Effect of obesity on airway and systemic inflammation in adults with asthma: a systematic review and meta-analysis

Abstract

BackgroundObesity is associated with more severe asthma, however, the mechanisms responsible are poorly understood. Obesity is also associated with low-grade systemic inflammation; it is possible that this inflammation extends to the airways of adults with asthma, contributing to worse asthma outcomes. Accordingly, the aim of this review was to examine whether obesity is associated with increased airway and systemic inflammation and adipokines, in adults with asthma.MethodsMedline, Embase, CINAHL, Scopus and Current Contents were searched till 11 August 2021. Studies reporting measures of airway inflammation, systemic inflammation and/or adipokines in obese versus non-obese adults with asthma were assessed. We conducted random effects meta-analyses. We assessed heterogeneity using the I2statistic and publication bias using funnel plots.ResultsWe included 40 studies in the meta-analysis. Sputum neutrophils were 5% higher in obese versus non-obese asthmatics (mean difference (MD)=5.0%, 95% CI: 1.2 to 8.9, n=2297, p=0.01, I2=42%). Blood neutrophil count was also higher in obesity. There was no difference in sputum %eosinophils; however, bronchial submucosal eosinophil count (standardised mean difference (SMD)=0.58, 95% CI=0.25 to 0.91, p<0.001, n=181, I2=0%) and sputum interleukin 5 (IL-5) (SMD=0.46, 95% CI=0.17 to 0.75, p<0.002, n=198, I2=0%) were higher in obesity. Conversely, fractional exhaled nitric oxide was 4.5 ppb lower in obesity (MD=−4.5 ppb, 95% CI=−7.1 ppb to −1.8 ppb, p<0.001, n=2601, I2=40%). Blood C reactive protein, IL-6 and leptin were also higher in obesity.ConclusionsObese asthmatics have a different pattern of inflammation to non-obese asthmatics. Mechanistic studies examining the pattern of inflammation in obese asthmatics are warranted. Studies should also investigate the clinical relevance of this altered inflammatory response.PROSPERO registeration numberCRD42021254525.

Exploring the association between asthma and chronic comorbidities: impact on clinical outcomes

“…Numerous studies provide evidence indicating that obesity is linked to a significant increase in various inflammatory markers, potentially intensifying the inflammatory processes in individuals with asthma. Asthmatic individuals who are obese demonstrate notably elevated levels of inflammatory markers, including blood and sputum neutrophils (176,187), bronchial sputum eosinophil count (187), sputum IL-5 (187), blood IL-6 (187,188), CRP (187,189,190), TNF-α (188), and leptin (187,188,(190)(191)(192), in comparison to their non-obese counterparts with asthma. Additionally, obese asthma patients often exhibit a distinct phenotype characterized by neutrophilic inflammation.…”

Ultra-Processed Foods Consumption and Asthma in the Western Diet

“…Western lifestyle includes Western dietary patterns with high caloric intake combined with low physical activity, which certainly play a key role in the development of obesity. This disease is related to poorer asthma control and lung function, as well as an increased risk of asthma exacerbations [1].…”

“…It is known that the causes involve, to a large extent, immunomodulation of the adaptive and specifically the innate immune systems. Moreover, causes seem to be markedly influenced by distinct environmental triggers and genetic interactions that challenge the immune system [1]. With this background, there are many research gaps in the knowledge, despite the fact that asthma is a global health problem affecting about 10-15% of children around the world [2] and more than 15% of school-aged children in Europe [3].…”

The Saudi initiative for asthma – 2024 update: Guidelines for the diagnosis and management of asthma in adults and children

“…[ 262 ] Studies has shown that obese asthmatics have a different pattern of inflammation when compared to non-obese asthmatics. [ 263 ] Therefore, Obese asthma patients have more symptoms, more frequent and severe exacerbations, reduced response to asthma medications, poor quality of life and more difficult to control asthma. [ 264 ] This could be in part related to reduced lung volumes, lack of fitness, and associated sleep apnea and GERD.…”