Patients with Type 2 diabetes may be more prone to brain degeneration, according to a study published in the journal Radiology .

Scientists led by Dr. R. Nick Bryan at the University of Pennsylvania found that patients with more severe forms of the disease had less brain tissue, as assessed by MRI scans of their brains, than those with milder forms of diabetes — even when those people's blood pressure was under control through treatment. Patients who had been diagnosed for 15 years or more had less gray matter than those who had the disease for four years or less. And for every 10 years a person has diabetes, the brain looks two years older than those of similar-age people without the disease.

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While previous studies hinted that diabetes was linked to brain degeneration, experts believed that the atrophy was mostly related to reduced blood flow to the brain; people with diabetes are at increased risk of stroke, for example, and their inability to properly control blood sugar is also linked to problems with the heart and poor circulation to fingers and toes.

But by examining the 614 people in the study, Bryan and his team uncovered another way that diabetes may be damaging the brain: by accelerating the rate at which brain tissue shrinks. “We found that diabetic patients have two strikes on the brain. There is the vascular effect, and now it looks as if there is a neurodegenerative insult on the brain too,” he says. Normally, humans lose about 1.5 cc to 2 cc of brain volume a year; diabetic patients, Bryan and his team calculated, lose about twice as much.

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It’s not clear how diabetes is contributing to this additional assault on brain tissue, but it’s possible that abnormal glucose metabolism could lead to more free-radical formation, which increases inflammation, quickening the demise of older brain cells.

What’s especially concerning is that this brain loss may be an independent contributor to Alzheimer’s disease in Type 2 diabetics. Studies have documented the higher risk of Alzheimer’s in people with diabetes, and this brain-atrophy couple explain why. Gail Musen at the Joslin Diabetes Center, for instance, is investigating whether changes in the way the brain processes insulin may make it easier for the protein amyloid to accumulate and form the plaques that are responsible for Alzheimer’s.

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The findings also suggest that younger patients who are diagnosed with diabetes may be facing faster cognitive decline than their nondiabetic peers. “These results suggest that the adverse effects probably start fairly early on in the disease,” Bryan says. “They may be subtle, but they probably start early.”

Bryan plans to follow the participants in the study to investigate ways to slow this process. His team will test whether aggressive treatment to lower their blood-sugar levels can have an effect on the brain loss. Half of the volunteers have been randomly assigned to such intensive therapy, while the remaining patients will continue their existing treatments.

For now, it’s too early for doctors or patients to change how they’re managing the disease. But the findings do make it clear that treating diabetes as soon as possible is critical to avoiding potentially harmful consequences. “Diabetes affects everything, and everything you do to control it, from exercise to proper diet and medication, are important to prevent blindness and keep you from losing a limb, and are also important for the brain,” says Musen.