Diabetes does not just take its toll on the heart, a new study in Japan has found. It dramatically increases the risks of developing Alzheimer's or dementia in later life.

Researchers from Kyushu University in Japan found that even when other risk factors of dementia such as high blood pressure, high cholesterol and smoking were taken into the account; the risks of vascular dementia and Alzheimer's from diabetes was still extremely high.

Dementia is a chronic mental disorder caused by brain disease or injury and marked by memory disorders, personality changes, and impaired reasoning.

1,017 individuals aged at least 60, were studied in Japan as a part of the study. These individuals were followed closely for 11 years, undergoing a glucose tolerance test after overnight fasting to determine whether they had diabetes.

They found 27 percent of the diabetics have developed dementia, compared to 21 percent of people without diabetes and therefore diabetics had doubled the risk of developing different forms of dementia, compared to individuals with normal blood glucose levels.

It's really important for the public health to understand that diabetes is a significant risk factor for all of these types of dementia, says Rachel Whitmer, PhD, an epidemiologist in the research division of Kaiser Permanente Northern California. She was not involved in the study.

Whitmer said the new study was done well and provides good evidence but further investigations need to be made to find out why people with diabetes are at a greater risk, Health.com reported.

So far research has found that diabetes could contribute to dementia because of Insulin resistance where high blood sugar can interfere with the body's ability to break down protein, forming brain plaque, which have been linked to Alzheimer's disease. High blood sugar has also been linked to damaging cells due to certain oxygen containing molecules.

The study also found that people with pre-diabetes or those with high blood sugar levels had a higher risk of developing dementia.

A Shot of Insulin Nasal Spray Could slow Alzheimer's Disease

Meanwhile, a recent study found that a daily dosage of insulin nasal spray could slow down the development of Alzheimer's disease, having a positive impact on improving the memory of moderate Alzheimer's sufferers

The pilot study led by Suzanne Craft of the Veterans Affairs Puget Sound Health Care System and carried out on a 104 patient found that insulin could improve memory of moderate Alzheimer sufferers and those with mild cognitive impairment (AMCI).

Patients who received 20 IU of intranasal insulin daily, over a period of four months, showed overall improvements to their cognitive functions, which were tested through story, recall tests.

The groups of patients at the average age of 72 were randomly divided into three and were given either a moderate, low or placebo dose of insulin spray through their nose.

Patients were told stories and tested over time to see how much of the details they could remember. After four months, those patients that were given the moderate 20 IU dose saw significant improvements in story recall and general thinking tests called ADAS-cog.

Those patients who were given a lower dose of the insulin also showed improvements. Our results suggest that the administration of intranasal insulin may have a therapeutic benefit for adults with aMCI or Alzheimer's disease, Craft and her colleagues wrote in the Archives of Neurology.

No similar associations were observed for the placebo group, suggesting that these correlations were not due to general factors such as disease progression, said Craft.

Alzheimer's patients are known to have decreased levels of insulin in their central nervous system, which can be critical for the normal functioning of the brain.

Dr. James Galvin of New York University Langone Medical Center said although the study was small, it provides some of the most convincing evidence to date that insulin treatment may alleviate symptoms of Alzheimer's disease, Reuters reported.

He also pointed to studies of large groups of people that have linked type 2 diabetes with Alzheimer's disease. Studies performed on mice that have been administered with insulin nasal spray have proven to improve their performance when genetically alters to develop Alzheimer's disease.  

To make these findings more than just hopeful, researchers must carry out a much larger, longer study, now scheduled to begin next summer. Results from the larger study will not be available for at least 18 months after that, according to Robert Bazell, chief Science and Health correspondent of NBC news.

Alzheimer's Facts and Figures:

An estimated 5.4 million people have Alzheimer's disease according to the Alzheimer's Association with 14.9 million unpaid caregivers and 183 billion dollars in annual cost. Alzheimer's is the most common form of dementia. It is a disease that progressively worsens over time in its early stages, memory loss is mild, but with late-stage Alzheimer's, individuals lose the ability to carry on a conversation and respond to their environment. It is the sixth leading cause of death in the United States.