Relationship Between Cardio-metabolic Parameters in Diabetic Non-smokers, Current Smokers, and Quitters: A Systematic Review and Meta-analysis

Smoking is associated with an increase in macrovascular and microvascular complications in people with diabetes. In addition to other concomitant vascular disturbances, it also appears to affect cardio-metric parameters. This may partly explain the acceleration of vascular complications in people with diabetes. This study aimed to investigate the relationship between smoking and its cessation in cardio-metric parameters in diabetes.

Searches were conducted in Medline, Embase, and CINAHL. After screening 6866 studies, 14 observational studies with a total of 98 978 participants with type 1 or type 2 diabetes were selected for the investigation.

Meta-analysis demonstrated that the mean difference of hemoglobin A1c (HBA1C) between non-smokers and smokers was 0.61% (95% confidence interval [CI] -0.88 to -0.33, P < 0.001). The difference in low-density lipoprotein cholesterol between non-smokers and smokers was 0.11 mmol/L (95% CI -20.21 to 0.01, P = 0.04). The difference in high-density lipoprotein cholesterol between non-smokers and smokers was 0.12 mmol/L (95% CI 0.08-0.15, P < 0.001). However, there was no statistically significant difference in blood pressure (BP) between the two groups. The difference in HBA1C between quitters and continuing smokers was not statistically significant at 10.0.10% (95 CI -0.42 to 0.21, P = 0.53). Conversely, the results revealed that over 10 years, HBA1C was comparable between non-smokers and quitters.

Smoking in patients with diabetes was widespread and should be the target of smoking cessation campaigns. Smoking cessation does not lead to an increase in HBA1C in the long term and may reduce vascular complications in diabetes by its desirable effect on the lipid profile.