No evidence of an increased mortality risk associated with low levels of glycated haemoglobin in a non-diabetic UK population

Breakthroughs in road mapping IL-35 mediated immunotherapy for type-1 and autoimmune diabetes mellitus

IL-35 is a recently discovered protein made up of IL-12α and IL-27β chains. It is encoded by IL12A and EBI3 genes. Interest in researching IL-35 has significantly increased in recent years, as evidenced by numerous scientific publications. Diabetes is on the rise globally, causing more illness and death in developing countries. The International Diabetes Federation (IDF) reports that diabetes is increasingly affecting children and teenagers, with varying rates across different regions. Therefore, scientists seek new diabetes treatments despite the growth of drug research. Recent research aims to emphasize IL-35 as a critical regulator of diabetes, especially type 1 and autoimmune diabetes. This review provides an overview of recent research on IL-35 and its link to diabetes and its associated complications. Studies suggest that IL-35 can offer protection against type-1 diabetes and autoimmune diabetes by regulating macrophage polarization, T-cell-related cytokines, and regulatory B cells (Bregs). This review will hopefully assist biomedical scientists in exploring the potential role of IL-35-mediated immunotherapy in treating diabetes. However, further research is necessary to determine the exact mechanism and plan clinical trials.

Prevalence of prediabetes and associated factors of prediabetic stages: a cross-sectional study among adults in Nepal

OBJECTIVES

To estimate the prevalence of prediabetes and to assess the association of prediabetic stages with sociodemographic, lifestyle and clinical factors DESIGN: Cross-sectional study at the screening and inclusion stage of a Diabetes Prevention Education Program (DiPEP) trial SETTING: The study was conducted in two urban communities in Nepal (October 2019-March 2020).

PARTICIPANTS

A total of 6222 residents of two study sites, aged 18-64 years and without a history of diabetes, were eligible for prediabetes screening. Exclusion criteria were pregnancy, history of diabetes and critical illness. A total of 291 participants with prediabetes were included in this study.

PRIMARY AND SECONDARY OUTCOME MEASURES

Prevalence of prediabetes based on glycated haemoglobin (HbA1c) criteria (5.7%-6.4%) was the primary outcome of the study. Odds Ratio and 95% CI were estimated to assess the associations between the outcome prediabetic stages (5.7%-5.9% vs 6.0%-6.4%) and sociodemographic, lifestyle and clinical factors in both unadjusted and adjusted models.

RESULTS

Out of 6222 screened participants, 308 (5%, 95% CI: 4.4% to 5.5%) individuals were detected with prediabetes based on HbA1c. The mean age of 291 responded participants was 50.3±7.6 years and 67% were females. Among them, 78% aged 45-64 years, 97% had central obesity, 90% had high waist-hip ratio, 63% were hypertensive and 66% had no family history of diabetes. Approximately, 54% and 46% of individuals with prediabetes had HbA1c of 5.7%-5.9% and 6.0%-6.4%, respectively. Female gender was associated with prediabetes with HbA1c 6.0%-6.4% (OR, 1.98, 95% CI: 1.07 to 3.67) in the adjusted model.

CONCLUSION

The estimated prevalence of prediabetes was 5% among screened participants, and female gender was associated with the prediabetic stage. As a large proportion of the population with prediabetes were not aware of their status, this study demonstrates a need for regular community screening programmes to detect individuals with prediabetes and provide them a comprehensive lifestyle intervention for diabetes prevention.

TRIAL REGISTRATION NUMBER

NCT04074148, 2019/783.

Glycated haemoglobin levels among 3295 hospitalized COVID-19 patients, with and without diabetes, and risk of severe infection, admission to an intensive care unit and all-cause mortality

AIM

To determine the risk of adverse outcomes across the spectrum of glycated haemoglobin (HbA1c) levels among hospitalized COVID-19 patients with and without diabetes.

MATERIALS AND METHODS

Danish nationwide registries were used to study the association between HbA1c levels and 30-day risk of all-cause mortality and the composite of severe COVID-19 infection, intensive care unit (ICU) admission and all-cause mortality. The study population comprised patients hospitalized with COVID-19 (3 March 2020 to 31 December 2020) with a positive polymerase chain reaction (PCR) test and an available HbA1c ≤ 6 months before the first positive PCR test. All patients had at least 30 days of follow-up. Among patients with diabetes, HbA1c was categorized as <48 mmol/mol, 48 to 53 mmol/mol, 54 to 58 mmol/mol, 59 to 64 mmol/mol (reference) and >64 mmol/mol. Among patients without diabetes, HbA1c was stratified into <31 mmol/mol, 31 to 36 mmol/mol (reference), 37 to 41 mmol/mol and 42 to 47 mmol/mol. Thirty-day standardized absolute risks and standardized absolute risk differences are reported.

RESULTS

We identified 3295 hospitalized COVID-19 patients with an available HbA1c (56.2% male, median age 73.9 years), of whom 35.8% had diabetes. The median HbA1c was 54 and 37 mmol/mol among patients with and without diabetes, respectively. Among patients with diabetes, the standardized absolute risk difference of the composite outcome was higher with HbA1c < 48 mmol/mol (12.0% [95% confidence interval {CI} 3.3% to 20.8%]) and HbA1c > 64 mmol/mol (15.1% [95% CI 6.2% to 24.0%]), compared with HbA1c 59 to 64 mmol/mol (reference). Among patients without diabetes, the standardized absolute risk difference of the composite outcome was greater with HbA1c < 31 mmol/mol (8.5% [95% CI 0.5% to 16.5%]) and HbA1c 42 to 47 mmol/mol (6.7% [95% CI 1.3% to 12.1%]), compared with HbA1c 31 to 36 mmol/mol (reference).

CONCLUSIONS

Patients with COVID-19 and HbA1c < 48 mmol/mol or HbA1c > 64 mmol/mol had a higher associated risk of the composite outcome. Similarly, among patients without diabetes, varying HbA1c levels were associated with higher risk of the composite outcome.

Association of glycated hemoglobin A1c levels with cardiovascular outcomes in the general population: results from the BiomarCaRE (Biomarker for Cardiovascular Risk Assessment in Europe) consortium

BACKGROUND

Biomarkers may contribute to improved cardiovascular risk estimation. Glycated hemoglobin A1c (HbA1c) is used to monitor the quality of diabetes treatment. Its strength of association with cardiovascular outcomes in the general population remains uncertain. This study aims to assess the association of HbA1c with cardiovascular outcomes in the general population.

METHODS

Data from six prospective population-based cohort studies across Europe comprising 36,180 participants were analyzed. HbA1c was evaluated in conjunction with classical cardiovascular risk factors (CVRFs) for association with cardiovascular mortality, cardiovascular disease (CVD) incidence, and overall mortality in subjects without diabetes (N = 32,496) and with diabetes (N = 3684).

RESULTS

Kaplan-Meier curves showed higher event rates with increasing HbA1c levels (log-rank-test: p < 0.001). Cox regression analysis revealed significant associations between HbA1c (in mmol/mol) in the total study population and the examined outcomes. Thus, a hazard ratio (HR) of 1.16 (95% confidence interval (CI) 1.02-1.31, p = 0.02) for cardiovascular mortality, 1.13 (95% CI 1.03-1.24, p = 0.01) for CVD incidence, and 1.09 (95% CI 1.02-1.17, p = 0.01) for overall mortality was observed per 10 mmol/mol increase in HbA1c. The association with CVD incidence and overall mortality was also observed in study participants without diabetes with increased HbA1c levels (HR 1.12; 95% CI 1.01-1.25, p = 0.04) and HR 1.10; 95% CI 1.01-1.20, p = 0.02) respectively. HbA1c cut-off values of 39.9 mmol/mol (5.8%), 36.6 mmol/mol (5.5%), and 38.8 mmol/mol (5.7%) for cardiovascular mortality, CVD incidence, and overall mortality, showed also an increased risk.

CONCLUSIONS

HbA1c is independently associated with cardiovascular mortality, overall mortality and cardiovascular disease in the general European population. A mostly monotonically increasing relationship was observed between HbA1c levels and outcomes. Elevated HbA1c levels were associated with cardiovascular disease incidence and overall mortality in participants without diabetes underlining the importance of HbA1c levels in the overall population.

Metabolic Dysfunction in Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is an autosomal recessive genetic disorder leading to paralysis, muscle atrophy, and death. Significant advances in antisense oligonucleotide treatment and gene therapy have made it possible for SMA patients to benefit from improvements in many aspects of the once devastating natural history of the disease. How the depletion of survival motor neuron (SMN) protein, the product of the gene implicated in the disease, leads to the consequent pathogenic changes remains unresolved. Over the past few years, evidence toward a potential contribution of gastrointestinal, metabolic, and endocrine defects to disease phenotype has surfaced. These findings ranged from disrupted body composition, gastrointestinal tract, fatty acid, glucose, amino acid, and hormonal regulation. Together, these changes could have a meaningful clinical impact on disease traits. However, it is currently unclear whether these findings are secondary to widespread denervation or unique to the SMA phenotype. This review provides an in-depth account of metabolism-related research available to date, with a discussion of unique features compared to other motor neuron and related disorders.

Emerging Diabetic Novel Biomarkers of the 21st Century

Diabetes is a growing epidemic with estimated prevalence of infected to reach ~592 million by the year 2035. An effective way to approach is to detect the disease at a very early stage to reduce the complications and improve lifestyle management. Although several traditional biomarkers including glucated hemoglobin, glucated albumin, fructosamine, and 1,5-anhydroglucitol have helped in ease of diagnosis, there is lack of sensitivity and specificity and are inaccurate in certain clinical settings. Thus, search for new and effective biomarkers is a continuous process with an aim of accurate and timely diagnosis. Several novel biomarkers have surged in the present century that are helpful in timely detection of the disease condition. Although it is accepted that a single biomarker will have its inherent limitations, combining several markers will help to identify individuals at high risk of developing prediabetes and eventually its progression to frank diabetes. This review describes the novel biomarkers of the 21st century, both in type 1 and type 2 diabetes mellitus, and their present potential for assessing risk stratification due to insulin resistance that will pave the way for improved clinical outcome.

Glycaemic markers and all-cause mortality in older adults with and without diabetes: the Atherosclerosis Risk in Communities (ARIC) study

AIMS/HYPOTHESIS

There is controversy regarding the performance of HbA1c in old age. We evaluated the prognostic value of HbA1c and other glycaemic markers (fructosamine, glycated albumin, fasting glucose) with mortality risk in older adults (66-90 years).

METHODS

This was a prospective analysis of 5636 participants (31% with diagnosed diabetes, mean age 76, 58% female, 21% black) in the Atherosclerosis Risk in Communities (ARIC) study, baseline 2011-2013. We used Cox regression to examine associations of glycaemic markers (modelled in categories) with mortality risk, stratified by diagnosed diabetes status.

RESULTS

During a median of 6 years of follow-up, 983 deaths occurred. Among older adults with diabetes, 30% had low HbA1c (<42 mmol/mol [<6.0%]) and 10% had high HbA1c (≥64 mmol/mol [≥8.0%]); low (HR 1.32 [95% CI 1.04, 1.68]) and high (HR 1.86 [95% CI 1.32, 2.62]) HbA1c were associated with mortality risk vs HbA1c 42-52 mmol/mol (6.0-6.9%) after demographic adjustment. Low fructosamine and glycated albumin were not associated with mortality risk. Both low and high fasting glucose were associated with mortality risk. After further adjustment for lifestyle and clinical risk factors, high HbA1c (HR 1.81 [95% CI 1.28, 2.56]), fructosamine (HR 1.96 [95% CI 1.43-2.69]), glycated albumin (HR 1.81 [95% CI 1.33-2.47]) and fasting glucose (HR 1.81 [95% CI 1.24, 2.66]) were associated with mortality risk. Low HbA1c and fasting glucose were no longer significantly associated with mortality risk. Among participants without diabetes, associations of glycaemic markers with mortality risk were less robust.

CONCLUSIONS/INTERPRETATION

Elevated HbA1c, fructosamine, glycated albumin and fasting glucose were associated with risk of mortality in older adults with diabetes. Low HbA1c and fasting glucose may be markers of poor prognosis but are possibly confounded by health status. Our findings support the clinical use of HbA1c in older adults with diabetes. Graphical abstract.

Lower carbohydrate and higher fat intakes are associated with higher hemoglobin A1c: findings from the UK National Diet and Nutrition Survey 2008-2016

PURPOSE

Evidence of low-carbohydrate, high-fat diets (LCHF) for type 2 diabetes (T2DM) prevention is scarce. We investigated how carbohydrate intake relates to HbA1c and T2DM prevalence in a nationally representative survey dataset.

METHODS

We analyzed dietary information (4-day food diaries) from 3234 individuals aged ≥ 16 years, in eight waves of the UK National Diet and Nutrition Survey (2008-2016). We calculated LCHF scores (0-20, higher score indicating lower  %food energy from carbohydrate, with reciprocal higher contribution from fat) and UK Dietary Reference Value (DRV) scores (0-16, based on UK dietary recommendations). Associations between macronutrients and diet scores and diabetes prevalence were analyzed (in the whole sample) using multivariate logistic regression. Among those without diabetes, analyses between exposures and %HbA1c (continuous) were analyzed using multivariate linear regression. All analyses were adjusted for age, sex, body mass index, ethnicity, smoking status, total energy intake, socioeconomic status and survey years.

RESULTS

In the overall study sample, 194 (6.0%) had diabetes. Mean intake was 48.0%E for carbohydrates, and 34.9%E for total fat. Every 5%E decrease in carbohydrate, and every 5%E increase in fat, was associated with 12% (95% CI 0.78-0.99; P = 0.03) and 17% (95% CI 1.02-1.33; P = 0.02) higher odds of diabetes, respectively. Each two-point increase in LCHF score is related to 8% (95% CI 1.02-1.14; P = 0.006) higher odds of diabetes, while there was no evidence for association between DRV score and diabetes. Among the participants without diagnosed diabetes (n = 3130), every 5%E decrease in carbohydrate was associated with higher %HbA1c by + 0.016% (95% CI 0.004-0.029; P = 0.012), whereas every 5%E increase in fat was associated with higher  %HbA1c by + 0.029% (95% CI 0.015-0.043; P < 0.001). Each two-point increase in LCHF score is related to higher  %HbA1c by + 0.010% (0.1 mmol/mol), while each two-point increase in the DRV score is related to lower  %HbA1c by - 0.023% (0.23 mmol/mol).

CONCLUSIONS

Lower carbohydrate and higher fat intakes were associated with higher HbA1c and greater odds of having diabetes. These data do not support low(er) carbohydrate diets for diabetes prevention.

Glycated Hemoglobin and All-Cause and Cause-Specific Mortality Among Adults With and Without Diabetes

CONTEXT

The patterns of associations between glycated Hb (HbA1c) and mortality are still unclear.

OBJECTIVE

To explore the extent to which ranges of HbA1c levels are associated with the risk of mortality among participants with and without diabetes.

DESIGN, SETTING, AND PATIENTS

This was a nationwide, community-based prospective cohort study. Included were 15,869 participants (median age 64 years) of the Health and Retirement Study, with available HbA1c data and without a history of cancer. Cox proportional hazards regression models were used to estimate hazard ratios with 95% CIs for mortality.

RESULTS

A total of 2133 participants died during a median follow-up of 5.8 years. In participants with diabetes, those with an HbA1c level of 6.5% were at the lowest risk of all-cause mortality. When HbA1c level was <5.6% or >7.4%, the increased all-cause mortality risk became statistically significant as compared with an HbA1c level of 6.5%. As for participants without diabetes, those with an HbA1c level of 5.4% were at the lowest risk of all-cause mortality. When the HbA1c level was <5.0%, the increased all-cause mortality risk became statistically significant as compared with an HbA1c level of 5.4%. However, we did not observe a statistically significant elevated risk of all-cause mortality above an HbA1c level of 5.4%.

CONCLUSIONS

A U-shaped and reverse J-shaped association for all-cause mortality was found among participants with and without diabetes. The corresponding optimal ranges for overall survival are predicted to be 5.6% and 7.4% and 5.0% and 6.5%, respectively.

A prospective study of low fasting glucose with cardiovascular disease events and all-cause mortality: The Women's Health Initiative

BACKGROUND

While there is increasing recognition of the risks associated with hypoglycemia in patients with diabetes, few studies have investigated incident cause-specific cardiovascular outcomes with regard to low fasting glucose in the general population.

OBJECTIVE

We hypothesized that low fasting glucose would be associated with cardiovascular disease risk and all-cause mortality in postmenopausal women.

METHODS

To test our hypothesis, we used both continuous incidence rates and Cox proportional hazards models in 17,287 participants from the Women's Health Initiative with fasting glucose measured at baseline. Participants were separated into groups based on fasting glucose level: low (<80mg/dL), normal/reference (80-99mg/dL), impaired (100-125mg/dL), and diabetic (≥126mg/dL).

RESULTS

Participants were free of cardiovascular disease at enrollment, had mean age of 62years, and were 52% Caucasian, 24% African American, 8% Asian, and 12% Hispanic. Median follow-up was 15years. Graphs of continuous incidence rates compared to fasting glucose distribution exhibited evidence of a weak J-shaped association with heart failure and mortality that was predominantly due to participants with treated diabetes. Impaired and diabetic fasting glucose were positively associated with all outcomes. Associations for low fasting glucose differed, with coronary heart disease (HR=0.64 (0.42, 0.98)) significantly inverse; stroke (0.73 (0.48, 1.13)), combined cardiovascular disease (0.91 (0.73, 1.14)), and all-cause mortality (0.97 (0.79, 1.20)) null or inverse and not significant; and heart failure (1.27 (0.80, 2.02)) positive and not significant.

CONCLUSIONS

Fasting glucose at the upper range, but not the lower range, was significantly associated with incident cardiovascular disease and all-cause mortality.

Association of high normal HbA1c and TSH levels with the risk of CHD: a 10-year cohort study and SVM analysis

This study aimed to determine the association between the clinical reference range of serum glycated hemoglobin A1c (HbA1c) and thyrotropin (TSH) and the risk of coronary heart disease (CHD) in non-diabetic and euthyroid patients. We examined baseline HbA1c and TSH in 538 healthy participants, and then analyzed the associations and potential value of these indicators for predicting CHD using Cox proportional hazard and support vector machine analyses. During the median follow-up of 120 months, 39 participants later developed CHD. The baseline HbA1c and TSH within the reference range were positively associated with CHD risk. No correlation and interaction were found between the baseline HbA1c and TSH for the development of CHD. Disease event-free survival varied among participants with different baseline HbA1c quintiles, whereas disease event-free survival was similar for different TSH tertiles. The combination of these baselines showed sensitivity of 87.2%, specificity of 92.7%, and accuracy of 92.3% for identifying the participants who will later develop CHD. Relatively high but clinically normal HbA1c and TSH levels may increase the risk of CHD. Therefore, the combination of these indicators can serve as a biomarker for identifying healthy individuals from those who would later develop CHD.

Novel biomarkers for prediabetes, diabetes, and associated complications

The number of individuals with prediabetes is expected to grow substantially and estimated to globally affect 482 million people by 2040. Therefore, effective methods for diagnosing prediabetes will be required to reduce the risk of progressing to diabetes and its complications. The current biomarkers, glycated hemoglobin (HbA1c), fructosamine, and glycated albumin have limitations including moderate sensitivity and specificity and are inaccurate in certain clinical conditions. Therefore, identification of additional biomarkers is being explored recognizing that any single biomarker will also likely have inherent limitations. Therefore, combining several biomarkers may more precisely identify those at high risk for developing prediabetes and subsequent progression to diabetes. This review describes recently identified biomarkers and their potential utility for addressing the burgeoning epidemic of dysglycemic disorders.

An investigation into the relationship between plain water intake and glycated Hb (HbA1c): a sex-stratified, cross-sectional analysis of the UK National Diet and Nutrition Survey (2008-2012)

The aim of this study was to analyse the association between plain water intake and glycated Hb (HbA1c) in the National Diet and Nutrition Survey (2008-2012) rolling survey. These data included diet (4-d diaries) and HbA1c (fasted blood sample) measures of 456 men and 579 women aged 44 (sd 18) years with full information on covariates of interest (age, ethnicity, BMI, smoking status, education, other beverage intake, energy intake and fibre). Data were analysed using sex-stratified linear and logistic regressions modelling the associations of cups per d (240 ml) of plain water with HbA1c, and odds of HbA1c≥5·5 %, respectively. Substitution analyses modelled the replacement of sugar-sweetened beverages, fruit juice and artificially sweetened beverages with plain water. After adjustment, 1 cup/d of plain water was associated with a -0·04 % lower HbA1c (95 % CI -0·07, -0·02) in men. In logistic regression, men had a 22 % (95 % CI 10, 32 %) reduced odds of HbA1c≥5·5 %/cup per d of plain water. There was no evidence of an association with either HbA1c or odds of HbA1c≥5·5 % in women. None of the substitution models was associated with a change in odds of HbA1c≥5·5 %. Plain water intake was associated with lower HbA1c in men but not in women. Substituting water for specific beverages was not associated with a reduced odds of HbA1c≥5·5 %, suggesting that the addition of water is the more pertinent factor. Future trials should test whether the relationships between water intake and HbA1c is causal as this could be a cost-effective and simple health intervention.

HbA1c and Risks of All-Cause and Cause-Specific Death in Subjects without Known Diabetes: A Dose-Response Meta-Analysis of Prospective Cohort Studies

Whether HbA_1c levels are associated with mortality in subjects without known diabetes remains controversial. Moreover, the shape of the dose–response relationship on this topic is unclear. Therefore, a dose–response meta-analysis was conducted. PubMed and EMBASE were searched. Summary hazard ratios (HRs) were calculated using a random-effects model. Twelve studies were included. The summary HR per 1% increase in HbA_1c level was 1.03 [95% confidence interval (CI) = 1.01–1.04] for all-cause mortality, 1.05 [95% CI = 1.02–1.07) for cardiovascular disease (CVD) mortality, and 1.02 (95% CI = 0.99–1.07) for cancer mortality. After excluding subjects with undiagnosed diabetes, the aforementioned associations remained significant for CVD mortality only. After further excluding subjects with prediabetes, all aforementioned associations presented non-significance. Evidence of a non-linear association between HbA_1c and mortality from all causes, CVD and cancer was found (all P_{non-linearity} < 0.05). The dose–response curves were relatively flat for HbA_1c less than around 5.7%, and rose steeply thereafter. In conclusion, higher HbA_1c level is associated with increased mortality from all causes and CVD among subjects without known diabetes. However, this association is driven by those with undiagnosed diabetes or prediabetes. The results regarding cancer mortality should be treated with caution due to limited studies.

Prediction by Low Plasma HbA1c of Mortality, Cardiac and Noncardiac Disease Risk: Modulation by Diabetic Status and Sex

AIM

The aim of the study was to evaluate the predictive value of HbA(1c) for risk of overall mortality or a composite endpoint of death and nonfatal events.

METHODS

Logistic regression retrospectively assessed the longitudinal association of measured HbA(1c) with outcome in 746 middle-aged adults, recruited from a tertiary health center and stratified to absence or presence of type 2 diabetes, using the recent American Diabetes Association criteria.

RESULTS

A total of 70 deaths and additional incident nonfatal events in 82 cases were recorded at a median of 3.1-year follow-up. Multivariable linear regression revealed among nondiabetic individuals HbA(1c) to be significantly associated--independent of fasted glucose--inversely with triglycerides and high-density lipoprotein cholesterol, distinct from the diabetic sample. Sex and diabetes status differed in baseline HbA1c values with respect to the development of outcome. Nondiabetic men who subsequently died exhibited significantly lower HbA(1c), as did men and women with incident coronary heart disease. Similar difference was observed for incident hypothyroidism and nondiabetic subjects developing malignancy. In logistic regression analysis, adjusted for sex, age, and fasting glucose, each 0.7% (SD, 1) decrement of baseline HbA(1c) predicted the composite endpoint in the nondiabetic sample (risk estimates, 1.49%; 95% confidence interval, 1.07-2.04), but not in the diabetic sample, whereas overall mortality in the whole sample was increased (risk estimates, 1.51%; 95% confidence interval, 1.05-2.17).

CONCLUSIONS

Inverse association of HbA(1c) with adverse outcomes in men and nondiabetic people indicates the involvement of HbA(1c) levels in autoimmune activation. The weaker inverse association with prevalent diabetes and in women is consistent with the operation of more pronounced confounding autoimmune processes.

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.

Association of the average rate of change in HbA1c with severe adverse events: a longitudinal evaluation of audit data from the Bavarian Disease Management Program for patients with type 2 diabetes mellitus

AIMS/HYPOTHESIS

In patients with type 2 diabetes mellitus, the effects of HbA1c variability on macrovascular events remain uncertain. The present investigation evaluates the association of HbA1c variability with non-fatal cardiovascular events, emergency admissions and episodes of severe hypoglycaemia in a cohort of patients newly started on insulin therapy.

METHODS

HbA1c variability was defined as the rate of change in values between observations. The medical records of 406,356 patients enrolled in a disease management programme for type 2 diabetes mellitus were analysed to identify a cohort of 13,777 patients with observed transition to insulin therapy. The cohort was observed for a period of at least 5 years. Cox regression models were applied to quantify the association of HbA1c variability with the events of interest.

RESULTS

The models reveal a significant non-linear association between HbA1c variability and the risk of experiencing myocardial infarction, stroke and hypoglycaemia. The lowest risk is seen with a variability of approximately 0.5% (5.5 mmol/mol) per quarter. Using Cox models to predict survival curves for the cohort with hypothetical HbA1c variability of 0.5% (5.5 mmol/mol) and 1.5% (16.4 mmol/mol) per quarter, the proportion experiencing myocardial infarction within 2 years increases significantly from 1% to 10%. The proportion experiencing stroke increases from 1% to 29%, hypoglycaemia from 2% to 24% and the risk of emergency admission from 2% to 21%.

CONCLUSIONS/INTERPRETATION

In patients newly started on insulin therapy, rapid and higher HbA1c variability is associated with an increased risk of myocardial infarction, stroke, severe hypoglycaemia and emergency admission.

Glycated hemoglobin and long-term prognosis in patients with suspected stable angina pectoris without diabetes mellitus: a prospective cohort study

OBJECTIVE

Associations of glycated hemoglobin A1c (HbA1c) levels to incident coronary and cardiovascular events among non-diabetic patients with coronary artery disease are unclear. We investigated relations of HbA1c to long-term prognosis in such patients.

METHODS

A prospective cohort of 2519 patients undergoing elective coronary angiography for suspected stable angina pectoris (SAP) was divided into pre-defined categories according to HbA1c (%) levels (<5.0, 5.0-5.6 (reference), 5.7-6.4), and followed for median 4.9 years. The primary end-point was major coronary events (including non-fatal and fatal acute myocardial infarctions, and sudden cardiac death). Secondary end-points were death from cardiovascular disease (CVD) and all-cause mortality. Hazard ratios (HRs) (95% confidence intervals [CIs]) were obtained by Cox regression.

RESULTS

Median age at inclusion was 62 years, 73% were males, median HbA1c was 5.6% and random plasma-glucose 5.4 mmol/L. After multivariate adjustment, HbA1c levels within the pre-diabetic range were not associated with risk of major coronary events, HR (95% CI): 1.13 (0.79-1.62); P=0.49, death from CVD or all-cause mortality HR (95% CI): 0.95 (0.55-1.66) and 1.04 (0.70-1.53), respectively; P≥0.85. Similarly, there was no significant association between HbA1c values within the lowest category and risk of study outcomes, (P≥0.18).

CONCLUSION

In non-diabetic patients with suspected SAP, there was no overall association between HbA1c levels and prognosis, questioning an independent role of glycemia in the pathogenesis of atherosclerotic complications in these patients.

Association between hemoglobin A1c and all-cause mortality: results of the mortality follow-up of the German National Health Interview and Examination Survey 1998

OBJECTIVE

This study examined the association of HbA1c-defined glycemic status and continuous HbA1c with all-cause mortality.

RESEARCH DESIGN AND METHODS

The study population comprised 6,299 participants (aged 18-79 years) of the German National Health Interview and Examination Survey 1998, who were followed up for mortality for an average of 11.6 years. Glycemic status was defined as known diabetes (self-reported diagnosis or intake of antidiabetic medication) and based on HbA1c levels according to American Diabetes Association diagnostic criteria as undiagnosed diabetes (≥6.5% [≥48 mmol/mol]), prediabetes with very high (6.0-6.4% [42-46 mmol/mol]) or high diabetes risk (5.7-5.9% [39-41 mmol/mol]), and normoglycemia (<5.7% [<39 mmol/mol]). Associations between glycemic status and mortality were examined by Cox regression adjusting for age, sex, education, lifestyle factors, anthropometric measures, and history of chronic diseases (reference: normoglycemia). Spline models were fitted to investigate associations between continuous HbA1c and mortality among participants without known diabetes.

RESULTS

Excess mortality risk was observed for participants with known diabetes (hazard ratio 1.41 [95% CI 1.08-1.84]) and undiagnosed diabetes (1.63 [1.23-2.17]) but not for those with high (1.02 [0.80-1.30]) or very high diabetes risk (0.87 [0.67-1.13]). Spline models revealed a U-shaped association, with lowest risk at HbA1c levels 5.4-5.6% (36-38 mmol/mol) and a significantly increased risk at ≤5.0% (≤31 mmol/mol) and ≥6.4% (≥46 mmol/mol).

CONCLUSIONS

Unlike known and undiagnosed diabetes, HbA1c levels in the prediabetic range were not associated with an increased mortality risk. The observed U-shaped relationship adds to existing evidence that not only high but also low HbA1c levels might be associated with all-cause mortality.

Glycated hemoglobin and all-cause and cause-specific mortality in Singaporean Chinese without diagnosed diabetes: the Singapore Chinese Health Study

OBJECTIVE

Glycated hemoglobin (HbA₁c) is a robust biomarker of the preceding 2 to 3 months average blood glucose level. The aim of this study was to examine the association between HbA₁c and mortality in a cohort of Southeast Asians.

RESEARCH DESIGN AND METHODS

Analysis of 7,388 men and women, mean age 62 years, from the Singapore Chinese Health Study who provided a blood sample at the follow-up I visit (1999-2004) and reported no history of diabetes, previous adverse cardiovascular events, or cancer. A total of 888 deaths were identified through 31 December 2011 via registry linkage. Participants represented a random study sample of potential control subjects for a nested case-control genome-wide association study of type 2 diabetes in the population. Hazard ratios (HRs) for all-cause and cause-specific mortality by six categories of HbA1c were estimated with Cox regression models.

RESULTS

Relative to participants with an HbA₁c of 5.4-5.6% (36-38 mmol/mol), participants with HbA₁c ≥6.5% (≥48 mmol/mol) had an increased risk of all-cause, cardiovascular, and cancer mortality during an average of 10.1 years of follow-up; HRs (95% CIs) were 1.96 (1.56-2.46), 2.63 (1.77-3.90), and 1.51 (1.04-2.18), respectively. No level of HbA1c was associated with increased risk of respiratory mortality. Levels <6.5% HbA₁c were not associated with mortality during follow-up. The results did not materially change after excluding observation of first 3 years post-blood draw.

CONCLUSIONS

HbA₁c levels consistent with undiagnosed type 2 diabetes (≥6.5%) are associated with an increased risk of all-cause and cause-specific mortality in Chinese men and women.

We can change the natural history of type 2 diabetes

As diabetes develops, we currently waste the first ∼10 years of the natural history. If we found prediabetes and early diabetes when they first presented and treated them more effectively, we could prevent or delay the progression of hyperglycemia and the development of complications. Evidence for this comes from trials where lifestyle change and/or glucose-lowering medications decreased progression from prediabetes to diabetes. After withdrawal of these interventions, there was no "catch-up"-cumulative development of diabetes in the previously treated groups remained less than in control subjects. Moreover, achieving normal glucose levels even transiently during the trials was associated with a substantial reduction in subsequent development of diabetes. These findings indicate that we can change the natural history through routine screening to find prediabetes and early diabetes, combined with management aimed to keep glucose levels as close to normal as possible, without hypoglycemia. We should also test the hypothesis with a randomized controlled trial.

Glycated hemoglobin measurement and prediction of cardiovascular disease

IMPORTANCE

The value of measuring levels of glycated hemoglobin (HbA1c) for the prediction of first cardiovascular events is uncertain.

OBJECTIVE

To determine whether adding information on HbA1c values to conventional cardiovascular risk factors is associated with improvement in prediction of cardiovascular disease (CVD) risk.

DESIGN, SETTING, AND PARTICIPANTS

Analysis of individual-participant data available from 73 prospective studies involving 294,998 participants without a known history of diabetes mellitus or CVD at the baseline assessment.

MAIN OUTCOMES AND MEASURES

Measures of risk discrimination for CVD outcomes (eg, C-index) and reclassification (eg, net reclassification improvement) of participants across predicted 10-year risk categories of low (<5%), intermediate (5% to <7.5%), and high (≥ 7.5%) risk.

RESULTS

During a median follow-up of 9.9 (interquartile range, 7.6-13.2) years, 20,840 incident fatal and nonfatal CVD outcomes (13,237 coronary heart disease and 7603 stroke outcomes) were recorded. In analyses adjusted for several conventional cardiovascular risk factors, there was an approximately J-shaped association between HbA1c values and CVD risk. The association between HbA1c values and CVD risk changed only slightly after adjustment for total cholesterol and triglyceride concentrations or estimated glomerular filtration rate, but this association attenuated somewhat after adjustment for concentrations of high-density lipoprotein cholesterol and C-reactive protein. The C-index for a CVD risk prediction model containing conventional cardiovascular risk factors alone was 0.7434 (95% CI, 0.7350 to 0.7517). The addition of information on HbA1c was associated with a C-index change of 0.0018 (0.0003 to 0.0033) and a net reclassification improvement of 0.42 (-0.63 to 1.48) for the categories of predicted 10-year CVD risk. The improvement provided by HbA1c assessment in prediction of CVD risk was equal to or better than estimated improvements for measurement of fasting, random, or postload plasma glucose levels.

CONCLUSIONS AND RELEVANCE

In a study of individuals without known CVD or diabetes, additional assessment of HbA1c values in the context of CVD risk assessment provided little incremental benefit for prediction of CVD risk.

Low hemoglobin A(1c) in nondiabetic adults: an elevated risk state?

OBJECTIVE

To identify predictors of low hemoglobin A(1c) (HbA(1c)) (<5.0%) and to investigate the association of low HbA(1c) with cause-specific mortality and risk of liver disease hospitalization.

RESEARCH DESIGN AND METHODS

Prospective cohort study of 13,288 participants in the Atherosclerosis Risk in Communities Study. Logistic regression was used to identify cross-sectional correlates of low HbA(1c), and Cox proportional hazards models were used to estimate the association of low HbA(1c) with cause-specific mortality.

RESULTS

Compared with participants with HbA(1c) in the normal range (5.0 to <5.7%), participants with low HbA(1c) were younger, less likely to smoke, had lower BMI, lower white cell count and fibrinogen levels, and lower prevalence of hypercholesterolemia and history of coronary heart disease. However, this group was more likely to have anemia and had a higher mean corpuscular volume. In adjusted Cox models with HbA(1c) of 5.0 to <5.7% as the reference group, HbA(1c) <5.0% was associated with a significantly increased risk of all-cause mortality (hazard ratio [HR]: 1.32, 95% CI: 1.13-1.55) and of cancer death (1.47, 95% CI: 1.16-1.84). We also noted nonsignificant trends toward increased risk of death from cardiovascular causes (1.27, 95% CI: 0.93-1.75) and respiratory causes (1.42, 95% CI: 0.78-2.56). There was a J-shaped association between HbA(1c) and risk of liver disease hospitalization.

CONCLUSIONS

No single cause of death appeared to drive the association between low HbA(1c) and total mortality. These results add to evidence that low HbA(1c) values may be a generalized marker of mortality risk in the general population.

Short-term impact of HbA1c on morbidity and all-cause mortality in people with type 2 diabetes: a Danish population-based observational study

AIMS/HYPOTHESIS

In a population-based setting, we investigated whether diabetes-related morbidity and all-cause mortality within 2 years of HbA(1c) measurement were associated with that HbA(1c) level in individuals with type 2 diabetes. The main objective was to compare outcomes in those with HbA(1c) ≥ and <7% (53 mmol/mol).

METHODS

Individuals with type 2 diabetes from Aarhus County, Denmark, were identified from public data files in a 3 year period (2001-2003). Stratifying the 17,760 individuals by HbA(1c), we estimated HRs for diabetes-related morbidities and all-cause mortality using Cox regression. Results were also stratified by treatment modality.

RESULTS

In total, 1,805 individuals experienced at least one diabetes-related morbidity and 1,859 individuals died. In general, the HRs in adjusted analyses of diabetes-related morbidity and mortality were increased for HbA(1c) ≥ 7% (53 mmol/mol): morbidity, HR 1.48 (95% CI 1.34, 1.63); and mortality, HR 1.26 (95% CI 1.15, 1.39). On grouping individuals according to HbA(1c) <5% (31 mmol/mol), 5.0-5.9% (31-41 mmol/mol), 6.0-6.9% (42-52 mmol/mol), 7.0-7.9% (53-63 mmol/mol), 8.0-8.9% (64-74 mmol/mol) and ≥ 9% (75 mmol/mol), the HRs for mortality formed a U shape, with HbA(1c) 6.0-6.9% (42-52 mmol/mol) at the lowest point. For diabetes-related morbidity, a dose-response pattern appeared (lowest for HbA(1c) < 5% [31 mmol/mol]). Patterns of HR differed with treatment modality.

CONCLUSIONS/INTERPRETATION

An HbA(1c) level ≥ 7% (53 mmol/mol) was associated with increased morbidity and mortality. Both high and very low levels of HbA(1c) were associated with increased mortality. A dose-response pattern appeared for morbidity. The impact of HbA(1c) level on morbidity and mortality depended on treatment modality.

Low HbA1c and mortality: causation and confounding

This commentary provides an overview of the clinically important data linking low or lowered HbA(1c) to increased total and CVD mortality in the general population, and in patients with diabetes. This sets the scene for a contribution in this issue of Diabetologia by Andersson et al (DOI: 10.1007/s00125-012-2584-3 ) that suggests that BMI might modify the relationship between HbA(1c) and mortality in patients with type 2 diabetes. The commentary provides a framework for the interpretation of epidemiological data from observational studies and clinical trials, and it addresses the clinical implications of this work. Finally, it highlights new research that is likely to advance this field.

HbA1c measured in stored erythrocytes is positively linearly associated with mortality in individuals with diabetes mellitus

Introduction

Observational studies have shown that glycated haemoglobin (HbA_1c) is related to mortality, but the shape of the association is less clear. Furthermore, disease duration and medication may modify this association. This observational study explored the association between HbA_1c measured in stored erythrocytes and mortality. Secondly, it was assessed whether disease duration and medication use influenced the estimates or were independently associated with mortality.

Methods

Within the European Prospective Investigation into Cancer and Nutrition a cohort was analysed of 4,345 individuals with a confirmed diagnosis of diabetes at enrolment. HbA_1c was measured in blood samples stored up to 19 years. Multivariable Cox proportional hazard regression models for all-cause mortality investigated HbA_1c in quartiles as well as per 1% increment, diabetes medication in seven categories of insulin and oral hypoglycaemic agents, and disease duration in quartiles.

Results

After a median follow-up of 9.3 years, 460 participants died. Higher HbA_1c was associated with higher mortality: Hazard Ratio for 1%-increase was 1.11 (95% CI 1.06, 1.17). This association was linear (P-nonlinearity =0.15) and persistent across categories of medication use, disease duration, and co-morbidities. Compared with metformin, other medication types were not associated with mortality. Longer disease duration was associated with mortality, but not after adjustment for HbA_1c and medication.

Conclusion

This prospective study showed that persons with lower HbA_1c had better survival than those with higher HbA_1c. The association was linear and independent of disease duration, type of medication use, and presence of co-morbidities. Any improvement of HbA_1c appears to be associated with reduced mortality risk.