 1965 and 1988 to 1994. Obesity among 2- to 19-year-olds is defined as a BMI at or above the 95th percentile of children of the same age and sex. This would be interpreted as the child weighing more than 95% of all of the other children of the same age range and sex. Additional categories include overweight from the 85th
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