Written on July 17, 2023 by Lori Mulligan, MPH. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.
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Obesity and asthma are two chronic conditions that affect millions of people. Obesity is considered one of the most important public health problems of the 21st century.
Worldwide, more than 1 billion people have obesity — 650 million adults, 340 million adolescents, and 39 million children, according to WHO. Asthma affected an estimated 262 million people in 2019 and caused 455,000 deaths.
Genetic and lifestyle factors such as diet, physical activity, and early exposure to micro-organisms are important factors that may contribute to the escalating prevalence of both conditions.
Corresponding with this global epidemic of obesity, the prevalence of obese patients with asthma has reached alarming levels. Obese patients with asthma are difficult to manage; they have worse lung function and symptoms and are less responsive to asthma treatment.
Systemic inflammation and mechanical effect, both due to the expansion of fatty tissue, have been proposed as the main reasons for the association between obesity and asthma.
People with a Body Mass Index (BMI) of 30 or more have a much higher risk of having asthma than those with a lower BMI. Seven percent of adults with a BMI in the normal range have asthma, but 11 percent of adults with a BMI classified as obese have asthma. And, for reasons not yet understood, this seems particularly a problem for women - nearly 15 percent of women who are obese suffer from asthma.
By race and Hispanic origin, current asthma prevalence was highest among adults with obesity for all groups. Patterns differed slightly among groups. For non-Hispanic black and Hispanic adults, the prevalence of asthma in those with obesity was higher than for those in the normal weight and overweight categories.
For non-Hispanic white adults, there was no significant difference in asthma prevalence between the obese and overweight categories.
For all age groups, current asthma prevalence was highest among adults with obesity, and there was no significant difference in asthma prevalence between those in the normal weight and overweight categories.
There was an increasing trend in asthma prevalence as weight increased, which was observed most clearly in the 60 and over age group.
From 2001 to 2014, there was an increasing trend in asthma prevalence among adults overall and among overweight adults. However, no significant trend was observed among adults in other weight categories.
Findings from an American Thoracic Society workshop on obesity and asthma concluded that obesity is a major risk factor for asthma, and that obesity-related asthma is likely different from other types of asthma (e.g., allergic, occupational, exercise-induced, nocturnal, aspirin-sensitive, and severe asthma).
According to research, obese subjects have increased asthma risk, and obese asthmatic patients have more symptoms, more frequent and severe exacerbations, reduced response to several asthma medications, and decreased quality of life. Obese asthma is a complex syndrome, including different phenotypes of disease that are just beginning to be understood.
For example, accumulation of fat in the thoracic and abdominal cavities leads to lung compression and an attendant reduction in lung volume, contributing to changes in the normal physiology and function of the lungs.
The mechanisms behind obesity-induced changes in lung function are complex, involving mechanical changes, and effects of adipokines and inflammatory cytokines from adipose or fatty tissue. Such changes cause asthma and asthma-like symptoms such as dyspnea, wheezing, and airway hyperresponsiveness.
Obesity also increases airway closure, which may exacerbate airway reactivity, affect the delivery of inhaled medications, and predispose to more severe derangement during exacerbations.
Obesity alters the distribution of ventilation towards the upper lobes, which likely contributes to ventilation inhomogeneity and the burden of respiratory disease.
In the next five years, researchers anticipate phenotyping both obesity and airway disease that will allow insights into the mechanical and immunological effects of obesity on lung function in diseases such as asthma. This will require more sophisticated measures of adiposity than BMI; measures incorporating assessments of metabolic dysfunction and regional fat distribution are needed.
We do know that obese patients often use more medications, suffer worse symptoms, and are less able to control their asthma than patients in a healthy weight range.
Obesity causes a variety of mechanical, metabolic, and immunological changes that can affect the airways. The treatment of asthma in people with obesity can be challenging as obesity is associated with poor response to standard controller medications. A tailored approach that involves combining pharmacologic and non-pharmacologic therapies, including weight loss, dietary interventions, and exercise, along with identification and treatment of obstructive sleep apnea, should therefore be considered in this population.
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