The study involved 2,269 men in Sweden who underwent testing at age 50 for diabetes, a disease caused by abnormal insulin levels.
During a follow-up period averaging 32 years, 102 of the participants were diagnosed with Alzheimer’s, 57 with vascular dementia, and 235 with other forms of dementia or cognitive impairment.
The authors, writing in the medical journal Neurology, concluded that the men with low insulin levels at age 50 were nearly 1.5 times more likely to develop Alzheimer’s than people without insulin problems, and that the risk remained significant regardless of blood pressure, body mass index and education level.
The findings “have important public health implications given the increasing numbers of people developing diabetes and the need for more powerful interventions,” said study author Elina Rönnemaa of Sweden’s Uppsala University.
“It’s possible that insulin problems damage blood vessels in the brain, which leads to memory problems and Alzheimer’s disease, but more research is needed to identify the exact mechanisms.”
The study also found that the link between diabetes and Alzheimer risk was strongest in people who did not have the APOE4 gene, which is known to increase risk of Alzheimer’s disease.
Rönnemaa said such a link shows that insulin problems are a key risk factor for Alzheimer’s when the APOE4 risk gene is missing.
Alzheimer’s is a progressive and fatal brain disease striking the elderly.