Higher intake of processed red meat, including bacon, hot dogs, and sausages, is associated with an elevated dementia risk, preliminary research shows.
Study participants who consumed 0.25 or more servings of processed meat per day, or roughly two servings per week, had a 15% higher risk for dementia compared with those who consumed less than 0.10 serving per day, which is about three servings per month.
"Our study found a higher intake of red meat — particularly processed red meat — was associated with a higher risk of developing dementia, as well as worse cognition," study author Yuhan Li, MHS, research assistant, Channing Division of Network Medicine, Brigham and Women's Hospital, Boston, told Medscape Medical News.
However, the study also showed that replacing processed red meat with nuts and legumes could potentially lower this increased risk.
The findings were presented on July 31 at the Alzheimer's Association International Conference (AAIC) 2024.
Inconsistent Research
Previous studies have shown an inconsistent association between red meat intake and cognitive health.
To assess the relationship between diet and dementia, the researchers used data from the Nurses' Health Study, which began recruiting female registered nurses aged 30-55 years in 1976, and the Health Professionals Follow-Up Study, which began recruiting male health professionals aged 40-75 in 1986.
They assessed processed red meat intake by validated semi-quantitative food frequency questionnaires administered every 2-4 years. Participants were asked how often they consumed a serving of processed red meat.
Investigators also assessed intake of unprocessed red meat, including beef, pork, or lamb as a main dish, in a sandwich or hamburger, or in a mixed dish.
The investigators also looked at participants' intake of nuts and legumes.
Dementia outcome was a composite endpoint of self-reported dementia and dementia-related death.
"Specifically, participants reported a physician diagnosis of Alzheimer's disease or other forms of dementia by questionnaire. Deaths were identified through state vital statistics records, the National Death Index, family reports, and the postal system," said Li.
Three Cognitive Outcomes
Researchers examined three outcomes: dementia, subjective cognitive decline, and objective cognitive function. For dementia, they ascertained incident cases in 87,424 individuals in the UK's National Health Service database without Parkinson's disease or baseline dementia, stroke, or cancer.
They longitudinally collected information on subjective cognitive decline from 33,908 Nurses' Health Study participants and 10,058 participants in the Health Professionals Follow-Up Study.
Cognitive function was assessed using the Telephone Interview for Cognitive Status (1995-2008) in a subset of 17,458 Nurses' Health Study participants.
Over a follow-up of 38 years (1980-2018), there were 6856 dementia cases in the Nurses' Health Study. Participants with processed red meat intake ≥ 0.25 serving/day, compared with < 0.10 serving/day, had 15% higher risk for dementia (hazard ratio [HR], 1.15; 95% CI, 1.08-1.23; P < .001).
In addition to an increased risk for dementia, intake of processed red meat was associated with accelerated cognitive aging in global cognition (1.61 years per 1–serving/day increment; 95% CI, 0.20, 3.03) and verbal memory (1.69 years per 1–serving/day increment; 95% CI, 0.13, 3.25; both P = .03).
Participants with processed red meat intake ≥ 0.25 serving/day had a 14% higher likelihood of subjective cognitive decline compared with those with intake < 0.10 serving/day (odds ratio [OR], 1.14; 95% CI, 1.04-1.24; P = .004).
For unprocessed red meat, consuming ≥ 1.00 serving/day vs < 0.50 serving/day was associated with a 16% higher likelihood of subjective cognitive decline (OR, 1.16; 95% CI, 1.04-1.30; P = .02).
Substitution Analysis
Researchers modeled the effects of replacing 1 serving/day of processed red meat with 1 serving/day of nuts and legumes on cognitive outcomes. They did this by treating food intakes as continuous variables and calculating the differences in coefficients of the two food items.
They found that substituting legumes and nuts was associated with a 23% lower risk for dementia (HR, 0.77; 95% CI, 0.69-0.86), 1.37 fewer years of cognitive aging (95% CI, -2.49 to -0.25), and 20% lower odds of subjective cognitive decline (OR, 0.80, 95% CI, 0.69-0.92).
The research cannot determine whether it's the processing method itself or the type of red meat that affects cognition, Li cautioned.
"Our study is an epidemiologic study, not a biological mechanism study, but based on our findings, red meat may be related to worse cognition, and processed red meat may add additional risk," she said.
She also noted that because the study focused solely on red meats, the study cannot determine the potential on the impact of other processed meats on cognition.
Although the study doesn't address a possible mechanism linking processed red meat with cognition, Li said it's possible such meats have high levels of relatively harmful substances, such as nitrites, N-nitroso compounds, and sodium, and that "these carry the additional risk to brain health."
There are currently no specific guidelines regarding the "safe" amount of processed meat consumption specifically related to cognition, said Li.
The study is important because of its large sample size, long follow-up period, and inclusion of repeated measurements of diet, the investigators noted. In addition, researchers assessed both processed and unprocessed red meat and evaluated multiple cognitive outcomes.
The investigators plan to assess the association between other modifiable factors and cognitive health.
Experts Weigh In
Commenting on the research for Medscape Medical News, Claire Sexton, DPhil, senior director of scientific programs and outreach at the Alzheimer's Association, agreed past studies on the topic have been "mixed," with only some studies reporting links between cognition or dementia and processed red meat.
Another unique aspect of the study, said Sexton, was the replacement analysis showing the brain benefits of eating nuts and legumes in place of processed red meat. "So, it's not just suggesting to people what not to do, but also what they can be doing instead."
That's why this large study with more than 130,000 adults that tracked individuals for close to 40 years in some cases "is so valuable," she added.
In a release from the Science Media Centre in the United Kingdom, several other experts commented on the study. Among them, Kevin McConway, PhD, emeritus professor of applied statistics at the Open University in the UK, said that "it's pretty well impossible to get a clear message from the information that is available so far about this research. It is a conference paper, and all we have seen so far is a press release, a brief summary of the research, and a diagram. There isn't a detailed, peer-reviewed research report, not yet anyway. Putting out limited information like this isn't the right way to report science."
McConway also noted that the observational study recorded participants' diets and dementia diagnoses over several years without assigning specific diets. Those who ate more red processed meat had higher rates of dementia and cognitive decline. However, it's unclear if these differences are due to red meat consumption or other factors, such as diet, age, ethnicity, or location.
Researchers typically adjust for these factors, but the available information doesn't specify what adjustments were made or their impact, he noted, and without detailed data, it's impossible to evaluate the study's quality. Although eating more red processed meat might increase dementia risk, more research is needed to confirm this, McConway added.
Also commenting, Sebastian Walsh, an NIHR doctoral fellow who researches population-level approaches to dementia risk reduction at University of Cambridge in the UK, said that without seeing the full paper, it's difficult to know exactly what to make of the study's findings.
"On the surface, this is a large and long study. But it isn't clear how the analysis was done — specifically what other factors were taken into account when looking at this apparent relationship between red meat and dementia.
"Despite a lot of research looking at specific foods and different diseases, the basic public health advice that eating a healthy, balanced diet is good for health is essentially unchanged. Most people know and accept this. What is most important is to find ways of supporting people, particularly those from poorer backgrounds, to follow this advice and address the obesity epidemic," said Walsh.
Note: This article originally appeared on Medscape.
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