Regular use of fish oil supplements can help reduce cognitive decline in older people, a new study finds. These pills are also linked to lower rate of brain shrinkage in old age.

The study, conducted by researchers at the Rhode Island Hospital, is published in the journal Alzheimer's & Dementia.

In the present research, the team wanted to know whether fish oil pills, known for their health benefits, could stave off Alzheimer's disease.

Alzheimer's disease, according to National Institute on Aging, is an irreversible, progressive brain disease that slowly destroys memory and thinking skills. People affected by the condition eventually lose the ability to carry out the simplest tasks of daily living. An estimated five million people in the U.S. have AD.

Fish oil supplements or omega-3 fatty acid pills are considered to be effective in improving memory and even reducing decline of cognitive abilities in older people. However, there is considerable doubt over the efficacy of these supplements.

Data for the study came from Alzheimer's Disease Neuroimaging Initiative (ADNI). The study participants underwent a series of neuropsychological tests and brain magnetic resonance imaging (MRI) at intervals of six months. The study included 229 adults with normal cognitive levels, 397 adults with mild cognitive impairment and 193 people with Alzheimer's disease.

Researchers found that use fish oil pills during the study was linked to a reduction in rates of cognitive decline. Thinking abilities were measured via Alzheimer's Disease Assessment Scale (ADAS-cog) and the Mini Mental State Exam (MMSE).

The team found that the pills were only beneficial to people who didn't have dementia at the beginning of the study.

"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," said Lori Daiello, PharmD, of the Alzheimer's Disease and Memory Disorders Center at Rhode Island Hospital, according to a news release.

 "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 AD, APOE-4. More research is needed, but these findings are promising and highlight the need for future studies to expand the current knowledge of the effects of FOS use on cognitive aging and AD," Daiello said.