Aim The relations between smoking and glycaemic parameters are not well explored. We compare HbA1c, fasting plasma glucose (FPG) and 2-hour plasma glucose (2H-PG) in current-, ex- and never-smokers. Methods This meta-analysis used individual data from 16 886 men and 18 539 women without known diabetes, in 12 DETECT-2 consortium studies and in the French D.E.S.I.R. and TELECOM studies. Means of the three glycaemic parameters in current-, ex- and never-smokers were modelled by linear regression, with study as a random factor. The I2 statistic evaluated heterogeneity among studies. Results HbA1c was 0.10 (95%CI:0.08,0.12) % [1.1 (0.9,1.3) mmol/mol] higher in current-smokers and 0.03 (0.01,0.05) % [0.3 (0.1,0.5) mmol/l] higher in ex-smokers, compared with never-smokers. For FPG, there was no significant difference between current- and never-smokers: −0.004 (−0.03,0.02) mmol/l but FPG was higher in ex-smokers: 0.12 (0.09,0.14) mmol/l. In comparison to never-smokers, 2H-PG was lower: −0.44 (−0.52,−0.37) mmol/l in current-smokers, with no difference for ex-smokers: 0.02 (−0.06,0.09) mmol/l. There was a large and unexplained heterogeneity among studies, with I2 always higher than 50%: after stratification by sex and adjustment for age and BMI, I2 changed little. In this study population, current-smokers had a prevalence of diabetes as screened by HbA1c, 1.30% higher and that screened by 2H-PG, 0.52% lower than in comparison to never-smokers. Conclusion Current-smokers had a higher HbA1c and a lower 2H-PG than never-smokers, across this heterogeneous group of studies; this will effect the chances of smokers being diagnosed with diabetes.

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Diabet. Med. 28, 1311–1318 (2011) Abstract Aim  We examined the ability of fasting plasma glucose and HbA1c to predict 5‐year incident diabetes for an Australian cohort and a Danish cohort and 6‐year incident diabetes for a French cohort, as defined by the corresponding criteria. Methods  We studied 6025 men and women from AusDiab (Australian), 4703 from Inter99 (Danish) and 3784 from DESIR (French), not treated for diabetes and with fasting plasma glucose < 7.0 mmol/l and HbA1c < 48 mmol/mol (6.5%) at inclusion. Diabetes was defined as fasting plasma glucose ≥ 7.0 mmol/l and/or treatment for diabetes or as HbA1c ≥ 48 mmol/mol (6.5%) and/or treatment for diabetes. Results  For AusDiab, incident fasting plasma glucose‐defined diabetes was more frequent than HbA1c‐defined diabetes (PMcNemar < 0.0001), the reverse applied to Inter99 (PMcNemar < 0.007) and for DESIR there was no difference (PMcNema = 0.17). Less than one third of the incident cases were detected by both criteria. Logistic regression models showed that baseline fasting plasma glucose and baseline HbA1c predicted incident diabetes defined by the corresponding criteria. The standardized odds ratios (95% confidence interval) for HbA1c were a little higher than for fasting plasma glucose, but not significantly so. They were respectively, 5.0 (4.1–6.1) and 4.1 (3.5–4.9) for AusDiab, 5.0 (3.6–6.8) and 4.8 (3.6–6.3) for Inter99, 4.8 (3.6–6.5) and 4.6 (3.6–5.9) for DESIR. Conclusions  Fasting plasma glucose and HbA1c are good predictors of incident diabetes defined by the corresponding criteria. Despite Diabetes Control and Complications Trial‐alignment of the three HbA1c assays, there was a large difference in the HbA1c distributions between these studies, conducted some 10 years ago. Thus, it is difficult to compare absolute values of diabetes prevalence and incidence based on HbA1c measurements from that time.

Aims The aim of this prospective study was to examine CVD risk reduction in type 1 diabetes (1) for people with favourable cardiovascular health metrics and (2) by clustering of these metrics. Methods Data from 2313 participants from the EURODIAB Prospective Complications Study were analysed. All had type 1 diabetes (51% men, mean ± SD age 32 ± 9 years). Seven cardiovascular health metrics were studied—smoking, BMI, physical activity, a diet score, total cholesterol/HDL-cholesterol ratio, combined systolic and diastolic BP and HbA1c—divided into favourable/less favourable categories. Cox proportional hazards models were used to calculate HRs (95% CIs) of incident CVD for each metric. Clusters were made by scoring each individual by the number of favourable metrics. Results A total of 163 people developed incident CVD during a mean ± SD follow-up of 7.2 ± 1.3 years. Participants with more favourable HbA1c levels of <57 mmol/mol (<7.4%) had a 37% significantly lower CVD risk than those with a less favourable HbA1c (HR [95% CI] 0.63 [0.44, 0.91]), and participants with a more favourable BP (systolic BP <112 mmHg and diastolic BP <70 mmHg) had a 44% significantly lower CVD risk than participants in the less favourable BP group (HR [95% CI] 0.56 [0.34, 0.92]). There was a dose–response relation with a lower HR observed with greater clustering of more favourable metrics: people with four or more favourable metrics had an HR of 0.37 (95% CI 0.18, 0.76), adjusted for sex and age at diabetes diagnosis, compared with those with no favourable metrics. Conclusions/interpretation Low HbA1c and low BP were protective cardiovascular health metrics in our study of people with type 1 diabetes. Targeting all cardiovascular health metrics could be more effective in preventing CVD than targeting single metrics. Graphical abstract

OBJECTIVETo compare incidences and risk factors for diabetes using seven definitions, with combinations of pharmacological treatment, fasting plasma glucose (FPG) ≥7.0 mmol/L, and HbA1c ≥6.5%.RESEARCH DESIGN AND METHODSParticipants aged 30–65 years from the Data from an Epidemiological Study on the Insulin Resistance Syndrome (DESIR) cohort were followed for 9 years.RESULTSMore men had incident diabetes as defined by FPG ≥7.0 mmol/L and/or treatment than by HbA1c ≥6.5% and/or treatment: 7.5% (140/1,867) and 5.3% (99/1,874), respectively (P < 0.009); for women incidences were similar: 3.2% (63/1,958) and 3.4% (66/1,954). Known risk factors predicted diabetes for almost all definitions. Among those with incident diabetes by FPG alone versus HbA1c alone, there were more men (78 vs. 35%), case patients were 8 years younger, and fewer were alcohol abstainers (12 vs. 35%) (all P < 0.005). A diabetes risk score discriminated well between those with and without incident diabetes for all definitions.CONCLUSIONSIn men, FPG definitions yielded more incident cases of diabetes than HbA1c definitions, in contrast with women. An FPG-derived risk score remained relevant for HbA1c-defined diabetes.

Hofer et al. (1) report on smoking and metabolic control in a large study that combines type 1 diabetes registries from Europe and the U.S., with a total of more than 20,000 patients.Smokers were found to have higher HbA 1c (8.5% vs. 7.9% [70 vs. 62 mmol/mol]); we presume this is in comparison with those who were not current smokers. These HbA 1c concentrations were adjusted for age-group, sex, duration of type 1 diabetes, and migration background/not non-Hispanic white. Although the percentage of smokers was higher in Europe than in the U.S., there were more ex-smokers in the U.S. The authors do not present the mean HbA 1c for the two continents separately, nor the relationship between values for smokers versus ex-smokers, and doing so would add value to their results.We have published a meta-analysis with individual data on more than 35,000 people who were not treated with glucose-lowering agents (2). We found that, in comparison with those who had never smoked, HbA 1c was higher by 0.10% (95% CI 0.08, 0.12) (1.1 mmol/mol [0.9, 1.3]) in current smokers and higher by 0.03% (0.01, 0.05) (0.3 mmol/mol [0.1, 0.5]) in ex-smokers. This relation remained consistent across sex, age, and BMI strata. In contrast, there was little difference in fasting plasma glucose for current smokers compared with neversmokers (20.004 mmol/L [20.06, 0.02]), but for ex-smokers fasting plasma glucose was higher by 0.12 mmol/L (0.09, 0.14).We question whether HbA 1c should be used alone to evaluate glycemic control in people with type 1 diabetes, particularly in those who smoke, as smoking may alter HbA 1c independent of glycemia. A continuous glucose monitoring study is required to compare the glucose profiles according to smoking habits in people with type 1 diabetes.

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