Dr. Elizabeth Devore of Brigham and Women's Hospital and Harvard Medical School in Boston said flavonoids, found in plants, have powerful antioxidant and anti-inflammatory properties.
The researchers used data from the Nurses' Health Study -- 121,700 female registered nurses ages 30-55 who completed health and lifestyle questionnaires beginning in 1976. Since 1980, participants were surveyed every four years regarding their frequency of food consumption.
The study published in the Annals of Neurology found women with a higher berry intake delayed cognitive aging by up to 2.5 years.
The authors cautioned that while they did control for other health factors in the modeling, they cannot rule out the possibility that the preserved cognition in those who eat more berries also may be influenced by other lifestyle choices, such as exercising more.
"We provide the first epidemiologic evidence that berries may slow progression of cognitive decline in elderly women," Devore said in a statement. "Our findings have significant public health implications as increasing berry intake is a fairly simple dietary modification to test cognition protection in older adults."