Some important points from the article:

> "The study was an observational one, not a clinical trial. It does not prove that eating an anti-inflammatory diet prevents brain aging and dementia, it only shows an association. An additional limitation is the short follow-up time of three years. Longer studies are needed to confirm and replicate these findings."

So it's more an indication than anything else. The actual concept proposed in the paper is:

> "Aging is characterized by a functional shift of the immune system towards a proinflammatory phenotype. This derangement has been associated with cognitive decline and has been implicated in the pathogenesis of dementia. Diet can modulate systemic inflammation; thus, it may be a valuable tool to counteract the associated risks for cognitive impairment and dementia."

So, they seem to be saying inflammation - an immune system response - becomes deranged during aging - so diets that reduce inflammatory responses or their effects might be helpful in countering dementia, as nerve cells are susceptible to inflammatory damage. Sounds plausible, but needs testing.