US researchers found that the presence of albuminuria, a marker of microvascular disease, was linked to greater declines in mental performance over five years.
They said the findings could apply to a much wider population of patients.
In the study, published in the Clinical Journal of the American Society of Nephrology, researchers studied 2,977 adults with diabetes aged about 62 years. People with diabetes have a greater risk of cognitive impairment from vascular causes.
Researchers measured levels of albuminuria and decline in eGFR as markers for microvascular disease.
Participants took three neuropsychological tests: one at the start of the study and at 20 and 40 months. They were tested on information processing speed, verbal memory and executive function.
Researchers found persistent albuminuria was linked to a 5% decline in information processing scores but not verbal memory or executive function performance.
Co-author Dr Joshua Barzilay of Kaiser Permanente of Georgia, US said: 'Our finding was a subtle change in cognition; however, were this decline to continue over 10 to 15 years it could translate into noticeable cognitive decline by the age of 75 to 80 years, when cognitive impairment generally becomes clinically evident.
'Given how common albuminuria and diabetes are in the older population, these findings have a great deal of importance from a population point of view. Moreover, albuminuria is also common among older people with hypertension without diabetes.'