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Table 3 Associations between serum bilirubin and airflow obstruction (FEV1/FVC ratio)

From: Serum bilirubin and chronic obstructive pulmonary disease (COPD): a systematic review

First author, year Measure Outcome Model covariates
Curjuric 2014 [18] Linear regression of relationship between ln(bilirubin) and FEV1/FVC ratio β = 0.5 (95% CI 0.1–1.0; p = 0.012) Sex, age, height, weight, education, study area, ever smoking, total pack years
MacDonald 2019 [20] Linear regression of log(2) bilirubin on FEV1/FVC slope β = − 0.7 (− 95% CI 1.6–0.2; p = 0.12) Age, sex, race, region, smoking status, treatment group, CD4 T-cell count, and HIV-RNA
Leem 2018 [15] Linear regression between ln(bilirubin) and decline in FEV1/FVC ratio (annual) β = 1.69 (p < 0.001) Age, sex, BMI, FEV1/FVC at baseline, smoking status
Leem 2019 [27] Linear mixed model for relationship between serum bilirubin and FEV1/FVC Estimated mean = − 0.45 (SE 1.72; p = 0.792) Age, sex, BMI, smoking
  1. COPD chronic obstructive pulmonary disease, aIRR adjusted incidence rate ratio, BMI body mass index, FEV1 forced expiratory volume in 1 s, FVC forced vital capacity, HIV human immunodeficiency virus, aRR adjusted rate ratio, ANOVA analysis of variance, CI confidence interval, SE standard error