Metabolically unhealthy obesity associated with emergency department usage for asthma
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Among patients with asthma, those with metabolically unhealthy obesity had significantly greater odds for visiting an ED for asthma symptoms in the previous year than patients with metabolically healthy obesity, according to a study.
Metabolically unhealthy obesity (MUO) and waist circumference also served as better metrics for measuring asthma symptom control compared with BMI alone, the researchers wrote in the study, published in Annals of Allergy, Asthma & Immunology.
“The prevalence of obesity and asthma are increasing worldwide, and both contribute significantly to morbidity and mortality,” Benjamin Greiner, DO, MPH, a resident in the department of internal medicine at The University of Texas Medical Branch in Galveston, Texas, told Healio.
“Unfortunately, while the co-occurrence between obesity and asthma is well understood, it is currently unclear why obesity has such a negative impact on asthma outcomes,” he said.
Greiner and his coauthor, Micah Hartwell, PhD, a clinical assistant professor in the department of psychiatry and behavioral sciences at Oklahoma State University Center for Health in Tulsa, Oklahoma, hypothesized that certain metabolic factors common in obesity contributed to the poor outcomes that prompted the study.
“Interestingly, nobody had researched how the metabolic components of obesity correlated with asthma outcomes like hospitalizations and ED visits before,” Greiner said.
Defining MUO as a BMI of 30 kg/m2 or greater and increased waist circumference, insulin resistance, low physical activity, hyperlipidemia or hypertension, the researchers reviewed 2011 to 2016 data from the National Health and Nutrition Examination Survey.
The study population (44.25% men; mean age, 46.41 years) consisted of patients with asthma and metabolically healthy (n = 2,685,858) or unhealthy (n = 17,011,880) obesity, 52.98% of whom never smoked tobacco. Participants with unhealthy vs. healthy obesity were older (47.87 years vs. 41.22 years) and a greater proportion had current asthma (50.09% vs. 7.91%).
Additionally, participants with MUO were significantly more likely to have been evaluated in the ED for asthma in the previous year than those with metabolically healthy obesity (12.16% vs. 0.61%; OR = 3.53; 95% CI, 1.54-8.09). This significance persisted when the researchers adjusted for age (adjusted OR = 3.8; 95% CI, 1.6-9.04).
The researchers did not, however, find any significant difference between participants with metabolically healthy or unhealthy obesity in prevalence of asthma attacks in the previous 12 months or in prevalence of physician-prescribed asthma medications.
Participants with increased waist circumferences had significantly greater odds for having had an asthma exacerbation in the previous 12 months compared with those with ideal waist circumferences (OR = 1.58; 95% CI, 1.09-2.26), which persisted following adjustments as well (aOR = 1.73; 95% CI, 1.05-2.84).
But there was no significant association between waist circumference and ED usage, nor were there statistically significant differences between BMI and asthma exacerbations or ED usage for asthma in the previous 12 months.
“The findings that BMI alone was not correlated with ED visits for asthma or asthma exacerbations was quite interesting and surprising to us,” Greiner said.
“This was contrasted by our findings that persons with metabolically unhealthy obesity, ie, those with elevated BMI plus insulin resistance, increased waist circumference, hypertension, hyperlipidemia and poor physical activity, were 3.53 times as likely to have an ED visit for asthma in the last 12 months compared to those with elevated BMI alone,” he continued.
These results aligned with the researchers’ hypotheses, although Greiner called it a very interesting finding because it supported the notion that many factors contribute to asthma morbidity beyond an elevated BMI.
Similarly, there were no statistically significant relationships between lipids including triglycerides, HDL and LDL and insulin resistance and asthma control.
Noting that obese asthma could be an independent diagnosis rather than two separate diagnoses, the researchers said it is important for clinicians to accurately assess obesity, although BMI might not be the best metric for measuring obesity-related complications in asthma.
Greiner called these findings particularly important for physicians in primary care as well as for subspecialists caring for persons with obesity and asthma.
“Physicians should recognize that stratifying risk for poor asthma control should incorporate an elevated BMI, plus other metabolic factors,” he said.
“This is contrary to most physician practices in which BMI is the only factor that is accounted for when diagnosing obesity and quantifying risk,” he continued. “Our findings will allow for physicians to improve their recommendations for patients with obesity and asthma.”
The researchers recommended adding waist circumference or metabolic health measurements to assessments of morbidity patterns among patients with obese asthma. They also said that reducing metabolic syndrome and improving weight control are paramount in asthma control.
“We plan to further our studies on metabolic factors contributing to asthma by assessing biological mechanisms using animal models,” Greiner said.
For more information:
Benjamin Greiner, DO, MPH, can be reached at bhgreine@utmb.edu.
Perspective
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Lindsey Moore, DO, FACAAI, FAAP
Asthma is a heterogenous, chronic respiratory disorder with a complex interplay of comorbidities that all impact asthma control.
In this cross-sectional analysis of patients enrolled in the NHANES database between 2011 and 2016, researchers divided patients with current asthma and obesity (BMI ≥ 30kg/m2) into metabolically healthy vs. unhealthy obesity groups. Objective measures were used to differentiate between groups, including waist circumference, insulin resistance, physical activity levels and metabolic syndrome components.
The study objectives included to determine the prevalence of patients with MUO and asthma and, secondarily, whether different components of obesity compared with BMI alone predicted asthma exacerbation rates.
This study demonstrated that patients with MUO had a higher prevalence of asthma than those with metabolically healthy obesity. Patients with MUO also were more likely to seek ED care for asthma than those patients with an elevated BMI alone.
There was no significant difference between groups when analyzing the prevalence of (self-managed) asthma attacks within the past 12 months or the prevalence of physician-prescribed asthma medications.
The results of this study are not surprising, as MUO likely represents a more severe or advanced form of obesity. Obesity has long been considered a pro-inflammatory state, with resultant increased Th1 cell polarization and monocyte activation, which both can affect lung function. The 2021 Global Initiative for Asthma, or GINA, guidelines characterize obesity as an asthma comorbidity and recommend checking age-adjusted BMI.
In an ideal setting, clinicians should address all asthma comorbidities during every clinic visit for asthma. In some cases, addressing comorbidities can alleviate the need for increasing doses of asthma controller therapies.
Providing effective and lasting weight loss strategies is challenging in a busy clinical setting. However, one should consider using this study’s findings to counsel patients in the early stages of a developing metabolic syndrome. Pointing out physical findings such as acanthosis nigricans or hypertension as early warning signs of worsening disease may be a more delicate and better received approach than discussing the concept of BMI alone.
Finally, it would be interesting to see whether a more even sample size between metabolically healthy vs. unhealthy obesity groups would yield similar results and thus more generalizability of the data.
Reference:
2021 GINA Report, Global Strategy for Asthma Management and Prevention. https://ginasthma.org/wp-content/uploads/2021/05/GINA-Main-Report-2021-V2-WMS.pdf. Accessed Aug. 1, 2022.
Perspective
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Obesity is a known risk factor and disease modifier of asthma among children and adults. Greiner and Hartwell’s study adds to the body of literature supporting how MUO is an important factor in asthma. Their study suggests that patients with MUO were significantly more likely to have had an ED visit for asthma. This finding reinforces how the clinician should consider the implications of obesity and metabolic syndrome in a patient’s asthma.
Physicians and other health care professionals can utilize both the GINA 2022 guidelines and the National Heart, Lung, and Blood Institute expert panel report to assist in patient care for asthma. A referral to a board-certified allergist-immunologist is critical to evaluate for potential triggers and comorbid factors of asthma and to provide expert care in the treatment of a patient’s asthma. Those interested in learning more about asthma and asthma management should visit the American College of Allergy, Asthma and Immunology website and the below references.
References:
Cloutier MM, et al. J Allergy Clin Immunol. 2020;doi:10.1016/j.jaci.2020.10.003.
Global Initiative for Asthma Global Strategy for Asthma Management and Prevention. https://ginasthma.org/gina-reports/. Accessed Aug. 1, 2022.
Peters U, et al. J Allergy Clin Immunol. 2018;doi:10.1016/j.jaci.2018.02.004.
Von Behren J, et al. Thorax. 2009;doi:10.1136/thx.2009.114579.
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