Hypoglycemia is common among patients being treated for type 2 diabetes, regardless of their level of glycemic control, according to findings from the Diabetes Study of Northern California (DISTANCE) survey.
The findings challenge the conventional wisdom that hypoglycemia occurs only among those with the lowest hemoglobin A1c levels, reported Dr. Kasia J. Lipska of Yale University, New Haven, Conn., and colleagues. The study was published online July 30 in Diabetes Care.
Among 9,094 adults with diabetes who participated in the survey, 11% reported experiencing severe hypoglycemia in the past year, with nearly 1 in 4 (24%) reporting more than three events during that time period. In an unadjusted analysis, those with HbA1c at the highest and lowest levels were most likely to experience hypoglycemia, the investigators said (Diabetes Care 2013 July 30 [doi: 10.2337/dc13-0610]).
Compared with those with "good" HbA1c levels of 7.0%-7.9%; the relative risk of hypoglycemia was 1.25 in those with "near normal" levels of less than 6%, 1.01 in those with "very good" levels of 6.0%-6.9%, 0.99 in those with "suboptimal" levels of 8.0%-8.9%, and 1.16 among those with "very poor" levels of 9% or greater, they explained.
However, the elevated relative risk was statistically significant only for those with HbA1c of 9% or greater, they noted, adding that while adjustment for demographic variables did not "alter the shape of the relationship," and while the point estimates for hypoglycemia risk remained higher at the two extremes of glycemic control, the differences in risk between each HbA1c category and the reference group did not differ significantly in the fully adjusted model.
Study participants were patients with type 2 diabetes aged 30-77 years, who were members of the Kaiser Permanente Northern California Diabetes Registry. The patients, who were using glucose-lowering therapy, were surveyed during 2005-2006 about episodes of severe hypoglycemia, such as episodes during which they passed out and/or required medical assistance.
Patients most likely to report hypoglycemic episodes were women; those taking more than four medications for chronic conditions; those using either insulin or a secretagogue during the preobservation period; and those with longer duration of disease, prior history of hypoglycemia, and multiple comorbidities, the investigators noted.
After examining the prevalence of hypoglycemia across potential effect modifiers, however, they found no significant interactions.
Prior studies have resulted in inconsistent findings about the relationship between glucose control and hypoglycemic events, but findings from the current study suggest that "hypoglycemia occurs across all levels of HbA1c, with higher risk associated with near-normal or very poor glycemic control," the investigators said.
The findings are important, they said, because several studies have shown that patients who experience severe hypoglycemia are at increased risk for a number of unfavorable health outcomes, including dementia, falls, fall-related fractures, cardiovascular events, poor health–related quality of life, and increased mortality. The researchers noted that in addition to efforts to limit adverse effects of overtreatment and to improve patient outcomes, efforts to consider the safety of the various glucose-lowering therapies in patients with higher HbA1c levels are needed.
"Poorly controlled diabetes appears to be associated with both higher risk of diabetic complications and higher risk of treatment-related hypoglycemia. Therefore, quality improvement efforts must balance the need to improve glucose levels with safety of antihyperglycemic therapy in this group," they said.
Though limited by a number of factors, including self-reporting of hypoglycemia without laboratory confirmation and a wide age range of participants, which limits applicability to elderly patients with diabetes, the findings in this usual-care setting nonetheless underscore the importance of directing efforts to improve the safety of glucose-lowering therapies. Such efforts must be directed not only to patients achieving intensive glucose control, but also to those with poorly controlled disease, the investigators concluded, noting that "future analyses are needed to identify management strategies and treatment factors that may mitigate hypoglycemia risk."
The DISTANCE survey was funded by numerous grants, including grants to individual authors or their employers from the National Institute on Aging and the National Heart, Lung, and Blood Institute.