Association between difference in blood pressure reduction and risk of cardiovascular events in a type 2 diabetes population: A meta-regression analysis.

AIM: Recent US recommendations indicate a target blood pressure (BP) of 130/80mmHg for patients with type 2 diabetes (T2D). Our aim was to characterize the association between risk of cardiovascular events and differences in BP decreases in randomized trials of a T2D population. METHODS: A systematic search was made for randomized clinical trials assessing the effects of antihypertensive treatments in T2D patients on mortality, and fatal and non-fatal cardiovascular events, using a meta-regression technique to explore the influence of BP decreases on treatment effects. RESULTS: A total of 88,503 patients from 44 randomized trials were included. There was no significant association between BP decreases and risk of all-cause or cardiovascular mortality, cardiovascular events or myocardial infarction. However, stroke risk was influenced by BP decreases: compared with no reduction, a 10-mmHg reduction in systolic BP was associated with a relative odds ratio (OR) decrease of 33% (OR: 0.67, 95% CI: 0.54-0.82), and a 5-mmHg diastolic BP reduction was associated with a relative OR decrease of 38% (OR: 0.62, 95% CI: 0.50-0.76). Restricting the analysis to double-blind studies did not change the results for diastolic BP. CONCLUSION: A reduction in BP lowers the risk of stroke, but does not appear to affect the risk of other cardiovascular events in a T2D population.

Efficacy and safety of DPP-4 inhibitors in patients with type 2 diabetes: Meta-analysis of placebo-controlled randomized clinical trials.

BACKGROUND: Guidelines for type 2 diabetes (T2D) recommend reducing HbA1c through lifestyle interventions and glucose-lowering drugs (metformin, then combination with dipeptidyl peptidase-4 inhibitors [DPP-4Is] among other glucose-lowering drugs). However, no double-blind randomized clinical trial (RCT) compared with placebo has so far demonstrated that DDP-4Is reduce micro- and macrovascular complications in T2D. Moreover, the safety of DPP-4Is (with increased heart failure and acute pancreatitis) remains controversial. METHODS: A systematic review of the literature (PubMed, Cochrane Library Central Register of Controlled Trials [CENTRAL] and https://clinicaltrials.gov), including all RCTs vs placebo published up to May 2015 and the Trial Evaluating Cardiovascular Outcomes with Sitagliptin (TECOS), published June 2015, was performed. Primary endpoints were all-cause mortality and death from cardiovascular causes; secondary endpoints were macrovascular and microvascular events. Safety endpoints were acute pancreatitis, pancreatic cancer, serious adverse events and severe hypoglycaemia. RESULTS: A total of 36 double-blind RCTs were included, allowing analyses of 54,664 patients. There were no significant differences in all-cause mortality (RR=1.03, 95% confidence interval [CI]=0.95-1.12), cardiovascular mortality (RR=1.02, 95% CI=0.92-1.12), myocardial infarction (RR=0.98, 95% CI=0.89-1.08), strokes (RR=1.02, 95% CI=0.88-1.17), renal failure (RR=1.06, 95% CI=0.88-1.27), severe hypoglycaemia (RR=1.14, 95% CI=0.95-1.36) and pancreatic cancer (RR=0.54, 95% CI=0.28-1.04) with the use of DPP-4Is. However, DDP-4Is were associated with an increased risk of heart failure (RR=1.13, 95% CI=1.01-1.26) and of acute pancreatitis (RR=1.57, 95% CI=1.03-2.39). CONCLUSION: There is no significant evidence of short-term efficacy of DPP-4Is on either morbidity/mortality or macro-/microvascular complications in T2D. However, there are warning signs concerning heart failure and acute pancreatitis. This suggests a great need for additional relevant studies in future.

Is HbA1c a valid surrogate for macrovascular and microvascular complications in type 2 diabetes?

Recent recommendations regarding type 2 diabetes (T2D) patients' treatments have focused on personalizing glycosylated haemoglobin (HbA1c) targets. Because the relationship between HbA1c and diabetes prognosis has been established from large prospective cohorts, it is valid to question the extrapolation from population-based risk reduction estimations to individual predictions. Our study aimed to investigate the relationship between HbA1c reductions and clinical outcomes in randomized controlled trials (RCTs), using a meta-regression approach. Included were RCTs comparing intensive vs. standard glucose-lowering regimens for cardiovascular events and microvascular complications in T2D patients. Eight studies (33,396 patients) providing data for HbA1c reductions were found. In our meta-regression, HbA1c decreases were not significantly associated with reductions in our main study outcomes: total and cardiovascular mortality. They were also not associated with any of the secondary endpoints, including myocardial infarction, stroke and severe hypoglycaemia. Sensitivity analysis showed a significant correlation only between HbA1c-lowering and severe hypoglycaemia (P = 0.014). Meta-regression analysis could find no significant association between HbA1c-lowering and a decrease in clinical outcomes, thereby questioning the use of HbA1c as a surrogate outcome for T2D-related complications. Thus, RCTs vs. placebo are urgently required to evaluate the risk-benefit ratios of therapeutic strategies beyond HbA1c control in T2D patients.

Effects of pharmacological treatments on micro- and macrovascular complications of type 2 diabetes: what is the level of evidence?

Antidiabetic drugs for type 2 diabetes receive marketing authorization if they show efficacy in reducing levels of HbA(1c). However, efficacy on this biological criterion does not necessarily reflect clinical benefit to patients. Several randomized clinical trials have shown that antidiabetic drugs reduce HbA(1c) without a corresponding reduction in clinical events. This suggests a need to focus on the clinical effectiveness (morbimortality criteria) of our available antidiabetic drugs. In this non-extensive review of the literature, it was found that none of the current antidiabetic drugs have clearly proven their superiority over placebo in the gold standard double-blind randomized clinical trials. Thus, in 2013, the level of evidence for the clinical efficacy of antidiabetic drugs is disappointing and does not support the millions of prescriptions being written for them.

[Some reflexions about double blind]. / Quelques réflexions sur le double insu.

LITERATURE FINDINGS: Randomized, double blind, placebo-controlled clinical trials are currently the best means of demonstrating the clinical effectiveness of drugs. The double blind procedure, when ethically and technically feasible, is a necessary condition for validating results and for causal attribution of the observed difference between the two groups to the tested drug's pharmacological effect. COMMENTS: In practice, however, it appears that patients and independent investigators can guess who receives the drug and who receives a placebo through side effects, which are usually more frequent in patients receiving the drug. This phenomenon effectively "breaks the blind" and represents as such a major methodological bias, which cannot be avoided as it is inseparable of the drug's effect. CONCLUSION: The impact of this "unavoidable" double blind breach nevertheless remains unclear. While it can reasonably be assumed that it may modify subjective symptoms such as anxiety or pain through suggestion, its influence on objective criteria remains to be demonstrated.