People diagnosed with type 2 diabetes before age 50 have double the risk of dementia, with each year earlier the risk increasing by 2%

Previously, type 2 diabetes was said to be a disease of the elderly, but in recent years, it has been affecting younger people, and one theory is that 'one in five type 2 diabetes patients is under the age of 40.' Research focusing on the timing of diagnosis of type 2 diabetes, an important risk factor for dementia, has revealed that the younger a person is when they developed type 2 diabetes, the higher their risk of dementia in later life.

Age at diagnosis of diabetes, obesity, and the risk of dementia among adult patients with type 2 diabetes | PLOS ONE

In this study, Bei Wu and her colleagues from the Rory Meyers School of Nursing at New York University analyzed data from the University of Michigan's Health and Retirement Study, conducted between 2002 and 2016, and the Diabetes Mail Survey, which was conducted among participants of the study.

Among 1,213 adults aged 50 years or older who had type 2 diabetes at the start of the study, 216 people (17.8%) developed dementia during the maximum 14-year follow-up period. When participants were divided by the age at which they were diagnosed with type 2 diabetes, 262 were under 50 years old, 378 were 50-59 years old, 419 were 60-69 years old, and 154 were 70 years old or older.

The research team then looked at the relationship between age at diagnosis of type 2 diabetes and dementia risk and found that people diagnosed with diabetes under the age of 50 were 1.9 times, or 90 percent, more likely to develop dementia than those diagnosed at age 70 or older.

The younger a person is when they are diagnosed with type 2 diabetes, the higher their risk of dementia (72% higher if they were between 50 and 59 years old, and 70% higher if they were between 60 and 69 years old). On average, each year earlier a person is diagnosed, the risk of dementia increases by 1.9%.

'It's not yet clear why being diagnosed with diabetes earlier increases the risk of dementia, but previous research has shown that people diagnosed with type 2 diabetes in middle age are more likely to have known risk factors for dementia, such as vascular complications, poor blood sugar control, and insulin resistance,' said Dr Wu, lead author of the study.

One notable factor was obesity. Of the subjects, 567 people (46.7%) were obese. Obese people who were diagnosed with type 2 diabetes under the age of 50 had more than three times the risk of dementia compared with non-obese people diagnosed at age 50 or older.

'Our study highlights the importance of age in diabetic diagnosis and suggests that specifically targeting obesity through diet, exercise, or medication may be useful in preventing dementia in young adults with diabetes,' said Wu.