Type 2 diabetes is a chronic, progressive disease that can have devastating complications, including hearing loss, blindness, heart disease, stroke, kidney failure, and vascular damage so severe that limb amputation is required. Now, a new study underscores the toll diabetes can mean on the brain. Type 2 diabetes has been found to be linked to an increased risk of Alzheimer's and other forms of dementia later in life. The younger the age at which diabetes is diagnosed, the greater the risk.
The results are particularly important given the prevalence of diabetes in American adults and the increasing rate of diabetes in younger people. Type 2 diabetes, formerly referred to as "adult diabetes" to differentiate it from the immune-related type 1 disease in adolescents that begins in childhood, occurs in younger people and is largely associated with rising obesity rates connected. The Centers for Disease Control and Prevention estimates that more than 34 million American adults have type 2 diabetes, including more than a quarter of those over 65. About 17.5 percent of 45 to 64 year olds suffer from type 2 disease, as does 4 percent of 18 to 44 year olds.
"This is an important study from a public health perspective," said Yale Diabetes Center director Dr. Silvio Inzucchi, who was not involved in the research. “The complications of diabetes are numerous, but the effects on the brain have not been well studied. Type 2 diabetes is now being diagnosed in children, and at the same time there is an aging population. "
For the new study, published in JAMA, British researchers tracked diabetes diagnoses in 10,095 men and women who were between 35 and 55 years old at the start of the project from 1985 to 1988 and who were free of the disease at the time.
They followed them with clinical exams every four or five years until 2019. At each visit, researchers took blood samples to assess fasting glucose levels, a measure used to detect diabetes, and recorded self-reported and doctor-diagnosed cases of type 2 disease.
The researchers also identified cases of dementia using UK government databases. In an average follow-up period of 32 years, 1,710 cases of type 2 diabetes and 639 cases of dementia were registered.
The researchers calculated that every occurrence of diabetes five years earlier was associated with a 24 percent increased risk of dementia. Compared to someone without diabetes, a 70-year-old man diagnosed with type 2 diabetes less than five years earlier had an 11 percent increased risk of dementia. However, a diagnosis at the age of 65 was associated with a 53 percent increased risk of future dementia, and a diagnosis at the age of 60 was associated with a 77 percent increased risk. A person diagnosed with type 2 between the ages of 55 and 59 had more than twice the risk of dementia in old age compared to someone in the same age group without diabetes.
The study was an observational study, so there was no evidence that diabetes caused dementia. But it was tedious, with a large study population. Researchers controlled many factors that influence risk for dementia, including race, education, heart disease, stroke, smoking, and physical activity, and the association between diabetes and dementia remained.
"This is extraordinary data," said Daniel Belsky, an assistant professor of epidemiology at Columbia Mailman School of Public Health who was not involved in the research. “These relationships between the onset of diabetes and the development of dementia show the importance of a life-course approach to preventing degenerative diseases.
"We are an aging population and the things we fear most are degenerative diseases like dementia, for which we have no cures, no therapies and very few modifiable avenues to prevention," said Dr. Belsky. "We can't wait until people are in their 70s."
Why diabetes is linked to dementia is unknown. "We can speculate about the mechanisms," said lead author of the study, Archana Singh-Manoux, research professor at the French national health institute INSERM. “Living long with diabetes and having hypoglycemic events is harmful, and there are also neurotoxic effects of diabetes. The brain uses enormous amounts of glucose. Insulin resistance can change the way the brain uses glucose in people with type 2 diabetes.
Type 2 can be managed and its complications reduced by monitoring blood sugar levels and carefully following a well-designed, personalized program of medication, exercise, and diet. Is it possible that such a routine could minimize the risk of dementia later in life?
"Those with better control had less cognitive decline than those with poor control," said Dr. Singh-Manoux. “So stick with your medication. Pay attention to your glycemic markers. That is the message for people with diabetes. "