Blood sugar levels in diabetic patients can play a role in affecting the brain or brain activity. Extremely high blood sugar in the 400 mg/dL (22 mmol/L) range or higher has been shown that it can be associated with some alteration in mental function and if it persists at these levels for extended periods, even mental changes can be seen. Hyperglycemia, if allowed to reach exceedingly high levels can lead to diabetic coma, but this should only occur in a person that is unaware they have diabetes and are not being treated, or diabetics that are not properly following treatment. Sometimes in response to treatment, diabetic patients can experience extremely low blood sugar, which if allowed to drop below 50 mg/dL (2.7 mmol/L) and continuing lower, will cause a progressive loss of mental function which will eventually lead to unconsciousness, seizures and even coma or death if not treated immediately.
However the most common and damaging complication of diabetes where the brain is concerned is stroke. Diabetes affects the brain through the effects it has on the cardiovascular system when the blood supply to the brain is cut off, which can result in a stroke. People that have had strokes often suffer from cognitive dysfunction and disability, stroke can even lead to death, in fact sixteen percent of diabetes-related deaths in people aged sixty-five and older occur as a result of stroke, which is two to four times as likely to occur in people with diabetes than in non diabetics. Diabetes is also a major factor in the development of other cerebrovascular diseases.