Unlike traditional antidiabetic therapies, which have never been associated with a significant reduction in stroke in a major trial, some of the newer drugs are showing that benefit, but the protection is not linked to tighter glycemic control.
In patients with type 2 diabetes mellitus (T2DM), the evidence is strong that "they are not working through glycemic control per se," according to Larry B. Goldstein, MD, chair of neurology, University of Kentucky College of Medicine, Lexington, Kentucky. "But it is not yet clear what the mechanism of benefit is."
In the past, several large randomized studies, such as the ACCORD trial, provided compelling evidence that tighter glycemic control does not translate into meaningful protection across stroke. Performed before many of the modern therapies were available, this lack of protection was observed with essentially "no heterogeneity across specific drugs," according to Dr. Goldstein.
In long-term results from ACCORD, published in 2011, the odds ratio for a fatal or nonfatal stroke was a nonsignificant 0.97 in favor of tight glycemic control relative to standard control. The wide confidence intervals ruled out any hint of statistical significance (95% CI, 0.77-1.33; P = .85). Dr. Goldstein provided data from numerous other studies and meta-analyses that drew the same conclusion.
Stroke Prevention With Antidiabetics
"What has changed is that we have new ways of glycemic control, and some of these do show protection against stroke," Dr. Goldstein said. Yet, the newer drugs do not do a better job at sustained reductions of HbA1c or other measures of reaching lower blood glucose reductions when adherence is similar.
"The level of glucose control with the newer agents is really about the same," Dr. Goldstein said at the Annual Meeting of the American Academy of Neurology, where he led a symposium called Controversies in Stroke Treatment and Prevention.
The newer agents, such as sodium-glucose co-transporter-2 inhibitors (SGLT2i) and glucagon-like peptide-1 receptor agonists (GLP-1RA), have been associated with significant and clinically meaningful reductions in cardiovascular events. However, it is not clear that even these two medications perform similarly for stroke prevention specifically.
Of these two drug classes, Dr. Goldstein said the evidence most strongly supports GLP-1 receptor agonists. He cited one meta-analysis of eight randomized studies that calculated a risk reduction of about 15% whether calculated for fatal or nonfatal strokes. For each the protection was highly statistically significant (P = .0002 and P < .001, respectively).
In contrast, the effect of SGLT2 inhibitors is weaker. In a study that distilled data from large cardiovascular trials with GLP-1RA, SGLT2i, dipeptidyl peptidase-4 inhibitors (DPP4i), and pioglitazone, a thiazolidinedione, only GLP-1RA drugs were associated with a highly significant (P < .001) reduction in risk of stroke. The risk reduction for pioglitazone reached significance (P = .025), but there was no signal of risk reduction for SGLT2i (P = .88) or for DPP4i (P = .5).
Weight Loss Potential Mechanism
Looking to explain the protection from stroke associated with some of the newer antidiabetic therapies, Gordon Kelley, MD, who leads the stroke program for AdventHealth Medical Group, Shawnee Mission, Kansas, suggested that weight loss is probably important.
"In our group, we work as a team to manage stroke risk in patients with diabetes, so I am not much involved in the choice of antidiabetic therapies, but it does seem that SGLT2 inhibitors and the GLP-1 receptor agonists share weight loss as an effect beyond glucose control," he said.
Dr. Goldstein agreed that weight loss is a potential contributor to the cardiovascular benefits of GLP-1RA and SGLT2i, but he indicated that it might not help explain the reduction in stroke, an effect demonstrated repeatedly with GLP-1RA but inconsistently with SGLT2i.
The argument against weight loss as the critical mechanism of stroke prevention from newer antidiabetic drugs is strengthened by studies that suggest weight loss with SGLT2i appears to be even better than on GLP-1RA. In a study published in a Pharmacy Journal, weight loss was about twice as great among T2DM patients after 6 months of treatment managed with SGLT2i relative to those on a GLP-1RA (-2.8 vs 1.15 kg; P = .014).
Newer Guideline Recommended
In the 2019 American College of Cardiology/American Heart Association guidelines on the Primary Prevention of Cardiovascular Disease, stroke reduction is not discussed as an isolated risk, but these guidelines do recommend GLP-1RA or SGLT2i after metformin for glycemic control in T2DM patients with atherosclerotic cardiovascular disease (ASCVD) risk factors. This is based on evidence that drugs of both classes reduce risk for ASCVD events. The risk reduction has been particularly strong for heart failure.
For the risk of stroke specifically in patients with T2DM, Dr. Goldstein recommended calculating the ASCVD risk with the simple but well validated ACC risk calculator that is available online and is quickly completed when values for patient risk factors are readily available. For those with greater than 10% risk of an event in the next 10 years, he thinks GLP-1RA are a reasonable choice for prevention of stroke and other ASCVD events.
"GLP-1RA is mentioned in the guidelines, so this is supported," said Dr. Goldstein, although adding that his choice of this class over SGLT2i is a personal if informed recommendation. He believes that the data favor GLP-1RA even if the exact mechanism of this protection is yet to be identified.
Dr. Goldstein and Dr. Kelley report no potential conflicts of interest.
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