Fish oil supplements may reduce the incidence of cognitive decline and improve memory function, according to a recent study.

Researchers from Rhode Island Hospital found that regular use of fish supplements was associated with a significant reduction in cognitive decline and brain atrophy in older adults.

It is estimated that more than 5 million people in the U.S. have Alzheimer's disease. It is the most common form of dementia and is the sixth leading cause of death in the United States.

"At least one person is diagnosed every minute with Alzheimer's disease and despite best efforts, we have not yet found a cure for this pervasive and debilitating disease," Lori Daiello, principal investigator of the study, said in a statement. "The field is currently engaged in numerous studies to find better treatments for people suffering with [Alzheimer's disease]; however, researching ways to prevent [Alzheimer's disease] or slow cognitive decline in normal aging is of utmost importance."

For the study, researchers examined the relationship between fish oil supplement use during the Alzheimer's Disease Neuroimaging Initiative (ADNI) and indicators of cognitive decline. Participants were assessed with neuropsychological tests and brain magnetic resonance imaging (MRI) every six months. The group included 229 older adults who were cognitively normal; 397 who were diagnosed with mild cognitive impairment; and 193 with Alzheimer's disease.

Researchers found that fish oil supplement use during the study was associated with significantly lower rates of cognitive decline as measured by the Alzheimer's Disease Assessment Scale (ADAS-cog), and the Mini Mental State Exam (MMSE), but this benefit was observed only for the group of participants without dementia at the time of enrollment.

"Additionally, serial brain imaging conducted during this study showed that the participants with normal cognition who reported taking fish oil supplements demonstrated less brain shrinkage in key neurological areas, compared to those who did not use the supplements," Daiello said. "Also, the positive findings on cognitive testing and brain MRI were only observed in persons who did not carry the best-studied genetic risk factor for [Alzheimer's Disease]. "

Daiello said the study is promising and highlights the need for future studies to expand the current knowledge of the effects of FOS use on cognitive aging and Alzheimer's disease.

The findings were recently published in the journal Alzheimer's & Dementia.