The researchers found that people diagnosed with diabetes in midlife may be at higher risk of cognitive decline than healthy individuals of the same age.
The research team, led by Elizabeth Selvin, PhD, an associate professor of epidemiology at Johns Hopkins, publish their findings in the journal Annals of Internal Medicine.
The investigators analyzed data from the Atherosclerosis Risk in Communities Study involving 15,792 middle-aged adults who had been followed since 1987.
The health of participants was assessed over four visits that took place around every 3 years between 1987 and 1998, while a fifth assessment was conducted between 2011 and 2013. On three of these assessments - which took place between 1990-1992, 1996-1998 and 2011-2013 - participants' cognitive function was also analyzed.
The team compared the rate of cognitive decline among study participants with the rate of age-related cognitive decline among the general population.
The results of the analysis revealed that participants with poorly controlled diabetes were 19% more likely to experience cognitive decline - reduced memory, word recall and executive functioning - than participants of the same age without diabetes.
In other words, the researchers explain, study participants with poorly controlled diabetes experienced cognitive decline around 5 years sooner than healthy individuals of the same age.
The team found that study participants with controlled or prediabetes (higher-than-normal blood sugar levels) were also at higher risk of cognitive decline than age-matched, healthy individuals, although the increased risk among these populations was smaller than that found among participants with poorly controlled diabetes.
Eat right, exercise at 50 to have a healthy brain at 70
Around 29.1 million Americans - or 9.3% of the US population - have diabetes, while 86 million Americans aged 20 and older have prediabetes.
According to Selvin, the team's findings highlight the importance of controlling diabetes through a combination of exercise, weight control and a healthy diet. She adds:
"The lesson is that to have a healthy brain when you're 70, you need to eat right and exercise when you're 50.
There is a substantial cognitive decline associated with diabetes, prediabetes and poor glucose control in people with diabetes. And we know how to prevent or delay the diabetes associated with this decline."
The researchers note that cognitive decline is strongly linked to progression toward dementia, and there are an increasing number of studies linking diabetes to the condition. A 2010 study reported by Medical News Today, for example, found that people with type 2 diabetes may be at higher risk of Alzheimer's disease - the most common form of dementia.
"If we can do a better job at preventing diabetes and controlling diabetes, we can prevent the progression to dementia for many people," notes Selvin. "Even delaying dementia by a few years could have a huge impact on the population, from quality of life to health care costs."
Last year, MNT reported on a study suggesting that a drug commonly used to treat diabetes - liraglutide - may be effective for reversing late-stage Alzheimer's disease.