Educational Attainment and Dementia: Mediation by Mid-Life Vascular Risk Factors

Mediators of educational differences in dementia risk later in life: evidence from the HUNT study

Despite a well-known inverse association between education and dementia risk, the mediating mechanisms are not well understood. We explored how lifestyle and health risk factors across the life-course mediate the relationship between education and dementia among adults aged 70 + years. We included 7,655 participants with dementia diagnoses and education information, using a historical cohort design linking prospective exposure data across the life course from the HUNT4 70 + Study with registry data from Statistics Norway and earlier HUNT surveys. We conducted causal mediation analysis to assess the mediating roles of occupational characteristics, lifestyle factors (smoking, physical inactivity), and health risk factors (obesity, hypertension, diabetes, hearing impairment, cardiovascular diseases, LDL cholesterol, depression, anxiety) assessed during early, middle, and late adulthood in the relationship between education and dementia in later life. Participants with lower education were more likely to have dementia with odds ratios of 1.99, 1.88, 1.83 for the model's accounting exposure to mediators during early, middle, and late adulthood, respectively. These associations were partially mediated by the joint effect of health and lifestyle risk factors from early through late adulthood (mediated 11.55-19.50%). Health risk factors from early to late adulthood jointly mediated 6.85-13.06% of the effect of low education on dementia risk later in life. Additionally, lifestyle factors during middle and late adulthood jointly mediated 4.11-4.96% of the total effect of low education on dementia risk later in life. Educational differences in dementia risk can partly mediated by lifestyle and health factors across the life course. These findings suggest potential targets to address varying dementia risks linked to education levels.

Parental Education, Midlife Hypertension, and Disparities in Late-Life Cognitive Test Scores: Application of an Equity-Focused Causal Decomposition Approach

BACKGROUND

Parental education is an important determinant of late-life cognition, but the extent to which intervening on midlife risk factors, such as hypertension, mitigates the impact of early-life factors is unclear. Novel methodological approaches, such as causal decomposition, facilitate the assessment of contributors to health inequities through hypothetical interventions on mediating risk factors.

METHODS

Using harmonized cohorts (Kaiser Healthy Aging and Diverse Life Experiences Study; Study of Healthy Aging in African Americans) and a ratio of mediator probability weights decomposition approach, we quantified disparities in late-life cognitive test scores (semantic memory, executive function, and verbal memory z-scores) across high versus low parental education, and evaluated whether socioeconomic disparities in late-life cognitive test scores would change if the corresponding disparity in midlife hypertension were eliminated.

RESULTS

We observed substantial disparities across levels of parental education in late-life cognitive test scores (eg, =-0.72 95% CI: -0.84 to -0.60 for semantic memory). Hypothetical intervention on midlife hypertension did not substantially reduce disparities in any cognitive domain. Patterns were similar when stratified by race.

CONCLUSIONS

Future work should evaluate other points of intervention across the lifecourse (eg, participant education) to reduce late-life cognitive disparities across levels of parental education.

Factors Associated with Cognitive Impairment among Adults of 55 Years and Older in Cameroon

Introduction

Cognitive impairment is a major cause of dependency in older people. The aim of this study was to identify factors associated with severe cognitive decline, as assessed by the mini-mental state examination (MMSE), in community-dwelling adults aged 55+ in Cameroon.

Method

Data are from a cross-sectional survey carried out in Cameroon. The cognitive status was assessed using the MMSE and a score of 18/30 or lower is considered as a proxy of severe cognitive decline.

Result

A total of 403 adults participated in the study. Of these, 16 (3.9%) had an MMSE score <18 and were considered to have cognitive impairment. The rate of severe cognitive decline increased with rising age, from 2.1% in those aged 55-64 years, to 3.3% in those aged 65-74, and 11% in those aged 75 and older. The factors associated with cognitive impairment (MMSE score <18) by multivariate analysis in our population are level of education (OR 0.10 [95% CI: 0.02-0.37], p < 0.01), body mass index (BMI) (OR 0.88 [95% CI: 0.78-0.99], p = 0.03), and IADL score (OR 0.12 [95% CI: 0.03-0.38], p < 0.001).

Conclusion

The three main factors associated with cognitive impairment were education, IADL (Instrumental Activity of Daily Living) dependency, and BMI. This study shows that among older people in sub-Saharan Africa, the effect of BMI, IADL dependency, and education on cognitive function appears similar to that observed in middle- and high-income countries.

Brain health equity and the influence of social determinants across the life cycle

Social determinants of health are social, economic and environmental factors known to influence health and development of infants, children and adults. Advancing equity in brain health relies upon interdisciplinary collaboration and recognition of the impact of social determinants on brain health through the lifespan and across generations. Critical periods of fetal, infant and early childhood development encompass intrinsic genetic and extrinsic environmental influences with complex gene-environment interactions. This review discusses the influence of social determinants on the continuum of brain health from preconception and pregnancy health, through fetal, infant and childhood neurodevelopment into adulthood. Opportunities for intervention to address the social determinants of brain health across the life cycle are highlighted.

Association of psychosocial state with subsequent risk of dementia: a prospective cohort study based on the UK Biobank

BACKGROUND

Multiple psychosocial factors have been associated with dementia, while the individual or joint effects of various psychosocial states on dementia remain unrevealed due to the complex interplay between those factors. Here, the authors examined the associations of psychosocial factors and patterns with subsequent risk of dementia, and if the associations could be modified by genetic susceptibility to dementia.

METHODS

UK Biobank dementia-free participants were followed from one year after recruitment (median date: 24 January, 2010) until 31 October, 2022. Psychosocial states were measured by 22 items related to five dimensions, including psychiatric history, recent stressful life events, current psychiatric symptoms, social contact, and individual socioeconomic state. We identified clusters of individuals with distinct psychosocial patterns using latent class analysis. Cox proportional hazards models were used to evaluate the association between psychosocial items, as well as psychosocial patterns, and risk of dementia. We further performed stratification analyses by apolipoprotein E (APOE) genotype, polygenic risk score (PRS) of dementia, and family history of dementia.

RESULTS

Of 497,787 included participants, 54.54% were female. During a median follow-up of 12.70 years, we identified 9,858 (1.98%) patients with newly diagnosed dementia. We identified seven clusters with distinct psychosocial patterns. Compared to individuals with a pattern of 'good state', individuals with other unfavorable patterns, featured by varying degrees of poor psychological state ('fair state' and 'mildly, moderately, and extremely poor psychological state'), low social contact or socioeconomic state ('living alone' and 'short education years'), were all at an increased risk of dementia (hazard ratios [HR] between 1.29 and 2.63). The observed associations showed no significant differences across individuals with varying APOE genotypes, levels of PRS, and family histories of dementia.

CONCLUSION

Unfavorable psychosocial patterns are associated with an increased risk of dementia, independent of genetic susceptibility. The findings highlight the importance of surveillance and prevention of cognitive decline among individuals with suboptimal psychosocial state.

The effect of diabetes in the multifaceted relationship between education and cognitive function

BACKGROUND

Education has been shown to be positively associated with cognitive performance. However, the pathways via lifestyle-related disease through which education is related to cognitive performance have not been sufficiently explored. Diabetes is an important lifestyle-related disease with increasing prevalence worldwide. Low education is associated with an increased risk of developing diabetes, while diabetes may also lead to a deterioration in cognitive performance. This study aims to explore if the associations between education and cognitive function is mediated by the diabetes status among older adults.

METHODS

The data utilized in this study were derived from the first two waves of the Dutch Lifelines Cohort Study (2006-2015). The analyzed sample included 26,131 individuals aged 50 years or above at baseline. The baseline assessment included measurements of educational attainment (exposure) and the potential mediator diabetes. The outcome of cognitive function was assessed using age-standardized reaction times from the psychomotor function and attention tasks, as measured by the Cogstate Brief Battery. The Cogstate Brief Battery was only conducted at the follow-up assessment, not at the baseline assessment. Faster reaction times correspond to higher cognitive performance. The study employed linear and logistic regression models, in addition to a causal mediation approach which estimated the average causal mediation effect (ACME).

RESULTS

Higher education was associated with a lower risk of diabetes (b= -0.1976, 95%CI= -0.3354; -0.0597) compared to low or middle education as well as with faster reaction times (b= -0.2023, 95%CI= -0.2246; -0.1798), implying better cognitive function. Diabetes was associated with slower reaction times (b = 0.0617, 95%CI = 0.0162; 0.1072). Most importantly, the mediation approach identified a significant indirect effect of education on cognitive function via the diabetes status (ACME= -0.00061, 95%CI= -0.00142; -0.00011).

DISCUSSION

The findings emphasize the potentially importance of diabetes in explaining the role of education in promoting healthy cognitive function and mitigating the risk of cognitive decline. Early detection and treatment of diabetes may be particularly beneficial for individuals with low or middle levels of education in order to maintain good levels of cognitive function.

Plasma IL-6 levels and their association with brain health and dementia risk: A population-based cohort study

BACKGROUND

Recent studies have associated immune abnormalities with dementia. IL-6 is a crucial cytokine in inflammatory responses, and recent evidence has linked elevated IL-6 levels to changes in brain structure and cognitive decline. However, the connection between IL-6 levels, cognition, brain volumes, and dementia risk requires exploration in large prospective cohorts.

METHODS

This study utilized a longitudinal cohort from the UK Biobank to analyze the correlation between IL-6 expression levels, cognitive performance, and cortical and subcortical brain volumes through linear regression. Additionally, we assessed the association between IL-6 levels and long-term dementia risk using Cox regression analysis. We also used one-sample Mendelian randomization to analyze the impact of genetic predisposition of dementia on elevated IL-6 levels.

RESULTS

A total of 50,864 participants were included in this study, with 1,391 new cases of all-cause dementia identified. Higher plasma IL-6 levels are associated with cortical and subcortical atrophy in regions such as the fusiform, thalamus proper, hippocampus, and larger ventricle volumes. IL-6 levels are negatively associated with cognitive performance in pair matching, numeric memory, prospective memory, and reaction time tests. Furthermore, elevated IL-6 levels are linked to a 23-35 % increased risk of all-cause dementia over an average follow-up period of 13.2 years. The one-sample Mendelian randomization analysis did not show associations between the genetic predisposition of dementia and elevated IL-6 levels.

CONCLUSIONS

Increased IL-6 levels are associated with worse cognition, brain atrophy, and a heightened risk of all-cause dementia. Our study highlights the need to focus on the role of peripheral IL-6 levels in managing brain health and dementia risk.

Gendered differences in the prevalence and associated factors of dementia in Ghana: a cross-sectional survey

BACKGROUND

Dementia as a global phenomenon has received significant attention in research due to the adverse effects it has on the daily functioning of its victims. Despite studies conducted in relation to the prevalence and associated factors of dementia in Ghana, not much attention has been paid to the influence of gender. The study, therefore, focused on estimating gender differences in the prevalence and associated factors of dementia in the Ashanti Region of Ghana.

METHODS

This study adopted a cross-sectional design with surveys to recruit 800 participants who were 45 years or older. The data was obtained using the standardized Rowland Universal Dementia Assessment Scale (RUDAS) together with information on the various associated factors. A series of logistic models comprising of the total sample model, male sample model, and female sample model were estimated to analyse the data. All data analyses were completed in Stata version 14.

RESULTS

The overall prevalence of dementia was 23.38% [95% CI:20.44, 26.31]. More females 24.56% [95% CI:20.81, 28.31] compared to males 21.31% [95% CI:16.57, 26.04] were at risk of dementia. Younger age, attaining formal education, and belonging to richer households were negatively associated with the risk of dementia. In the total sample model, younger age and attaining formal education were negatively associated with dementia risk. In the male-female stratified models, education and household wealth index were negatively associated with dementia risk in the male sample while age and education were negatively related to dementia risk in the female sample.

CONCLUSION

The study concludes that there are gendered differences in the prevalence and factors associated with the risk of dementia in Ghana. As such, interventions and programmes to identify dementia cases must be gender sensitive. Specifically, when addressing dementia risk in males, interventions should be directed towards those with lower wealth status. Likewise, when developing programmes to mitigate dementia risk in women, particular attention should be given to women in the oldest age category.

Role of cardiovascular health factors in mediating social inequalities in the incidence of dementia in the UK: two prospective, population-based cohort studies

Background

The contribution of modifiable risk factors to social inequalities in dementia, observed in longitudinal studies, remains unclear. We aimed to quantify the role of cardiovascular health factors, assessed using Life's Essential 8 (LE8) score, in mediating social inequalities in incidence of dementia and, for comparison, in incidence of stroke, coronary heart disease, and mortality.

Methods

In this prospective, population-based cohort study, we collected data from the UK Whitehall II Study and UK Biobank databases. Participants were included if data were available on SEP, outcomes and LE8 (smoking, physical activity, diet, body mass index, blood pressure, fasting blood glucose, lipid levels, sleep duration). The primary outcome was incident dementia and secondary outcomes were stroke, coronary heart disease, and mortality. Outcomes were derived from electronic healthcare records. Socioeconomic position (SEP) was measured by occupation in Whitehall II and education in UK Biobank. Counterfactual mediation analysis was used to quantify the extent to which LE8 score explained the associations of SEP with all outcomes. Analyses involved Cox regression, accelerated failure time models, and linear regression; and were adjusted for age, sex, and ethnicity.

Findings

Between 10.09.1985 and 29.03.1988, a total of 9688 participants (mean age ± SD 44.9 ± 6.0; 67% men) from the Whitehall II study, and between 19.12.2006 and 01.10.2010, 278,215 participants (mean age ± SD 56.0 ± 8.1; 47% men) from the UK Biobank were included. There were 606 and 4649 incident dementia cases over a median (interquartile range) follow-up of 31.7 (31.1-32.7) and 13.5 (12.7-14.1) years respectively in Whitehall II and UK Biobank. In Whitehall II, the hazard ratio was 1.85 [95% CI 1.42, 2.32] for the total effect of SEP on dementia and 1.20 [1.12, 1.28] for the indirect effect via the LE8, the proportion mediated being 36%. In UK Biobank, the total effect of SEP on dementia was 1.65 [1.54, 1.78]; the indirect effect was 1.11 [1.09, 1.12], and the proportion mediated was 24%. The proportions mediated for stroke, coronary heart disease, and mortality were higher, ranging between 34% and 63% in Whitehall II and between 36% and 50% in UK Biobank.

Interpretation

In two well-characterised cohort studies, up to one third of the social inequalities in incidence of dementia was attributable to cardiovascular health factors. Promotion of cardiovascular health in midlife may contribute to reducing social inequalities in risk of dementia, in addition to cardiovascular diseases and all-cause mortality. This study used adult measures of SEP, further research is warranted using lifecourse measures of SEP.

Funding

NIH (RF1AG062553).

Association of socioeconomic status and poststroke cognitive function: A systematic review and meta-analysis

BACKGROUND

Stroke survivors are at high risk of coping with cognitive problems after stroke. In recent decades, the relationship between socioeconomic status (SES) and health-related outcomes has been a topic of considerable interest. Learning more about the potential impact of SES on poststroke cognitive dysfunction is of great importance.

OBJECTIVE

The purpose of this systematic review and meta-analysis was to summarize the association between SES and poststroke cognitive function by quantifying the effect sizes of the existing studies.

METHOD

We searched studies from PubMed, Ovid, Embase, Cochrane, Scopus, and PsychINFO up to January 30th 2024 and the references of relevant reviews. Studies reporting the risk of poststroke cognitive dysfunction as assessed by categorized SES indicators were included. The Newcastle-Ottawa scale and the Agency for Healthcare Research and Quality were used to evaluate the study quality. Meta-analyses using fixed-effect models or random-effect models based on study heterogeneity were performed to estimate the influence of SES on cognitive function after stroke, followed by subgroup analyses stratified by study characteristics.

RESULTS

Thirty-four studies were eligible for this systematic review and meta-analysis. Of which, 19 studies reported poststroke cognitive impairment (PSCI) as the outcome, 13 reported poststroke dementia (PSD), one reported both PSCI and PSD, and one reported vascular cognitive impairment no dementia. The findings showed that individuals with lower SES levels had a higher risk of combined poststroke cognitive dysfunction (odds ratio (OR) = 1.91, 95% confidence interval (CI) = 1.59-2.29), PSCI (OR = 2.09, 95% CI = 1.57-2.78), and PSD (OR = 1.95, 95% CI = 1.48-2.57). Subgroup analyses stratified by SES indicators demonstrated the protective effects of education and occupation against the diagnoses of combined poststroke cognitive dysfunction, PSCI, and PSD.

CONCLUSIONS

Stroke survivors belonging to a low SES are at high risk of poststroke cognitive dysfunction. Our findings add evidence for public health strategies to reduce the risk of poststroke cognitive dysfunction by reducing SES inequalities.