Obesity and asthma

Abstract

Obesity is a vast public health problem and both a major risk factor and disease modifier for asthma in children and adults. 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. We examine the epidemiology and characteristics of this syndrome in children and adults, as well as the changes in lung function seen in each age group. We then discuss the better recognized factors and mechanisms involved in disease pathogenesis, focusing particularly on diet and nutrients, the microbiome, inflammatory and metabolic dysregulation, and the genetics/genomics of obese asthma. Finally, we describe current evidence on the effect of weight loss and mention some important future directions for research in the field.

Keywords: Asthma; metabolic syndrome; microbiome; obese asthma; obesity.

Figure 1. Obese asthma syndrome

The syndrome of obese asthma likely includes many phenotypes: those typically seen in lean individuals, now complicated by obesity; disease newly arising in obese individuals; and perhaps a separate phenotype characterized by increased response to environmental pollutants. Much work remains to be done to understand whether these are unique phenotypes that require individualized therapeutic approaches.

Figure 2. Effect of obesity on biomarkers and clinical outcomes of asthma in adults

Proposed pathways that have been found altered in obesity and asthma in adults. Solid arrows indicate the effect of obesity. Dashed arrows inside brackets indicate changes that have been seen after weight loss. *Pathway has not been studied or no significant associations have been reported.

Figure 3. FEV1/FVC in adolescents with metabolic syndrome

Metabolic syndrome (MS) and asthma synergistically reduce FEV1/FVC in adolescents. Data from NHANES. Models adjusted for age, sex, race/ethnicity, health insurance, family history of asthma, tobacco smoke exposure, C-reactive protein, and BMI z-score. Reproduced with permission from JACI 2015 (PMID 25748066).

Figure 4. Factors contributing to the syndrome of obesity-related asthma

AHR: Airway hyperreactivity. ASM: Airway smoth muscle. ERV: Expiratory reserve volume. FRC: Functional residual capacity. GWAS: Genome-wide association study. NO: Nitric oxide. SCFAs: Short-chain fatty acids