Living conditions leave their mark on brain health

How the brain ages is not determined solely by biological processes and disease. Where and under what conditions people grow up, their educational opportunities, financial resources, working lives, and access to healthcare may also be associated with differences that emerge over the years.

An international study whose research team included Dr. Agustin Ibanez of Istanbul Medipol University comprehensively examined how this relationship varies across healthy aging, Alzheimer’s disease, and frontotemporal lobar degeneration.

Published in Alzheimer’s & Dementia under the title “Social vulnerability shapes deep clinical phenotypes and brain health in aging and dementia across Latin America” the study found that greater social disadvantage was associated with a range of outcomes, from cognitive abilities and independence in daily life to mental health.

3,941 PEOPLE FROM SIX COUNTRIES WERE STUDIED
The study included a total of 3,941 participants from Argentina, Brazil, Chile, Colombia, Mexico, and Peru. Of these, 2,226 had no cognitive impairment, while 1,245 had been diagnosed with Alzheimer’s disease and 470 with frontotemporal lobar degeneration.

The researchers did not limit their assessment of social conditions to income or educational attainment. Education, material resources, occupation, childhood experiences, social relationships, access to healthcare, economic circumstances, and traumatic experiences were evaluated together. The clinical manifestations of brain health were assessed using 37 different indicators, ranging from memory, language, attention, and planning to daily living skills and mental health.

Of the participants, 56.8 percent were classified as having lower social disadvantage, while 43.2 percent were in the higher social disadvantage group. The analyses showed that people in the more disadvantaged group generally had poorer outcomes in areas such as memory, language, attention, information-processing speed, planning, and cognitive flexibility.

Notably, this association was not limited to people diagnosed with dementia. Similar differences were also observed among cognitively healthy participants.

THE AREAS AFFECTED VARIED ACROSS GROUPS
The areas most strongly associated with social conditions were not the same across all groups.

Among people without cognitive impairment, cognitive abilities such as memory and planning stood out. Among people with Alzheimer’s disease, the ability to maintain independence in daily life was prominent alongside cognitive performance, while in the frontotemporal lobar degeneration group, differences in the ability to understand other people’s emotions and intentions, as well as behavioral and psychological symptoms, were particularly notable.

Assessments of daily living revealed a similar pattern. More socially disadvantaged participants diagnosed with Alzheimer’s disease or frontotemporal lobar degeneration experienced greater difficulty with everyday activities such as managing money and medication, preparing meals, shopping, transportation, and household tasks. Dementia symptoms were also more severe in these groups.

In terms of mental health, social disadvantage was generally associated with more depressive symptoms. Differences in anxiety levels were particularly pronounced among people with Alzheimer’s disease, while behavioral and psychological symptoms stood out in both the Alzheimer’s disease and frontotemporal lobar degeneration groups.

EDUCATION ALONE DOES NOT EXPLAIN THE PATTERN
One of the study’s important findings was that the relationship between social conditions and brain health could not be explained solely by educational attainment.

The researchers found that the association persisted even after accounting for the effects of education. Moreover, the social conditions that emerged as most relevant varied across groups. Among cognitively healthy individuals, education, material resources, and occupational conditions appeared more prominent, whereas in the Alzheimer’s disease and frontotemporal lobar degeneration groups, factors extending across different stages of life, including childhood experiences and access to healthcare, also became important.

The findings were also not specific to a single country. When the six countries were analyzed separately, the association between social disadvantage and brain health indicators followed the same overall direction in Argentina, Brazil, Chile, Colombia, Mexico, and Peru.

UNDERSTANDING BRAIN HEALTH REQUIRES LOOKING ACROSS THE LIFE COURSE
The study identifies an important association but does not establish a cause-and-effect relationship. In other words, the findings do not demonstrate that disadvantaged living conditions directly cause Alzheimer’s disease or another form of dementia.

The primary reason is that the study compared participants at a particular point in time. Longitudinal studies that follow participants over extended periods are therefore needed to determine how social conditions may shape brain health over the years and through which mechanisms the observed differences emerge.

Nevertheless, by examining nearly 4,000 people across six countries and considering numerous social factors extending across different stages of life, the study demonstrates the importance of approaching brain health from a broader perspective. The findings suggest that efforts to understand aging and dementia should consider not only the biological characteristics of the brain but also people’s life-course experiences, ranging from education and financial resources to childhood experiences and access to healthcare.