Researchers at Western University have published the first study in the world showing a decline in the incidence of dementia at a whole population level, which they believe is connected to the overall decline in strokes.

Between 2002 and 2013, the incidence of stroke and dementia rates in Ontario decreased by 32.4 per cent and 7.4 per cent respectively.

Dr. Vladimir Hachinski, distinguished university professor, and Dr. Luciano Sposato, associate professor, at Western's Schulich School of Medicine & Dentistry, along with a team of researchers from the Institute of Clinical Evaluative Sciences, analyzed data for patients 20 years and older, living in Ontario, who were diagnosed with stroke between April 1, 2002, and March 31, 2014.

All major dementias have a vascular component, including 80 per cent of Alzheimer's disease incidents. "Silent" strokes - strokes which are not readily visible - occur five times as often as visible strokes which affect the body noticeably. These "silent" strokes may affect thinking, mood, personality and ultimately may lead to dementia.

Dr. Hachinski credits the Ontario government's decision to implement an integrated stroke strategy in 2003, with the decline in strokes. "It looks like by preventing strokes, you can prevent some cases of dementia," said Dr. Hachinski. "It's time the stroke and dementia communities started to work together."

Dr. Sposato agrees that Ontario's stroke strategy was timely and that primary prevention has also improved in general in Ontario. "When some risk factors for stroke were increasing in the population, such as hypertension, obesity, and diabetes, there was a significant improvement in how those medical conditions were treated in Ontario," said Dr. Sposato. "The most important message is that by treating risk factors, we can prevent both stroke and dementia."

The study Declining Incidence of Stroke and Dementia: Coincidence or Prevention Opportunity? was published in the December issue of JAMA Neurology.