Background: Diabetes mellitus (DM) impacts multiple body systems, including lung function, and this impact can be further complicated by smoking. The connection between blood sugar control and lung health in individuals with diabetes who smoke has been extensively studied, but findings have been varied. This systematic review sought to compile and assess the research on how blood sugar control influences lung function in smokers with diabetes.
Methods: We searched several databases, including PubMed, EMBASE, Cochrane Library, Web of Science, Scopus, CINAHL, PsycINFO, and Google Scholar, in line with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We included studies that looked at lung function tests in smokers with diabetes and examined the relationship with blood sugar control, as indicated by hemoglobin A1c (HbA1c) levels. We conducted thorough quality assessments, data extraction, and analysis.
Results: We identified five relevant studies. The data from these studies indicated a clear trend: smokers with diabetes who had higher HbA1c levels typically showed worse lung function than those with better blood sugar control. Decreases in forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) were the most frequently observed issues. Some studies also pointed to a complex relationship between HbA1c levels and lung function, particularly when HbA1c was below 7.0%.
Conclusion: Our review indicates that smokers with DM who have poor blood sugar control tend to have worse lung function. These findings highlight the importance of managing blood sugar to help maintain lung health in these individuals. Further long-term research is needed to clarify the exact relationship and whether improving blood sugar control can reverse lung problems.
Keywords: diabetes mellitus; glycemic control; hba1c; pulmonary function; smoking.
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