Processed Red Meat Tied to Increased Dementia Risk

Higher intake of processed red meat, including bacon, hot dogs, and bologna, is associated with a significantly elevated risk for cognitive decline and dementia, results of a large, long-term study suggested.

Individuals who consumed more than a quarter of a serving of processed meat per day, roughly two whole servings per week, had a 13% higher dementia risk compared with those who consumed less than a 10th of a serving per day, which equates to approximately three whole servings per month. A typical serving of red meat is approximately three ounces.

However, substituting one serving per day of processed red meat with a serving of fish, nuts and legumes, or chicken was associated with a 28%,19%, and 16% lower risk for dementia, respectively.

“Red meat is high in saturated fat and has been shown in previous studies to increase the risk of type II diabetes and heart disease, which are both linked to reduced brain health,” study investigator Dong Wang, MD, ScD, of Brigham and Women’s Hospital in Boston, Massachusetts, said in a press release. 

“Our study found processed red meat may increase the risk of cognitive decline and dementia, but the good news is that it also found that replacing it with healthier alternatives, like nuts, fish, and poultry, may reduce a person’s risk,” he added.

The findings were published online on January 15 in Neurology. 

A More Comprehensive Study

Several previous studies have explored the relationship between red meat consumption and cognitive health, with inconsistent results. However, most of this research has been limited by small sample sizes with short follow-up, and some of these studies did not distinguish between processed and unprocessed red meat. 

To determine the relationship between long-term red meat consumption and dementia, the researchers analyzed data from two large, nationwide cohort studies: the NHS and the HPFS. 

All participants were dementia-free at baseline. Those with baseline dementia, stroke, or cancer, who were missing red meat intake data, or who had implausible total energy intake at baseline were excluded. Individuals with Parkinson’s disease were also excluded at baseline and during follow-up. 

The study’s primary outcome was dementia, defined as a composite endpoint of self-reported dementia and deaths attributed to dementia. 

Dementia cases were determined by self-report of physician diagnosis or death from dementia collected through the National Death Index and family reports. 

The analysis included 133,771 participants (64.4% women) with a mean baseline age of 48.9 years. Of these individuals 11,173 developed dementia up to 43 years later. 

The researchers also analyzed dementia deaths as a secondary outcome. Every 2 years, participants were asked to report a physician diagnosis of Alzheimer’s disease or other dementia types. 

Diets were assessed using a validated food questionnaire that measured how often specific foods were consumed. 

No Link to Unprocessed Meat?

After adjusting for potential confounders, researchers found that participants who consumed a quarter serving of processed red meat per day, the equivalent of two servings per week, had a 13% (hazard ratio, 1.13; 95% CI, 1.08-1.19; P<.001 higher="" risk="" of="" developing="" dementia="" compared="" with="" those="" who="" only="" consumed="" it="" three="" times="" per="" month.="" wp_automatic_readability="77">

The association between dementia and unprocessed red meat, such as hamburger meat or steak, did not reach statistical significance.

The investigators analyzed objective cognitive function using standard measures and, after adjusting for potential confounders, found that eating two or more servings per week was associated with accelerated aging in global cognition by 1.61 years per each additional serving per day (95% CI, 0.20-3.03) and in verbal memory by 1.69 years for each additional serving per day (95% CI, 0.13-3.25). 

Unprocessed red meat was not significantly associated with any measure of objective cognitive function. 

Subjective cognitive decline (SCD) was also assessed in all participants via questionnaire, which included questions about memory, executive function, attention, and visuospatial skills. 

The findings showed SCD was more pronounced among those who consumed more than a quarter serving of processed red meat per day, with a 14% higher risk for SCD compared with those who consumed less than a 10th of a serving per day (relative risk [RR], 1.14; 95% CI, 1.04-1.25). 

In addition, consuming one or more servings per day of unprocessed red meat was associated with a 16% increased risk for SCD vs intake of less than half a serving per day (RR, 1.16; 95% CI, 1.03-1.30). 

Investigators also validated dementia outcomes against the apolipoprotein E (APOE) genotype and found there was a fourfold increased risk for dementia in participants with the APOE4 vs the APOE3 genotype and an eightfold increased risk in those diagnosed before age 80 years.

Potential Mechanism in the Gut? 

On terms of determining potential mechanisms, investigators are focusing on the role of the gut microbiome. 

One possible culprit is trimethylamine N-oxide, a byproduct of bacterial digestion of meat, which might contribute to cognitive decline by promoting the buildup of amyloid and tau proteins associated with Alzheimer’s disease. 

In addition, the saturated fat and high salt content in red meat could negatively affect the health of brain cells. 

“Large, long-term cohort studies are essential for investigating conditions like dementia, which can develop over decades,” Wang said. “We are continuing to piece together this story to understand the mechanisms causing dementia and cognitive decline.”

“Reducing how much red meat a person eats and replacing it with other protein sources and plant-based options could be included in dietary guidelines to promote cognitive health. More research is needed to assess our findings in more diverse groups,” he added.

The study’s limitations include its observational design, which cannot rule out the possibility of residual confounding. In addition, self-reporting of dementia is prone to misclassification. 

Recall bias in the assessment of red meat intake is another limitation. However, the investigators noted that validation studies show red meat intake is reasonably well measured.