The association between smoking cessation and glycaemic control in patients with type 2 diabetes: a THIN database cohort study

Lancet Diabetes Endocrinol. 2015 Jun;3(6):423-430. doi: 10.1016/S2213-8587(15)00082-0. Epub 2015 Apr 29.

Abstract

Background: Smoking increases the risk of developing type 2 diabetes. However, several population studies also show a higher risk in people 3-5 years after smoking cessation than in continuing smokers. After 10-12 years the risk equates to that of never-smokers. Small cohort studies suggest diabetes control deteriorates temporarily during the first year after quitting. We examined whether or not quitting smoking was associated with altered diabetes control in a population study, for how long this association persisted, and whether or not this association was mediated by weight change.

Methods: We did a retrospective cohort study (Jan 1, 2005, to Dec 31, 2010) of adult smokers with type 2 diabetes using The Health Improvement Network (THIN), a large UK primary care database. We developed adjusted multilevel regression models to investigate the association between a quit event, smoking abstinence duration, change in HbA1c, and the mediating effect of weight change.

Findings: 10 692 adult smokers with type 2 diabetes were included. 3131 (29%) quit smoking and remained abstinent for at least 1 year. After adjustment for potential confounders, HbA1c increased by 0·21% (95% CI 0·17-0·25; p<0·001; [2·34 mmol/mol (95% CI 1·91-2·77)]) within the first year after quitting. HbA1c decreased as abstinence continued and became comparable to that of continual smokers after 3 years. This increase in HbA1c was not mediated by weight change.

Interpretation: In type 2 diabetes, smoking cessation is associated with deterioration in glycaemic control that lasts for 3 years and is unrelated to weight gain. At a population level, this temporary rise could increase microvascular complications.

Funding: National Institute for Health Research School for Primary Care Research.

Publication types

  • Comparative Study

MeSH terms

  • Aged
  • Blood Glucose / metabolism
  • Cohort Studies
  • Databases, Factual*
  • Diabetes Mellitus, Type 2 / blood*
  • Diabetes Mellitus, Type 2 / epidemiology
  • Diabetes Mellitus, Type 2 / therapy*
  • Female
  • Glycated Hemoglobin A / metabolism*
  • Humans
  • Male
  • Middle Aged
  • Regression Analysis
  • Retrospective Studies
  • Smoking Cessation*
  • Time Factors
  • Treatment Outcome
  • United Kingdom / epidemiology
  • Weight Gain / physiology

Substances

  • Blood Glucose
  • Glycated Hemoglobin A