A new study with over 2100 subjects and published in the journal Neurology  confirms results of a study published already in 2016 by the University of Oxford/UK in 2015 showing that especially the DHA and B-vitamin status in elderly people (average 66 years) with mild cognitive impairment reduces the velocity of brain shrinkage and thus development of dementia symptoms .
The big difference between the two studies is that in the new study published in 2022 the preventive effects of a higher DHA level in the red blood cells (RBC) was seen already in subjects of much younger age (average 45 years) showing no symptoms of cognitive decline. Higher DHA levels in the RBC were associated with a larger hippocampus (area of the brain responsible for memory) and better cognitive function in mid-aged subjects not carrying the APOE-e4 gene. (Note: carriers of the APOE-e4 gene have shown to develop more frequently dementia than non-carriers.) Those subjects with a lower DHA concentration in their RBC showed a significant smaller (shrunken) hippocampus and have a higher risk of developing cognitive decline further on in their life.
The scientists conclude that already mid-aged people should make sure to have a good EPA+DHA level in their RBC membranes (minimum 8% ) to prevent or slow down the development of age-related brain shrinkage and consequential dementia. Everyone can test their EPA+DHA levels in their RBC. Just get your “Omega-3 Index” analyzed (see https://vitalremedymd.com/pages/omega-3-index-basic ) and if you should have a low DHA+EPA level (below 8%) you should seriously consider to take a good quality omega-3 supplement, rich in DHA (see: https://vitalremedymd.com/products/vitaloils1000-1month )
 Oulhaj A., Jerneren F., Refsum H., et.al., Omega-3 Fatty Acid Status Enhances the Prevention of Cognitive Decline by B Vitamins in Mild Cognitive Impairment. Journal of Alzheimer´s Disease 50 (2016) 547-557. DOI 10.3233/JAD-150777
 Satizabal CL, Himali JJ, Beiser AS, Ramachandran V, Melo van Lent D, Himali D, Aparicio HJ, Maillard P, DeCarli CS, Harris W, Seshadri S. Association of Red Blood Cell Omega-3 Fatty Acids With MRI Markers and Cognitive Function in Midlife: The Framingham Heart Study. Neurology. 2022 Oct 5:10.1212/WNL.0000000000201296. doi: 10.1212/WNL.0000000000201296. Epub ahead of print. PMID: 36198518.