There’s some disappointing news for diabetics: Keeping blood sugar levels very low apparently does not prevent the loss of thinking abilities of elderly people with type 2 diabetes, a major federal study has found.

Elderly people with type 2 diabetes are about twice as likely as those without the disease to develop cognitive problems, including dementia. That prompted researchers to believe that intensively lowering blood sugar levels with drugs and lifestyle changes could help prevent that.

To test this hypothesis, Lenore J. Launer of the National Institute on Aging studied about 2,977 patients participating in the so-called ACCORD trial, which was testing a variety of possible benefits of very low blood sugar levels for diabetics. The trial began in 2001. The ACCORD trial results stunned the medical world in 2008 when researchers reported that aggressively driving blood sugar levels as close to normal as possible in high-risk diabetes patients appeared to actually increase the risk of dying from a heart attack or stroke. That part of the trial was halted in 2008.

In a paper published online Tuesday in the journal The Lancet Neurology, researchers said that the patients on the intensive therapy of keeping blood sugars very low did have larger brains after about 40 months, but that did not translate into preventing declines in their thinking abilities.

“While these findings do not support the use of intensive therapy to reduce the possible effects of diabetes on the brains of older people, it remains important for older adults with type 2 diabetes to continue well-established regimens to keep their blood glucose levels under control,” Launer said in a written statement. “Cognitive health is of particular concern in type 2 diabetes. We will continue to investigate how managing blood sugar levels might be employed to protect people with diabetes from increased risk of cognitive decline as they age.”

In an editorial accompanying the study, Geert Jan Biessels of the University Medical Center in the Netherlands said more research was needed to explore ways to protect the minds of diabetics.

“To identify other potential treatment targets, we need large prospective observational cohort studies that have sufficient statistical power to identify determinants of accelerated cognitive decline and dementia in type 2 diabetes,” Biessels wrote.