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Type 2 Diabetes Has a Key Role in Rising Alzheimer’s Cases

Aug 29, 2009

Over the next 40 years there could be a flood of dementia associated with Type 2 diabetes. 

The outlook may be dire, researchers said at the International Conference on Alzheimer’s Disease. If the trends in child and adolescent obesity continue unabated, by 2040, one-third of the 81 million expected Alzheimer’s cases worldwide may be a direct result of obesity-driven diabetes, Mary Haan, Ph.D., University of California, San Francisco, said at the meeting. 

Dr. Haan who is the primary investigator on the Sacramento Area Latino Study on Aging (SALSA), a prospective cohort study that has been ongoing since 1997 stated, “We need to identify the contributions to this increase in dementia and figure out how to decrease this burden…. In the setting of diabetes and Alzheimer’s, this means we need to think about intervening earlier in the process and treating across the life span. Our focus should be prevention, which is probably more effective when begun at younger ages.” 

Dr. Haan said that SALSA consists entirely of Mexican-Americans, whose high rates of Type 2 diabetes, metabolic syndrome, and hypertension create an ideal population in which to study the impact of these disorders on cognition. 

At the meeting, Dr. Haan presented 9 years of follow-up data on this group of 1,789 men and women (mean baseline age 72 years). At study entrance, 33% of the group had Type 2 diabetes and 40% had a body mass index of more than 25 kg/m2. More than half had metabolic syndrome. 

Over 9 years, 158 incident cases of dementia or non-dementia cognitive impairment developed. After controlling for age, gender, girth, diabetes treatment, fasting insulin, and C-reactive protein, Dr. Haan said the presence of diabetes at baseline more than doubled the risk of dementia or cognitive impairment. “This translates into a population attributable risk of 19%,” she said. “Nineteen percent of all these dementia cases were the direct result of Type 2 diabetes.”

When carried forward in accordance with the projected increases in obesity, that 19% figure means that by 2040, 24 million cases of dementia could be directly tied to Type 2 diabetes, Dr. Haan said. 

Unfortunately, “There are no randomized controlled trials that support the notion that we should be treating [cognitive impairment] with an antidiabetic drug,” she said. Instead, the most effective method is probably to prevent obesity and insulin resistance – the two factors that most strongly influence the development of diabetes. 

Suzanne Craft, Ph.D., agreed, “The concern is this current epidemic of diabetes associated with insulin resistance, in conjunction with a rapidly aging population, foreshadows an epidemic of Alzheimer’s.” And while it makes sense to investigate the impact that diabetes treatment might have on cognition, an incredibly effective intervention already exists.