ABSTRACT
IntroductionObservational studies have indicated an association between iron status and risk of sepsis and severe COVID-19. However, these findings may be affected by residual confounding, reverse causation. MethodsIn a two-sample Mendelian randomization study using inverse variance weighted method, we estimated the effect of genetically-predicted iron biomarkers (serum iron, transferrin saturation (TSAT), total iron binding capacity (TIBC) and ferritin) on risk of sepsis and risk of being hospitalized with COVID-19. For the COVID-19 outcomes we additionally conducted sex-stratified analyses. Weighted median, Weighted mode and MR Egger were used as sensitivity analyses. ResultsFor risk of sepsis, one standard deviation increase in genetically-predicted serum iron was associated with odds ratio (OR) of 1.14 (95% confidence interval [CI] 1.01 to 1.29, P=0.031). The findings were supported in the analyses for transferrin saturation and total iron binding capacity, while the estimate for ferritin was inconclusive. We found a tendency of higher risk of hospitalization with COVID-19 for serum iron; OR 1.29 (CI 0.97-1.72, P=0.08), where sex stratified analyses showed OR 1.63 (CI 0.94-2.86, P=0.09) for women and OR 1.21 (CI 0.92-1.62, P=0.17) for men. Sensitivity analyses supported the main findings and did not suggest bias due to pleiotropy. ConclusionsOur findings suggest a causal effect of genetically-predicted higher iron status and risk of hospitalization due to sepsis and indications of an increased risk of being hospitalized with COVID-19. These findings warrant further studies to assess iron status in relation to severe infections, including the potential of improved management.
ABSTRACT
Given the highly variable clinical phenotype of Coronavirus disease 2019 (COVID-19), a deeper analysis of the host genetic contribution to severe COVID-19 is important to improve our understanding of underlying disease mechanisms. Here, we describe an extended GWAS meta-analysis of a well-characterized cohort of 3,260 COVID-19 patients with respiratory failure and 12,483 population controls from Italy, Spain, Norway and Germany/Austria, including stratified analyses based on age, sex and disease severity, as well as targeted analyses of chromosome Y haplotypes, the human leukocyte antigen (HLA) region and the SARS-CoV-2 peptidome. By inversion imputation, we traced a reported association at 17q21.31 to a highly pleiotropic [~]0.9-Mb inversion polymorphism and characterized the potential effects of the inversion in detail. Our data, together with the 5th release of summary statistics from the COVID-19 Host Genetics Initiative, also identified a new locus at 19q13.33, including NAPSA, a gene which is expressed primarily in alveolar cells responsible for gas exchange in the lung.
ABSTRACT
ObjectivesTo investigate whether there is a causal effect of cardiometabolic traits on risk of sepsis and severe covid-19. DesignMendelian randomisation analysis. SettingUK Biobank and HUNT study population-based cohorts for risk of sepsis, and genome-wide association study summary data for risk of severe covid-19 with respiratory failure. Participants12,455 sepsis cases (519,885 controls) and 1,610 severe covid-19 with respiratory failure cases (2,205 controls). ExposureGenetic variants that proxy body mass index (BMI), lipid traits, systolic blood pressure, lifetime smoking score, and type 2 diabetes liability - derived from studies considering between 188,577 to 898,130 participants. Main outcome measuresRisk of sepsis and severe covid-19 with respiratory failure. ResultsHigher genetically proxied BMI and lifetime smoking score were associated with increased risk of sepsis in both UK Biobank (BMI: odds ratio 1.38 per standard deviation increase, 95% confidence interval [CI] 1.27 to 1.51; smoking: odds ratio 2.81 per standard deviation increase, 95% CI 2.09-3.79) and HUNT (BMI: 1.41, 95% CI 1.18 to 1.69; smoking: 1.93, 95% CI 1.02-3.64). Higher genetically proxied BMI and lifetime smoking score were also associated with increased risk of severe covid-19, although with wider confidence intervals (BMI: 1.75, 95% CI 1.20 to 2.57; smoking: 3.94, 95% CI 1.13 to 13.75). There was limited evidence to support associations of genetically proxied lipid traits, systolic blood pressure or type 2 diabetes liability with risk of sepsis or severe covid-19. Similar findings were generally obtained when using Mendelian randomization methods that are more robust to the inclusion of pleiotropic variants, although the precision of estimates was reduced. ConclusionsOur findings support a causal effect of elevated BMI and smoking on risk of sepsis and severe covid-19. Clinical and public health interventions targeting obesity and smoking are likely to reduce sepsis and covid-19 related morbidity, along with the plethora of other health-related outcomes that these traits adversely affect. Summary boxesO_ST_ABSWhat is already known on this topicC_ST_ABSO_LISepsis and severe covid-19 are major contributors to global morbidity and mortality. C_LIO_LICardiometabolic risk factors have been associated with risk of sepsis and severe covid-19, but it is unclear if they are having causal effects. C_LI What this study addsO_LIUsing Mendelian randomization analyses, this study provides evidence to support that higher body mass index and lifetime smoking score both increase risk of sepsis and severe covid-19 with respiratory failure. C_LIO_LIClinical and public health interventions targeting obesity and smoking are likely to reduce sepsis and covid-19 related morbidity, along with the plethora of other health-related outcomes that these traits adversely affect. C_LI