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Hypoglycemia associated with heart rate variability in type 1 diabetes
Young adults with type 1 diabetes and a history of moderate to severe hypoglycemia were more likely to develop loss of heart rate variability, a marker of autonomic dysfunction, than those with minor or no hypoglycemia, according to recent findings.
“We found, in patients with type 1 diabetes, significant association between [cardiovascular autonomic neuropathy] and moderate/severe hypoglycemia according to the [hypoglycemia] score,” Ticiana Paes Silva, MD, of the division of endocrinology and metabolism at Federal University of Sao Paulo, Brazil, and colleagues wrote. “These results are consistent with previous studies that showed severe hypoglycemic episodes associated with impaired [CV] autonomic tests.”
Silva and colleagues analyzed data from 99 young adults with type 1 diabetes recruited between February 2011 and December 2013 (mean age, 26 years; 45.5% men; mean HbA1c, 8.4%; mean diabetes duration, 12.8 years; mean BMI, 23.3 kg/m²). Researchers assessed heart rate variability indices by spectral analysis; one abnormal test result was used to define impaired spectral analysis. Researchers evaluated severity of hypoglycemia by a hypoglycemia score; patients were stratified by absent or minor hypoglycemia, or moderate or severe hypoglycemia groups.
Within the cohort, 78 patients were categorized as having absent or minor hypoglycemia and 21 as having moderate or severe hypoglycemia. Patients in the moderate/severe group were older (mean age, 33 years) and had a longer duration of diabetes (mean, 16.09 years) and higher rates of macrovascular complications (mean, 19%).
In logistic regression analysis adjusted for clinical and metabolic variables, researchers found that impaired heart rate variability on spectral analysis remained an independent predictor of moderate or severe hypoglycemia (OR = 3.44; 95% CI, 1.11-10.62), as did nephropathy (OR = 4.07; 95% CI, 1.25-13.18) and macrovascular complications (OR = 12.14; 95% CI, 1.14-129.19).
When analyzed individually, researchers also found that impaired results on the Ewing battery occurred more frequently in the moderate/severe hypoglycemia group, and that heart rate variability time domain measures of normal RR intervals were lower vs. the absent/minor hypoglycemia group. Frequency domain measures were also lower in the moderate/severe group.
“This reflects an imbalance of sympathetic over parasympathetic activity in this group of patients,” the researchers wrote. “Our results are compatible with the loss of cardio protective effect of vagal activity in patients with moderate/severe hypoglycemia. This may result in worse outcomes related to progression to dangerous arrhythmias for this group of patients.” – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.
AUTHORS: Silva TP, Rolim LC, Filho CS, Zimmerman LM, Malerbi F, Dib SA
BACKGROUND: The occurrence of hypoglycemia has been associated with the presence of cardiovascular autonomic neuropathy. Cardiovascular autonomic reflex tests are the gold standard diagnostic method for cardiovascular autonomic neuropathy. Nevertheless, impaired heart rate variability indices on spectral analysis have been reported before cardiovascular autonomic reflex test abnormalities arise ...