From a recent study published in JAMA network openedresearchers investigated whether anti-inflammatory diets support cognitive functions in patients with cardiometabolic diseases (CMD).
Study: Anti-inflammatory diet and dementia in older adults with cardiometabolic diseases. Image credits: Elena Eryomenko/Shutterstock.com
Background
CMDs such as insulin-independent diabetes, heart disease and stroke are associated with an increased risk of dementia, especially when they coexist. Studies associate inflammation with the pathophysiological features of CMDs and dementia, and dietary habits can modulate systemic inflammation.
Elevated levels of inflammatory biomarkers are associated with Western diets that are heavy on eggs, high-fat dairy products, red meat, processed foods and refined grains.
In contrast, diets rich in fruits, vegetables, whole grains, seafood and legumes reduce levels of inflammatory biomarkers.
Studies associate lower dietary inflammation with a lower risk of cognitive decline and favorable MRI indicators of brain aging. However, the efficacy of anti-inflammatory diets in improving cognition in CMD patients is uncertain.
About the study
The current study researchers examined the potential cognitive benefits of anti-inflammatory diets in older adults with cardiometabolic diseases.
The researchers involved 84,342 adult United Kingdom Biobank participants aged 60 years or older, with baseline assessments conducted between March 13, 2006 and October 1, 2010.
They excluded individuals with dementia, insulin-dependent diabetes, and those with missing CMD data. The primary study outcome was early-onset dementia, identified from medical records and self-reported.
The researchers conducted joint effects analyzes to assess the status of cardiometabolic diseases and diet-related inflammation in relation to dementia risk and magnetic resonance imaging (MRI) markers of neurodegeneration and vascular injury in the brain.
A total of 8,917 participants without chronic neurological conditions underwent MRI between May 2, 2014 and March 13, 2020 to measure their gray matter volumes (GMV), total brain volume (TBV), hippocampal volumes (HV), white matter volumes (WMV), and white matter hyperintensity volumes ( WMHV).
Researchers identified baseline CMDs such as heart disease, stroke, and insulin-independent diabetes from health records.
They calculated Dietary Inflammatory Index (DII) scores based on 31 nutrients consumed between February 8, 2011 and June 15, 2012, evaluated using the 24-hour Oxford WebQ diet assessment.
Points up to -1.5 indicated anti-inflammatory potential, above -1.5 but less than 0.5 indicated neutral, and 0.5 or higher indicated pro-inflammatory potential.
Researchers followed participants through January 20, 2022. They used Cox proportional hazards regressions to calculate hazard ratios (HR) for analysis. Study covariates included race, education, body mass index (BMI), smoking status, caloric intake, physical activity, socioeconomic status, hypertension, use of antihypertensive medications, and apolipoprotein E (APOE) status.
MRI covariates included time between scans, assessment centers, and table and head positions in MRI scanners.
Researchers conducted sensitivity analyses, applying Fine and Gray’s regressions to unimputed information and restricting participants to those who completed at least two dietary assessments, excluding individuals diagnosed with dementia within five years.
They also determined the association of DII scores with systemic inflammatory biomarkers such as serological C-reactive protein (CRP) levels and assessed the stability of the DII score in dietary assessments.
Results
The average age of the participants was 64 years; 51% were female and 37% had at least a college education. At baseline, 14,079 (17%) had one or more cardiometabolic diseases.
CMD patients tended to be less educated, older, physically inactive, and more socioeconomically disadvantaged male Asian black smokers with elevated BMI and hypertension. Individuals who underwent MRI had lower age, less socioeconomic deprivation, and better risk profiles for vascular injury.
During 12 years (median) follow-up, 1,559 individuals (1.90%) were diagnosed with dementia. The joint effects analysis yielded an HR of 2.4 for dementia in CMD patients following pro-inflammatory diets and 1.7 for individuals with CMDs consuming foods with anti-inflammatory potential.
Individuals with CMDs who consumed anti-inflammatory diets rather than pro-inflammatory diets showed a 31% lower risk of dementia (HR, 0.7) among CMD patients who consumed anti-inflammatory foods.
Brain MRI scans of individuals consuming anti-inflammatory diets showed significantly higher GMV and lower WMHV levels. Using Laplace regressions, CMD patients who ate anti-inflammatory foods developed dementia two years after those with CMDs ate those anti-inflammatory foods.
Sensitivity analyzes yielded similar results with stable DII scores across nutritional assessments. However, Fine and Gray’s regressions yielded attenuated HR values for dementia, indicating that the competing risk of death could influence the results.
Conclusions
The study found that patients with cardiometabolic diseases who consumed anti-inflammatory foods had a reduced incidence of dementia, higher GMV and lower WMHV levels, indicating less neurodegeneration and vascular damage.
The findings suggest that anti-inflammatory diets improve cognitive function in people with cardiometabolic diseases. Anti-inflammatory foods can reduce systemic inflammation, delaying the onset of dementia.
Longitudinal brain MRI studies may increase knowledge of the links between dietary inflammation and brain diseases, especially with regard to risk factors such as cardiometabolic disorders.