CD4 and chronic obstructive pulmonary disease: The risk factors reported in included studies varying from demographics (sex, age, race, height, weight, body mass index (BMI), waist-to-hip ratio (WHR), family history, and so forth), comorbidity status (viral hepatitis infection, tuberculosis (TB), hypertension (HTN), diabetes mellitus (DM), chronic obstructive pulmonary disease (COPD), dyslipidemia, lipodystrophy, and so forth) to HIV-related factors (HIV infection route, CD4 count, HIV RNA viral load, HIV diagnosis, ART regimen, and so forth) (Table S4, S5).