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PHILADELPHIA -- Eating two servings of processed red meat a week over decades raised the odds of subsequent dementia, a prospective study of 130,000 healthcare professionals showed.

Over up to 43 years of follow-up, participants in the Nurses' Health Study and the Health Professionals Follow-Up Study who ate at least a fourth of a daily serving of processed red meat -- approximately two servings a week -- had a significant 14% higher risk of dementia compared with those who averaged less than a tenth of a serving per day, reported Yuhan Li, MHS, of Harvard T.H. Chan School of Public Health in Boston, in a poster presented at the Alzheimer's Association International Conference.

Each additional daily serving of processed red meat was associated with an extra 1.61 years of cognitive aging in global cognition and 1.69 years in verbal memory. A serving of processed red meat was equivalent to two slices of bacon, one hot dog, or 2 ounces of sausage, salami, bologna, or similar foods.

In contrast, replacing a daily serving of processed red meat with a daily serving of nuts or legumes was tied to a 20% lower risk of developing dementia and 1.37 fewer years of cognitive aging in global cognition, Li said. A serving of nuts or legumes included a tablespoon of peanut butter, an ounce of nuts, or 8 ounces of soy milk.

No significant relationship emerged between unprocessed red meat, like hamburger or steak, and dementia. However, eating one or more daily servings of unprocessed red meat was tied to a 16% increase in subjective cognitive decline, compared with eating less than half a serving per day.

"Study results have been mixed on whether there is a relationship between cognitive decline and meat consumption in general, so we took a closer look at how eating different amounts of both processed and unprocessed meat affects cognitive risk and function," Li said.

"Processed red meat has also been shown to raise the risk of cancer, heart disease, and diabetes," Li said. It may affect the brain because it has high levels of nitrites and sodium, she suggested.

Previous research from the and the has reported that heart-healthy foods like olive oil were tied to lower odds of dementia mortality. Data from the U.K. Biobank have also shown that ultra-processed foods were associated with higher dementia incidence, and substituting these foods for healthier options lowered dementia risk.

But all these have been observational studies, subject to reporting errors and confounding. Clinical trials are now trying to determine whether diet and other lifestyle changes actually influence brain health.

The ongoing study of 2,000 older adults, for example, will obtain "more specific, data-driven answers about lifestyle and dementia," said Heather Snyder, PhD, senior vice president of medical and scientific relations of the Alzheimer's Association.

"This 2-year clinical trial will evaluate whether lifestyle interventions that target many risk factors -- including diet -- can protect cognitive function in older adults," Snyder told MedPage Today. POINTER is scheduled to be completed in 2025.

For the present analysis, Li and co-authors included 87,424 women who had been followed in the Nurses' Health Study from 1980 to 2023, and 46,347 men in the Health Professionals Follow-Up Study followed from 1986 to 2023.

Investigators prospectively evaluated their eating habits and subsequent dementia. Dementia was a composite endpoint of self-reported dementia and deaths due to dementia. Food intake was derived from food frequency questionnaires every 2 to 4 years.

Global cognition and memory scores were determined through the Telephone Interview for Cognitive Status (TICS) and other tests among 17,458 women. Subjective cognitive decline was assessed by questionnaires completed by 33,908 women and 10,058 men.

Among the limitations of the analysis was that it focused only on certain aspects of diet, and adjustments made for other variables were unknown. The study's observational nature also means it could not establish whether a causal link exists between processed red meat intake and dementia.

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