COPD, metabolic syndrome, respiratory symptoms, and functional incapacity in smokers, ex-smokers, and never-smokers aged 40-59 in Almaty, Kazakhstan: a cross-sectional study

Background:  No study has reported the relationship between smoking status with chronic obstructive pulmonary diseases (COPD) and metabolic syndrome (MetS) in Kazakhstan. The aim of this study was to assess the associations between health outcomes, including COPD, MetS, respiratory symptoms, and functional incapacity, with the cigarette smoking status. Methods:  The cross-sectional study recruited 500 smokers, 200 ex-smokers, and 200 never-smokers aged 40-59 in Almaty, Kazakhstan. Questions assessed socio-demographic, clinical characteristics, and smoking behavior. Blood glucose and lipid profiles were determined after overnight fasting. COPD was defined according to the GOLD 2017 statement. Respiratory symptoms and functional incapacity were assessed by the COPD Assessment Test (CAT) and 6-min walk test (6MWT), respectively. Logistic regression models were used to assess the associations. Results:  The prevalence of COPD among smokers, ex-smokers and never-smokers were 5.5%, 3.0% and 3.0%, respectively. Respiratory symptoms based on CAT were more prevalent among smokers (42.8%) as compared to ex-smokers (42.8% vs 17.0%; aOR 3.43, 95% CI 2.25–5.23) and never-smokers (42.8% vs 12.5%; aOR 5.44, 95% CI 3.42–8.65). Current smokers were more likely to walk less than 450 meters during 6MWT as compared to never-smokers (16.5% vs 5.0%; aOR 3.72, 95% CI 1.86–7.44). No significant association was found between the smoking status with COPD and MetS.  Conclusions:  Respiratory symptoms are common among the current smokers, even if most of them had preserved pulmonary function defined by spirometry.