Hypoglycemia Linked to Dementia

A single episode of low blood sugar severe enough to require prompt medical attention increases a person's risk of developing dementia in old age, a study in people with diabetes suggests. More than one bout of hypoglycemia seems to heighten the risk even further, researchers report in the April 15 Journal of the American Medical Association. Chronically high blood sugar is known to increase the risk of dementia, but less is known about the long-term effects of periodic low blood sugar, says study coauthor Rachel Whitmer of the Kaiser Permanente Division of Research in Oakland, Calif.

She and her colleagues analyzed medical records dating from 1980 to 2002 and identified nearly 17,000 people who had type 2 diabetes but no signs of dementia, mild cognitive impairment or even memory complaints during the time span. The people averaged 65 years of age when surveyed in the mid-1990s.

The scientists noted any low blood sugar episodes requiring a trip to a hospital or other emergency facility. For such treatment, Whitmer says, a patient would have gone beyond just being shaky and weak. "These were events where patients may have fainted or passed out or may have been unable to communicate with others -- and were brought in," she says.

The scientists then checked for any dementia diagnoses from 2003 to 2007 in this population and found 1,822 cases.

After accounting for differences in age, weight, race, education, gender and diabetes history, the team found that people with one severe low blood sugar episode on their record were 45 percent more likely to have dementia in their later years than were people who hadn't had blood sugar crashes. Those with two or more episodes faced more than double the risk. The authors hypothesize that a glucose shortage in brain cells might play a role.

"This is a worrisome association," says Philip Cryer of Washington University in St. Louis. But he notes that the find doesn't prove that one factor causes the other. "I wouldn't want doctors and patients to overreact to this hypoglycemia issue and leave blood sugar levels to run high."