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Researchers found that people over the age of 60 with a genetic risk of didn't experience the expected increase in cognitive decline and dementia risk if they ate relatively large quantities of meat.

Swedish researchers say their findings may help develop more individually tailored dietary advice.

They explained that APOE is a gene that affects the risk of .

In Sweden, around 30% of the population are carriers of the gene combinations APOE 3/4 or APOE 4/4.

But, among people with , those with the genotypes account for nearly 70%.

When the presented an overview of research on the link between diet and dementia last year, more research was requested to assess a possible link between meat consumption and the development of dementia.

Dr. Jakob Norgren said: "This study tested the hypothesis that people with APOE 3/4 and 4/4 would have a reduced risk of cognitive decline and dementia with higher meat intake, based on the fact that APOE4 is the evolutionarily oldest variant of the APOE gene and may have arisen during a period when our evolutionary ancestors ate a more animal-based diet."

The study, published in , followed more than 2,100 Swedes, who were all aged 60 or older and had no diagnosis of dementia at the outset, for up to 15 years.

The association between self-reported diet and cognitive health measures was analysed, adjusting for age, sex, education and lifestyle factors.

Among those who ate less meat, the group with APOE 3/4 and 4/4 had more than twice the risk of dementia than people without the gene variants.

However, the increased risk of cognitive decline and dementia in the risk groups was not seen in the fifth of participants who consumed the most .

Their average consumption was estimated at around 870 grams of meat per week, standardized to a daily energy intake of 2,000 calories.

Study first author Dr. Norgren, of the in Solna, Sweden, said: "Those who ate more meat overall had significantly slower cognitive decline and a lower risk of dementia, but only if they had the APOE 3/4 or 4/4 gene variants."

He added: "There is a lack of dietary research into brain health, and our findings suggest that conventional dietary advice may be unfavourable to a genetically defined subgroup of the population.

"For those who are aware that they belong to this genetic risk group, the findings offer hope; the risk may be modifiable through lifestyle changes."

The study also found that the is important.

Study co-author Dr. Sara Garcia-Ptacek said: "A lower proportion of processed meat in total meat consumption was associated with a lower risk of dementia regardless of APOE genotype."

The research team also found a "significant" reduction in the chances of an early death in carriers of APOE 3/4 and 4/4 who ate higher quantities of unprocessed meat.

The researchers pointed out that the research was observational, and needs to be followed up with intervention studies that can better demonstrate causal relationships.

Dr. Norgren said: "Clinical trials are now needed to develop dietary recommendations tailored to APOE genotype."

He added: "Since the prevalence of APOE4 is about twice as high in the Nordic countries as in the Mediterranean countries, we are particularly well suited to conduct research on tailored dietary recommendations for this risk group."