Persons with diabetes have a much greater chance of developing dementia than others, new research indicates.

Scientists from Kyushu University in Fukuoka, Japan, report that diabetics have a greater risk of developing Alzheimer's disease and other dementias, such as vascular dementia. Vascular dementia occurs when blood vessels that provide the brain with oxygen are damaged.

The study is reported in the journal Neurology.

Our findings emphasize the need to consider diabetes as a potential risk factor for dementia, said study author Dr. Yutaka Kiyohara. Diabetes is a common disorder, and the number of people with it has been growing in recent years all over the world. Controlling diabetes is now more important than ever.

Their study included 1,017 individuals aged at least 60 years. They underwent a glucose tolerance test after fasting overnight to determine whether they had diabetes. They were followed up closely for 11 years on average and then assessed for signs of dementia, which 232 of them developed during this period. The study found that those with diabetes had double the risk of developing dementia, compared to individuals with normal blood glucose levels.

Dementia refers to a considerable loss of cognitive abilities, including memory capacity, which is severe enough to undermine social or occupational functioning.

Dementia is not merely a problem of memory. It reduces the ability to learn, reason, retain or recall past experience and there is also loss of patterns of thoughts, feelings and activities.

Additional mental and behavioral problems often affect people who have dementia, and may influence quality of life, caregivers and the need for institutionalization. As dementia worsens individuals may neglect themselves.

Proper differential diagnosis between the types of dementia (cortical and subcortical) will require, at the least, referral to a specialist. Duration of symptoms must be evident for at least six months for a diagnosis of dementia or organic brain syndrome to be made.

Dementia is much less common under 65 years of age. Alzheimer's disease is still the most frequent cause, but inherited forms of dementia are rising. Frontotemporal lobar degeneration and Huntington's disease account for most of the remaining cases.