Diabetes ages the mind about five years faster than normal, and those diagnosed in their 50s are far more likely to experience mental decline by age 70, researchers said Monday.
The study in the journal Annals of Internal Medicine was based on more than 15,000 US adults followed from 1987 to 2013.
They found 19 percent more mental decline than expected in participants with poorly controlled diabetes, and smaller declines for those with controlled diabetes and pre-diabetes.
The race of the patients had no factor in their outcomes.
"The lesson is that to have a healthy brain when you're 70, you need to eat right and exercise when you're 50," said lead author Elizabeth Selvin, an associate professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health.
"There is a substantial cognitive decline associated with diabetes, pre-diabetes and poor glucose control in people with diabetes. And we know how to prevent or delay the diabetes associated with this decline."
Diabetes can strike when a person has elevated sugar (glucose) levels in the blood, damaging tissues, causing blindness and nerve damage.
Diabetes can often be controlled through diet and exercise, as well as medication.
"If we can do a better job at preventing diabetes and controlling diabetes, we can prevent the progression to dementia for many people," Selvin said.
Dementia costs the United States more than $159 billion a year, and that figure is expected to skyrocket in the coming years as the population ages, according to the researchers.