There is no evidence that one causes the other. The fact that victims of Alzheimer's, a form of dementia, die of any other disease, malady, etc, such as a heart attack or stroke, is attributable only to the overal degeneration of the brain and body; in other words, it is a coincidence.
For more information, visit the following web page:
http://www.webmd.com/alzheimers/guide/alzheimers-disease-symptoms-types