The hallmark of Alzheimer’s disease (AD) is the deposition of amyloid plaques and neurofibrillary tangles in the brain. Elevated levels of brain-pathologies, including amyloid-β and neurofibrillary tangles, initiate a series of molecular events leading to neuronal damage and, ultimately, cognitive impairment.
Alzheimer’s disease is the most common form of dementia. Around 1 in 9 adults over 65 years in the United States currently have this condition.
However, not all individuals with pathologies in the brain experience cognitive dysfunction; some can maintain function despite damage from the accumulation of brain pathologies. This phenomenon, known as cognitive resilience (defined as performing better than expected given the burden of neuropathology), has been proposed as a moderator between brain pathology and clinical outcomes and has recently become an active area of research.
One example is that late-life cognitive activities and physical activity are associated with a better cognitive score independently of brain pathologies. Identifying modifiable lifestyle factors that act independently of brain pathologies is critical in AD research because pharmacological interventions that focus on brain pathology have failed to reduce or slow cognitive decline.
Among modifiable lifestyle factors, diet is crucial in cognitive decline and AD dementia. A dietary protocol that has shown a slowing in cognitive decline in older adults and reduced the risk of AD dementia is the MIND diet, a hybrid of the Mediterranean diet with the Dietary Approaches to Stop Hypertension (DASH) diet.
This diet emphasizes consuming leafy green vegetables, other vegetables, berries, legumes, fish, nuts, and whole grains while limiting the consumption of butter, cheese, and red meat.
Recently, researchers from the Rush University Medical Center in Chicago investigated the ability of the diet to improve cognitive function in older adults independent of brain pathology levels.
The study analyzed data collected by the Rush Memory and Aging Project (MAP) on 569 deceased individuals. The Rush MAP is a longitudinal study involving adults over 65 years of age whose objective is to identify environmental and genetic factors associated with AD development.
The Rush MAP conducts annual assessments to evaluate cognitive health, lifestyle, and risk factors associated with AD. The study also performs postmortem analyses on brains donated by participants to assess changes associated with AD.
In a new study, they used a questionnaire to calculate the MIND diet score based on how frequently the study participants consumed foods deemed healthy or unhealthy according to the MIND diet.
The researchers had access to data from comprehensive cognitive tests conducted close to the participants’ deaths. After a participant’s death, the team conducted a postmortem analysis to identify brain changes associated with AD and other conditions known to result in age-related cognitive decline.
About one-third of the participants had a clinical diagnosis of AD before their death. However, the researchers were able to identify two-thirds of the participants as having AD based on high levels of brain pathologies revealed by the postmortem analyses.
They found a positive correlation between the MIND diet score and cognitive function before the participants’ deaths. The MIND diet was associated with a slower rate of decline in cognitive function with aging.
To minimize the possibility of the patient’s reports being inaccurate due to cognitive impairment, researchers re-analyzed the data after excluding individuals with mild cognitive impairment at the onset of data collection.
Their results indicate that the potential effects of diet on cognitive function are unlikely to be mediated by influencing the levels of brain pathologies associated with AD and other brain conditions.
They concluded that the MIND diet is associated with better cognitive functioning independently of common brain pathology, suggesting that the MIND diet may contribute to cognitive resilience in the elderly.
Klodian Dhana, et al. MIND Diet, Common Brain Pathologies, and Cognition in Community-Dwelling Older Adults. Journal of Alzheimer’s Disease, vol. 83, no. 2, pp. 683-692, 2021. DOI 10.3233/JAD-210107.