HbA1c variability is associated with microalbuminuria development in type 2 diabetes: a 7-year prospective cohort study

Long-term Glycemic Variability and Risk of Adverse Outcomes: A Systematic Review and Meta-analysis

OBJECTIVE

Glycemic variability is emerging as a measure of glycemic control, which may be a reliable predictor of complications. This systematic review and meta-analysis evaluates the association between HbA1c variability and micro- and macrovascular complications and mortality in type 1 and type 2 diabetes.

RESEARCH DESIGN AND METHODS

Medline and Embase were searched (2004-2015) for studies describing associations between HbA1c variability and adverse outcomes in patients with type 1 and type 2 diabetes. Data extraction was performed independently by two reviewers. Random-effects meta-analysis was performed with stratification according to the measure of HbA1c variability, method of analysis, and diabetes type.

RESULTS

Seven studies evaluated HbA1c variability among patients with type 1 diabetes and showed an association of HbA1c variability with renal disease (risk ratio 1.56 [95% CI 1.08-2.25], two studies), cardiovascular events (1.98 [1.39-2.82]), and retinopathy (2.11 [1.54-2.89]). Thirteen studies evaluated HbA1c variability among patients with type 2 diabetes. Higher HbA1c variability was associated with higher risk of renal disease (1.34 [1.15-1.57], two studies), macrovascular events (1.21 [1.06-1.38]), ulceration/gangrene (1.50 [1.06-2.12]), cardiovascular disease (1.27 [1.15-1.40]), and mortality (1.34 [1.18-1.53]). Most studies were retrospective with lack of adjustment for potential confounders, and inconsistency existed in the definition of HbA1c variability.

CONCLUSIONS

HbA1c variability was positively associated with micro- and macrovascular complications and mortality independently of the HbA1c level and might play a future role in clinical risk assessment.

Direct association of visit-to-visit HbA1c variation with annual decline in estimated glomerular filtration rate in patients with type 2 diabetes

Background/Aims

This study examined associations of visit-to-visit variability of glycemic control with annual decline in estimated glomerular filtration rate (eGFR) in patients with type 2 diabetes attending an outpatient clinic.

Methods

Intrapersonal mean and coefficient of variation (CV) of 8-12 measurements of HbA1c and those of 4-6 measurements of fasting and post-breakfast plasma glucose (FPG and PPG, respectively) during the first 12 months after enrollment were calculated in a cohort of 168 patients with type 2 diabetes. Annual changes in eGFR were computed using 52 (median) creatinine measurements obtained over a median follow-up of 6.0 years. Multivariate linear regressions assessed the independent correlates of changes in eGFR.

Results

CV-HbA1c (standardized β、-0.257、p = 0.004) were significantly and log urine albumin/creatinine ratio (standardized β、-0.155、p = 0.085) and smoking (standardized β、-0.186、p = 0.062) tended to be associated with annual eGFR decline independently of mean HbA1c, age, sex, BMI, waist circumference, diabetes duration and therapy, means and CVs of FPG, PPG and systolic blood pressure, baseline eGFR, and uses of anti-hypertensive and lipid-lowering medications. Association between HbA1c variability and renal function decline was stronger in patients with albumin/creatinine ratio ≧ 30 mg/g than in those with normoalbuminuria (r = -0.400, p = 0.003 and r = -0.169, p = 0.07, respectively).

Conclusions

Consistency of glycemic control is important to preserve kidney function in type 2 diabetic patients, in particular, in those with nephropathy.

Association between hemoglobin A1c variability and subclinical coronary atherosclerosis in subjects with type 2 diabetes

AIMS

We examined the association between hemoglobin A1c (HbA1c) variability and subclinical coronary atherosclerosis in subjects with type 2 diabetes.

METHODS

We used the multidetector coronary computed tomography data collected from subjects with type 2 diabetes who did not have a history of cardiovascular disease or angina symptoms. HbA1c measurements preceding the date of cardiac imaging were retrospectively collected, and intraindividual SD (HbA1c-SD), CV and adjusted SD of HbA1c measurements were calculated. Subclinical coronary atherosclerosis was defined as calcium score >400 without any cardiac symptoms.

RESULTS

A total of 595 subjects were categorized according to the median value of each HbA1c variability indicators. The prevalence of subclinical coronary atherosclerosis was higher in higher HbA1c variability group compared with lower HbA1c variability group. Multivariable logistic regression analysis showed that higher HbA1c-SD and -CV were associated with the presence of subclinical coronary atherosclerosis, independent of mean HbA1c level in subjects with diabetes duration ≤10 years (OR [95% CI]; HbA1c-SD, 2.894 [1.105-7.584]; HbA1c-CV, 2.540 [1.022-6.316]).

CONCLUSIONS

Long-term stabilization of blood glucose level might be important in preventing subclinical coronary atherosclerosis in subjects with earlier period of type 2 diabetes.

Predicting non-diabetic renal disease in type 2 diabetic adults: The value of glycated hemoglobin

AIMS

The indications for renal biopsy in type 2 diabetes mellitus (T2D) are not well established. We investigated the prevalence, spectrum, and predictors of biopsy-proven non-diabetic renal disease (NDRD) in T2D.

METHODS

An observational, single-center, retrospective study of T2D adults who underwent renal biopsies (N = 51) over 10 years for nephrotic-range proteinuria, microscopic hematuria, or rapidly declining renal function.

RESULTS

Thirty-five (68.6%) biopsies were diagnostic of NDRD, and 16 (31.4%) revealed isolated diabetic nephropathy. The most common NDRDs were interstitial nephritis (20%), progressive crescentic glomerulonephritis (14%), membranous nephropathy (11%), and focal segmental glomerulosclerosis (11%). The odds for NDRD declined by 97% in the presence of diabetic retinopathy (P < 0.001). The deterioration of HbA1c during the year before biopsy predicted NDRD even after adjusting for diabetic retinopathy (OR, 7.65; 95% CI, 1.36-123.04; P = 0.003). A model based on the interaction between the HbA1c values 12 months before biopsy and the absolute change in these values during the preceding year predicted NDRD with 73.7% sensitivity and 75% specificity (AUC, 0.77; 95% CI, 0.59-0.94).

CONCLUSIONS

This study demonstrated a considerably high prevalence of NDRD in T2D adults undergoing renal biopsy. The absence of diabetic retinopathy, lower HbA1c values 12 months before biopsy and greater deterioration in HbA1c prior to biopsy predicted NDRD in T2D. Further studies are needed to validate the findings.

The association between glycemic variability and diabetic cardiovascular autonomic neuropathy in patients with type 2 diabetes

Background

It is presently unclear whether glycemic variability is associated with diabetic cardiovascular autonomic neuropathy (CAN). The aim of this study was to examine whether short- and/or long-term glycemic variability (GV) contribute to CAN.

Methods

A total of 110 patients with type 2 diabetes who underwent three-day continuous glucose monitoring (CGM) completed five standardized autonomic neuropathy tests. Short-term GV was measured by the standard deviation (SD), coefficient of variation (CV) of glucose, and the mean amplitude of glycemic excursions (MAGE) in CGM. HbA1c variability was calculated from the intrapersonal SD, adjusted SD, and CV of serial HbA1c over 2-year period. CAN was defined as the presence of at least two abnormal parasympathetic function tests. The severity of CAN was evaluated by total scores of five autonomic function tests.

Results

In univariate analysis, not only SD and CV in CGM but also all parameters of HbA1c variability were significantly higher in the patients with CAN (n = 47, 42.7 %) than in those without CAN. In multivariate analysis, CV (Odds ratio [OR] 1.07, 95 % confidence interval [CI] 1.01–1.13; p = 0.033), but neither SD nor MAGE in CGM, independently correlated with the presence of CAN. All parameters of HbA1c variability, such as SD of HbA1c (OR 12.10 [95 % CI 2.29–63.94], p = 0.003), adjusted SD of HbA1c (OR 17.02 [95 % CI 2.66–108.86], p = 0.003), and log CV of HbA1c (OR 24.00 [95 % CI 3.09–186.48], p = 0.002), were significantly associated with the presence of CAN. The patients with higher HbA1c variability had an increased risk of advanced CAN.

Conclusion

CV in CGM and all parameters of HbA1c variability were independently associated with the presence of CAN in patients with inadequately controlled type 2 diabetes requiring CGM.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-015-0233-0) contains supplementary material, which is available to authorized users.

Both high and low HbA1c predict incident heart failure in type 2 diabetes mellitus

BACKGROUND

Type 2 diabetes mellitus is an independent risk factor for heart failure development, but the relationship between incident heart failure and antecedent glycemia has not been evaluated.

METHODS AND RESULTS

The Genetics of Diabetes Audit and Research in Tayside Study study holds data for 8683 individuals with type 2 diabetes mellitus. Dispensed prescribing, hospital admission data, and echocardiography reports were linked to extract incident heart failure cases from December 1998 to August 2011. All available HbA1c measures until heart failure development or end of study were used to model HbA1c time-dependently. Individuals were observed from study enrolment until heart failure development or end of study. Proportional hazard regression calculated heart failure development risk associated with specific HbA1c ranges accounting for comorbidities associated with heart failure, including blood pressure, body mass index, and coronary artery disease. Seven hundred and one individuals with type 2 diabetes mellitus (8%) developed heart failure during follow up (mean 5.5 years, ±2.8 years). Time-updated analysis with longitudinal HbA1c showed that both HbA1c <6% (hazard ratio =1.60; 95% confidence interval, 1.38-1.86; P value <0.0001) and HbA1c >10% (hazard ratio =1.80; 95% confidence interval, 1.60-2.16; P value <0.0001) were independently associated with the risk of heart failure.

CONCLUSIONS

Both high and low HbA1c predicted heart failure development in our cohort, forming a U-shaped relationship.

β-cell dysfunction: Its critical role in prevention and management of type 2 diabetes

Type 2 diabetes (T2DM) is characterized by insulin resistance and β-cell dysfunction. Although, in contrast to type 1 diabetes, insulin resistance is assumed to be a major pathophysiological feature of T2DM, T2DM never develops unless β-cells fail to compensate insulin resistance. Recent studies have revealed that a deficit of β-cell functional mass is an essential component of the pathophysiology of T2DM, implying that β-cell deficit is a common feature of both type 1 and type 2 diabetes. β-cell dysfunction is present at the diagnosis of T2DM and progressively worsens with disease duration. β-cell dysfunction is associated with worsening of glycemic control and treatment failure; thus, it is important to preserve or recover β-cell functional mass in the management of T2DM. Since β-cell regenerative capacity appears somewhat limited in humans, reducing β-cell workload appears to be the most effective way to preserve β-cell functional mass to date, underpinning the importance of lifestyle modification and weight loss for the treatment and prevention of T2DM. This review summarizes the current knowledge on β-cell functional mass in T2DM and discusses the treatment strategy for T2DM.

Association between the extent of urinary albumin excretion and glycaemic variability indices measured by continuous glucose monitoring

AIMS

The contribution of glycaemic variability to the microvascular complication of diabetes has not been established. We examined whether there is an independent association between indices of glycaemic variability in continuous glucose monitoring and extent of albuminuria.

METHODS

A total of 173 patients with Type 2 diabetes (without insulin therapy, n = 96; with insulin therapy, n = 77) who had unexplained large fluctuations in blood glucose values underwent three-day continuous glucose monitoring. We used a multinomial logistic regression model to determine whether the indices of glycaemic variability independently affected the odds of having a spot urine albumin/creatinine ratio of 30-299 mg/g and ≥ 300 mg/g.

RESULTS

Higher standard deviation (P = 0.002), mean of daily differences (P = 0.023) and mean amplitude of glycaemic excursion (P = 0.043) significantly increased the odds of having a urine albumin/creatinine ratio of ≥ 300 mg/g. In multivariable analysis, only higher standard deviation, but not mean amplitude of glycaemic excursion and mean of daily differences, independently increased the odds of having a urine albumin/creatinine ratio of ≥ 300 mg/g (P = 0.025). Coefficient of variation (sd/mean) was not associated with the odds of having a urine albumin/creatinine ratio of 30-299 or ≥ 300 mg/g.

CONCLUSIONS

The independent association between standard deviation and the extent of albuminuria was lost when the measures were normalized by mean glucose level. At least in terms of relative measures of glycaemic variability, we failed to demonstrate an independent association between glycaemic variability and albuminuria extent in patients with inadequately controlled Type 2 diabetes.

Relationship of HbA1c variability, absolute changes in HbA1c, and all-cause mortality in type 2 diabetes: a Danish population-based prospective observational study

OBJECTIVE

We assessed the relationship of mortality with glycated hemoglobin (HbA1c) variability and with absolute change in HbA1c.

DESIGN

A population-based prospective observational study with a median follow-up time of 6 years.

METHODS

Based on a validated algorithm, 11 205 Danish individuals with type 2 diabetes during 2001-2006 were identified from public data files, with at least three HbA1c measurements: one index measure, one closing measure 22-26 months later, and one measurement in-between. Medium index HbA1c was 7.3%, median age was 63.9 years, and 48% were women. HbA1c variability was defined as the mean absolute residual around the line connecting index value with closing value. Cox proportional hazard models with restricted cubic splines were used, with all-cause mortality as the outcome.

RESULTS

Variability between 0 and 0.5 HbA1c percentage point was not associated with mortality, but for index HbA1c ≤8% (64 mmol/mol), a variability above 0.5 was associated with increased mortality (HR of 1 HbA1c percentage point variability was 1.3 (95% CI 1.1 to 1.5) for index HbA1c 6.6-7.4%). For index HbA1c≤8%, mortality increased when HbA1c declined, but was stable when HbA1c rose. For index HbA1c>8%, change in HbA1c was associated with mortality, with the lowest mortality for greatest decline (HR=0.9 (95% CI 0.80 to 0.98) for a 2-percentage point decrease).

CONCLUSIONS

For individuals with an index HbA1c below 8%, both high HbA1c variability and a decline in HbA1c were associated with increased mortality. For individuals with index HbA1c above 8%, change in HbA1c was associated with mortality, whereas variability was not.

HbA1C variability and the risk of renal status progression in Diabetes Mellitus: a meta-analysis

OBJECTIVE

To explore the association between glycated hemoglobin (A1C) variability and renal disease progression in patients with diabetes mellitus.

METHODS

A comprehensive search was performed using the PubMed and Embase databases (up to April 26, 2014). The hazard ratio (HR) was pooled per unit increase in the standard deviation of A1C (A1C-SD) to evaluate the dose-response relationship between A1C-SD and the risk of nephropathy.

RESULTS

Eight studies with a total of 17,758 subjects provided the HR for A1C-SD and were included in the final meta-analysis. The pooled HR results demonstrated that A1C-SD was significantly associated with the progression of renal status (HR for both T1DM and T2DM 1.43, 95% confidence interval [CI] 1.24-1.64; HR for T1DM 1.70, 95%CI 1.41-2.05; HR for T2DM 1.20, 95%CI 1.12-1.28). A1C-SD was significantly correlated with new-onset microalbuminuria (HR for T1DM 1.63, 95%CI 1.28-2.07; HR for T2DM 1.23, 95%CI 1.08-1.39). These outcomes were also supported in subgroup analyses. Furthermore, sensitivity analyses demonstrated that the results were robust.

CONCLUSIONS

A1C variability is independently associated with the development of microalbuminuria and the progression of renal status in both type 1 and 2 diabetes patients. A standard method for measuring A1C variability is essential for further and deeper analyses. In addition, future studies should assess the effect of reducing A1C variability on nephropathy complication.

Glycemic variability and oxidative stress: a link between diabetes and cardiovascular disease?

Diabetes is associated with a two to three-fold increase in risk of cardiovascular disease. However, intensive glucose-lowering therapy aiming at reducing HbA1c to a near-normal level failed to suppress cardiovascular events in recent randomized controlled trials. HbA1c reflects average glucose level rather than glycemic variability. In in vivo and in vitro studies, glycemic variability has been shown to be associated with greater reactive oxygen species production and vascular damage, compared to chronic hyperglycemia. These findings suggest that management of glycemic variability may reduce cardiovascular disease in patients with diabetes; however, clinical studies have shown conflicting results. This review summarizes the current knowledge on glycemic variability and oxidative stress, and discusses the clinical implications.

Assessment of the association between glycemic variability and diabetes-related complications in type 1 and type 2 diabetes

Chronic hyperglycemia is the main risk factor for the development of diabetes-related complications in both type 1 and type 2 diabetes, but it is thought that frequent or large glucose fluctuations may contribute independently to diabetes-related complications. A systematic literature review was performed using the PubMed, EMBASE and Cochrane Library databases with searches limited to studies published from June 2002 to March 2014, in English and including ≥50 patients. Twenty eight articles were included in the final review. Eighteen studies reported the association between glucose variability and diabetes-related complications exclusively in type 2 diabetes. A positive association between increased variability and microvascular complications and coronary artery disease was consistently reported. Associations between glucose variability and other macrovascular complications were inconsistent in type 2 diabetes. Seven studies examined the association between glucose variability and complications exclusively in type 1 diabetes. Increased glucose variability appears to play a minimal role in the development of micro- and macrovascular complications in type 1 diabetes. Consistent findings suggest that in type 2 diabetes glucose variability is associated with development of microvascular complications. The role of increased glucose variability in terms of microvascular and macrovascular complications in type 1 diabetes is less clear; more data in are needed.

Chronic kidney disease in type 2 diabetes: lessons from the Renal Insufficiency And Cardiovascular Events (RIACE) Italian Multicentre Study

The Renal Insufficiency And Cardiovascular Events (RIACE) Italian Multicentre Study is an ongoing observational survey that examines the role of estimated glomerular filtration rate (eGFR) as an independent predictor of cardiovascular and renal outcomes in 15,773 Italian subjects with type 2 diabetes. The analysis of data collected at the enrollment visit provided a picture of chronic kidney disease (CKD) and its association with other complications, risk factors for cardiovascular disease (CVD) and treatments in a large contemporary cohort. Main results of this analysis were that (a) non-albuminuric renal impairment is the predominant clinical phenotype in patients, particularly women, with reduced eGFR; (b) concordance between CKD and diabetic retinopathy is low, with only a minority of patients with renal dysfunction presenting with any or advanced retinal lesions; (c) the non-albuminuric form is associated with a significant prevalence of CVD, especially at the level of the coronary vascular bed; (d) CKD is associated with hemoglobin (Hb) A1c variability more than with average HbA1c, whereas retinopathy and CVD are not; (e) in elderly individuals with moderate-to-severe eGFR reduction, use of agents which are not recommended, such as sulphonylureas and metformin, is still frequent; and (f) though complications are generally more prevalent in men (except non-albuminuric renal impairment) women show a less favorable CVD risk profile and achieve therapeutic targets to a lesser extent than men, despite the fact that treatment intensity is not lower. These data update existing information on the natural history of CKD in patients with type 2 diabetes.

Impact of visit-to-visit glycemic variability on the risks of macrovascular and microvascular events and all-cause mortality in type 2 diabetes: the ADVANCE trial

OBJECTIVE

There is no consensus on the importance of visit-to-visit glycemic variability in diabetes. Therefore, we assessed the effects of visit-to-visit variability (VVV) in HbA1c and fasting glucose on major outcomes in the ADVANCE (Action in Diabetes and Vascular Disease: Preterax and Diamicron MR Controlled Evaluation) trial.

RESEARCH DESIGN AND METHODS

ADVANCE was a factorial randomized controlled trial of intensive glucose control and blood pressure lowering in patients with type 2 diabetes. VVV in the intensive glucose treatment group was defined using the SD of five measurements of HbA1c and glucose taken 3-24 months after randomization. Outcomes were combined macro- and microvascular events and all-cause mortality occurring post 24 months. Sensitivity analyses were performed using other indices of variability and in the standard glucose treatment group.

RESULTS

Among 4,399 patients in the intensive group, an increase in VVV of HbA1c was associated with an increased risk of vascular events (P = 0.01) and with mortality (P < 0.001): highest versus lowest tenth hazard ratio (95% CI) 1.64 (1.05-2.55) and 3.31 (1.57-6.98), respectively, after multivariable adjustment. A clear association was also observed between VVV of fasting glucose and increased risk of vascular events (P < 0.001; 2.70 [1.65-4.42]). HbA1c variability was positively associated with the risk of macrovascular events (P = 0.02 for trend), whereas glucose variability was associated with both macro- and microvascular events (P = 0.005 and P < 0.001 for trend, respectively). Sensitivity analyses using other indices, and patients in the standard glucose treatment group, were broadly consistent with these results.

CONCLUSIONS

Consistency of glycemic control is important to reduce the risks of vascular events and death in type 2 diabetes.

Evaluating self-management behaviors of diabetic patients in a telehealthcare program: longitudinal study over 18 months

BACKGROUND

Self-management is an important skill for patients with diabetes, and it involves frequent monitoring of glucose levels and behavior modification. Techniques to enhance the behavior changes of diabetic patients have been developed, such as diabetes self-management education and telehealthcare. Although the patients are engaged in self-management activities, barriers to behavior changes remain and additional work is necessary to address the impact of electronic media and telehealthcare on patient self-care behaviors.

OBJECTIVE

The aims of this study were to (1) explore the behaviors of diabetic patients interacting with online applications, (2) determine the impact of a telehealthcare program among 7 self-care behaviors of the patients, and (3) determine the changes in glycosylated hemoglobin (HbA1c) levels.

METHODS

A telehealthcare program was conducted to assist the patients with 7 self-care activities. The telehealthcare program lasted for 18 months and included the use of a third-generation mobile telecommunications glucometer, an online diabetes self-management system, and a teleconsultant service. We analyzed the data of 59 patients who participated in the telehealthcare program and 103 who did not. The behavioral assessments and the HbA1c data were collected and statistically analyzed to determine whether the telehealthcare services had an impact on the patients. We divided the 18-month period into 3 6-month intervals and analyzed the parameters of patients assisted by the telehealthcare service at different time points. We also compared the results of those who were assisted by the telehealthcare service with those who were not.

RESULTS

There was a significant difference in monitoring blood glucose between the beginning and the end of the patient participation (P=.046) and between the overall period and the end of patient participation (P<.001). Five behaviors were significantly different between the intervention and control patients: being active (P<.001), healthy eating (P<.001), taking medication (P<.001), healthy coping (P=.02), and problem solving (P<.001). Monitoring of blood glucose was significantly different (P=.02) during the 6-12 month stage of patient participation between the intervention and control patients. A significant difference between the beginning and the 6-12 month stage of patient participation was observed for the mean value of HbA1c level (P=.02), and the differences between the overall HbA1c variability and the variability of each 6-month interval was also significant.

CONCLUSIONS

Telehealthcare had a positive effect on diabetic patients. This study had enhanced blood glucose monitoring, and the patients in the program showed improvements in glycemic control. The self-care behaviors affect patient outcomes, and the changes of behavior require time to show the effects.

Association between serum ferritin and microalbuminuria in Type 2 diabetes in Taiwan

AIMS

Serum ferritin has been found closely related with diabetes and glucose metabolism, but its impact on diabetic nephropathy remains unknown. This study aimed to explore the association between serum ferritin and microalbuminuria in Type 2 diabetes.

METHODS

Eight hundred and fifty-one subjects with Type 2 diabetes were selected from a cohort participating in a glycaemic control study in Taiwan in 2008. We used urine albumin:creatinine ratio to define microalbuminuria; serum ferritin was divided into quartiles for analysis. Logistic regression and trend tests were used to delineate the association between serum ferritin and microalbuminuria.

RESULTS

Subjects with diabetes with higher ferritin tended to have more metabolic disorders, higher high-sensitivity C-reactive protein and higher prevalence of microalbuminuria. Compared with those in the lowest quartile, subjects with diabetes in the highest ferritin quartile were 55% (P = 0.029) more likely to have microalbuminuria. After controlling for demographics, metabolic profiles and other inflammatory markers, the association between serum ferritin levels and microalbuminuria remained significant (P for trend < 0.001). This independent relationship was not changed either for those who had better glycaemic control or those who had not used an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker.

CONCLUSIONS

The current study shows hyperferritinemia may be an independent risk factor of nephropathy in patients with Type 2 diabetes.

Do data in the literature indicate that glycaemic variability is a clinical problem? Glycaemic variability and vascular complications of diabetes

In recent years glycaemic variability (GV) has emerged as a determinant of vascular complications of both type 1 and type 2 diabetes mellitus. In type 1 diabetes analysis of data of GV show conflicting results on both micro- and macro-vascular complications. In non-diabetic subjects blood glucose after loading is a stronger predictor of cardiovascular complications than fasting glucose. In type 2 diabetes both coefficient of variation of fasting blood glucose and postprandial blood glucose predict cardiovascular events. Also, long term variability of HbA1c has been associated predominantly with diabetic nephropathy, less frequently with retinopathy. Intervention trials to evaluate the effect of postprandial glucose have been conducted only in prediabetes or in type 2 diabetes and the data are not conclusive. In vitro and in vivo data have shown the mechanisms that are at the basis of the adverse cardiovascular effects of GV, mainly associated with oxidative stress; the atherogenic action of postprandial glucose also involves insulin sensitivity, postprandial increase in serum lipids and glycaemic index of food. Thus, correction of GV emerges as a target to be pursued in clinical practice in order to safely reduce mean blood glucose (and thus glycated haemoglobin) and for its direct effects on vascular complications of diabetes.

HbA1c variability as an independent correlate of nephropathy, but not retinopathy, in patients with type 2 diabetes: the Renal Insufficiency And Cardiovascular Events (RIACE) Italian multicenter study

OBJECTIVE

To examine the association of hemoglobin (Hb) A1c variability with microvascular complications in the large cohort of subjects with type 2 diabetes from the Renal Insufficiency And Cardiovascular Events (RIACE) Italian Multicenter Study.

RESEARCH DESIGN AND METHODS

Serial (3-5) HbA1c values collected in a 2-year period before enrollment were available from 8,260 subjects from 9 centers (of 15,773 patients from 19 centers). HbA1c variability was measured as the intraindividual SD of 4.52 ± 0.76 values. Diabetic retinopathy (DR) was assessed by dilated funduscopy. Chronic kidney disease (CKD) was defined based on albuminuria, as measured by immunonephelometry or immunoturbidimetry, and estimated glomerular filtration rate (eGFR) was calculated from serum creatinine.

RESULTS

Median and interquartile range of average HbA1c (HbA1c-MEAN) and HbA1c-SD were 7.57% (6.86-8.38) and 0.46% (0.29-0.74), respectively. The highest prevalence of microalbuminuria, macroalbuminuria, reduced eGFR, albuminuric CKD phenotypes, and advanced DR was observed when both HbA1c parameters were above the median and the lowest when both were below the median. Logistic regression analyses showed that HbA1c-SD adds to HbA1c-MEAN as an independent correlate of microalbuminuria and stages 1-2 CKD and is an independent predictor of macroalbuminuria, reduced eGFR, and stages 3-5 albuminuric CKD, whereas HbA1c-MEAN is not. The opposite was found for DR, whereas neither HbA1c-MEAN nor HbA1c-SD affected nonalbuminuric CKD.

CONCLUSIONS

In patients with type 2 diabetes, HbA1c variability affects (albuminuric) CKD more than average HbA1c, whereas only the latter parameter affects DR, thus suggesting a variable effect of these measures on microvascular complications.

Hemoglobin A1c variability as an independent correlate of cardiovascular disease in patients with type 2 diabetes: a cross-sectional analysis of the renal insufficiency and cardiovascular events (RIACE) Italian multicenter study

BACKGROUND

Previous reports have clearly indicated a significant relationship between hemoglobin (Hb) A1c change from one visit to the next and microvascular complications, especially nephropathy (albuminuria and albuminuric chronic kidney disease, CKD). In contrast, data on macrovascular disease are less clear. This study was aimed at examining the association of HbA1c variability with cardiovascular disease (CVD) in the large cohort of subjects with type 2 diabetes from the Renal Insufficiency and Cardiovascular Events (RIACE) Italian Multicenter Study.

METHODS

Serial (3-5) HbA1c values obtained during the 2-year period preceding recruitment, including that obtained at the enrolment, were available from 8,290 subjects from 9 centers (out of 15,773 patients from 19 centers). Average HbA1c and HbA1c variability were calculated as the intra-individual mean (HbA1c-MEAN) and standard deviation (HbA1c-SD), respectively, of 4.52 ± 0.76 values. Prevalent CVD, total and by vascular bed, was assessed from medical history by recording previous documented major acute events. Diabetic retinopathy (DR) was assessed by dilated fundoscopy. CKD was defined based on albuminuria, as measured by immunonephelometry or immunoturbidimetry, and estimated glomerular filtration rate, as calculated from serum creatinine.

RESULTS

HbA1c-MEAN, but not HbA1c-SD, was significantly higher (P<0.0001) in subjects with history of any CVD (n. 2,133, 25.7%) than in those without CVD (n. 6,157, 74.3%). Median and interquartile range were 7.78 (7.04-8.56) and 7.49 (6.81-8.31), respectively, for HbA1c-MEAN, and 0.47 (0.29-0.75) and 0.46 (0.28-0.73), respectively, for HbA1c-SD. Logistic regression analyses showed that HbA1c-MEAN, but not HbA1c-SD (and independent of it), was a significant correlate of any CVD. Similar findings were observed in subjects with versus those without any coronary or cerebrovascular event or myocardial infarction. Conversely, none of these measures were associated with stroke, whereas both correlated with any lower limb vascular event and HbA1c-SD alone with ulceration/gangrene. All these associations were independent of known CVD risk factors and microvascular complications (DR and CKD).

CONCLUSIONS

In patients with type 2 diabetes, HbA1c variability has not a major impact on macrovascular complications, at variance with average HbA1c, an opposite finding as compared with microvascular disease, and particularly nephropathy.

TRIAL REGISTRATION

ClinicalTrials.Gov NCT00715481.