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Table 2 Associations between serum bilirubin and FEV1

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

First author, year Measure Outcome Model covariates
Longitudinal studies    
Apperley 2015 [13] Linear regression of relationship between bilirubin quintile and FEV1 decline years 2–5 FEV1 decline 57.0 (SD 70.7) mL/year in quintile 5 vs 66.3 (SD 64.8) mL/year in quintile 1 (p for trend = 0.001) Age, sex, BMI, race, FEV1 at baseline, LMCR, and pack-years smoked
Leem 2018 [15] Linear regression between ln(bilirubin) and FEV1 decline mL/yr β = − 13.09 (p < 0.001) Age, sex, BMI, FEV1 at baseline, smoking status
MacDonald 2019 [20] Linear regression between log(2) bilirubin and FEV1 mL/yr β = -2.1 (95% CI − 8.6 to 4.4; p = 0.53) Age, sex, race, region, smoking status, treatment group, CD4 T-cell count, and HIV-RNA
Cross-sectional studies    
Horsfall 2014 [14] Mixed linear regression of relationship between ln (bilirubin) and FEV1, 2 stage least squares β = 133 (95% CI 37–228; p = 0.007) Age, sex, height, smoking status, region of birth
Schunemann 1997 [21] Linear regression of FEV1% predicted against bilirubin β = 10.35 (SE 5.90; p = 0.082) Age, height, gender, smoking status (former vs lifelong non-smoker)
Yang 2015 [16] Pearson’s correlation for relationship between total bilirubin and FEV1 r/t = 0.203 (p < 0.001) None—included in MV analysis but details of model not included
Leem 2019 [27] Linear mixed model for relationship between serum bilirubin and FEV1 Estimated mean = 0.04 (SE 0.08; p = 0.607) Age, sex, BMI, smoking
Curjuric 2014 [18] Linear regression of relationship between ln(bilirubin) and FEV1 β = 13.8 (95% CI − 15.5 to 43.2; p = 0.356) Sex, age, height, weight, education, study area, ever smoking, total pack years
  1. FEV1 forced expiratory volume in 1 s, BMI body mass index, LMCR logarithm of methacholine reactivity, MV multivariate, ln natural log, HIV human immunodeficiency virus, CI confidence interval, SE standard error