With as many as 24 million people worldwide afflicted with dementia, researchers are looking for correlations in genetics, diet and environment.

Since many of these people live in low- and middle-income countries, the solution to reducing instances of dementia may be a cost-effective one:  more oily fish , according to a paper in the American Journal of Clinical Nutrition.

Oily fish are rich in omega-3 long-chain polyunsaturated fatty acids, which some studies have suggested are positively related to cognitive function in later life.  A few studies have been less convincing that increased meat consumption may be related to cognitive decline.  The authors of the new study propose that this relation is not due to poor overall nutritional status in those with dementia, because meat consumption tended to be higher in this group. There was no relation between meat consumption and dementia.

To examine the fish connection, a group of international researchers studied older people in 7 middle- to low-income countries.   Data from 14,960 participants (≥65 y of age) living in China, India, Cuba, the Dominican Republic, Venezuela, Mexico, and Peru were analyzed. Dietary habits were assessed by using standard, culturally appropriate face-to-face interviews, and dementia was diagnosed by using validated culturally and educationally fair criteria. 

In each of the study countries, except India, there was an inverse association between fish consumption and dementia prevalence. These data extend to low- and middle-income countries previous conclusions from industrialized countries that increased fish consumption is associated with lower dementia prevalence in later life.