People with insulin resistance and Type 2 diabetes may be more likely to develop plaques in the brain linked with Alzheimer's disease, Japanese researchers have found.

Insulin resistance is the stage before Type 2 diabetes, when the hormone insulin becomes less effective in lowering blood sugar.

Type 2 diabetes, Alzheimer's disease and obesity rates are all on the rise worldwide, said study author Dr. Kensuke Sasaki of Kyushu University in Fukuoka, Japan.

The study, published in this week's issue of the journal Neurology, looked at 135 people (74 men and 61 women) with an average age of 67 from Hisayama, Japan.

Participants had several diabetes glucose tests to measure their blood sugar levels and were monitored for symptoms of Alzheimer's for 10 to 15 years.

During that time, about 16 per cent developed the disease that affects memory, behaviour and social adaptation.

When participants died, researchers examined their autopsied brains for the plaques and other physical evidence linked to Alzheimer's.

People who had abnormal results on three tests of blood sugar control had an increased risk of developing plaques, the researchers found.

Plaques were found in 72 per cent of people with insulin resistance and 62 per cent of people with no signs of insulin resistance.

Amyloid plaques are found in the brains of people with the disease, but it is unclear whether the plaques cause Alzheimer's or are a symptom of it.

"Further studies are needed to determine if insulin resistance is a cause of the development of these plaques," said Sasaki in a release. "It's possible that by controlling or preventing diabetes, we might also be helping to prevent Alzheimer's disease."

This study had a longer observation period than previous research that looked at the possible link between Type 2 diabetes and Alzheimer's.