Health and Socioeconomic Inequities as Contributors to Brain Health
Population aging will lead to a dramatic increase in dementia prevalence across the world. Dementia is the most costly illness in the United States, with an estimated yearly expenditure around $200 billion. Differences in rates of dementia among diverse populations have garnered recent attention, and it is now accepted that health and socioeconomic disparities are stronger determinants than race or cultural identifiers of the differences in dementia prevalence. While the leading risk factors for dementia, including age and genetic risk, are not yet modifiable, a reasonable proportion of risks are attributable to conditions that can be changed across an individual’s life span. Dementia prevention depends on actions that promote brain health. Access to quality education, healthy diet, and the treatment of conditions (such as diabetes, hypertension, and smoking) that are major risk factors for developing dementia are not equally available across different countries or even between different regions of the same country. Therefore, health and socioeconomic disparities are contributors to brain health.
Dementia is more prevalent and occurs 10 years earlier in low- and middle-income countries than in high-income countries, an example of disparities in socioeconomic conditions across countries contributing to brain health. It is believed that this difference is a consequence of a higher vulnerability to dementia of the population living in low- and middle-income countries because of conditions associated with low socioeconomic status, such as barriers in access to formal education and leisure activities, poor nutrition, poor living conditions, and stress, that can negatively affect brain health. Low educational attainment, for instance, is associated with higher risk of developing symptoms of dementia and earlier symptom onset by up to 8 years. In turn, lower educational attainment has been linked to poor diabetes control and worse cognitive performance in the context of cerebrovascular lesions. Low socioeconomic status in childhood is associated with smaller hippocampal volumes, a higher burden of cerebrovascular lesions, and a higher prevalence of smoking and obesity in adulthood.
Further examples of socioeconomic conditions contributing to brain health include access to quality diet, protection against head injuries, and exposure to stressful situations. Consuming a healthy diet, for instance, is implicated in preserving cognition. A healthy diet, rich in fruits, vegetables, whole grains, fish, and nuts, is not easily accessible for people from a low socioeconomic background because of its expense. Processed foods high in sugar and saturated fats are cheaper and more accessible. Head trauma is also linked to dementia risk. Such injuries can be prevented with use of helmets that are not widely available globally or equally enforced by governments. Posttraumatic stress disorder, a consequence of war, displacement, extreme poverty, and domestic and sexual violence, has also been associated with a higher risk of cognitive impairment.
Low socioeconomic status explains a substantial portion of the racial/ethnic and sex differences reported in dementia rates. In the United States, the highest dementia incidence is found among groups self-identifying as African American or Native American, while an intermediate risk is seen among groups of Latino American groups compared with non-Hispanic groups. Accelerated rates of cognitive decline are seen among African American individuals compared with older non-Hispanic white individuals. Yet, statistical models that adequately adjust for the social determinants of health find minimal if any influence of race/ethnicity alone.