Table 2 Associations between serum bilirubin and FEV₁

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