Diabetes drug GLP-1 tied to halved stroke risk in study of 171,917 Swedes

A sweeping analysis of nearly every newly diagnosed person with type 2 diabetes in Sweden has delivered one of the clearest real-world answers yet to a question that has divided cardiologists and diabetologists for years: which of the modern glucose-lowering drugs actually protect the brain? The answer, published in eClinicalMedicine, is strikingly uneven. Glucagon-like peptide-1 receptor agonists, the injectable drug class behind some of the most talked-about medications in medicine today, were associated with roughly half the risk of ischemic stroke compared with periods when patients were not taking them. Two other popular drug classes, SGLT2 inhibitors and DPP-4 inhibitors, showed no clear protective signal at all.

The study, led by Anastasios Mavridis and colleagues at Sahlgrenska University Hospital and the University of Gothenburg, drew on the Swedish National Diabetes Register, a national quality registry that captures the vast majority of diabetes care in the country. The researchers followed 171,917 individuals who were registered for the first time between January 2013 and December 2019, accumulating more than 1.6 million clinical registrations and up to seven years of follow-up per person. During that window, 2,734 people suffered an ischemic stroke and 428 a hemorrhagic stroke. Because Sweden links its health registries through unique personal identity numbers, the team could connect each patient’s laboratory values, prescriptions, comorbidities and stroke outcomes into a single longitudinal record of routine clinical care.

What sets the analysis apart from most real-world studies is how it handled the messy dynamics of actual treatment. In clinical practice, patients switch drugs, stop and restart, and their blood pressure, weight, kidney function and cholesterol evolve alongside those decisions. Standard observational analyses typically adjust for characteristics measured once, at baseline, an approach that can badly distort estimates when treatment and risk factors influence each other over time. The Swedish team instead used inverse probability of treatment weighting within a marginal structural model, a statistical framework designed precisely for this treatment-confounder feedback. Each patient’s exposure status was updated at every registry visit, drawing on pharmacy dispensing records to reconstruct when drugs were actually in use, and weights were recalculated to balance clinical characteristics across treated and untreated intervals.

The headline result concerns GLP-1 receptor agonists. Across weighted time-varying Cox models, use of these drugs was associated with a 54 percent lower hazard of ischemic stroke (hazard ratio 0.46, 95 percent confidence interval 0.29 to 0.72) and a 49 percent lower hazard of total stroke (hazard ratio 0.51, 95 percent confidence interval 0.33 to 0.79). For hemorrhagic stroke the point estimate pointed in the same direction but the confidence interval was wide, spanning 0.28 to 2.28, reflecting the small number of bleeding events. By contrast, SGLT2 inhibitors showed no clear association with any stroke subtype, with an ischemic stroke hazard ratio of 0.94, and DPP-4 inhibitors were likewise neutral, at 1.17 for ischemic stroke.

To place these numbers in context, the authors systematically searched PubMed for meta-analyses of both randomized trials and observational studies, screening 274 abstracts and 102 full texts. The picture that emerged explains why the field has been so confused. For SGLT2 inhibitors, meta-analyses of randomized controlled trials consistently reported no effect on stroke, with effect sizes between 0.84 and 1.30, while observational meta-analyses suggested a protective association between 0.75 and 0.87. For GLP-1 receptor agonists, both trial and observational syntheses agreed on a protective effect, roughly a 10 to 20 percent risk reduction. DPP-4 inhibitors were neutral in trials. The new Swedish findings align with the randomized trial evidence for all three classes, and they do so using a method that many earlier observational studies lacked.

Why did previous real-world studies so often disagree with the trials? The authors argue that the answer lies largely in methodology. Most prior observational work adjusted only for baseline variables, which is appropriate for estimating the effect of initial treatment assignment but poorly suited to dynamic treatment patterns. When patients frequently switch or discontinue therapy, an intention-to-treat style estimator loses information about whether prescriptions are actually filled and says little about the hazard at any given moment of drug use. By updating exposure, covariates and concomitant medications throughout follow-up, the marginal structural model approach directly targets the question of what happens while patients are on treatment, which may partly explain why the GLP-1 association observed here was stronger than the 10 to 20 percent reductions typically reported in randomized trials.

The authors are careful to caution against over-interpreting that larger magnitude. Their estimates reflect treatment use during follow-up, not the effect of starting a drug in a treatment-naive patient, and the two estimands are not directly comparable. Differences in adherence, persistence, study populations and residual confounding may all contribute. As with any observational study, unmeasured confounding remains a possibility, and the team acknowledges that substantial missing data in several clinical variables, handled through two-level multiple imputation, means the results depend on the adequacy of the imputation models. The hemorrhagic stroke analyses were also limited by small event counts, and the comparison with published meta-analyses was explicitly contextual rather than a formal evidence synthesis.

Biologically, the divergence between drug classes makes considerable sense. Beyond lowering glucose, GLP-1 receptor agonists reduce systolic blood pressure, body weight and post-meal lipaemia, improve endothelial function and dampen vascular inflammation. Experimental work suggests anti-atherosclerotic effects through reduced oxidative stress, better nitric oxide bioavailability and modulation of macrophage activity within plaques, potentially stabilizing the vulnerable lesions that cause ischemic strokes. Intriguingly, GLP-1 receptors are also expressed in the central nervous system, and preclinical models hint at direct neuroprotective properties, including reduced excitotoxicity, less neuroinflammation and diminished apoptotic signalling. SGLT2 inhibitors, by contrast, deliver their cardiovascular and renal benefits largely through osmotic diuresis, natriuresis and improved cardiac loading, mechanisms that may not target the atherosclerotic and thromboembolic pathways most relevant to ischemic stroke. Some researchers have even hypothesized that SGLT2 inhibition raises hematocrit and blood viscosity, potentially offsetting cerebrovascular gains.

The clinical implications are nuanced rather than revolutionary. The authors suggest that GLP-1 receptor agonists may reasonably be considered part of a stroke-prevention strategy in type 2 diabetes, but they are emphatic that the established benefits of SGLT2 inhibitors and DPP-4 inhibitors for heart failure, kidney disease and other outcomes must remain central to prescribing decisions. Treatment choices, they argue, should be informed by the totality of evidence for each individual patient, weighing the distinct benefit profiles of each class. Because the study drew on Sweden’s universal healthcare system, the findings are most applicable to settings with similar care structures, and the cohort, restricted to people newly registered from 2013 onward, may not fully represent those with long-standing diabetes.

For a field wrestling with how to translate landmark cardiovascular outcome trials into everyday practice, this study offers a methodological template as much as a clinical finding. By embracing the time-varying chaos of real-world care rather than freezing patients at their baseline characteristics, the Swedish team produced observational estimates that line up with the randomized evidence, resolving a discordance that has persisted across dozens of published syntheses. Future work, the authors note, should focus on how these findings can feed into personalized glucose-lowering strategies that optimize stroke prevention, a goal that becomes more attainable when trial data and real-world data finally tell the same story.

Subject of Research: Effects of SGLT2 inhibitors, GLP-1 receptor agonists, and DPP-4 inhibitors on stroke risk in type 2 diabetes

Article Title: The effect of SGLT2 inhibitors, GLP-1 receptor agonists, or DPP-4 inhibitors on stroke risk in type 2 diabetes: a nationwide longitudinal cohort study in Sweden with contextualisation analysis

Article References: The effect of SGLT2 inhibitors, GLP-1 receptor agonists, or DPP-4 inhibitors on stroke risk in type 2 diabetes: a nationwide longitudinal cohort study in Sweden with contextualisation analysis. (n.d.). https://doi.org/10.1016/j.eclinm.2026.104220

Image Credits: AI Generated

DOI: 10.1016/j.eclinm.2026.104220

Keywords: type 2 diabetes, stroke, GLP-1 receptor agonists, SGLT2 inhibitors, DPP-4 inhibitors, Swedish National Diabetes Register, marginal structural models, ischemic stroke, hemorrhagic stroke, pharmacoepidemiology, cardiovascular outcomes, real-world evidence