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Ten-Year Tracking of Midlife Social Determinants
Initiated in 1985, the CARDIA study recruited 5,115 adults aged 18 to 30 across four U.S. cities: Birmingham, Chicago, Minneapolis, and Oakland. Investigators tracked participants through longitudinal assessments spanning over three decades.
Dintica and colleagues examined 3,488 participants with a mean age of 40. The team calculated a comprehensive “social determinants of health index” by evaluating 12 distinct items across five core domains: economic stability, education level, social context, physical environment, and healthcare access. Participants were divided into four groups based on their index scores to compare cognitive trajectories and brain MRI changes over a 10-year period.
Accelerated Decline in Processing Speed and Working Memory
Cognitive evaluations measured psychomotor speed, sustained attention, working memory, verbal memory, and executive function. Individuals in the most socially disadvantaged group experienced significantly faster declines in processing speed, sustained attention, and working memory over the decade compared to the most advantaged group. Baseline testing revealed immediate disparities: on a 133-point composite scale measuring speed and attention, the most disadvantaged group averaged 60.80 points, compared to 72.36 points for the most advantaged group.
Over 10 years of follow-up, scores for processing speed and working memory in the most disadvantaged cohort dropped by an average of 0.72 points every five years, outpacing the 0.55-point decline observed in the most advantaged group. These disparities persisted even after researchers adjusted for vascular risk factors such as hypertension and diabetes, as well as depressive symptoms. However, tests evaluating verbal memory and executive function showed no statistically significant differences in the rate of decline between the two groups.
Rapid Brain Volume Loss and Vascular Injury Markers
A subset of 645 participants underwent repeat brain MRI scans, revealing that structural brain deterioration also advanced more rapidly among socially disadvantaged individuals. Researchers tracked white matter hyperintensities (WMH) and total gray matter volume over the 10-year period.
While baseline white matter hyperintensities showed no statistically significant difference initially, longitudinal tracking revealed that WMH volume expanded by a factor of 1.07 every five years in the most disadvantaged group, compared to a factor of 1.04 in the most advantaged group. Similarly, total gray matter volume shrank by an average of 2.02 cubic centimeters every five years in the disadvantaged group, versus a 1.46 cubic-centimeter reduction in the most advantaged cohort.
Economic Stability and Healthcare Access Drive Risk
When evaluating individual domains within the social determinants index, researchers found that economic stability, healthcare access, and education level demonstrated the most consistent associations with cognitive performance. A one-standard-deviation decrease in economic stability corresponded to a 3.84-point drop in processing speed and attention scores, a 0.97-point drop in executive function, and a 0.29-point drop in verbal memory.
The study authors note that chronic economic stress and poor healthcare access can delay the effective management of vascular risk factors like hypertension and disrupt stress hormone regulation. While the findings highlight important risk factors tied to socioeconomic environments, the research team acknowledged limitations, including a study population restricted to Black and white participants and a retention bias toward healthier, higher-income individuals in the MRI subset.
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