Fig. 3

Pooled estimates for the effect of spirometric SAO measured using FEV₃/FVC (a) and FEF_25-75 (b) on physical and mental quality of life in the BOLD study. Spirometric SAO: Small airways obstruction. Overall: spirometric SAO defined as FEV₃/FVC or FEF_25-75 less than the lower limit of normal (LLN). Male/Female: spirometric SAO as FEV₃/FVC or FEF_25-75 < LLN stratified by sex. Isolated spirometric SAO: FEV₃/FVC or FEF_25-75 < LLN with FEV₁/FVC ≥ LLN. Physical and mental QoL measured using the SF-12 questionnaire. Negative regression coefficient indicates that having SAO is associated with a reduction in SF-12 score in comparison to not having SAO. I² values of 0%, 25%, 50%, and 75% considered no, low, moderate, and high heterogeneity. Covariates in the adjusted model: sex, education level, body mass index, smoking status, accumulated cigarette pack-years, passive smoking, occupational exposure to dust, use of solid fuels for cooking/heating for > 6 months in a lifetime, reported doctor-diagnosed or history of tuberculosis, spirometric restriction, family history of COPD, CVD, hypertension, and diabetes. Estimates based on the analysis of 31 sites, the following sites could not be included in the analysis either due to low response rate to the questionnaire; Turkey (Adana) and China (Guangzhou) or where QoL was measured using a different tool; Benin (Sémé-Kpodji), Cameroon (Limbe), Jamaica, Kyrgyzstan (Chui), Kyrgyzstan (Naryn), Malaysia (Penang), Pakistan (Karachi), Sri Lanka (Colombo)