To What Extent do Social Determinants of Health Modulate Presentation, ITU Admission and Outcomes among Patients with SARS-COV-2 Infection? An Exploration of Household Overcrowding, Air Pollution, Housing Quality, Ethnicity, Comorbidities and Frailty

Background

Internationally, researchers have called for evidence to support tackling health inequalities during the severe acute respiratory syndrome coronavirus 2 (COVID19) pandemic. Despite the 2020 Marmot review highlighting growing health gaps between wealthy and deprived areas, studies have not explored social determinants of health (ethnicity, frailty, comorbidities, household overcrowding, housing quality, air pollution) as modulators of presentation, intensive care unit (ITU) admissions and outcomes among COVID19 patients. There is an urgent need for studies examining social determinants of health including socioenvironmental risk factors in urban areas to inform the national and international landscape.

Methods

An in-depth retrospective cohort study of 408 hospitalized COVID19 patients admitted to the Queen Elizabeth Hospital, Birmingham was conducted. Quantitative data analyses including a two-step cluster analysis were applied to explore the role of social determinants of health as modulators of presentation, ITU admission and outcomes.

Results

Patients admitted from highest Living Environment deprivation indices were at increased risk of presenting with multi-lobar pneumonia and, in turn, ITU admission whilst patients admitted from highest Barriers to Housing and Services (BHS) deprivation Indies were at increased risk of ITU admission. Black, Asian and Minority Ethnic (BAME) patients were more likely, than Caucasians, to be admitted from regions of highest Living Environment and BHS deprivation, present with multi-lobar pneumonia and require ITU admission.

Conclusion

Household overcrowding deprivation and presentation with multi-lobar pneumonia are potential modulators of ITU admission. Air pollution and housing quality deprivation are potential modulators of presentation with multi-lobar pneumonia. BAME patients are demographically at increased risk of exposure to household overcrowding, air pollution and housing quality deprivation, are more likely to present with multi-lobar pneumonia and require ITU admission. Irrespective of deprivation, consideration of the Charlson Comorbidity Score and the Clinical Frailty Score supports clinicians in stratifying high risk patients.

Pseudomonas aeruginosa Induced Airway Epithelial Injury Drives Fibroblast Activation: A Mechanism in Chronic Lung Allograft Dysfunction

Bacterial infections after lung transplantation cause airway epithelial injury and are associated with an increased risk of developing bronchiolitis obliterans syndrome. The damaged epithelium is a source of alarmins that activate the innate immune system, yet their ability to activate fibroblasts in the development of bronchiolitis obliterans syndrome has not been evaluated. Two epithelial alarmins were measured longitudinally in bronchoalveolar lavages from lung transplant recipients who developed bronchiolitis obliterans syndrome and were compared to stable controls. In addition, conditioned media from human airway epithelial cells infected with Pseudomonas aeruginosa was applied to lung fibroblasts and inflammatory responses were determined. Interleukin-1 alpha (IL-1α) was increased in bronchoalveolar lavage of lung transplant recipients growing P. aeruginosa (11.5 [5.4-21.8] vs. 2.8 [0.9-9.4] pg/mL, p < 0.01) and was significantly elevated within 3 months of developing bronchiolitis obliterans syndrome (8.3 [1.4-25.1] vs. 3.6 [0.6-17.1] pg/mL, p < 0.01), whereas high mobility group protein B1 remained unchanged. IL-1α positively correlated with elevated bronchoalveolar lavage IL-8 levels (r(2)  = 0.6095, p < 0.0001) and neutrophil percentage (r(2)  = 0.25, p = 0.01). Conditioned media from P. aeruginosa infected epithelial cells induced a potent pro-inflammatory phenotype in fibroblasts via an IL-1α/IL-1R-dependent signaling pathway. In conclusion, we propose that IL-1α may be a novel therapeutic target to limit Pseudomonas associated allograft injury after lung transplantation.

TNFα from classically activated macrophages accentuates epithelial to mesenchymal transition in obliterative bronchiolitis

Bronchiolitis obliterans syndrome is characterized by fibrotic obliteration of small airways which severely impairs graft function and survival after lung transplantation. Bronchial epithelial cells from the transplanted lung can undergo epithelial to mesenchymal transition and this can be accentuated by activated macrophages. Macrophages demonstrate significant plasticity and change phenotype in response to their microenvironment. In this study we aimed to identify secretory products from macrophages that might be therapeutic targets for limiting the inflammatory accentuation of epithelial to mesenchymal transition in bronchiolitis obliterans syndrome. TNFα, IL-1β and IL-8 are elevated in bronchoalveolar lavage from lung transplant patients prior to diagnosis of bronchiolitis obliterans syndrome. Classically activated macrophages secrete more TNFα and IL-1β than alternatively activated macrophages and dramatically accentuate TGF-β1-driven epithelial to mesenchymal transition in bronchial epithelial cells isolated from lung transplant patients. Blocking TNFα, but not IL-1β, inhibits the accentuation of epithelial to mesenchymal transition. In a pilot unblinded therapeutic intervention in five patients with progressive bronchiolitis obliterans syndrome, anti-TNFα treatment improved forced expiratory volume in 1 second and 6-min walk distances in four patients. Our data identify TNFα as a potential new therapeutic target in bronchiolitis obliterans syndrome deserving of a randomized placebo controlled clinical trial.