From the Guidelines
Asthma and obesity are strongly associated, with obesity increasing the risk of developing asthma, particularly in females.
Key Findings
- Numerous cross-sectional epidemiologic studies indicate an increased prevalence of asthma in the obese 1.
- The relationship between obesity and asthma is much stronger in females than in males, with a birth cohort study showing that raised body mass index (BMI) was associated with asthma and atopy in women but not in men 1.
- Population attributable fraction calculations estimated that 28% of asthma developing in women after 9 years of age is due to being overweight 1.
- Weight reduction is recommended in obese patients with asthma to improve asthma control, as a small randomized parallel group study has shown improved asthma control following weight reduction in obese patients with asthma 1.
- Obesity may exacerbate asthma through chronic low-grade systemic inflammation and increased serum leptin, which has pro-inflammatory effects 1.
Mechanisms
- The mechanistic relationship between obesity and asthma is complex, but may involve chronic low-grade systemic inflammation, increased serum leptin, and airway hyperresponsiveness 1.
- Leptin, a member of the IL-6 family of cytokines, has pro-inflammatory effects and may contribute to the increased incidence of asthma in the obese 1.
Clinical Implications
- Obesity is a significant risk factor for asthma, and weight reduction should be recommended to obese patients with asthma to improve asthma control 1.
- Clinicians should be aware of the potential for obesity to exacerbate asthma and monitor patients with asthma for signs of obesity-related complications, such as sleep apnea 1.
From the Research
Association Between Asthma and Obesity
The relationship between asthma and obesity is complex and multifaceted. Studies have shown that obesity is a common co-morbidity with asthma, and is associated with increased risk for asthma exacerbations, worse respiratory symptoms, and poor control 2. The exact mechanisms underlying this association are not fully understood, but are thought to involve mechanical alterations of the airways and lung parenchyma, as well as systemic and airway inflammatory and metabolic dysregulation 3, 4.
Key Findings
- Obesity is a risk factor for incident asthma, and the relationship between the two conditions appears to be weight-dependent, causal, and partly genetic 5.
- There are two distinct phenotypes of asthma in obese individuals: allergic asthma in children, which worsens pre-existing asthma, and non-allergic, late-onset asthma, which develops as a consequence of obesity 3, 5.
- Obesity-related inflammation, including the infiltration of adipose tissue by macrophages and the production of pro-inflammatory cytokines, is thought to play a key role in the development and severity of asthma in obese individuals 5.
- Reduction of weight through diet, exercise, or bariatric surgery has been shown to reduce inflammatory activity and improve asthma and lung function 5.
Mechanisms Underlying the Association
- Mechanical effects of obesity, including fewer deep inspirations leading to increased airway hyperresponsiveness 3.
- Inflammatory pathway driven by obesity-related cytokines (adipokines) 3, 4.
- Environmental and lifestyle changes, including exposures in utero, physical activity, and diet, which may contribute to the development of asthma in predisposed individuals 3, 4.
Clinical Implications
- Obesity is significantly associated with decreased lung function, and asthmatics have a higher risk than non-asthmatics 6.
- Annual change in body mass index (BMI) is an independent risk factor for decreased lung function and accelerated decline in forced vital capacity (FVC) 6.
- BMI is the best indicator to predict poor pulmonary function in individuals with asthma 6.