There is no cure for Alzheimer's disease or other forms of dementia, which affect an estimated 28 million people globally and according to researchers from Sweden and the U.S. more people will be at risk of Alzheimer's as the "baby boom" generation ages.

What causes Alzheimer's is unclear but researchers believe there is a link with diet and exercise, and they have now found clear links with diabetes.

Researchers from the Karolinska Institute in Sweden have found that not only does diabetes type 2 up the risk of Alzheimer's but the risk is also there for people who have raised blood sugar levels, but have not yet developed diabetes type 2; and that risk is greater if the person also has severe hypertension (high blood pressure).

Dr. Weili Xu and colleagues followed 1,173 people aged 75 and older for nine years and found that more than 300 developed Alzheimer's and those with borderline diabetes had an almost 70 percent increased risk of developing dementia and Alzheimer's disease.

Previous studies have shown the link with diabetes and Alzheimer's disease but far more people have pre-diabetes than those with diabetes type 2.

In the U.S. 14.6 million people have diabetes, while as many as 41 million are thought to have pre-diabetes.

The numbers with Alzheimer's disease is expected to increase as people live longer and more people develop diabetes over the coming decades, and Alzheimer's rates may go up even faster than was previously thought.

In other research two teams which studied patients taking diabetes medications known as glitazones or thiazolidinediones (TZDs), and found that those prescribed TZDs constituted almost 20 percent fewer new cases of Alzheimer's than those who took insulin.

Dr. David Geldmacher of the University of Virginia and colleagues tested pioglitazone in Alzheimer's patients who did not have diabetes and found a slower progression of the disease in 12 out of 25 patients who took pioglitazone.

Rachel Whitmer of Kaiser Permanente in Oakland, California, studied 22,852 patients with type 2 diabetes for eight years and found those with very poor blood sugar control were much more likely to develop dementia, while those with the worst blood glucose levels, were 78 percent more likely to get dementia.

Experts say physical activity is probably the single best way to regulate your blood sugar levels and the research on glitazone drugs is promising not only to treat, but to prevent Alzheimer's disease.