Bowl of sugar with diabetes monitoring instruments

A health condition strongly associated with diabetes may be linked to lower odds of developing Alzheimer’s disease, according to the surprising results of a new public health study from the University of Hawaiʻi at Mānoa.

The condition, called insulin resistance, is considered a precursor to Type 2 diabetes. The new study showed that Japanese men in their 70s and 80s with insulin resistance had lower odds of developing Alzheimer’s and dementia than men who did not have insulin resistance.

“Our findings suggest that more research is needed to better understand the relationship between insulin resistance and cognitive disorders such as Alzheimer’s disease in older adults,” said Thomas Lee, lead author of the study and an assistant professor of epidemiology with the Office of Public Health Studies in the Myron B. Thompson School of Social Work.

Surprising results

Normally, the cells of the body respond to insulin by taking up sugar from the blood and using it for energy. But in people with insulin resistance, the cells of the body do not respond properly to insulin, leaving too much sugar in the blood.

In the study, Lee and his colleagues looked at data from the health records from 1,544 Japanese men participating in an ongoing study called the Kuakini Honolulu-Asia Aging Study, which began in 1991 and is focused on studying the risk factors associated with neurodegenerative disorders.

At the start, study participants underwent a physical exam that included blood tests. None had Alzheimer’s disease at baseline. Three years later, another physical exam was done and, by then, 80 men had developed Alzheimer’s. The researchers compared the men who had developed the disease with those who had not.

After adjusting for factors, such as hypertension (high blood pressure) and smoking, the link between insulin resistance and a lower odds of dementia held.

Previous studies had linked Type 2 diabetes with an increased risk of Alzheimer’s disease, but how exactly the link may work is not clear. The researchers noted that the new study excluded men with Type 2 diabetes at the onset, which may have affected the results.

“Alzheimer’s disease is a debilitating condition and there are projected to be 84 million cases worldwide by 2040,” said Kamal Masaki, a co-author on the study and professor of geriatrics with the UH Mānoa John A. Burns School of Medicine. “We need a better understanding of the roles of blood sugar and insulin in this disease.”

The paper is published in the Journal of the Neurological Sciences.