Very Low Blood Sugar Linked to Dementia
Study Raises Concerns About Aggressive Diabetes Treatment in Older Patients
April 17, 2009 -- New research that suggests a link between dangerously low blood sugar and dementia in older patients with type 2 diabetes raises more questions about the strategy of aggressively treating diabetes patients to achieve tight glycemic control.
Older patients in the study whose blood sugar fell so low that they ended up in the hospital were found to have a higher risk for dementia than patients with no history of treatment for low blood sugar, known medically as hypoglycemia.
Having uncontrolled diabetes is associated with an increased risk for Alzheimer's disease and other age-related dementias in elderly patients.
The thinking has been that aggressive treatment to achieve tight glycemic control would lower this risk.
But the new study suggests such treatment may do more harm than good in older patients if blood sugar levels drop to very low levels.
Several other recent high-profile studies have raised similar concerns.
Researcher Rachel Whitmer, PhD, of Kaiser Permanente Division of Research in Oakland, Calif., says understanding the impact of blood sugar on cognitive function is older patients is critical.
"We are in the midst of an epidemic of type 2 diabetes and we are going to see more dementia than we have ever seen before as these patients age," she tells WebMD. "We really have to get a handle on the role of glycemic control in this."
Blood Sugar and Dementia
The study included 16,667 patients with type 2 diabetes enrolled in a northern California diabetes registry. The average age of the patients at study entry was 65.
Whitmer and colleagues examined more than two decades of medical records to determine whether the participants had ever been hospitalized or treated in a hospital emergency department for hypoglycemia.
Symptoms of hypoglycemia can include dizziness, disorientation, fainting, and even seizures. Mild to moderate episodes often don't require treatment, but severe episodes can lead to hospitalization.
None of the study participants had a diagnosis of dementia when they were enrolled in the study in 2003. Four years later, however, 1,822 of the more than 16,600 patients (11%) had been diagnosed with dementia.
Compared to patients with no history of low blood sugar requiring treatment, patients with a single episode of hospital-treated hypoglycemia were found to have a 26% increase in dementia risk.
Patients treated three or more times for hypoglycemia had nearly double the dementia risk of patients who had never been treated.
The study appears in this week's issue of Journal of the American Medical Association.
Aggressive Treatment: Risks vs. Benefits
Alan M. Jacobson, MD, is the director of psychiatric and behavioral research at Harvard Medical School's Joslin Diabetes Center.
He calls the study "compelling" but adds that more research is needed to prove that severe hypoglycemia is a cause of dementia.