In a study of over 2.3 million people, women with type 2 diabetes were found to have a 134 percent greater risk of developing vascular dementia. Men who have type 2 diabetes have a 73 percent greater risk of developing vascular dementia. Women who have type 2 diabetes have a 53 percent greater risk of developing Alzheimer's. Men who have type 2 diabetes have a 49 percent higher risk of developing Alzheimer's.
Some commentators see the connection as so strong that they call dementia "type 3 diabetes". That's an overstatement, but diabetics who do not control their blood sugar levels are unquestionably at higher risk of late-life neurocognitive impairment. Here are seven things every diabetic needs to know about managing diabetes to prevent dementia.
1. The higher your blood sugar level, the greater your risk of developing dementia
A study of 2,067 members of Group Health, a nonprofit HMO in the US State of Washington, found that it is blood sugar levels, not just whether or not you have diabetes, that influences risk of dementia. Group Health patients whose blood sugar levels averaged 190 mg/dl were 40 percent more likely to develop dementia than patients whose blood sugar levels averaged 160 mg/dl. Patients whose blood sugar levels averaged 115 mg/dl were 18 percent more likely to develop diabetes than patients whose blood sugar levels averaged 100 mg/dl. Even "prediabetes" increases the risk of dementia.
2. Diabetes can cause mild cognitive impairment as well as dementia
People who have diabetes in their fifties tend to have cognitive impairment in their seventies. A study of 5,987 people at the Johns Hopkins Bloomberg School of Public Health found that even when diabetes was not linked to full-blown dementia, people who had diabetes for 20 years or more scored 30 percent lower on tests designed to measure memory, reasoning, problem solving and planning. They were not so impaired that they were diagnosed with dementia, but they were not as intellectually active as they had been earlier in life.
3. The longer you have had diabetes, the greater the risk of dementia
A study of Swedish twins led by Dr Margaret Gatz of the University of Southern California found that the association between type 2 diabetes and dementia was stronger when diabetes was diagnosed before 65 than when it was diagnosed at 65 or older. Dr Gatz believes that diabetes and dementia may both be diseases caused by an underlying process that has not yet been identified.
4. The absolute risk of developing dementia if you have type 2 diabetes is significant
Statistics are often used for scaremongering. A 100 percent increase in a risk of one percent is a risk of two percent. However, the absolute risk of dementia for diabetics is scary but not scaremongering. If you don't have type 2 diabetes, you have about a 10 percent risk of developing either vascular dementia or Alzheimer's disease at some point in your life. If you have type 2 diabetes, that risk goes up to 30 percent. That's significant.
5. Diabetes acts synergistically (but not in a good way) with other risk factors for dementia.
Type 2 diabetes is a risk factor for vascular dementia and Alzheimer's. High blood pressure, high LDL cholesterol, smoking, excessive drinking, carrying the APOE ɛ4 gene, and advancing age are also risk factors for vascular dementia and Alzheimer's. When these risk factors occur together, however, they aren't just additive. High blood sugar levels accelerate the rate at which these other disease factors work to destroy brain tissue.
6. It is important to keep blood sugar levels from getting either too high or too low
A single episode of hypoglycemia may increase the risk of developing dementia by as much as 54 percent. Multiple episodes of hypoglycemia may double that.
High blood sugar levels are linked to dementia. However, a history of hypoglycemic crises (blood sugar levels that went dangerously low) is also linked to developing dementia. You don't want to control your blood sugar levels so tightly that you lose consciousness from hypoglycemia. Many doctors give their diabetic patients a slightly higher target HbA1C (under eight percent, rather than under seven percent) when there are risk factors for dementia.
7. To reduce dementia risk, it is more important to manage diabetes than to manage cholesterol and blood pressure
Let's be clear. If you have too much bad LDL, you need to get it down (probably with statins). If your blood pressure is over 120/80, even if you have "borderline" high blood pressure, you have to get it under control. However, managing your diabetes is more important to your future brain health than managing either cholesterol or hypertension. It is not enough to have great blood pressure if you let your blood sugar levels soar or sink.