A recent study confirmed a shocking finding of 14 years ago (which studied 2,568 Japanese American men) that low fasting insulin in middle age doubles the risk of dementia in later years.
Insulin deficiency itself is one of the key components of Alzheimer's and that low levels of insulin or insulin resistance are associated with poor brain function.
These researchers concluded that low insulin must involve a new pathway to dementia different from the well-known metabolic pathway in diabetes.
Reduced brain metabolism may not be the factor linking low insulin to dementia but rather it may be the role of insulin as a growth factor maintaining the function of neurons that may be vital.
Neurology 2018:Epub 2018 Jul 11