Education, wealth, and job type shape aging brains and cognitive health

New findings reveal how education, wealth, and career paths can delay cognitive decline, promoting longer healthy years and shorter impaired states in aging adults.

Participants with higher education or professional occupations spent, on average, more years in a healthy cognitive state compared to those with lower socioeconomic positions, highlighting the role of “cognitive reserve” in aging.

In a recent study published in the journal Scientific Reports, researchers investigated the role of various indicators of socioeconomic position (SEP) in the transition between cognitive states and mortality. Often measured by wealth, income, education, and occupation, SEP has been recognized as a significant determinant factor for dementia risk.

The study further emphasizes that SEP indicators impact both the risk of cognitive decline and the potential for reversion from cognitive impairment to healthier states. Some reports indicate that people from lower socioeconomic backgrounds spend a greater proportion of their later years with cognitive impairment than those from higher socioeconomic backgrounds.

Further, while previous research has shown an association, the role of socioeconomic inequalities in the transition from a healthy cognitive state to mild cognitive impairment (MCI) or dementia remains partially unclear.

About the study

In the present study, researchers examined associations of specific socioeconomic markers with the transition between cognitive states and mortality. They used data from waves 4 (2008-09) to 9 (2018-19) of the ongoing English Longitudinal Study of Aging. Cognitive status groups were derived: no cognitive impairment (NOCI), dementia, and cognitive impairment no dementia (CIND). The CIND group included MCI subjects and those with other (non-dementia) forms of cognitive impairment.

SEP was measured using three indicators – the highest level of occupation, household wealth excluding pensions, and education. Covariates included sex, age, and marital status. Researchers collected information on socioeconomic indicators and covariates at the study's baseline (wave 4) and tracked cognitive transitions over the next 10 years.

Individuals in manual or routine occupations faced significantly higher risks of transitioning to dementia and had fewer chances of cognitive recovery compared to those in managerial roles, suggesting that job type impacts long-term brain health.

The researchers used a continuous-time Markov model to estimate the transition probabilities between cognitive states (dementia, NOCI, and CIND) while adjusting for age and sex in most cases.

A state was classified as transient if it could continue transitioning to another; otherwise, it was considered an absorbing state. Death was considered an absorbing state. Overall, seven transitions were possible: 1) NOCI to CIND, 2) NOCI to dementia, 3) NOCI to death, 4) CIND to dementia, 5) CIND to NOCI (reversion), 6) CIND to death, and 7) dementia to death.

For each transition type, hazard ratios were used to understand how each socioeconomic indicator correlated with transition risks. Time spent in each state and the probabilities of entering each state were also calculated. Besides, the sojourn time, or expected duration in each state, and the mean length of stay in different states were estimated. Except for CIND-to-dementia and NOCI-to-dementia transitions, models included age, sex, and marital status covariates.

Findings

The study analyzed a cohort of 8,442 participants aged approximately 67 years on average. Most participants were female (55.7%) and married (65.3%). Notably, there were 3,898 NOCI-to-CIND, 3,361 CIND-to-NOCI, 25 NOCI-to-dementia, and 336 CIND-to-dementia transitions. Further, 295 NOCI-to-death, 192 dementia-to-death, and 1,231 CIND-to-death transitions occurred.

The transition probability from NOCI to dementia or death was markedly low. By contrast, the transition from dementia to death was relatively high, with a probability of 21%. Higher education was associated with lower transition probabilities from NOCI to CIND and dementia. Participants with higher education were more likely to revert from CIND to NOCI.

Further, higher education was inversely related to dementia-to-death transition probability; subjects with lower education had a higher mortality risk. Participants in the lowest wealth tertile had a lower NOCI-to-CIND transition probability; the highest wealth tertile had a higher probability of the CIND-to-NOCI reverse transition. Increasing age was associated with a greater likelihood of transitions, except for the reverse transition.

Moreover, individuals with higher-level, professional or managerial occupations had the lowest probability of transitioning to dementia or CIND. In contrast, more disadvantaged occupations increased the probability of transition to dementia, while more advantaged occupations increased the likelihood of reverse transition. Manual/routine occupation elevated the probability of transition to dementia or death relative to managerial/professional occupations.

The highest education level was associated with reductions of 43%, 69%, and 39% in the risk of NOCI-to-CIND, CIND-to-dementia, and dementia-to-death transitions, respectively, when compared to the lowest education level. Moreover, more advantaged occupations were associated with a reduced risk of the NOCI-to-CIND transition. Higher wealth was associated with a higher likelihood of CIND-to-NOCI reversion.

Socioeconomic indicators were not associated with the NOCI-to-dementia transition. People with degree-level education consistently spent more time in the NOCI state at any given age than those with lower education. People who were professionally qualified, wealthy, and well-educated at age 80 had shorter remaining time in dementia or CIND states. Socioeconomically advantaged people had longer sojourn time in the NOCI state and shorter periods in dementia and CIND states.

Conclusions

In summary, this study reveals that a significant portion of older adults transitioned between cognitive states during the study period. Wealthy, highly educated, and professionally qualified individuals had reduced hazards of transitioning to CIND and dementia.

Moreover, socioeconomically advantaged participants exhibited a greater likelihood of CIND-to-NOCI reversion; they spent less time in impaired cognitive states and more time in healthy states than disadvantaged groups. This study highlights the role of socioeconomic inequalities in cognitive health and suggests that socioeconomically advantaged individuals may have protective benefits that delay or reduce cognitive decline.

Journal reference:

• Gireesh A, Sacker A, McMunn A, Bhatt R, Cadar D. Socioeconomic inequalities linked to the transitioning to neurocognitive disorders and mortality. Scientific Reports, 2024, DOI: 10.1038/s41598-024-74125-w, https://www.nature.com/articles/s41598-024-74125-w