A diabetes diagnosis at midlife may raise a person’s risk for cognitive decline during the next 20 years, according to new data published in the Annals of Internal Medicine.
“Studies have shown cross-sectional associations between HbA1c level and cognitive scores in persons with diabetes. However, there is little evidence prospectively linking better glycemic control to slower cognitive decline, and few studies have examined whether chronic hyperglycemia below the threshold for a diagnosis of diabetes (‘prediabetes’) is associated with long-term cognitive impairment,” the researchers wrote.
To gain more insight into this potential relationship, Elizabeth Selvin, PhD, MPH, an associate professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health, and colleagues evaluated data from the Atherosclerosis Risk in Communities (ARIC) study.
The study started following 15,792 adults aged 48 to 67 years at baseline from communities in Maryland, North Carolina, Minnesota and Mississippi. Participants underwent evaluation during four visits approximately 3 years apart, beginning between 1987 and 1989, as well as during a fifth visit between 2011 and 2013.
The researchers assessed cognition at visits two (1990 to 1992), four (1996 to 1998) and five.
Results showed that diabetes in midlife was linked to a 19% greater cognitive decline over 20 years (adjusted global Z score difference=–0.15; 95% CI, –0.22 to –0.08) vs. no diabetes.
Participants with prediabetes, defined as HbA1c of 5.7% to 6.4%, demonstrated significantly greater cognitive decline than those with HbA1c levels less than 5.7%.
Similarly, those with poorly controlled diabetes, defined as HbA1c of 7.0% or higher, demonstrated greater cognitive decline, as compared with participants with controlled diabetes (adjusted global Z score difference=–0.16; P=.071), according to the data.
The researchers also observed a relationship between diabetes duration and level of cognitive decline later in life. Specifically, longer duration of disease was linked to greater late-life cognitive decline (P for trend<.001).
No significant differences between black and white persons in rates of cognitive decline were found (P for interaction=.44).
“The lesson is that to have a healthy brain when you’re 70, you need to eat right and exercise when you’re 50,” Dr. Selvin said in a press release. “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.”
Dr. Selvin pointed out that these results stress the importance of weight control, exercise and a healthy diet to avert the development of diabetes.
“If we can do a better job at preventing diabetes and controlling diabetes, we can prevent the progression to dementia for many people. Even delaying dementia by a few years could have a huge impact on the population, from quality of life to health care costs,” Dr. Selvin said.
In 2010, dementia-related costs were estimated to be more than $159 billion per year nationwide. As the population ages, these costs are expected to increase by almost 80% by 2040, according to the release.
Researchers have also become more cognizant of causes of dementia, especially the link between cognitive impairment and abnormalities in blood vessels in the brain.
“There are many ways we can reduce the impact of cerebral blood vessel disease — by prevention or control of diabetes and hypertension, reduction in smoking, increase in exercise and improvements in diet,” co-researcher A. Richey Sharrett, MD, DrPH, an adjunct professor at the Johns Hopkins Bloomberg School of Public Health, said in the release.
“Knowing that the risk for cognitive impairments begins with diabetes and other risk factors in midlife can be a strong motivator for patients and their doctors to adopt and maintain long-term healthy practices.”