Hypoglycemia and Cardiovascular Disease: Lessons from Outcome Studies

Association of hypoglycaemia with the risks of arrhythmia and mortality in individuals with diabetes - a systematic review and meta-analysis

Background

Hypoglycaemia has been linked to an increased risk of cardiac arrhythmias by causing autonomic and metabolic alterations, which may be associated with detrimental outcomes in individuals with diabetes(IWD), such as cardiovascular diseases (CVDs) and mortality, especially in multimorbid or frail people. However, such relationships in this population have not been thoroughly investigated. For this reason, we conducted a systematic review and meta-analysis.

Methods

Relevant papers published on PubMed, Embase, Cochrane, Web of Knowledge, Scopus, and CINHAL complete from inception to December 22, 2022 were routinely searched without regard for language. All of the selected articles included odds ratio, hazard ratio, or relative risk statistics, as well as data for estimating the connection of hypoglycaemia with cardiac arrhythmia, CVD-induced death, or total death in IWD. Regardless of the heterogeneity assessed by the I2 statistic, pooled relative risks (RRs) and 95% confidence intervals (CI) were obtained using random-effects models.

Results

After deleting duplicates and closely evaluating all screened citations, we chose 60 studies with totally 5,960,224 participants for this analysis. Fourteen studies were included in the arrhythmia risk analysis, and 50 in the analysis of all-cause mortality. Hypoglycaemic patients had significantly higher risks of arrhythmia occurrence (RR 1.42, 95%CI 1.21-1.68), CVD-induced death (RR 1.59, 95% CI 1.24-2.04), and all-cause mortality (RR 1.68, 95% CI 1.49-1.90) compared to euglycaemic patients with significant heterogeneity.

Conclusion

Hypoglycaemic individuals are more susceptible to develop cardiac arrhythmias and die, but evidence of potential causal linkages beyond statistical associations must await proof by additional specifically well planned research that controls for all potential remaining confounding factors.

Hypoglycaemia and Cardiovascular Disease Risk in Patients with Diabetes

Hypoglycaemia represents an important side effect of insulin therapy and insulin secretagogues. It can occur in both type 1 and type 2 diabetes mellitus patients. Also, some associations between hypoglycaemia and cardiovascular (CV) risk have been reported. Several mechanisms may be involved, including the sympathoadrenal system, hypokalaemia, endothelial dysfunction, coagulation, platelets, inflammation, atherothrombosis and impaired autonomic cardiac reflexes. This narrative review discusses the associations of hypoglycaemia with CV diseases, including coronary heart disease (CHD), cardiac arrhythmias, stroke, carotid disease and peripheral artery disease (PAD), as well as with dementia. Severe hypoglycaemia has been related to CHD, CV and all-cause mortality. Furthermore, there is evidence supporting an association between hypoglycaemia and cardiac arrhythmias, potentially predisposing to sudden death. The data linking hypoglycaemia with stroke, carotid disease and PAD is limited. Several factors may affect the hypoglycaemia-CV relationships, such as the definition of hypoglycaemia, patient characteristics, co-morbidities (including chronic kidney disease) and antidiabetic drug therapy. However, the association between hypoglycaemia and dementia is bilateral. Both the disorders are more common in the elderly; thus, glycaemic goals should be carefully selected in older patients. Further research is needed to elucidate the impact of hypoglycaemia on CV disease.

Effects of Recommendations for Diabetes Management at Hospital Discharge on Long-Term Diabetes Control

OBJECTIVE

To determine the impact of diabetes-specific recommendations at 1 year after hospital discharge on glycemic control and diabetes care in an outpatient setting.

METHODS

A total of 139 patients with type 2 diabetes on a basal-bolus insulin regimen during hospitalization were included in the statistical analysis. We gathered data on treatment regimens after 12 to 16, 26 to 30, and 52 to 56 weeks following discharge as well as glycosylated hemoglobin (HbA1c) levels for all patients. Prescriptions for diabetes therapy were retrieved. All changes in insulin or oral/noninsulin injectable drug regimens were recorded.

RESULTS

Half of the patients (n = 69) were discharged on their preadmission regimen (no change), and a change in the home treatment was recommended in the other half (n = 70). In the group of patients whose preadmission therapy was adjusted, HbA1c decreased from 9.6% (80 mmol/mol) to 8.5% (69 mmol/mol) (P = .0004) 1 year after discharge. In the group of patients discharged on their preadmission regimen, no significant changes in HbA1c levels during the study were observed. At follow-ups occurring 12 to 16 weeks after discharge, 52% (95% CI: 37.4%-66.3%) of patients in the change group had their treatment modified, compared with 18.6% (95% CI: 9.7%-30.9%) in the no-change group. In the group of patients discharged on their preadmission regimen, no significant change was observed. At the beginning of the study, patients in the change treatment group had higher HbA1c levels than patients in the no-change group (9.6 ± 2.0 vs 8.6 ± 1.7, P < .001). At the end of the study, no significant changes in terms of HbA1c levels were found between the groups (8.8 ± 1.9 vs 8.5 ± 1.9, P = .2).

CONCLUSIONS

Significant improvement in diabetes control occurred 1 year after hospital discharge in patients who underwent modifications in their treatment. This supports the relevance of providing and implementing proper care recommendations at transition.

Single prognostic cut-off value for admission glycemia in acute myocardial infarction has been used although high-risk stems from hyperglycemia as well as from hypoglycemia (a narrative review)

All original articles and meta-analysis use the single cut-off value to distinguish high-risk hyperglycemic from other acute myocardial infarction (AMI) patients. The mortality rate is 3.9 times higher in non-diabetic AMI patients with admission glycemia ≥6.1mmol compared to normoglycemic non-diabetic AMI patients. On the other hand, admission hypoglycemia in AMI is an important predictor of mortality. Because both admission hypo- and hyperglycemia correspond to higher in-hospital mortality, this graph is recognized as "J or U shaped curve". The review suggests two cut-off values for admission glycemia for risk assessment in AMI instead of single one because hypoglycemia as well as hyperglycemia represents a high-risk factor.

Selectivity of beta-blockers, cardiovascular and all-cause mortality in people with hypoglycaemia: An observational study

BACKGROUND AND AIMS

The association of beta-blockers and their selectivity with mortality and cardiovascular events in patients with and without hypoglycaemia is unknown.

METHODS AND RESULTS

Insulin-treated patients with diabetes were identified within the UK CPRD database. All-cause deaths, cardiovascular events, and hypoglycaemic episodes were captured to assess the interaction between beta-blocker therapy and selectivity with hypoglycaemia. 13,682 patients, of which 2036 (14.9%) with at least one hypoglycaemic episode, were included; 3148 deaths and 1235 cardiovascular events were recorded during a median of 2.3 and 4.7 years in patients with and without incident hypoglycaemia, respectively. Treatment with any beta-blocker was not associated with risk of death in both patients with and without hypoglycaemia, without significant interaction. Compared to no therapy, non-selective beta-blockers were associated with higher risk of death in patients without hypoglycaemia (hazard ratio (HR) 2.93 [1.26-6.83] in the fully adjusted model) but not in those with hypoglycaemia; interactions was not significant. For beta1-selective beta-blockers, there was no association with mortality in both patients with and without hypoglycaemia, without significant interaction. After missing data imputation, results were consistent for non-selective beta-blockers (HR in patients without hypoglycaemia 1.59 [1.22-2.08]) while indicated a reduced risk of death for beta1-selective beta-blockers in patients with hypoglycaemia (HR 0.76 [0.61-0.94]). Due to few cardiovascular events, complete-case analysis compared only any vs no beta-blocker therapy and indicated no associations with therapy or interaction by hypoglycaemia.

CONCLUSION

In patients with hypoglycaemic episodes, treatment with beta1-selective beta-blockers may potentially reduce the risk of death. These explorative findings and the potential role of confounding by indication need to be evaluated in other studies.

DEVOTE 3: temporal relationships between severe hypoglycaemia, cardiovascular outcomes and mortality

AIMS/HYPOTHESIS

The double-blind Trial Comparing Cardiovascular Safety of Insulin Degludec vs Insulin Glargine in Patients with Type 2 Diabetes at High Risk of Cardiovascular Events (DEVOTE) assessed the cardiovascular safety of insulin degludec. The incidence and rates of adjudicated severe hypoglycaemia, and all-cause mortality were also determined. This paper reports a secondary analysis investigating associations of severe hypoglycaemia with cardiovascular outcomes and mortality.

METHODS

In DEVOTE, patients with type 2 diabetes were randomised to receive either insulin degludec or insulin glargine U100 (100 units/ml) once daily (between dinner and bedtime) in an event-driven, double-blind, treat-to-target cardiovascular outcomes trial. The primary outcome was the first occurrence of an adjudicated major adverse cardiovascular event (MACE; cardiovascular death, non-fatal myocardial infarction or non-fatal stroke). Adjudicated severe hypoglycaemia was the pre-specified secondary outcome. In the present analysis, the associations of severe hypoglycaemia with both MACE and all-cause mortality was evaluated in the pooled trial population using time-to-event analyses, with severe hypoglycaemia as a time-dependent variable and randomised treatment as a fixed factor. An investigation with interaction terms indicated that the effect of severe hypoglycaemia on the risk of MACE and all-cause mortality were the same for both treatment arms, and so the temporal association for severe hypoglycaemia with subsequent MACE and all-cause mortality is reported for the pooled population.

RESULTS

There was a non-significant difference in the risk of MACE for individuals who had vs those who had not experienced severe hypoglycaemia during the trial (HR 1.38, 95% CI 0.96, 1.96; p = 0.080) and therefore there was no temporal relationship between severe hypoglycaemia and MACE. There was a significantly higher risk of all-cause mortality for patients who had vs those who had not experienced severe hypoglycaemia during the trial (HR 2.51, 95% CI 1.79, 3.50; p < 0.001). There was a higher risk of all-cause mortality 15, 30, 60, 90, 180 and 365 days after experiencing severe hypoglycaemia compared with not experiencing severe hypoglycaemia in the same time interval. The association between severe hypoglycaemia and all-cause mortality was maintained after adjustment for the following baseline characteristics: age, sex, HbA1c, BMI, diabetes duration, insulin regimen, hepatic impairment, renal status and cardiovascular risk group.

CONCLUSIONS/INTERPRETATION

The results from these analyses demonstrate an association between severe hypoglycaemia and all-cause mortality. Furthermore, they indicate that patients who experienced severe hypoglycaemia were particularly at greater risk of death in the short term after the hypoglycaemic episode. These findings indicate that severe hypoglycaemia is associated with higher subsequent mortality; however, they cannot answer the question as to whether severe hypoglycaemia serves as a risk marker for adverse outcomes or whether there is a direct causal effect.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01959529.

The Association of Severe Hypoglycemia With Incident Cardiovascular Events and Mortality in Adults With Type 2 Diabetes

OBJECTIVE

There is suggestive evidence linking hypoglycemia with cardiovascular disease, but few data have been collected in a community-based setting. Information is lacking on individual cardiovascular outcomes and cause-specific mortality.

RESEARCH DESIGN AND METHODS

We conducted a prospective cohort analysis of 1,209 participants with diagnosed diabetes from the Atherosclerosis Risk in Communities (ARIC) study (analytic baseline, 1996-1998). Severe hypoglycemic episodes were identified using first position ICD-9 codes from hospitalizations, emergency department visits, and ambulance calls through 2013. Cardiovascular events and deaths were captured through 2013. We used adjusted Cox regression models with hypoglycemia as a time-varying exposure.

RESULTS

There were 195 participants with at least one severe hypoglycemic episode during a median fellow-up of 15.3 years. After severe hypoglycemia, the 3-year cumulative incidence of coronary heart disease was 10.8% and of mortality was 28.3%. After adjustment, severe hypoglycemia was associated with coronary heart disease (hazard ratio [HR] 2.02, 95% CI 1.27-3.20), all-cause mortality (HR 1.73, 95% CI 1.38-2.17), cardiovascular mortality (HR 1.64, 95% CI 1.15-2.34), and cancer mortality (HR 2.49, 95% CI 1.46-4.24). Hypoglycemia was not associated with stroke, heart failure, atrial fibrillation, or noncardiovascular and noncancer death. Results were robust within subgroups defined by age, sex, race, diabetes duration, and baseline cardiovascular risk.

CONCLUSIONS

Severe hypoglycemia is clearly indicative of declining health and is a potent marker of high absolute risk of cardiovascular events and mortality.

Current perspectives on cardiovascular outcome trials in diabetes

Cardiovascular disease (CVD) is one of the most common diabetes-associated complications, as well as a leading cause for death in type 2 diabetes patients (T2D). Despite the well-known correlation between the two, up until the 2008 FDA industry guidance for licensing of new anti-hyperglycemic drugs, which required an investigation of cardiovascular outcomes (CVO) of glucose-lowering agents, only a few studies had looked into the relationship between glucose lowering drugs and cardiovascular (CV) risk. Thereafter, CVOT design has focused on non-inferiority short-term studies on high-risk patient populations aiming at capturing CV safety issues. Despite the wealth of information and useful data provided by CVOTs, this approach still suffers from certain limitations. The present review will condense the main results of the most recently completed CVOTs, reflect on the lessons learned, discuss on the issues presented by current CVOT design and offer some suggestions for improvement.