Type 2 diabetes mellitus is associated with Mild Cognitive Impairment (often presenting as short-term memory loss that is either subjective or confirmed by rigorous memory tests) as well as dementia (moderate to severe short-term memory loss that causes a lack of independence). Furthermore, insulin resistance, the hall mark of adult onset or type 2 diabetes, increases the risk of developing Alzheimer’s disease.

Results from the Honolulu aging study provide an example of the association of the balance of glucose and insulin with risk of dementia. Study participants who had either very high or very low levels of serum insulin were more likely than those in between to become demented over the course of 5 years. Other studies, but not all, have shown this link between insulin resistance, impaired glucose metabolism, diabetes and dementia.

You have probably read the headlines generated by a recently published study demonstrating that intranasally administered insulin improved memory and “may be a potential treatment for Alzheimer’s disease.” The study recruited 104 adults with an average age of 72 who had a diagnosis of either mild cognitive impairment (66% of total number of subjects) or mild to moderate Alzheimer’s disease (33%). Participants were treated with either 20 or 40 IU of insulin intranasal for 4 months. Those treated with the lower dose showed improved memory over the course of the study whereas those treated with placebo got worse. The effects were statistically significant but small.

These results are intriguing but very preliminary. For example, the number of participants was small and already had cognitive decline to be included in the study. Alzheimer’s disease unfolds over a course of decades. This study lasted only 4 months. As with studies of the effects of blood sugar on memory, there appears to be a reversed “U” shaped relationship. Too much or too little insulin or blood sugar does not improve memory. Finally, there is a special device needed to administer the insulin through the nose. This device is not available.

While we wait for all of this to be sorted out, we all need attend to risk factors for type 2 diabetes. Risk factors include a family history of diabetes; being older than 45; hypertension; metabolic syndrome; “good” cholesterol less than 35 mg/dl and/or triglycerides greater than 250 mg. dl; history of gestational diabetes; polycystic ovary syndrome; inactive (exercise less than three times per week); and ethnicity (black, Hispanic/Latino, Native American, or Asian). If you have any of these risk factors, monitor blood sugars and get a baseline measure of your memory. Those who develop type 2 diabetes and changes in memory are at risk of cognitive decline.