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Diabetes duration an important predictor of stroke in patients with AF
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In patients with diabetes and atrial fibrillation, the duration of diabetes may be a more important predictor of ischemic stroke than glycemic control.
Utilizing data from the ATRIA California community-based cohort of patients with AF, Jeffrey M. Ashburner, PhD, MPH, from the division of internal medicine at Massachusetts General Hospital, and colleagues assessed the association between diabetes duration and elevated HbA1c with stroke risk in patients who had AF and diabetes. The researchers focused on the time periods during which patients were not assigned anticoagulation therapy.
The initial cohort consisted of 13,559 adults aged 18 years and older who were diagnosed with nonvalvular AF. Patients were identified between July 1996 and December 1997 and followed through September 2003. The researchers then identified those patients with diabetes and AF.
Of the 2,101 patients with diabetes included in the duration analysis, 39.8% had been diagnosed within 3 years of the start of the study, whereas 60.2% had diabetes for more than 3 years. Patients with a longer duration of diabetes were more likely to be older and to have experienced a previous ischemic stroke. In addition, they were more likely to also have a diagnosis of chronic HF, coronary disease, peripheral artery disease, hypertension or kidney dysfunction.
The HbA1c analysis included 1,933 patients with diabetes, 45.7% of whom had an HbA1c level of less than 7% at baseline, 35.7% had an HbA1c level between 7% and 8.9%, and 18.6% had an HbA1c level of at least 9%. Patients with poor glycemic control were younger, more likely to use insulin and had diabetes for a longer time than those patients with lower HbA1c levels.
Duration of diabetes vs. glycemic control
According to the findings, 137 validated ischemic stroke events were reported among the patients in the duration analysis. A diabetes duration of at least 3 years was associated with an increased rate of ischemic stroke compared with patients with a shorter duration (adjusted HR = 1.74; 95% CI, 1.1-2.76). Age did not appear to be a determining factor, according to the researchers. Compared with patients without diabetes, patients with diabetes for a longer period of time (> 3 years) had an increased rate of ischemic stroke (adjusted HR = 1.62; 95% CI, 1.31-2), but those patients with a lesser duration did not have an increased risk.
During follow-up in the HbA1c analysis, 104 validated schemes were reported. The researchers observed that, contrary to previous studies, poor glycemic control (HbA1c 9%) was not linked to increased stroke risk compared with lower HbA1c levels.
“Our results for diabetes duration are consistent with prior research conducted within a general population of patients, which found an increased rate of ischemic stroke as duration increased compared with nondiabetic patients,” the researchers wrote. “However, our results for HbA1c in diabetic patients with AF are not consistent with prior research conducted in diabetic patients in general. In our study, increased HbA1c did not have a substantial effect on the rate of ischemic stroke, whereas elevated HbA1c was significantly associated with ischemic stroke in predominantly non-AF populations.”
The researchers concluded that accounting for duration of diabetes may improve stroke risk models for patients with AF.
Limitations, interpretation discussed
In a related editorial, Zachary Bloomgarden, MD, clinical professor of medicine, endocrinology, diabetes and bone disease at Mount Sinai Hospital in New York and Endocrine Today Editorial Board member, and Sameer Bansilal, MD, MS, assistant professor of medicine and cardiology at Mount Sinai Hospital, noted that the “disease and cost burden of AF is expected to double over the next 25 years.”
Zachary Bloomgarden
The editorialists discussed several limitations of the study. “It appears entirely possible ... that the apparent lack of effect of important differences in glycemic control in the present analysis may be an artifact of an insufficient period to ascertain the effect of such an intervention. Furthermore, the cohort studied, individuals ascertained based on the presence of AF, represents a group for whom the benefit of glycemic control may be inherently limited,” Bloomgarden and Bansilal wrote. “We must be careful not to use observations of such cohorts to incorrectly conclude that glycemic interventions for persons with diabetes as a group are unlikely to offer macrovascular benefit.” – by Tracey Romero
Disclosure: Ashburner reports no relevant financial disclosures. Please see full study for a list of all other researchers’ relevant financial disclosures. Bloomgarden reports various financial ties with Amgen, AstraZeneca, Baxter International, Boehringer Ingelheim, CVS Caremark, Johnson & Johnson, Merck, Novartis, Novo Nordisk, Pfizer, Regeneron, Roche Holdings and St. Jude Medical. Bansilal reports no relevant financial disclosures.
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