Abstract
BackgroundSmoking is associated with increased macrovascular and microvascular complications in people with diabetes. In addition to other concomitant vascular perturbations, it also seems to influence the cardiometabolic parameters, which may partly explain the accelerated rate of vascular complications in smokers with diabetes. While smoking cessation is advocated as a universal component of the management of diabetes, there is some anecdotal evidence that HbA1c could increase following smoking cessation. The aim of this review is to explore the relationship between smoking and its cessation on cardiometabolic parameters in diabetes.MethodsSearches were conducted on Medline, EMBASE and CINAHL up to March 2016. After screening 6866 studies (Additional file 1), 14 observational studies with a total of 98,978 participants’ with either type 1 or type 2 diabetes were selected for review. Narrative synthesis and meta-analyses were carried out to explore the relationship between smoking and its cessation.ResultsMeta-analysis showed that the pooled mean difference of HbA1c between non-smokers and smokers was −0.61% (95% CI −0.88 to −0.33, p < 0.0001). The difference in LDL cholesterol between non-smokers and smokers was −0.11 mmol/l (95% CI −0.21 to −0.01, p = 0.04). The difference in HDL 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 between the two groups. The difference in HbA1c between quitters and continued smokers was not statistically significant −0.10% (95% CI −0.42 to 0.21, p = 0.53). However, a narrative synthesis revealed that over a period of 10 years, the HbA1c was comparable between non-smokers and quitters.ConclusionNon-smokers have a statistically significant lower HbA1c and more favourable lipid profile compared to smokers. Smoking cessation does not lead to an increase in HbA1c in long-term and may reduce vascular complications in diabetes by its favourable impact on lipid profile.Electronic supplementary materialThe online version of this article (doi:10.1186/s12933-016-0475-5) contains supplementary material, which is available to authorized users.
Highlights
Smoking is associated with increased macrovascular and microvascular complications in people with diabetes
A number of studies demonstrated a positive correlation between smoking cessation and developing diabetes suggesting that smoking cessation may have a detrimental impact on glucose metabolism [16,17,18]
In this study for lipid profiles we focused on high-density lipoprotein cholesterol (HDL-C) and lowdensity lipoprotein cholesterol (LDL-C)
Summary
Smoking is associated with increased macrovascular and microvascular complications in people with diabetes. The aim of this review is to explore the relationship between smoking and its cessation on cardiometabolic parameters in diabetes. A number of studies have demonstrated that smoking is associated with increased cardiovascular mortality in people with diabetes [6, 7]. It is not entirely clear whether this increased mortality in smokers is due to atherogenic metabolic profile or due to the direct toxic effects of nicotine and other toxic substances in cigarettes on the cardiovascular milieu. Due to the risk of weight gain and the potential risk of worsening glycaemic control, there is a significant anxiety about the benefit of smoking cessation in people with diabetes [19, 20]. The aim of this systematic review and meta-analysis was to explore the precise relationship of the cardiometabolic profiles in smokers, non-smokers, and quitters with diabetes
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