Kidney Disease Research Updates
Fall 2009

Hypoglycemia a Serious Risk for People with CKD

Hypoglycemia, or low blood sugar, is a serious risk for people with chronic kidney disease (CKD), especially among those with diabetes, according to an analysis of the records of more than a quarter-million patients. The analysis, which was funded by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), is the first epidemiological study to examine the incidence of hypoglycemia among patients with CKD.

"Our primary objective was to examine a large national cohort of patients to determine the incidence of hypoglycemia in patients with versus without CKD, both with and without diabetes," wrote Maureen F. Moen, a medical student at the University of Maryland School of Medicine, and co-authors in the June issue of the Clinical Journal of the American Society of Nephrology. Moen was a recipient of the American Society of Nephrology’s Student Scholar Program, which provides funding for medical students to engage in basic or clinical research.

Dangerous Combination

People with CKD often have diabetes. In fact, diabetes is the single greatest cause of CKD. Current diabetes treatment guidelines emphasize intensive glucose control, the goal of which is to keep blood sugar as close to normal as possible to avoid long-term complications of high blood sugar, called hyperglycemia.

Treating diabetes in people with CKD, however, warrants special considerations, according to Moen and co-authors. CKD affects insulin metabolism and the body’s ability to store glycogen and release glucose. And blood glucose-lowering diabetes drugs that are normally cleared by the kidneys may persist longer in the bloodstream of people with CKD. "The confluence of these factors may contribute to a greater risk for hypoglycemia among patients with CKD and may be an unintended consequence of therapy to treat hyperglycemia." In contrast to hyperglycemia's potential long-term complications, hypoglycemia can be an acutely dangerous condition resulting in disorientation, heart attack, or death.

Analysis

To gauge the incidence of hypoglycemia, the researchers analyzed data from a large cohort assembled by the Veteran’s Health Administration. Included were participants who sought care between October 1, 2004, and September 30, 2005; had their kidney function assessed during the year prior to their visit; and had at least one blood glucose measure taken.

Hypoglycemic events and their severity were tabulated for four groups: CKD with diabetes, CKD without diabetes, no CKD with diabetes, and no CKD without diabetes. The cohort was about 96 percent male, 80 percent Caucasian, and 19 percent African American. Among the 29 percent of participants with CKD, about 50 percent had diabetes, whereas only about 33 percent of participants without CKD had diabetes.

Among participants with diabetes, the presence of CKD was associated with a twofold increase in the rate of hypoglycemic events. Nondiabetic participants with CKD also experienced a higher frequency of hypoglycemia. "It is likely that the occurrence of hypoglycemia in patients with diabetes, with or without CKD, is largely related to use of diabetic therapies," wrote Moen and co-authors. "However, in the case of patients without diabetes and with CKD, the underlying cause is not entirely clear."

The researchers also measured hypoglycemic events occurring within 1 day of death, both in outpatient and inpatient settings. Risk of death increased with the severity of hypoglycemic events, but surprisingly, risk of death was generally lower among patients with CKD. The investigators attributed this phenomenon to "an unmeasured, increased intensity and quality of care in this patient population relative to patients without CKD."

The findings, according to the report, "may account for some portion of the excess cardiovascular morbidity and mortality seen in CKD." The authors urge care providers to consider the risk of hypoglycemia for both diabetes and CKD populations.

The NIDDK has fact sheets and easy-to-read booklets about CKD and diabetes. For more information or to obtain copies, visit www.niddk.nih.gov

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NIH Publication No. 10–4531
October 2009