HbA1c, fasting and 2 h plasma glucose in current, ex- and never-smokers: a meta-analysis

Global variation in diabetes diagnosis and prevalence based on fasting glucose and hemoglobin A1c

Fasting plasma glucose (FPG) and hemoglobin A1c (HbA1c) are both used to diagnose diabetes, but these measurements can identify different people as having diabetes. We used data from 117 population-based studies and quantified, in different world regions, the prevalence of diagnosed diabetes, and whether those who were previously undiagnosed and detected as having diabetes in survey screening, had elevated FPG, HbA1c or both. We developed prediction equations for estimating the probability that a person without previously diagnosed diabetes, and at a specific level of FPG, had elevated HbA1c, and vice versa. The age-standardized proportion of diabetes that was previously undiagnosed and detected in survey screening ranged from 30% in the high-income western region to 66% in south Asia. Among those with screen-detected diabetes with either test, the age-standardized proportion who had elevated levels of both FPG and HbA1c was 29-39% across regions; the remainder had discordant elevation of FPG or HbA1c. In most low- and middle-income regions, isolated elevated HbA1c was more common than isolated elevated FPG. In these regions, the use of FPG alone may delay diabetes diagnosis and underestimate diabetes prevalence. Our prediction equations help allocate finite resources for measuring HbA1c to reduce the global shortfall in diabetes diagnosis and surveillance.

Ethnicity Affects A1C Levels in Patients With Diagnosed Type 2 Diabetes in Southern Israel

Purpose

To assess whether ethnicity affects the association between A1C and fasting glucose in people with type 2 diabetes.

Methods

This investigation was an epidemiological, cross-sectional study based on computerized medical records of the Southern District of Clalit Health Services. The study population comprised patients ≥40 years of age with type 2 diabetes who underwent blood tests between 8 August 2015 and 20 July 2020. A normal-error multiple linear regression model was used to assess differences in associations among ethnic groups (i.e., Arabs, Ethiopian Jews, and non-Ethiopian Jews) and A1C.

Results

A total of 59,432 patients with type 2 diabetes were included in the study. Of these, 1,804 were Jews of Ethiopian origin, 49,296 were non-Ethiopian Jews, and 8,332 were Arabs. Compared with non-Ethiopian Jews, A1C levels were increased by 0.1% (1 mmol/mol) among Ethiopian Jews and by 0.3% (3 mmol/mol) among Arabs. Ethnicity was a strong predictor of A1C, explaining 0.6% of its variance. An A1C level of 7% (53 mmol/mol) correlated with fasting glucose levels of 141, 136, and 126 mg/dL in non-Ethiopian Jews, Ethiopian Jews, and Arabs, respectively.

Conclusion

Ethnic differences in A1C should be considered by clinicians, researchers, and policymakers.

Estimates of bladder cancer burden attributable to high fasting plasma glucose: Findings of the Global Burden of Disease Study 2019

BACKGROUND

High fasting plasma glucose (FPG) has been listed as one of the risk factors for bladder cancer. We here estimated the global, regional, and national levels of bladder cancer burden attributable to high FPG from 1990 to 2019.

METHODS

Bladder cancer data attributable to high FPG were extracted from the Global Burden of Disease Study 2019, and analyzed by age, sex, year, and location. Age-standardized rates were utilized to evaluate the burden between different populations. The temporal trend of the burden was estimated through the Joinpoint analysis.

RESULTS

In 2019, high FPG contributed to 22,823.33 (95% uncertainty interval [UI], 4694.88-48,962.26) deaths and 399,654.91 (95% UI, 81,609.35-865,890.95) disability-adjusted life years (DALYs) of bladder cancer globally. Since 1990, the global age-standardized death and DALY rates of bladder cancer attributable to high FPG increased apparently by 39.18% and 41.48%, respectively. During the last 30 years, high FPG-related age-standardized death and DALY rates of bladder cancer have increased in all countries. In 2019, Central Europe showed the greatest high FPG-related age-standardized death and DALY rates of bladder cancer, but Andean Latin America had the lowest rates. Nationally, Lebanon showed the greatest high FPG-related age-standardized death and DALY rates of bladder cancer in 2019. High FPG-attributable deaths and DALYs of bladder cancer were more considerable among males and older people. Countries with high SDI showed higher levels of age-standardized death and DALY rates of bladder cancer due to high FPG and presented remarkable upward trends in rates in the last 30 years.

CONCLUSIONS

Globally, the high FPG-associated bladder cancer burden has remarkably increased in all countries, and showed a higher level among countries with higher SDI. Monitoring FPG levels among patients with bladder cancer is critical to lower the corresponding burden.

Racial disparity in gestational diabetes mellitus and the association with sleep-disordered breathing and smoking cigarettes: a cross-sectional study

BACKGROUND

Gestational diabetes mellitus (GDM) prevalence has risen in the U.S. and worldwide over the past decade. Minority groups, especially Asian and Hispanic women, are often disproportionately affected by GDM. Identifying modifiable risk factors such as sleep-disordered breathing and smoking and their interaction with race/ethnicity could play a pivotal role in preventing GDM.

METHODS

Data from the 2017-2018 National Health and Nutrition Examination Surveys (NHANES) were used to run a survey-weighted multivariable logistic regression assessing the association between sleep-disordered breathing and smoking with GDM among women aged 15-60 (n = 1326). The interaction term of the two predictors and race/ethnicity was introduced to the model to assess the interaction effect. The analyses were adjusted for age, marital status, education level, and BMI.

RESULTS

Approximately 13% of the participants reported having GDM. The lowest prevalence was observed among Non-Hispanic Blacks (7.8%) and the highest was among Other (15.5%). Sleep-disordered breathing was significantly associated with GDM (OR = 1.69, 95% CI 1.05, 2.73). No statistically significant association was observed between smoking and GDM (OR = 1.03, 95% CI 0.47, 2.27), and neither was the association between race/ethnicity and GDM. Furthermore, none of the interaction effects were statistically significant.

CONCLUSION

Preventive strategies targeting GDM should focus on improving modifiable risk factors, such as sleep-disordered breathing. It is important to screen women with sleep-disordered breathing and monitor their blood sugar before becoming pregnant to prevent the development of GDM. Future studies are recommended to understand the lower prevalence of GDM among Black women and the higher prevalence among "Other" race group which mostly includes Asian women.

Association between smoking and glycemic control in men with newly diagnosed type 2 diabetes: a retrospective matched cohort study

BACKGROUND

Longitudinal data on the association between smoking and glycemic control in men with newly diagnosed type 2 diabetes (T2DM) is scarce. Therefore, this study aimed to examine the extent of the association between smoking and glycemic control in this population.

METHODS

The retrospective cohort study identified 3044 eligible men with T2DM in a medical centre in Taiwan between 2002 and 2017. Smokers (n = 757) were matched 1:1 with non-smokers using propensity score-matching. All of them were followed for one year. Glycated haemoglobin (HbA1c) levels were measured at 0, 3, 6, 9, and 12 months after enrolment. Generalised estimating equations were used to assess smoking status-by-time interaction to determine the difference in HbA1c reduction between the two cohorts. All analyses were performed in 2020.

RESULTS

The estimated maximal difference in HbA1c reduction between smokers and non-smokers was 0.33% (95% CI, 0.05-0.62%) at 3 months of follow-up. For patients with body mass index (BMI) <25 kg/m², the difference in HbA1c reduction between smokers and non-smokers was much larger (0.74%, 95% CI, 0.35-1.14%) than in those with a higher BMI.

CONCLUSIONS

Our findings show that smoking was independently associated with unfavourable glycemic control among men with newly diagnosed T2DM, and such a detrimental association could be stronger in men with a lower BMI.

Glycaemic control and its associated factors in patients with type 2 diabetes in the Middle East and North Africa: An updated systematic review and meta-analysis

Aims

To examine the patient‐related factors that have been linked to glycaemic control in people living with type 2 diabetes mellitus in Middle Eastern countries.

Design

A systematic review and meta‐analysis.

Data Sources

A computerized search was conducted using the databases MEDLINE (via PubMed and Ovid), EMBASE, Scopus and CINAHL to identify peer‐reviewed articles published in English between 1 January 2010 and 21 May 2020. On 28 June 2021, the search was updated with the same keywords and databases; however, no further relevant studies were identified.

Review Methods

Extracted data were analysed using Review Manager 5.4.

Results

The final sample consisted of 54 articles with a total of 41,079 participants. Pooled data showed an increased risk of inadequate glycaemic control in smokers [OR = 1.26, 95% confidence interval (CI): 1.05, 1.52; p = .010], obese patients (OR = 1.30, 95% CI: 1.10, 1.54; p = .002), patients with elevated waist to hip ratio (OR = 1.62, 95% CI: 1.16, 2.26; p = .004) and longer disease duration (OR = 2.01, 95% CI: 1.64, 2.48; p < .001). A lower risk of inadequate control was associated with physical activity (OR = 0.40, 95% CI: 0.24, 0.67; p < .001) and self‐management (OR = 0.49, 95% CI: 0.29, 0.82; p = .006).

Conclusion

These findings highlight the opportunity to address factors to improve glycaemic control. Further longitudinal studies are required to better understand these variations, to assess all predictors of glycaemic control in participants with type 2 diabetes, and to provide a strong basis for future measures to optimize glycaemic control.

Incidence rates and predictors of microvascular and macrovascular complications in patients with type 2 diabetes: Results from the longitudinal global discover study

BACKGROUND

Micro- and macrovascular complications are a major cause of morbidity and mortality in people with type 2 diabetes (T2D). We sought to understand the global incidence rates and predictors of these complications.

METHODS

We examined the incidence of vascular complications over 3 years of follow-up in the DISCOVER study-a global, observational study of people with T2D initiating second-line glucose-lowering therapy. Hierarchical Cox proportional hazards regression models examined factors associated with development of micro- and macrovascular complications during follow-up.

RESULTS

Among 11,357 people with T2D from 33 countries (mean age 56.9 ± 11.7 years, T2D duration 5.7 ± 5.1 years, HbA1c 8.4 ± 1.7%), 19.0% had a microvascular complication at enrolment (most commonly neuropathy), and 13.2% had a macrovascular complication (most commonly coronary disease). Over 3 years of follow-up, 16.0% developed an incident microvascular complication, and 6.6% had an incident macrovascular complication. At the end of 3 years of follow-up, 31.5% of patients had at least one microvascular complication, and 16.6% had at least one macrovascular complication. Higher HbA1c and smoking were associated with greater risk of both incident micro- and macrovascular complications. Known macrovascular complications at baseline was the strongest predictor for development of new microvascular complications (HR 1.40, 95% CI 1.21 -1.61) and new macrovascular complications (HR 3.39, 95% CI 2.84 -4.06).

CONCLUSIONS

In this global study, both the prevalence and 3-year incidence of vascular complications were high in patients with relatively short T2D duration, highlighting the need for early risk-factor modification.

Impact of smoking on gestational diabetes mellitus and offspring birthweight in primiparous women

INTRODUCTION

Smoking has been shown to affect glucose homeostasis and increase the risk for type 2 diabetes mellitus. Further, gestational diabetes mellitus (GDM) and smoking are known to influence offspring birthweight. The effect of smoking on glucose homeostasis in pregnancy is less studied and the findings are inconsistent. The aim of this study was to evaluate the effect of smoking on risk for GDM and to evaluate the impact of smoking and GDM on offspring birthweight.

MATERIAL AND METHODS

This is an observational cohort study encompassing 4111 Finnish primiparous women from the city of Vantaa, Finland, who delivered a singleton child between 2009 and 2015. Data were obtained from Finnish national registers. Study participants had complete oral glucose tolerance test results and were divided into three groups according to smoking status: non-smokers (I), smokers who quit during first trimester (II), and smokers who continued after first trimester (III).

RESULTS

Prevalence of GDM was 19.8%, 24.3%, and 26.6% in non-smokers, those who quit, and those who continued after the first trimester, respectively (P = .004 for differences between groups). The odds ratio for GDM in smokers who continued after the first trimester compared with non-smokers was 1.65 (95% CI 1.09-2.57) after adjustments for age, prepregnancy body mass index, education, and cohabitation. In women without GDM, offspring birthweight was lowest in those who continued smoking after the first trimester (P = .010 for differences between groups). In women with GDM, smoking status did not influence offspring birthweight.

CONCLUSIONS

Smoking during pregnancy is associated with an increased risk for GDM. Offspring birthweight is lowest in women who continue smoking after the first trimester. If pregnancy is complicated by GDM, offspring birthweight is not influenced by smoking.

Factors associated with glycaemic control in adults with Type 1 diabetes: a registry-based analysis including 7601 individuals from 34 centres in Norway

AIMS

To use data from the Norwegian Diabetes Registry for Adults and Statistics Norway to assess factors associated with glycaemic control in type 1 diabetes.

METHODS

The analyses included all individuals aged ≥18 years who had a type 1 diabetes duration of >2 years and a recorded value in the registry between 2013 and 2015 (n=7601). Predicted mean HbA_1c levels for subgroups of participants were assessed using linear regression analysis.

RESULTS

Young age (18-25 years), low education levels, smoking, living alone, exercising infrequently, monitoring glucose infrequently, high insulin requirements, low frequency of symptomatic hypoglycaemia, history of ketoacidosis and a BMI <18.5 kg/m² were associated with a 2-12-mmol/mol (0.2-1.1%) higher HbA_1c level. Those with 10-15 years of diabetes duration had 5-mmol/mol (0.5%) higher HbA_1c level than those who had a diabetes duration of 2-5 years. Sex, participation (ever) in a diabetes education course, or ever experiencing serious hypoglycaemia were not associated with glycaemic control.

CONCLUSIONS

We present representative national data on factors that were associated with glycaemic control. A better understanding and awareness of these factors, together with technological advances in diabetes management, could lead to more personalized management strategies, better glycaemic control and a lower risk of diabetes complications.

The effect of smoking on the risk of gestational diabetes mellitus and the OGTT profile during pregnancy

OBJECTIVE

To analyze the relationship between smoking and the risk of GDM, as well as with the OGTT profile during pregnancy.

PATIENTS AND METHODS

A total of 7437 pregnant women were studied. OGTT was performed at the 3rd trimester. Women were categorized as non-smokers (A), as those who ceased smoking at pregnancy (B), and as smokers (C).

RESULTS

5434 (73.1%) women were group A, 1191 (16%) group B and 812 (10.9%) group C. The rates of GDM among the groups were: A 33.7%, B 34.2%, C 34.2% (ns). However, the number of individuals requiring insulin treatment was significantly different: A 39.2%, B 47.5%, C 50.6% (p < 0.001). Regarding OGTT, fasting glucose levels were significantly higher in group C (89 ± 13 vs 86 ± 12 mg/dl) compared to A, whereas 3-h glucose values were significantly lower (104 ± 33 vs 112 ± 32 mg/dl) (p < 0.001). Group B demonstrated intermediate glucose concentrations. Similar findings were observed in women without GDM. In women with GDM, higher 1-h glucose levels were measured in group C (210 ± 31 vs 205 ± 28 mg/dl) compared with A (p = 0.024). Further, group C sub-analysis found that those who smoked more than 10 cigarettes showed significantly lower 3-h glucose levels (111 ± 31 vs 128 ± 40 mg/dl) compared to those who smoked less than 10 (p = 0.006). HbA1c in women with GDM was higher in group C (4.6 ± 0.6 vs 4.5 ± 0.6%) compared with A (p = 0.027).

CONCLUSIONS

The present study did not show any correlation between smoking and GDM risk. However, OGTT profile and HbA1c differed according to smoking status in women with and without GDM.

Association Between Glycaemic Control and the Intake of Thiazide Diuretics, Beta Blockers and Levothyroxine in People Without Diabetes

OBJECTIVE

The pharmacological additional information for many medications includes warnings stating that the blood sugar control may be worsened by the intake of certain drugs. However a quantification of the effects is missing. This may result in confusion for patients as well as for their physicians. The aim of this study was to assess a potential association between medication (beta blockers, thiazides, levothyroxine) and HbA_1c in people without diabetes.

METHODS

In this cross-sectional study we analysed data from 2 921 people (7 699 visits) without diabetes (age 46.6 y; 69.1% women; BMI 27.6±6.4 kg/m²; HbA_1c 5.2%) who had at least one HbA_1c determination and a complete documentation of their drug intake. An oral glucose tolerance test was not performed. The participants were divided in 8 groups (no regular drug intake, levothyroxine alone, beta blockers alone, thiazides alone, combination 2 of 3, combination of all 3). Patients with known distorting influences of the HbA_1c were excluded.

RESULTS

People with no regular drug intake had an HbA_1c of 5.4% [35.8 mmol/mol]. The HbA_1c of the group that took all 3 drugs in combination was 5.6% [38.2 mmol/mol]. A multiple linear mixed model showed an increase in HbA_1c for thiazides (β=0.0558, p=0.025) and a decrease for combination of levothyroxine and thiazide (β=-0.0765, p=0.010).

CONCLUSION

Thiazides and the combination of levothyroxine and thiazides were associated with slight changes in HbA_1c. In this study there was no association between the intake of beta blockers and HbA_1c. At least for people without diabetes these effects seem to be of minor importance.

Effects of reduced exposure to cigarette smoking on changes in biomarkers of potential harm in adult smokers: results of combined analysis of two clinical studies

Purpose: Nonconventional vapor products (NVP), designed to reduce exposure to cigarette smoke toxicants (CSTs), could cause changes in biomarkers of potential harm (BoPH). Although, NVPs reduced CSTs exposure compared to conventional cigarettes (CC), the changes in the BoPH values varied among the studies. Hence, further information on BoPH using NVPs is needed. Material and methods: The data of two similarly designed studies using a kind of NVP, a noncombustion and nonheating inhaler type of smokeless tobacco product (NCIT) used under 31-day confinement, were pooled, and the differences in 15 BoPH between smokers and nonsmokers at baseline and between the 1 mg tar CC (CC1) group and NCIT group at Day 28/29 were analyzed. Results: At baseline, the levels of eight BoPH (red blood cells, white blood cells, 8-epi-prostaglandin F2α, 8-hydroxy-2'-deoxyguanosine, malondialdehyde, 11-dehydrothromboxane B2, total cholesterol and glucose) were significantly different between smokers and nonsmokers. At Day 28/29, the levels of six BoPH were significantly different between NCIT and CC1 (8-epi-prostaglandin F2α, malondialdehyde, 11-dehydrothromboxane B2: CC1 > NCIT, total bilirubin, low-density lipoprotein cholesterol and total cholesterol: CC1 < NCIT). Conclusions: Reduced exposure to CSTs has favorable effects on BoPH associated with oxidative stress, antioxidant capacity and platelet activation/coagulation but not in lipid metabolism.

Mediation of the association of smoking and microvascular complications by glycemic control in type 1 diabetes

Studies have demonstrated the adverse effects of smoking on the risk of microvascular complications; however, few have also examined the potential mediating effects of glycemic control. Using data from the Diabetes Control and Complications Trial (DCCT 1983–1993), we describe the acute and long-term risks of smoking on glycemic control and microvascular complications in a well-characterized cohort of participants with type 1 diabetes. The DCCT recorded self-reported smoking behaviors, glycemic exposure based on HbA1c, and complications status. Generalized linear mixed models were used to assess whether time-dependent measurements of smoking predict HbA1c levels. Cox proportional hazard models were used to assess time-dependent smoking exposures as predictors of retinopathy and nephropathy. During a mean of 6.5 years of follow-up, current smokers had consistently higher HbA1c values and were at a higher risk of retinopathy and nephropathy compared with former and never smokers. These risk differences were attenuated after adjusting for HbA1c suggesting that the negative association of smoking on glycemic control is partially responsible for the adverse association of smoking on the risk of complications in type 1 diabetes. These findings support the potential for a beneficial effect of smoking cessation on complications in type 1 diabetes.

Pathophysiological Characteristics Underlying Different Glucose Response Curves: A Latent Class Trajectory Analysis From the Prospective EGIR-RISC Study

OBJECTIVE

Glucose measurements during an oral glucose tolerance test (OGTT) are useful in predicting diabetes and its complications. However, knowledge of the pathophysiology underlying differences in glucose curve shapes is sparse. We examined the pathophysiological characteristics that create different glucose curve patterns and studied their stability and reproducibility over 3 years of follow-up.

RESEARCH DESIGN AND METHODS

We analyzed data from participants without diabetes from the observational cohort from the European Group for the Study of Insulin Resistance: Relationship between Insulin Sensitivity and Cardiovascular Disease study; participants had a five-time point OGTT at baseline (n = 1,443) and after 3 years (n = 1,045). Measures of insulin sensitivity and secretion were assessed at baseline with a euglycemic-hyperinsulinemic clamp and intravenous glucose tolerance test. Heterogeneous glucose response patterns during the OGTT were identified using latent class trajectory analysis at baseline and at follow-up. Transitions between classes were analyzed with multinomial logistic regression models.

RESULTS

We identified four different glucose response patterns, which differed with regard to insulin sensitivity and acute insulin response, obesity, and plasma levels of lipids and inflammatory markers. Some of these associations were confirmed prospectively. Time to glucose peak was driven mainly by insulin sensitivity, whereas glucose peak size was related to both insulin sensitivity and secretion. The glucose patterns identified at follow-up were similar to those at baseline, suggesting that the latent class method is robust. We integrated our classification model into an easy-to-use online application that facilitates the assessment of glucose curve patterns for other studies.

CONCLUSIONS

The latent class analysis approach is a pathophysiologically insightful way to classify individuals without diabetes based on their response to glucose during an OGTT.

Association between smoking and glycemic control in diabetic patients: Results from the Risk Evaluation of cAncers in Chinese diabeTic Individuals: A lONgitudinal (REACTION) study

BACKGROUND

A number of primary studies suggested that active smoking could be independently associated with incident diabetes. However less is known about the effect of active smoking and smoking cessation on glycemic control in patients with diabetes. The aim of this study was to evaluate the associations of active smoking and smoking cessation with glycemic control in diabetic patients.

METHODS

The present was a cross-sectional study of 10 551 men and 15 297 women with diabetes from the Risk Evaluation of cAncers in Chinese diabeTic Individuals: a lONgitudinal (REACTION) study. Risk factors for glycemic control and the association of active smoking with glycemic control were evaluated using logistic regression models. Poor glycemic control was defined as HbA1c ≥7.0%.

RESULTS

Current smokers have an increased risk of poor glycemic control, and the multivariable-adjusted odds ratio (OR) and 95% confidence intervals (CI) of HbA1c ≥7.0% with current smoking were 1.49 (1.35-1.66) in men and 1.56 (1.13-2.15) in women. Further analysis demonstrated a dose-dependent relationship between active smoking and the risk of poor glycemic control in men. Former smokers who quit smoking for <10 years remained at increased risk of poor glycemic control, with the risk leveling off after 10 years of smoking cessation compared with non-smokers, but risk in former smokers was significantly lower than that in current smokers.

CONCLUSIONS

Active smoking is a modifiable risk factor for poor glycemic control in Chinese diabetic patients.

Interaction of diabetes and smoking on stroke: a population-based cross-sectional survey in China

OBJECTIVES

Diabetes and smoking are known independent risk factors for stroke; however, their interaction concerning stroke is less clear. We aimed to explore such interaction and its influence on stroke in Chinese adults.

DESIGN

Cross-sectional study.

SETTING

Community-based investigation in Xuzhou, China.

PARTICIPANTS

A total of 39 887 Chinese adults who fulfilled the inclusion criteria were included.

METHODS

Participants were selected using a multistage stratified cluster method, and completed self-reported questionnaires on stroke and smoking. Type 2 diabetes mellitus (DM2) was assessed by fasting blood glucose or use of antidiabetic medication. Interaction, relative excess risk owing to interaction (RERI), attributable proportion (AP) and synergy index (S) were evaluated using a logistic regression model.

RESULTS

After adjustment for age, sex, marital status, educational level, occupation, physical activity, body mass index, hypertension, family history of stroke, alcohol use and blood lipids, the relationships between DM2 and stroke, and between smoking and stroke, were still significant: ORs were 2.75 (95% CI 2.03 to 3.73) and 1.70 (95% CI 1.38 to 2.10), respectively. In subjects with DM2 who smoked, the RERI, AP and S values (and 95% CIs) were 1.80 (1.24 to 3.83), 0.52 (0.37 to 0.73) and 1.50 (1.18 to 1.84), respectively.

CONCLUSIONS

The results suggest there are additive interactions between DM2 and smoking and that these affect stroke in Chinese adults.

Association between White Blood Cell Counts within Normal Range and Hemoglobin A1c in a Korean Population

BACKGROUND

We examined whether white blood cell (WBC) count levels within normal range, could be associated with hemoglobin A1c (HbA1c) levels.

METHODS

Among the 11,472 people (≥19 years of age) who participated in the 2011 to 2012 Korea National Health and Nutrition Examination, subjects with chronic disease or illness, including 807 patients with diabetes currently taking anti-diabetic medications and/or 1,149 subjects with WBC levels <4,000 or >10,000/μL were excluded.

RESULTS

Overall, adjusted HbA1c levels increased across the WBC quartiles (5.55%±0.01%, 5.58%±0.01%, 5.60%±0.01%, and 5.65%±0.01%, P<0.001) after adjusting for confounding factors, such as age, gender, fasting plasma glucose, college graduation, smoking history, waist circumference, presence of hypertension, serum total cholesterol, serum triglyceride, and presence of anemia. The adjusted proportions (%) of HbA1c levels of ≥5.7%, ≥6.1%, and ≥6.5% showed significant increases across WBC quartiles (P<0.001, P=0.002, and P=0.022, respectively). Logistic regression analyses of WBC quartiles for the risk of HbA1c levels of ≥5.7%, ≥6.1%, and ≥6.5%, using the variables above as covariates, showed that the odds ratios of the fourth quartile of WBCs were 1.59 (95% confidence interval [CI], 1.35 to 1.89; P<0.001), 1.78 (95% CI, 1.31 to 2.42; P<0.001), and 2.03 (95% CI, 1.13 to 3.64; P=0.018), using the first quartile of WBCs as the reference.

CONCLUSION

HbA1c levels were positively associated with WBC levels within normal range in a general adult population.

Influence of cigarette smoking on hormone and lipid metabolism in women in late reproductive stage

BACKGROUND

The aim of the study was to analyze lipid and hormone metabolism, body mass index (BMI), and age parameters in late reproductive stage women in relation to cigarette smoking.

METHODS

The study enrolled 345 healthy late reproductive stage women living in Poland; 13.33% were smokers. The first part of the study assessed lipid metabolism (total cholesterol, high-density lipoprotein [HDL], low-density lipoprotein [LDL], and triglycerides) and hormone metabolism (estradiol [E2], follicle-stimulating hormone [FSH], and anti-Müllerian hormone [AMH] levels) in women in the early phase of the follicular menstrual cycle. The second part of study was carried out using the diagnostic survey method, with a standardized questionnaire (Primary Care Evaluation of Mental Disorders [PRIME-MD]) and the authors' own research tools.

RESULTS

The women were aged 42.3±4.5 years (mean ± SD). The BMI (24.8±4.04 kg/m2) did not differ significantly between the groups. The women who smoked cigarettes had a statistically significantly (p<0.05) lower level of HDL as well as higher LDL and triglyceride levels (p<0.05). Differences were also shown in hormone levels: non-smoking participants had statistically significantly higher levels of E2 and FSH (p<0.05). In the group of non-smoking women, age was a predictor exerting a significant positive impact on the levels of total cholesterol, LDL, triglycerides, and AMH (p<0.05). BMI contributed to a decline in HDL and triglyceride levels. In the group of smoking women, age significantly positively influenced the level of E2, and negatively influenced AMH. BMI was associated with a significant decrease in the HDL level.

CONCLUSION

Smoking cigarettes affects the physical health of women in late reproductive stage through negative influences on lipid and hormone metabolism, among other factors. Age is an unmodifiable factor adversely affecting both lipids and hormones. Higher BMI has a negative influence on lipid metabolism in both groups of women in this study.

Glucose patterns during an oral glucose tolerance test and associations with future diabetes, cardiovascular disease and all-cause mortality rate

AIMS/HYPOTHESIS

In addition to blood glucose concentrations measured in the fasting state and 2 h after an OGTT, intermediate measures during an OGTT may provide additional information regarding a person's risk of future diabetes and cardiovascular disease (CVD). First, we aimed to characterise heterogeneity of glycaemic patterns based on three time points during an OGTT. Second, we compared the incidences of diabetes and CVD and all-cause mortality rates among those with different patterns.

METHODS

Our cohort study included 5861 participants without diabetes at baseline from the Danish Inter99 study. At baseline, all participants underwent an OGTT with measurements of plasma glucose levels at 0, 30 and 120 min. Latent class mixed-effects models were fitted to identify distinct patterns of glycaemic response during the OGTT. Information regarding incident diabetes, CVD and all-cause mortality rates during a median follow-up time of 11, 12 and 13 years, respectively, was extracted from national registers. Cox proportional hazard models with adjustment for several cardiometabolic risk factors were used to compare the risk of diabetes, CVD and all-cause mortality among individuals in the different latent classes.

RESULTS

Four distinct glucose patterns during the OGTT were identified. One pattern was characterised by high 30 min but low 2 h glucose values. Participants with this pattern had an increased risk of developing diabetes compared with participants with lower 30 min and 2 h glucose levels (HR 4.1 [95% CI 2.2, 7.6]) and participants with higher 2 h but lower 30 min glucose levels (HR 1.5 [95% CI 1.0, 2.2]). Furthermore, the all-cause mortality rate differed between the groups with significantly higher rates in the two groups with elevated 30 min glucose. Only small non-significant differences in risk of future CVD were observed across latent classes after confounder adjustment.

CONCLUSIONS/INTERPRETATION

Elevated 30 min glucose is associated with increased risk of diabetes and all-cause mortality rate independent of fasting and 2 h glucose levels. Therefore, subgroups at high risk may not be revealed when considering only fasting and 2 h glucose levels during an OGTT.

Diabetic by HbA1c, Normal by OGTT: A Frequent Finding in the Mexico City Diabetes Study

CONTEXT

The agreement between glucose-based and hemoglobin A1c (HbA1c)-based American Diabetes Association criteria in the diagnosis of normal glucose tolerance, prediabetes, or diabetes is under scrutiny. A need to explore the issue among different populations exists.

OBJECTIVE

Examine the results obtained with both methods in the diagnosis of the glycemic status.

DESIGN

The Mexico City Diabetes Study is a population-based, prospective investigation.

SETTING

Low-income elder urban community.

PARTICIPANTS

All 854 participants without known diabetes had both oral glucose tolerance test (OGTT) and HbA1c measurements on the same day of the 2008 phase.

INTERVENTIONS

Standardized protocol: questionnaires, anthropometry, and biomarkers.

MAIN OUTCOME

Diagnostic classification of American Diabetes Association criteria.

RESULTS

We found by OGTT normal glucose tolerance (NGT) in 512 (59.9%) participants, prediabetes [impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT)] in 261 (30.5%), and diabetes in 81 (9.4%). In total, 232 in the NGT group (45.3%) and 158 in the prediabetes group (60.5%) had HbA1c ≥6.5%. Body mass index, waist circumference, and blood pressure were significantly different among OGTT-defined diabetic status groups but not in the HbA1c-diagnosed group. We identified 404 participants in the NGT group with confirmed NGT throughout all phases of the Mexico City Diabetes Study. Of these, 184 (45.5%) had HbA1c ≥6.5%. In a vital/diabetes status follow-up performed subsequently, we found that, of these, 133 remained nondiabetic, 3 had prediabetes, 7 had diabetes, and 13 had died without diabetes; we were unable to ascertain the glycemic status in 5 and vital status in 23.

CONCLUSIONS

Normal OGTT coexisting with elevated HbA1c is a common finding in this cohort. It is possible that this finding is not mediated by hyperglycemia. This might occur in similar populations.

Metrics for glycaemic control - from HbA1c to continuous glucose monitoring

As intensive treatment to lower levels of HbA_1c characteristically results in an increased risk of hypoglycaemia, patients with diabetes mellitus face a life-long optimization problem to reduce average levels of glycaemia and postprandial hyperglycaemia while simultaneously avoiding hypoglycaemia. This optimization can only be achieved in the context of lowering glucose variability. In this Review, I discuss topics that are related to the assessment, quantification and optimal control of glucose fluctuations in diabetes mellitus. I focus on markers of average glycaemia and the utility and/or shortcomings of HbA_1c as a 'gold-standard' metric of glycaemic control; the notion that glucose variability is characterized by two principal dimensions, amplitude and time; measures of glucose variability that are based on either self-monitoring of blood glucose data or continuous glucose monitoring (CGM); and the control of average glycaemia and glucose variability through the use of pharmacological agents or closed-loop control systems commonly referred to as the 'artificial pancreas'. I conclude that HbA_1c and the various available metrics of glucose variability reflect the management of diabetes mellitus on different timescales, ranging from months (for HbA_1c) to minutes (for CGM). Comprehensive assessment of the dynamics of glycaemic fluctuations is therefore crucial for providing accurate and complete information to the patient, physician, automated decision-support or artificial-pancreas system.

Tobacco and diabetes: clinical relevance and approach to smoking cessation in diabetic smokers

Smoking is, together with diabetes mellitus, one of the main risk factors for cardiovascular disease. Diabetic patients have unique features and characteristics, some of which are not well known, that cause smoking to aggravate the effects of diabetes and impose difficulties in the smoking cessation process, for which a specificand more intensive approach with stricter controls is required. This review details all aspects with a known influence on the interaction between smoking and diabetes, both as regards the increased risk of macrovascular and microvascular complications of diabetes and the factors with an impact on the results of smoking cessation programs. The treatment guidelines for these smokers, including the algorithms and drug treatment patterns which have proved most useful based on scientific evidence, are also discussed.

Heterogeneity in glucose response curves during an oral glucose tolerance test and associated cardiometabolic risk

We aimed to examine heterogeneity in glucose response curves during an oral glucose tolerance test with multiple measurements and to compare cardiometabolic risk profiles between identified glucose response curve groups. We analyzed data from 1,267 individuals without diabetes from five studies in Denmark, the Netherlands and the USA. Each study included between 5 and 11 measurements at different time points during a 2-h oral glucose tolerance test, resulting in 9,602 plasma glucose measurements. Latent class trajectories with a cubic specification for time were fitted to identify different patterns of plasma glucose change during the oral glucose tolerance test. Cardiometabolic risk factor profiles were compared between the identified groups. Using latent class trajectory analysis, five glucose response curves were identified. Despite similar fasting and 2-h values, glucose peaks and peak times varied greatly between groups, ranging from 7-12 mmol/L, and 35-70 min. The group with the lowest and earliest plasma glucose peak had the lowest estimated cardiovascular risk, while the group with the most delayed plasma glucose peak and the highest 2-h value had the highest estimated risk. One group, with normal fasting and 2-h values, exhibited an unusual profile, with the highest glucose peak and the highest proportion of smokers and men. The heterogeneity in glucose response curves and the distinct cardiometabolic risk profiles may reflect different underlying physiologies. Our results warrant more detailed studies to identify the source of the heterogeneity across the different phenotypes and whether these differences play a role in the development of type 2 diabetes and cardiovascular disease.

Insulin resistance and β-cell function in smokers: results from the EGIR-RISC European multicentre study

AIMS

Tobacco smoking is known to increase the long-term risk of developing Type 2 diabetes mellitus, but the mechanisms involved are poorly understood. This observational, cross-sectional study aims to compare measures of insulin sensitivity and β-cell function in current, ex- and never-smokers.

METHODS

The study population included 1246 people without diabetes (mean age 44 years, 55% women) from the EGIR-RISC population, a large European multicentre cohort. Insulin sensitivity was measured using a hyperinsulinaemic, euglycaemic clamp and the homeostatic model assessment - insulin resistance (HOMA-IR) index. Two β-cell function parameters were derived from measures during an oral glucose tolerance test: the early insulin response index and β-cell glucose sensitivity. Additionally, the areas under the curve during the oral glucose tolerance test were calculated for glucose, insulin and C-peptide.

RESULTS

According to smoking habits, there were differences in insulin sensitivity, which was lower in women who smoked, and in β-cell glucose sensitivity, which was lower in men who smoked, but these associations lost significance after adjustment. However, after adjustment, the areas under the glucose and the C-peptide curves during the oral glucose tolerance test were significantly higher in men who smoked.

CONCLUSIONS

Smoking habits were not independently associated with insulin sensitivity or β-cell function in a healthy middle-aged European population. Health-selection bias, methodological shortcomings or a true lack of causal links between smoking and impaired insulin sensitivity/secretion are possible explanations. The mechanisms behind the observed increased glucose and C-peptide areas under the curve during the oral glucose tolerance test in male smokers need to be further evaluated.

Association between Alcohol Intake and Hemoglobin A1c in the Korean Adults: The 2011-2013 Korea National Health and Nutrition Examination Survey

BACKGROUND

Although alcohol consumption is commonly encountered in clinical practice, few studies have investigated the clinical significance of alcohol intake on the use of the hemoglobin A1c (HbA1c) level.

OBJECTIVES

This study was performed to investigate the association between alcohol intake and HbA1c level in the general population.

METHODS

Among the 24,594 participants who participated in the 2011-2013 Korea National Health and Nutrition Examination Survey (KNHANES), 12,923 participants were analyzed in this study. We excluded diabetic patients currently taking antidiabetes medication. We compared the HbA1c level and proportions of patients with an HbA1c level of ≥5.7%, ≥6.1%, and ≥6.5% according to the fasting plasma glucose (FPG) concentration range and the amount of alcohol intake. The average amounts of daily alcohol intake were categorized into three groups: 0 g/day, <30 g/day, ≥30 g/day.

RESULTS

The mean HbA1c level was 5.65%, and the mean FPG concentration was 95.3 mg/dl. The percentages of patients with an HbA1c level of ≥5.7%, ≥6.1%, and ≥6.5% were 42.6%, 13.4%, and 4.5%, respectively. The average amount of alcohol intake was 12.3 g/day. The percentages of subjects with alcohol intake 0, <30, and ≥ 30 g/day were 16.5%, 69.7%, and 13.8%, respectively. There was a significant positive relationship between alcohol intake and FPG concentration (P < 0.001), the prevalence of impaired fasting glucose (P < 0.001), and the prevalence of diabetes (P < 0.001). However, there was no significant relationship between the alcohol intake and HbA1c level. Overall, the adjusted HbA1c levels decreased across alcohol intake (5.70% ± 0.01%, 5.66% ± 0.01%, and 5.55% ± 0.01%) after adjustment for confounding factors such as age, sex, FPG concentration, college graduation, smoking history, presence of hypertension, waist circumference, serum total cholesterol concentration, serum high-density lipoprotein cholesterol concentration, serum triglyceride concentration, presence of anemia, serum white blood cell count, and serum alanine aminotransferase concentration (P < 0.001). The adjusted proportions (%) of patients with an HbA1c level of ≥5.7% (P < 0.001), ≥6.1% (P < 0.001), and ≥6.5% (P < 0.001) showed significant negative trends across alcohol intake after adjustment for confounders. Logistic regression analyses showed that, when using the group that abstained as the control, the group that consumed ≥ 30g/day was negatively associated with the risk of an HbA1c level of ≥5.7% (P < 0.001), ≥6.1% (P < 0.001), and ≥6.5% (P < 0.001), using the above-mentioned variables as covariates.

CONCLUSIONS

Higher alcohol intake was associated with lower HbA1c levels, even after adjusting for confounding factors, including the FPG concentration, in this nationally representative sample of Korean adults. These results suggest that excessive drinking shifts the HbA1c level downward, which might complicate use of the HbA1c level for the diagnosis of diabetes or prediabetes.

Smoking affects the oral glucose tolerance test profile and the relationship between glucose and HbA1c in gestational diabetes mellitus

AIMS

Current smokers in the general population have a lower 2 h plasma glucose after an oral glucose tolerance test (OGTT) and a higher HbA1c than non-smokers, but the relationships between OGTT/HbA1c and smoking status have not been addressed in pregnancy. We analysed glycaemic measurements in women with gestational diabetes mellitus in relation to smoking status.

METHODS

We performed a review of the prospectively collected database of the diabetes and pregnancy clinic. We included women with gestational diabetes mellitus and a singleton pregnancy who delivered between 1986 and 2006. Bivariate and multivariate analyses were used to evaluate patient characteristics in relation to smoking status.

RESULTS

A total of 2361 women met the inclusion criteria: 556 (23.5%) were active smokers, 266 (11.3%) quit during pregnancy and 1539 (65.2%) were non-smokers. Most baseline characteristics were similar across groups. Diagnostic OGTT was performed at a gestational age of [median (25th, 75(th) centiles)] 29 weeks (26, 33). Women who smoked at the beginning of pregnancy had a higher 1-h plasma glucose than non-smokers [11.8 (11, 12.7), 11.6 (11, 12.6) and 11.5 (10.8, 12.5) mmol/l, for active smokers, those who quit during pregnancy and non-smokers, respectively, P < 0.001] and a lower 3-h plasma glucose [7.3 (5.9, 8.4), 7.6 (6.4, 8.7) and 8.0 (6.8, 9.0) mmol/l, respectively, P < 0.001]. HbA1c was higher in women who smoked at the beginning of pregnancy. Multiple regression analysis confirmed the independent association of smoking status with HbA1c and OGTT plasma glucose.

CONCLUSIONS

In women with gestational diabetes mellitus who smoke at the beginning of pregnancy, the shape of the OGTT is consistent with accelerated glucose absorption, and HbA1c is higher than expected for glycaemic values.

No Change in Serum Incretins Levels but Rise of Leptin Levels After Smoking Cessation: a Pilot Study

The mechanisms behind the changes of body weight after smoking cessation are only partially understood. To this end, we explored the possible effects of smoking cessation on incretin hormones, leptin and selected anthropometric, biochemical and other hormonal parameters. Twenty-two non-obese male adult smokers attending an ambulatory smoking cessation program in Prague, Czech Republic, were examined at the baseline. Thirteen patients (mean age 37.92±2.66 years, mean body mass index 25.56±0.69 kg/m2) successfully quit smoking and were examined three months after smoking cessation; relapsed smokers were not followed up. The patients underwent 2-h liquid meal test with Fresubin and repeated blood sampling for measurements of blood glucose, gastric inhibitory polypeptide (GIP), glucagon-like peptide 1 (GLP-1), amylin, insulin, leptin, peptide-YY (PYY) and pancreatic polypeptide (PP). Three months after smoking cessation, body weight increased (4.35±3.32 kg, p<0.001). Leptin levels increased significantly in all repeated samples, while levels of GIP, GLP-1, amylin, insulin, PYY and PP remained unchanged. In conclusions, smoking cessation increased leptin levels probably owing to weight gain while it did not influence incretin levels.

Are There Clinical Implications of Racial Differences in HbA1c? Yes, to Not Consider Can Do Great Harm!

Studies that have compared HbA1c levels by race have consistently demonstrated higher HbA1c levels in African Americans than in whites. These racial differences in HbA1c have not been explained by measured differences in glycemia, sociodemographic factors, clinical factors, access to care, or quality of care. Recently, a number of nonglycemic factors and several genetic polymorphisms that operate through nonglycemic mechanisms have been associated with HbA1c Their distributions across racial groups and their impact on hemoglobin glycation need to be systematically explored. Thus, on the basis of evidence for racial differences in HbA1c, current clinical guidelines from the American Diabetes Association state: "It is important to take…race/ethnicity…into consideration when using the A1C to diagnose diabetes." However, it is not clear from the guidelines how this recommendation might be actualized. So, the critical question is not whether racial differences in HbA1c exist between African Americans and whites; the important question is whether the observed differences in HbA1c level are clinically meaningful. Therefore, given the current controversy, we provide a Point-Counterpoint debate on this issue. In the point narrative below, Dr. Herman provides his argument that the failure to acknowledge that HbA1c might be a biased measure of average glycemia and an unwillingness to rigorously investigate this hypothesis will slow scientific progress and has the potential to do great harm. In the counterpoint narrative that follows Dr. Herman's contribution, Dr. Selvin argues that there is no compelling evidence for racial differences in the validity of HbA1c as a measure of hyperglycemia and that race is a poor surrogate for differences in underlying causes of disease risk.-William T. CefaluEditor in Chief, Diabetes Care.

Tobacco Use, Insulin Resistance, and Risk of Type 2 Diabetes: Results from the Multi-Ethnic Study of Atherosclerosis

INTRODUCTION

Tobacco use is associated with insulin resistance and incident diabetes. Given the racial/ethnic differences in smoking patterns and incident type 2 diabetes our objective was to evaluate the association between tobacco use and insulin resistance (IR) as well as incident type 2 diabetes mellitus in a contemporary multiethnic cohort.

METHODS AND RESULTS

We studied 5,931 Multi- Ethnic Study of Atherosclerosis (MESA) participants who at baseline were free of type 2 diabetes (fasting glucose ≥7.0 mmol/l (126 mg/dl) and/or use of insulin or oral hypoglycemic medications) categorized by self-reported tobacco status and reclassified by urinary cotinine (available in 58% of participants) as never, current or former tobacco users. The association between tobacco use, IR (fasting plasma glucose, insulin, and the homeostatic model assessment of insulin resistance (HOMA-IR)) and incident diabetes over 10 years was evaluated using multivariable linear regression and Cox proportional hazards models, respectively. Mean age of the participants was 62 (±10) years, 46% were male, 41% Caucasian, 12% Chinese, 26% African American and 21% Hispanic/Latino. IR biomarkers did not significantly differ between current, former, and never cigarette users (P >0.10) but showed limited unadjusted differences for users of cigar, pipe and smokeless tobacco (All P <0.05). Fully adjusted models showed no association between dose or intensity of tobacco exposure and any index of IR. When stratified into participants that quit smoking vs. those who continued smoking during the 10-year study there was no difference in serum glucose levels or frequency of diabetes. In fully adjusted models, there was no significant difference in diabetes risk between former or current cigarette smokers compared to never smokers [HR (95% CI) 1.02 (0.77,1.37) and 0.81 (0.52,1.26) respectively].

CONCLUSION

In a contemporary multi-ethnic cohort, there was no independent association between tobacco use and IR or incident type 2 diabetes. The role smoking plays in causing diabetes may be more complicated than originally thought and warrants more in-depth large contemporary multi-ethnic studies.

Cigarette Smoking Is Associated with a Lower Prevalence of Newly Diagnosed Diabetes Screened by OGTT than Non-Smoking in Chinese Men with Normal Weight

Different studies have produced conflicting results regarding the association between smoking and diabetes mellitus, and detailed analysis of this issue in Chinese males based on nationwide samples is lacking. We explored the association between cigarette smoking and newly-diagnosed diabetes mellitus (NDM) in Chinese males using a population-based case-control analysis; 16,286 male participants without previously diagnosed diabetes were included. Prediabetes and NDM were diagnosed using the oral glucose tolerance test. The cohort included 6,913 non-smokers (42.4%), 1,479 ex-smokers (9.1%) and 7,894 current smokers (48.5%). Age-adjusted glucose concentrations (mmol/L) were significantly lower at fasting and 120 min in current smokers than non-smokers (5.25 vs. 5.30, 6.46 vs. 6.55, respectively, both P < 0.01). After adjustment for demographic and behavioral variables (age, region, alcohol consumption status, physical activity, education, and family history of diabetes), logistic regression revealed significant negative associations between smoking and NDM in males of a normal weight (BMI < 25 kg/m2: adjusted odds ratio [AOR] = 0.75, P = 0.007; waist circumference < 90 cm: AOR = 0.71, P = 0.001) and males living in southern China (AOR = 0.75, P = 0.009), but not in males who were overweight/obese, males with central obesity, or males living in northern China. Compared to non-smokers, current smokers were less likely to be centrally obese or have elevated BP (AOR: 0.82 and 0.74, both P < 0.05), and heavy smokers (≥ 20 pack-years) were less likely to have elevated TG (AOR = 0.84, P = 0.012) among males of a normal weight. There were no significant associations between quitting smoking and metabolic disorders either among males of a normal weight or males who were overweight/obese. In conclusion, smokers have a lower likelihood of NDM than non-smokers among Chinese males with a lower BMI/smaller waist.

HbA1c levels in non-diabetic older adults - No J-shaped associations with primary cardiovascular events, cardiovascular and all-cause mortality after adjustment for confounders in a meta-analysis of individual participant data from six cohort studies

BACKGROUND

To determine the shape of the associations of HbA1c with mortality and cardiovascular outcomes in non-diabetic individuals and explore potential explanations.

METHODS

The associations of HbA1c with all-cause mortality, cardiovascular mortality and primary cardiovascular events (myocardial infarction or stroke) were assessed in non-diabetic subjects ≥50 years from six population-based cohort studies from Europe and the USA and meta-analyzed. Very low, low, intermediate and increased HbA1c were defined as <5.0, 5.0 to <5.5, 5.5 to <6.0 and 6.0 to <6.5% (equals <31, 31 to <37, 37 to <42 and 42 to <48 mmol/mol), respectively, and low HbA1c was used as reference in Cox proportional hazards models.

RESULTS

Overall, 6,769 of 28,681 study participants died during a mean follow-up of 10.7 years, of whom 2,648 died of cardiovascular disease. Furthermore, 2,493 experienced a primary cardiovascular event. A linear association with primary cardiovascular events was observed. Adjustment for cardiovascular risk factors explained about 50% of the excess risk and attenuated hazard ratios (95 confidence interval) for increased HbA1c to 1.14 (1.03-1.27), 1.17 (1.00-1.37) and 1.19 (1.04-1.37) for all-cause mortality, cardiovascular mortality and cardiovascular events, respectively. The six cohorts yielded inconsistent results for the association of very low HbA1c levels with the mortality outcomes and the pooled effect estimates were not statistically significant. In one cohort with a pronounced J-shaped association of HbA1c levels with all-cause and cardiovascular mortality (NHANES), the following confounders of the association of very low HbA1c levels with mortality outcomes were identified: race/ethnicity; alcohol consumption; BMI; as well as biomarkers of iron deficiency anemia and liver function. Associations for very low HbA1c levels lost statistical significance in this cohort after adjusting for these confounders.

CONCLUSIONS

A linear association of HbA1c levels with primary cardiovascular events was observed. For cardiovascular and all-cause mortality, the observed small effect sizes at both the lower and upper end of HbA1c distribution do not support the notion of a J-shaped association of HbA1c levels because a certain degree of residual confounding needs to be considered in the interpretation of the results.

The Associations Between Smoking Habits and Serum Triglyceride or Hemoglobin A1c Levels Differ According to Visceral Fat Accumulation

BACKGROUND

Whether smokers and former smokers have worse lipid profiles or glucose levels than non-smokers remains unclear.

METHODS

The subjects were 1152 Japanese males aged 42 to 81 years. The subjects were divided according to their smoking habits (nonsmokers, former smokers, and current smokers) and their visceral fat area (VFA) (<100 cm(2) and ≥100 cm(2)).

RESULTS

The serum triglyceride (TG) levels of 835 males were assessed. In the VFA ≥100 cm(2) group, a significantly greater proportion of current smokers (47.3%) exhibited TG levels of ≥150 mg/dL compared with former smokers (36.4%) and non-smokers (18.8%). The difference in TG level distribution between former smokers and non-smokers was also significant. However, among the subjects with VFA of <100 cm(2), the TG levels of the three smoking habit groups did not differ. The serum hemoglobin A1c (HbA1c) levels of 877 males were also assessed. In the VFA <100 cm(2) group, significantly higher proportions of current smokers (17.9%) and former smokers (14.9%) demonstrated HbA1c levels of ≥5.6% compared with non-smokers (6.3%). In contrast, in the VFA ≥100 cm(2) group, significantly fewer former smokers displayed HbA1c levels of ≥5.6% compared with non-smokers and current smokers. Furthermore, the interaction between smoking habits and VFA was associated with the subjects' TG and HbA1c concentrations, and the associations of TG and HbA1c concentrations and smoking habits varied according to VFA.

CONCLUSIONS

Both smoking habits and VFA exhibited associations with TG and HbA1c concentrations. The associations between smoking habits and these parameters differed according to VFA.

Association between Self-Reported Smoking and Hemoglobin A1c in a Korean Population without Diabetes: The 2011-2012 Korean National Health and Nutrition Examination Survey

Background

Several Western studies have revealed that among non-diabetics, glycosylated hemoglobin A1c (HbA1c) levels are higher in smokers than non-smokers. While studies conducted in Western populations consistently support this association, a recent meta-analysis reported that studies carried out in non-Western populations, including studies of Chinese, Egyptian, and Japanese-Americans, did not detect any significant differences in HbA1c levels between smokers and non-smokers.

Objectives

We assessed the association between smoking habits and HbA1c levels in the general Korean adult population using data from the Korean National Health and Nutrition Examination Survey (KNHANES) performed in 2011–2012.

Methods

A total of 10,241 participants (weighted n=33,946,561 including 16,769,320 men and 17,177,241 women) without diabetes were divided into four categories according to their smoking habits: never smokers (unweighted n/ weighted n= 6,349/19,105,564), ex-smokers (unweighted n/ weighted n= 1,912/6,207,144), current light smokers (<15 cigarettes per day, unweighted n/ weighted n=1,205/5,130,073), and current heavy smokers (≥15 cigarettes per day, unweighted n/ weighted n=775/3,503,781).

Results

In age- and gender-adjusted comparisons, the HbA1c levels of each group were 5.52 ± 0.01% in non-smokers, 5.49 ± 0.01% in ex-smokers, 5.53 ± 0.01% in light smokers, and 5.61 ± 0.02% in heavy smokers. HbA1c levels were significantly higher in light smokers than in ex-smokers (p = 0.033), and in heavy smokers compared with light smokers (p < 0.001). The significant differences remained after adjusting for age, gender, fasting plasma glucose, heavy alcohol drinking, hematocrit, college graduation, and waist circumference. Linear regression analyses for HbA1c using the above-mentioned variables as covariates revealed that a significant association between current smoking and HbA1c (coefficient 0.021, 95% CI 0.003–0.039, p = 0.019).

Conclusions

Current smoking was independently associated with higher HbA1c levels in a cigarette exposure-dependent manner in a representative population of Korean non-diabetic adults. In this study, we have observed an association between smoking status and HbA1c levels in non-diabetics drawn from a non-Western population, consistent with previous findings in Western populations.

Association between the presence of iron deficiency anemia and hemoglobin A1c in Korean adults: the 2011-2012 Korea National Health and Nutrition Examination Survey

Few studies have investigated the clinical effect of iron deficiency anemia (IDA) on the use of the Hemoglobin A1c (HbA1c) as a screening parameter for diabetes or prediabetes. We investigated the association between IDA and HbA1c levels in Korean adults.Among the 11,472 adults (≥19 years of age) who participated in the 2011-2012 Korea National Health and Nutrition Examination Survey (a cross-sectional and nationally representative survey conducted by the Korean Center for Disease Control for Health Statistics), 807 patients with diabetes currently taking anti-diabetes medications were excluded from this study. We compared the weighted HbA1c levels and weighted proportion (%) of HbA1c levels of ≥5.7%, ≥6.1%, and ≥6.5% according to the range of fasting plasma glucose (FPG) levels and the presence of IDA.Among 10,665 participants (weighted n = 35,229,108), the prevalence of anemia and IDA was 7.3% and 4.3%, respectively. The HbA1c levels were higher in participants with IDA (5.70% ± 0.02%) than in normal participants (5.59% ± 0.01%; P < 0.001), whereas there was no significant difference in FPG levels. In participants with an FPG level of <100 mg/dL and 100 to 125 mg/dL, the weighted HbA1c level was higher in those with IDA (5.59% ± 0.02% and 6.00% ± 0.05%) than in normal participants (5.44% ± 0.01% and 5.82% ± 0.01%) after adjusting for confounders such as age, sex, FPG level, heavy alcohol drinking, waist circumference, and smoking status as well as after exclusion of an estimated glomerular filtration rate of <60 mL/min/1.73 m (P < 0.001, <0.01). The weighted proportions (%) of an HbA1c level of ≥5.7% and ≥6.1% were also higher in participants with IDA than in normal participants (P < 0.001, <0.05). However, the weighted HbA1c levels in individuals with an FPG level ≥126 mg/dL and a weighted proportion (%) of an HbA1c level of ≥6.5% showed no significant differences according to the presence of IDA.In conclusion, the presence of IDA shifted the HbA1c level upward only in the normoglycemic and prediabetic ranges, not in the diabetic range. Therefore, IDA should be considered before using HbA1c as a screening test for prediabetes.

Dose- and time-dependent association of smoking and its cessation with glycemic control and insulin resistance in male patients with type 2 diabetes mellitus: the Fukuoka Diabetes Registry

Objective

Cigarette smoking is an important modifiable risk factor for cardiovascular diseases. However, the effect of smoking and its cessation on glycemic control in diabetic patients has not been fully examined yet. The aim of the present study was to examine the association of smoking status with glycemic level and markers of insulin resistance and secretion in patients with type 2 diabetes mellitus.

Research Design and Methods

A total of 2,490 Japanese male patients with type 2 diabetes mellitus aged ≥20 years were divided according to smoking status, amount of cigarettes smoked and years since quitting. The associations with glycemic level and markers of insulin resistance and secretion were examined cross-sectionally.

Results

HbA_1c levels increased progressively with increases in both number of cigarettes per day and pack-years of cigarette smoking compared with never smokers (P for trend = 0.001 and <0.001, respectively), whereas fasting plasma glucose did not. On the other hand, HbA_1c, but not fasting plasma glucose, decreased linearly with increase in years after smoking cessation (P for trend <0.001). These graded relationships persisted significantly after controlling for the confounders, including total energy intake, current drinking, regular exercise, depressive symptoms, and BMI. In addition, a homeostasis model assessment of insulin resistance and high-sensitivity C-reactive protein also showed similar trends.

Conclusions

Smoking and its cessation showed dose- and time-dependent relationship with glycemic control and insulin resistance in patients with type 2 diabetes mellitus. These findings may highlight the importance of smoking cessation in the clinical management of diabetes mellitus.

Smoking and long-term risk of type 2 diabetes: the EPIC-InterAct study in European populations

OBJECTIVE

The aims of this study were to investigate the association between smoking and incident type 2 diabetes, accounting for a large number of potential confounding factors, and to explore potential effect modifiers and intermediate factors.

RESEARCH DESIGN AND METHODS

The European Prospective Investigation into Cancer and Nutrition (EPIC)-InterAct is a prospective case-cohort study within eight European countries, including 12,403 cases of incident type 2 diabetes and a random subcohort of 16,835 individuals. After exclusion of individuals with missing data, the analyses included 10,327 cases and 13,863 subcohort individuals. Smoking status was used (never, former, current), with never smokers as the reference. Country-specific Prentice-weighted Cox regression models and random-effects meta-analysis were used to estimate hazard ratios (HRs) for type 2 diabetes.

RESULTS

In men, the HRs (95% CI) of type 2 diabetes were 1.40 (1.26, 1.55) for former smokers and 1.43 (1.27, 1.61) for current smokers, independent of age, education, center, physical activity, and alcohol, coffee, and meat consumption. In women, associations were weaker, with HRs (95% CI) of 1.18 (1.07, 1.30) and 1.13 (1.03, 1.25) for former and current smokers, respectively. There was some evidence of effect modification by BMI. The association tended to be slightly stronger in normal weight men compared with those with overall adiposity.

CONCLUSIONS

Former and current smoking was associated with a higher risk of incident type 2 diabetes compared with never smoking in men and women, independent of educational level, physical activity, alcohol consumption, and diet. Smoking may be regarded as a modifiable risk factor for type 2 diabetes, and smoking cessation should be encouraged for diabetes prevention.