Parental or early life socioeconomic position, childhood IQ, measures of early growth (such as infant head circumference and childhood height), educational attainment, occupational characteristics, and various measures of social integration have all been linked to cognitive function and neurocognitive disorders in adulthood and old age (Glymour & Manley, 2008). Individual socioeconomic position may affect cognitive status or diagnoses through: (1) material conditions; (2) psychosocial conditions (such as status); (3) direct cognitive stimulation; or (4) test-taking skills (Glymour & Manley, 2008) .
Geronimus et al. (2006) attributed many racial and ethnic disparities in health to "weathering," the accumulated consequences of exposure to economic and social adversity. Having financial resources leads to health-enhancing conditions such as healthy housing, high-quality food, safe working conditions, and access to high-quality medical care (and the reverse is true as well). Occupation influences health both through stress and material deprivation, and through toxic work conditions (Glymour & Manley, 2008).
Poverty often reduces access to educational opportunities or is associated with poor-quality education, thereby increasing the likelihood of adult poverty, which may increase the risk of depression and cognitive impairment (Glymour & Manley, 2008). If the effect of education on cognitive aging is primarily through material advantages, then credentials may be more important than quality. But if education's effect is because of cognitive skills or engagement, then school quality is more important. Resources available to parents are also very important to a child's cognitive development, and differences in parental socioeconomic status predict dementia. Extra schooling appears to have substantial benefits for memory function in the elderly (Glymour & Manley, 2008).
Additional evidence for the link between cognitive impairment and low income, less education, and having lived in a rural area comes from the 2006 Health and Retirement Study. All of these socioeconomic characteristics are more common among people with cognitive impairment, as shown in Figure 4 (Alzheimer's Association, 2011). For example, 89% of Hispanics over age 55 with cognitive impairment possess less than 12 years of education, compared to 49% of those with normal cognition.
FIGURE 4. Socioeconomic Characteristics by Cognitive Impairment and Race/Ethnicity, 2006 Health and Retirement Study
SOURCE: Alzheimer's Association, 2011.