IMPACT OF SMOKING CESSATION ON GLYCAEMIC CONTROL IN PATIENTS WITH TYPE 2 DIABETES MELLITUS: A SYSTEMATIC REVIEW

Abstract

Objective: To systematically evaluate the effect of smoking cessation on glycaemic control — indexed by HbA1c, fasting blood glucose and insulin resistance — in adults with T2DM.

Methods: A PRISMA 2020-compliant search of PubMed/MEDLINE and Google Scholar was conducted through March 2025. Of 56 records identified, 24 underwent full-text review; six studies (N = 15,744; five countries) met all inclusion criteria. Evaluation of quality using the Cochrane RoB 2 tool for RCTs and ROBINS-I for observational studies.

Results: the number of records included were six studies: two RCTs, two cohort studies, one retrospective cohort, and one cross-sectional observational study. Two observational studies documented a transient short-term HbA1c increase post-cessation, primarily attributed to weight gain. One large cross-sectional study provided supportive associative evidence of a dose- and time-dependent inverse connection among cessation duration, HbA1c, and insulin resistance; however, its design precludes causal inference. One retrospective cohort showed significant HbA1c reduction at six months despite weight gain. Both RCTs reported null findings, reflecting critically insufficient cessation rates.

Conclusions: Cessation follows a temporally biphasic glycaemic trajectory: a transient early deterioration followed by sustained long-term improvement. Proactive weight management — including GLP-1 receptor agonist therapy where indicated — is essential to optimise post-cessation metabolic outcomes. Adequately powered long-term RCTs are urgently required.