Methods to Address Self-Selection and Reverse Causation in Studies of Neighborhood Environments and Brain Health

Patterns of Factors in the National Institute on Aging Health Disparities Research Framework Domains and Mild Cognitive Impairment Risk

Introduction

Alzheimer's disease and related dementias are public health and social care challenges. This study used the National Institute on Aging Health Disparities Research Framework to organize potential cognitive impairment risk factors. It aimed to examine patterns of environmental, sociocultural, behavioral, and biological factors and identify key components that predict mild cognitive impairment risk.

Methods

This study comprised 2,812 participants from the Mayo Clinic Study of Aging who were cognitively unimpaired at baseline (aged ≥50 years, mean age [SD]=68.9 [9.7] years, 50.4% female). Analyses utilized a 2-stage approach using factor and principal component analyses to group factors from multiple National Institute on Aging Health Disparities Research Framework domains and identify components that predict cognitive impairment risk. Using a cohort study design, the resulting composite scores were considered as covariates for incident mild cognitive impairment analysis using Cox proportional hazards models.

Results

Three principal components explained 40.30% of the variance and were differentially associated with mild cognitive impairment risk. One component (Principal Component 2), which included factors from all 4 domains of the National Institute on Aging Health Disparities Research Framework (including social, group, and playing game activities [sociocultural domain]; exercise and physical activity [behavioral domain]; education/occupation [environmental domain]; and absence of cardiometabolic risk factors/health self-rating [biological domain]), was associated with lower mild cognitive impairment risk (hazard ratio=0.80, 95% CI=0.73, 0.89). The other 2 principal components, also including factors from multiple framework domains, were associated with increased mild cognitive impairment risk.

Conclusions

Derived principal components included factors from multiple framework domains, supporting the multietiology pathways leading to cognitive impairment. These principal components were differentially associated with mild cognitive impairment risk. Identifying key factors from multiple National Institute on Aging Health Disparities Research Framework domains associated with cognitive impairment risk has implications for effectively targeting interventions at multiple levels (e.g., medical, societal, policy) to avert or delay cognitive impairment risk.

Life-course neighbourhood deprivation and brain structure in older adults: the Lothian Birth Cohort 1936

Neighbourhood disadvantage may be associated with brain health but the importance of exposure at different stages of the life course is poorly understood. Utilising the Lothian Birth Cohort 1936, we explored the relationship between residential neighbourhood deprivation from birth to late adulthood, and global and local neuroimaging measures at age 73. A total of 689 participants had at least one valid brain measures (53% male); to maximise the sample size structural equation models with full information maximum likelihood were conducted. Residing in disadvantaged neighbourhoods in mid- to late adulthood was associated with smaller total brain (β = -0.06; SE = 0.02; sample size[N] = 658; number of pairwise complete observations[n]=390), grey matter (β = -0.11; SE = 0.03; N = 658; n = 390), and normal-appearing white matter volumes (β = -0.07; SE = 0.03; N = 658; n = 390), thinner cortex (β = -0.14; SE = 0.06; N = 636; n = 379), and lower general white matter fractional anisotropy (β = -0.19; SE = 0.06; N = 665; n = 388). We also found some evidence on the accumulating impact of neighbourhood deprivation from birth to late adulthood on age 73 total brain (β = -0.06; SE = 0.02; N = 658; n = 276) and grey matter volumes (β = -0.10; SE = 0.04; N = 658; n = 276). Local analysis identified affected focal cortical areas and specific white matter tracts. Among individuals belonging to lower social classes, the brain-neighbourhood associations were particularly strong, with the impact of neighbourhood deprivation on total brain and grey matter volumes, and general white matter fractional anisotropy accumulating across the life course. Our findings suggest that living in deprived neighbourhoods across the life course, but especially in mid- to late adulthood, is associated with adverse brain morphologies, with lower social class amplifying the vulnerability.

Applying Bradford Hill to assessing causality in systematic reviews: A transparent approach using process tracing

BACKGROUND

Bradford Hill (BH) viewpoints are widely used to assess causality in systematic reviews, but their application has often lacked reproducibility. We describe an approach for assessing causality within systematic reviews ('causal' reviews), illustrating its application to the topic of income inequality and health. Our approach draws on principles of process tracing, a method used for case study research, to harness BH viewpoints to judge evidence for causal claims.

METHODS

In process tracing, a hypothesis may be confirmed by observing highly unique evidence and disconfirmed by observing highly definitive evidence. We drew on these principles to consider the value of finding supportive or contradictory evidence for each BH viewpoint characterised by its uniqueness and definitiveness.

RESULTS

In our exemplar systematic review, we hypothesised that income inequality adversely affects self-rated health and all-cause mortality. BH viewpoints 'analogy' and 'coherence' were excluded from the causal assessment because of their low uniqueness and low definitiveness. The 'experiment' viewpoint was considered highly unique and highly definitive, and thus could be particularly valuable. We propose five steps for using BH viewpoints in a 'causal' review: (1) define the hypothesis; (2) characterise each viewpoint; (3) specify the evidence expected for each BH viewpoint for a true or untrue hypothesis; (4) gather evidence for each viewpoint (e.g., systematic review meta-analyses, critical appraisal, background knowledge); (5) consider if each viewpoint was met (supportive evidence) or unmet (contradictory evidence).

CONCLUSIONS

Incorporating process tracing has the potential to provide transparency and structure when using BH viewpoints in 'causal' reviews.

Association between brain resting-state functional activities and migraine: a bidirectional mendelian randomization study

Researchers have conducted extensive research on the correlation between brain resting-state functional activities (RSFA) and migraine. However, we still do not fully understand the exact nature of the causal relationship between these RSFA and migraine. We conducted a bidirectional two-sample Mendelian randomization (MR) study to investigate the causal association between migraine and RSFA. We gathered summary statistics from genome-wide association studies for 191 resting-state functional magnetic resonance imaging phenotypes. We employed various analytical methods for bidirectional two-sample MR analyses. This included inverse variance weighted, weighted median, MR Egger, and the constrained maximum likelihood approaches. We also conducted pleiotropy and heterogeneity analyses to evaluate the robustness and reliability. We found the functional connectivity between the default mode and the central executive network (OR = 1.39, p = 4.77 × 10-4, FDR corrected p value = 0.040) and the intensity of spontaneous brain activity in the calcarine or lingual gyrus within the visual network (OR = 0.74, p = 5.94 × 10-4, FDR corrected p value = 0.040) having a causal effect on the risk of migraine. Our MR analysis provided genetic support for these networks, which may play an important role in influencing migraine susceptibility.

Prolonged moderate to vigorous physical activity may lead to a decline in cognitive performance: a Mendelian randomization study

Objective

This study investigates the causal relationship between moderate to vigorous physical activity and cognitive performance.

Methods

Genetic loci strongly related to moderate to vigorous physical activity from genome-wide association studies were used as instrumental variables. These were combined with genetic data on cognitive performance from different Genome-Wide Association Study (GWAS) to conduct a two-sample Mendelian randomization analysis. The primary analysis used inverse variance weighting within a random effects model, supplemented by weighted median estimation, MR-Egger regression and other methods, with results expressed as Beta coefficient.

Results

This study selected 19 SNPs closely related to physical activity as instrumental variables. The multiplicative random-effects Inverse-Variance Weighted (IVW) analysis revealed that moderate to vigorous physical activity was negatively associated with cognitive performance (Beta = -0.551; OR = 0.58; 95% CI: 0.46-0.72; p < 0.001). Consistent results were obtained using the fixed effects IVW model (Beta = -0.551; OR = 0.58; 95% CI: 0.52-0.63; p < 0.001), weighted median (Beta = -0.424; OR = 0.65; 95% CI: 0.55-0.78; p < 0.001), simple mode (Beta = -0.467; OR = 0.63; 95% CI: 0.44-0.90; p < 0.001), and weighted mode (Beta = -0.504; OR = 0.60; 95% CI: 0.44-0.83; p < 0.001). After adjusting for BMI, smoking, sleep duration, and alcohol intake frequency, the multivariate MR analysis also showed a significant association between genetically predicted MVPA and cognitive performance, with Beta of -0.599 and OR = 0.55 (95% CI: 0.44-0.69; p < 0.001).

Conclusion

The findings of this study indicate that genetically predicted moderate to vigorous physical activity may be associated with a decline in cognitive performance.

Neighbourhood environments and cognitive health in the longitudinal Personality and Total Health (PATH) through life study: A 12-year follow-up of older Australians

BACKGROUND

Urban neighbourhood environments may impact older adults' cognitive health. However, longitudinal studies examining key environmental correlates of cognitive health are lacking. We estimated cross-sectional and longitudinal associations of neighbourhood built and natural environments and ambient air pollution with multiple cognitive health outcomes in Australian urban dwellers aged 60+ years.

METHODS

The study included 1160 participants of the PATH Through Life study (60+ cohort) who were followed up for 12 years (four assessments; 2001/02 to 2013/15) and with data on socio-demographics, health, cognitive functions and diagnoses, and full residential address. Neighbourhood environmental features encompassed population and street-intersection densities, non-commercial land use mix, transit points, presence of blue space, percentages of commercial land, parkland and tree cover, and annual average PM2.5 and NO2 concentrations. All exposures except for tree cover were assessed at two time points. Generalised additive mixed models estimated associations of person-level average, and within-person changes in, exposures with cognitive functions. Multi-state hidden Markov models estimated the associations of neighbourhood attributes with transitions to/from mild cognitive impairment (MCI).

RESULTS

Dense, destination-rich neighbourhoods were associated with a lower likelihood of transition to MCI and reversal to no MCI. Positive cross-sectional and longitudinal associations of non-commercial land use mix, street intersection density and percentage of commercial land were observed especially with global cognition and processing speed. While access to parkland and blue spaces were associated with a lower risk of transition to MCI, the findings related to cognitive functions were mixed and supportive of an effect of parkland on verbal memory only. Higher levels of PM2.5 and NO2 were consistently associated with steeper declines and/or decreases in cognitive functions and worse cognitive states across time.

CONCLUSION

To support cognitive health in ageing populations, neighbourhoods need to provide an optimal mix of environmental complexity, destinations and access to the natural environment and, at the same time, minimise ambient air pollution.

Midlife Residential Greenness and Late-Life Cognitive Decline among Nurses' Health Study Participants

BACKGROUND

Midlife residential exposure to greenspace may slow cognitive decline by increasing opportunities for physical activity and social connection, restoring attention, or reducing stress or adverse environmental exposures. However, prospective studies on the association between greenness and cognitive decline are sparse.

OBJECTIVE

We investigated the prospective association between greenness at midlife and cognitive decline later in life. We explored effect measure modification by apolipoprotein E (APOE)-ɛ4 carrier status, neighborhood socioeconomic status (NSES), and rural/urban regions.

METHODS

The Nurses' Health Study (N = 121,700 ) started in 1976 with married female nurses, 30-55 years of age, located across 11 US states. We examined 16,962 nurses who were enrolled in a substudy starting in 1995-2001 (mean age = 74 y ) through 2008. We assessed average summer residential greenness in a 270 -m buffer using Landsat Normalized Difference Vegetation Index data from 1986-1994. Starting in 1995-2001, participants underwent up to four repeated measures of five cognitive tests. A global composite score was calculated as the average of all z -scores for each task to evaluate overall cognition. We used linear mixed models to evaluate the association of average greenness exposure at midlife with cognitive decline in later life, adjusted for age, education, NSES, and depression.

RESULTS

In adjusted models, higher midlife greenness exposure [per interquartile range (IQR): 0.18] was associated with a 0.004-unit (95% CI: 0.001, 0.006) slower annual rate of cognitive decline. For comparison, we found that 1 year of age is related to a - 0.006 mean annual difference for global cognition in the full sample; thus, higher midlife greenness appeared equivalent to slowing cognitive decline by ∼ 8 months. In analysis exploring gene-environment interactions, we found that among APOE-ɛ4 carriers, an IQR increase in greenness was associated with a rate of decline that was slower by 0.01 units of global composite score (95% CI: 0.0004, 0.02). This association was attenuated among APOE-ɛ4 noncarriers. We did not observe associations between greenness and baseline or annual rate of cognitive decline of verbal memory.

DISCUSSION

Higher midlife greenness exposure is associated with slower cognitive decline later in life. Future research is necessary to confirm these findings. https://doi.org/10.1289/EHP13588.

Linking sequences of exposure to residential (dis)advantage, individual socioeconomic status, and health

Life course theories suggest that the relationship between residential (dis)advantage and health is best understood by examining the ordering and duration of cumulative exposures across the life course. This study employs sequence and cluster analysis on two decades of residential histories linked to the Survey of the Health of Wisconsin to define typologies of exposure to residential (dis)advantage and use these typologies to predict self-rated fair/poor health. Exposure to residential (dis)advantage is mostly stable across the adult life course and greater disadvantage predicts fair/poor health. Longitudinal exposures to residential (dis)advantage shape health independently of and in tandem with individual-level resources.

The Dynamics of Cardiovascular Risk-An Analysis of the Prospective Urban Rural Epidemiology (PURE) Poland Cohort Study

Background: The purpose of this study was to analyze the major cardiovascular risk (CVR) factors and their trends in the study population. Methods: The results of subjects in the Polish Prospective Urban and Rural Epidemiological Study (PURE) study group were interpreted. CVR was calculated for each participant according to the Systematic Coronary Risk Evaluation (SCORE2) scale or the Systematic Coronary Risk Evaluation-Older Persons (SCORE2-OP) scale. Data from the beginning of the analysis (2013) and nine years later (2022) were included. In addition, the use of lipid-lowering therapy (LLT) and meeting the low-density lipoprotein cholesterol (LDL-c) target criterion at the beginning and end of the study were analyzed. Results: Patients in the high and very high CVR groups who had abnormal LDL-c results accounted for 64% and 91% of their group in 2013 and 70% and 92% in 2022, respectively. Conclusions: Regardless of age, patients using LLT at the start of the analysis had a greater increase in future CVR, especially if they had lipid abnormalities at the start of the study. This may be due to reverse causality and multimorbidity in these patients, highlighting the importance of appropriate treatment of lipid abnormalities.

Genetic evidence for the causal relationships between migraine, dementia, and longitudinal brain atrophy

BACKGROUND

Migraine is a neurological disease with a significant genetic component and is characterized by recurrent and prolonged episodes of headache. Previous epidemiological studies have reported a higher risk of dementia in migraine patients. Neuroimaging studies have also shown structural brain atrophy in regions that are common to migraine and dementia. However, these studies are observational and cannot establish causality. The present study aims to explore the genetic causal relationship between migraine and dementia, as well as the mediation roles of brain structural changes in this association using Mendelian randomization (MR).

METHODS

We collected the genome-wide association study (GWAS) summary statistics of migraine and its two subtypes, as well as four common types of dementia, including Alzheimer's disease (AD), vascular dementia, frontotemporal dementia, and Lewy body dementia. In addition, we collected the GWAS summary statistics of seven longitudinal brain measures that characterize brain structural alterations with age. Using these GWAS, we performed Two-sample MR analyses to investigate the causal effects of migraine and its two subtypes on dementia and brain structural changes. To explore the possible mediation of brain structural changes between migraine and dementia, we conducted a two-step MR mediation analysis.

RESULTS

The MR analysis demonstrated a significant association between genetically predicted migraine and an increased risk of AD (OR = 1.097, 95% CI = [1.040, 1.158], p = 7.03 × 10- 4). Moreover, migraine significantly accelerated annual atrophy of the total cortical surface area (-65.588 cm2 per year, 95% CI = [-103.112, -28.064], p = 6.13 × 10- 4) and thalamic volume (-9.507 cm3 per year, 95% CI = [-15.512, -3.502], p = 1.91 × 10- 3). The migraine without aura (MO) subtype increased the risk of AD (OR = 1.091, 95% CI = [1.059, 1.123], p = 6.95 × 10- 9) and accelerated annual atrophy of the total cortical surface area (-31.401 cm2 per year, 95% CI = [-43.990, -18.811], p = 1.02 × 10- 6). The two-step MR mediation analysis revealed that thalamic atrophy partly mediated the causal effect of migraine on AD, accounting for 28.2% of the total effect.

DISCUSSION

This comprehensive MR study provided genetic evidence for the causal effect of migraine on AD and identified longitudinal thalamic atrophy as a potential mediator in this association. These findings may inform brain intervention targets to prevent AD risk in migraine patients.

The associations of serum vitamin D status and vitamin D supplements use with all-cause dementia, Alzheimer's disease, and vascular dementia: a UK Biobank based prospective cohort study

BACKGROUND

Prior studies on vitamin D and dementia outcomes yielded mixed results and had several important limitations.

OBJECTIVES

We aimed to assess the associations of both serum vitamin D status and supplementation with all-cause dementia, Alzheimer's disease (AD), and vascular dementia (VD) incidence.

METHODS

With a prospective cohort study design, we comprehensively assessed the associations of vitamin D and multivitamin supplementation, as well as vitamin D deficiency {25-hydroxyvitamin D [25(OH)D] <30 nmol/L}, and insufficiency [25(OH)D 30 to <50 nmol/L], with the 14-year incidence of all-cause dementia, AD, and VD in 269,229 participants, aged 55 to 69, from the UK Biobank.

RESULTS

Although 5.0% reported regular vitamin D use and 19.8% reported multivitamin use, the majority of participants exhibited either vitamin D deficiency (18.3%) or insufficiency (34.0%). However, vitamin D deficiency was less prevalent among users of vitamin D (6.9%) or multivitamin preparations (9.5%) than among nonusers (21.5%). Adjusted Cox regression models demonstrated 19% to 25% increased risk of all 3 dementia outcomes for those with vitamin D deficiency [hazard ratio (HR) 95% confidence interval (CI)]: 1.25 (1.16, 1.34) for all-cause dementia; 1.19 (1.07-1.31) for AD; 1.24 (1.08-1.43) for VD] and 10% to 15% increased risk of those with vitamin D insufficiency [HR (95% CI): 1.11 (1.05, 1.18) for all-cause dementia; 1.10 (1.02-1.19) for AD; 1.15 (1.03-1.29) for VD]. Regular users of vitamin D and multivitamins had 17% and 14% lower risk of AD [HR (95% CI): 0.83 (0.71, 0.98)] and VD [HR (95% CI): 0.86 (0.75, 0.98)] incidence, respectively.

CONCLUSIONS

Although our findings indicate the potential benefits of vitamin D supplementation for dementia prevention, randomized controlled trials are essential for definitive evidence.

Brain Health and Cognition in Older Adults: Roadmap and Milestones towards the Implementation of Preventive Strategies

In this narrative review, we delve into the evolving concept of brain health, as recognized by the WHO, focusing on its intersection with cognitive decline. We emphasize the imperative need for preventive strategies, particularly in older adults. We describe the target population that might benefit the most from risk-based approaches-namely, people with subjective cognitive decline. Additionally, we consider universal prevention in cognitively unimpaired middle-aged and older adults. Delving into multidomain personalized preventive strategies, we report on empirical evidence surrounding modifiable risk factors and interventions crucial in mitigating cognitive decline. Next, we highlight the emergence of brain health services (BHS). We explain their proposed role in risk assessment, risk communication, and tailored interventions to reduce the risk of dementia. Commenting on ongoing BHS pilot experiences, we present the inception and framework of our own BHS in Monza, Italy, outlining its operational structure and care pathways. We emphasize the need for global collaboration and intensified research efforts to address the intricate determinants of brain health and their potential impact on healthcare systems worldwide.

Artificial intelligence for dementia prevention

INTRODUCTION

A wide range of modifiable risk factors for dementia have been identified. Considerable debate remains about these risk factors, possible interactions between them or with genetic risk, and causality, and how they can help in clinical trial recruitment and drug development. Artificial intelligence (AI) and machine learning (ML) may refine understanding.

METHODS

ML approaches are being developed in dementia prevention. We discuss exemplar uses and evaluate the current applications and limitations in the dementia prevention field.

RESULTS

Risk-profiling tools may help identify high-risk populations for clinical trials; however, their performance needs improvement. New risk-profiling and trial-recruitment tools underpinned by ML models may be effective in reducing costs and improving future trials. ML can inform drug-repurposing efforts and prioritization of disease-modifying therapeutics.

DISCUSSION

ML is not yet widely used but has considerable potential to enhance precision in dementia prevention.

HIGHLIGHTS

Artificial intelligence (AI) is not widely used in the dementia prevention field. Risk-profiling tools are not used in clinical practice. Causal insights are needed to understand risk factors over the lifespan. AI will help personalize risk-management tools for dementia prevention. AI could target specific patient groups that will benefit most for clinical trials.

Modifications of 24-h movement behaviors to prevent obesity in retirement: a natural experiment using compositional data analysis

BACKGROUND

Retirement often leads to a more passive lifestyle and may therefore lead to weight gain. This study aims to investigate longitudinal associations between changes in 24-h movement behaviors and BMI and waist circumference in relation to the transition from work to retirement.

METHODS

The study population included 213 retiring public sector workers (mean age 63.5 years, standard deviation 1.1) from the Finnish Retirement and Aging study. Before and after retirement participants wore an Axivity accelerometer on their thigh and filled in a daily log for at least four days to measure daily time spent sleeping, in sedentary behavior (SED), light physical activity (LPA) and moderate-to-vigorous physical activity (MVPA). Also, their body mass index (BMI) and waist circumference were measured repeatedly. Compositional linear regression analysis and isotemporal substitution analysis were used to study associations between one-year changes in 24-h movement behaviors and concurrent changes in BMI and waist circumference.

RESULTS

An increase in MVPA in relation to sleep, SED and LPA was associated with a decreasing BMI (β = -0.60, p = 0.04) and waist circumference (β = -2.14, p = 0.05) over one year from before retirement to after retirement. In contrast, increasing sleep in relation to SED, LPA and MVPA was associated with an increasing BMI (β = 1.34, p = 0.02). Reallocating 60 min from MVPA to SED or sleep was estimated to increase BMI by on average 0.8-0.9 kg/m2 and waist circumference by 3.0 cm during one year.

CONCLUSIONS

During the transition from work to retirement, increasing MVPA was associated with a slight decrease in BMI and waist circumference, whereas increasing sleep was associated with an increasing BMI. Common life transitions, like retirement, should be considered when giving recommendations and guidance for physical activity and sleep.

Neighborhood Characteristics and Elevated Blood Pressure in Older Adults

Importance

The local environment remains an understudied contributor to elevated blood pressure among older adults. Untargeted approaches can identify neighborhood conditions interrelated with racial segregation that drive hypertension disparities.

Objective

To evaluate independent associations of sociodemographic, economic, and housing neighborhood factors with elevated blood pressure.

Design, Setting, and Participants

In this cohort study, the sample included Health and Retirement Study participants who had between 1 and 3 sets of biennial sphygmomanometer readings from 2006 to 2014 or 2008 to 2016. Statistical analyses were conducted from February 5 to November 30, 2021.

Exposures

Fifty-one standardized American Community Survey census tract variables (2005-2009).

Main Outcomes and Measures

Elevated sphygmomanometer readings over the study period (6-year period prevalence): a value of at least 140 mm Hg for systolic blood pressure and/or at least 90 mm Hg for diastolic blood pressure. Participants were divided 50:50 into training and test data sets. Generalized estimating equations were used to summarize multivariable associations between each neighborhood variable and the period prevalence of elevated blood pressure, adjusting for individual-level covariates. Any neighborhood factor associated (Simes-adjusted for multiple comparisons P ≤ .05) with elevated blood pressure in the training data set was rerun in the test data set to gauge model performance. Lastly, in the full cohort, race- and ethnicity-stratified associations were evaluated for each identified neighborhood factor on the likelihood of elevated blood pressure.

Results

Of 12 946 participants, 4565 (35%) had elevated sphygmomanometer readings (median [IQR] age, 68 [63-73] years; 2283 [50%] male; 228 [5%] Hispanic or Latino, 502 [11%] non-Hispanic Black, and 3761 [82%] non-Hispanic White). Between 2006 and 2016, a lower likelihood of elevated blood pressure was observed (relative risk for highest vs lowest tertile, 0.91; 95% CI, 0.86-0.96) among participants residing in a neighborhood with recent (post-1999) in-migration of homeowners. This association was precise among participants with non-Hispanic White and other race and ethnicity (relative risk, 0.91; 95% CI, 0.85-0.97) but not non-Hispanic Black participants (relative risk, 0.97; 95% CI, 0.85-1.11; P = .48 for interaction) or Hispanic or Latino participants (relative risk, 0.84; 95% CI, 0.65-1.09; P = .78 for interaction).

Conclusions and Relevance

In this cohort study of older adults, recent relocation of homeowners to a neighborhood was robustly associated with reduced likelihood of elevated blood pressure among White participants but not their racially and ethnically marginalized counterparts. Our findings indicate that gentrification may influence later-life blood pressure control.

Diversity of Studies on Neighborhood Greenspace and Brain Health by Racialized/Ethnic Group and Geographic Region: A Rapid Review

Studies examining associations between greenspace and Alzheimer's disease and related dementia (ADRD) outcomes are rapidly on the rise, yet no known literature reviews have summarized the racialized/ethnic group and geographic variation of those published studies. This is a significant gap given the known disparities in both greenspace access and ADRD risk between racialized/ethnic groups and between developed versus developing countries. In this rapid literature review, we (1) describe the diversity of published greenspace-brain health studies with respect to racialized/ethnic groups and geographic regions; (2) determine the extent to which published studies have investigated racialized/ethnic group differences in associations; and (3) review methodological issues surrounding studies of racialized/ethnic group disparities in greenspace and brain health associations. Of the 57 papers meeting our inclusion criteria as of 4 March 2022, 21% (n = 12) explicitly identified and included individuals who were Black, Hispanic/Latinx, and/or Asian. Twenty-one percent of studies (n = 12) were conducted in developing countries (e.g., China, Dominican Republic, Mexico), and 7% (n = 4) examined racialized/ethnic group differences in greenspace-brain health associations. None of the studies were framed by health disparities, social/structural determinants of health, or related frameworks, despite the known differences in both greenspace availability/quality and dementia risk by racialized/ethnic group and geography. Studies are needed in developing countries and that directly investigate racialized/ethnic group disparities in greenspace-brain health associations to target and promote health equity.

Life-course neighbourhood deprivation and brain structure in older adults: The Lothian Birth Cohort 1936

Neighbourhood disadvantage may be associated with brain health but the importance at different stages of the life course is poorly understood. Utilizing the Lothian Birth Cohort 1936, we explored the relationship between residential neighbourhood deprivation from birth to late adulthood, and global and regional neuroimaging measures at age 73. We found that residing in disadvantaged neighbourhoods in mid- to late adulthood was associated with smaller total brain (β=-0.06; SE=0.02; n=390) and grey matter volume (β=-0.11; SE=0.03; n=390), thinner cortex (β=-0.15; SE=0.06; n=379), and lower general white matter fractional anisotropy (β=-0.19; SE=0.06; n=388). Regional analysis identified affected focal cortical areas and specific white matter tracts. Among individuals belonging to lower occupational social classes, the brain-neighbourhood associations were stronger, with the impact of neighbourhood deprivation accumulating across the life course. Our findings suggest that living in deprived neighbourhoods is associated with adverse brain morphologies, with occupational social class adding to the vulnerability.

Causal relationships between migraine and microstructural white matter: a Mendelian randomization study

BACKGROUND

Migraine is a disabling neurological disorder with the pathophysiology yet to be understood. The microstructural alteration in brain white matter (WM) has been suggested to be related to migraine in recent studies, but these evidence are observational essentially and cannot infer a causal relationship. The present study aims to reveal the causal relationship between migraine and microstructural WM using genetic data and Mendelian randomization (MR).

METHODS

We collected the Genome-wide association study (GWAS) summary statistics of migraine (48,975 cases / 550,381 controls) and 360 WM imaging-derived phenotypes (IDPs) (31,356 samples) that were used to measure microstructural WM. Based on instrumental variables (IVs) selected from the GWAS summary statistics, we conducted bidirectional two-sample MR analyses to infer bidirectional causal associations between migraine and microstructural WM. In forward MR analysis, we inferred the causal effect of microstructural WM on migraine by reporting the odds ratio (OR) that quantified the risk change of migraine for per 1 standard deviation (SD) increase of IDPs. In reverse MR analysis, we inferred the causal effect of migraine on microstructural WM by reporting the β value that represented SDs of changes in IDPs were caused by migraine.

RESULTS

Three WM IDPs showed significant causal associations (p < 3.29 × 10- 4, Bonferroni correction) with migraine and were proved to be reliable via sensitivity analysis. The mode of anisotropy (MO) of left inferior fronto-occipital fasciculus (OR = 1.76, p = 6.46 × 10- 5) and orientation dispersion index (OD) of right posterior thalamic radiation (OR = 0.78, p = 1.86 × 10- 4) exerted significant causal effects on migraine. Migraine exerted a significant causal effect on the OD of left superior cerebellar peduncle (β = - 0.09, p = 2.78 × 10- 4).

CONCLUSIONS

Our findings provided genetic evidence for the causal relationships between migraine and microstructural WM, bringing new insights into brain structure for the development and experience of migraine.

Neighborhood greenspace and cognition: The cardiovascular health study

OBJECTIVES

We examined whether greenspace measures (overall percent greenspace and forest, and number of greenspace types) were associated with clinically adjudicated dementia status.

METHODS

In a sample of non-demented older adults (n = 2141, average age = 75.3 years) from the Cardiovascular Health and Cognition Study, Cox proportional hazard and logistic regression analyses were used to estimate associations of baseline greenspace with risks of incident dementia and MCI, respectively, while adjusting for demographics, co-morbidities, and other neighborhood factors. We derived quartiles of percent greenness (greenspace), forest (percent tree canopy cover), and tertiles of greenspace diversity (number of greenspace types) for 5-km radial buffers around participant's residences at study entry (1989-1990) from the 1992 National Land Cover Dataset. Dementia status and mild cognitive impairment (MCI) over 10 years was clinically adjudicated.

RESULTS

We observed no significant association between overall percent greenspace and risk of mild cognitive impairment or dementia and mostly null results for forest and greenspace diversity. Forest greenspace was associated with lower odds of MCI (OR quartile 4 versus 1: 0.54, 95% CI: 0.29-0.98) and greenspace diversity was associated with lower hazard of incident dementia (HR tertile 2 versus 1: 0.70, 95% CI = 0.50-0.99).

DISCUSSION

We found divergent results for different types of greenspace and mild cognitive impairment or dementia. Improved greenspace type and diversity measurement could better characterize the association between greenspace and cognition.

Rural residence across the life course and late-life cognitive decline in KHANDLE: A causal inference study

Background

Modifiable risks for dementia are more prevalent in rural populations, yet there is a dearth of research examining life course rural residence on late-life cognitive decline.

Methods

The association of rural residence and socioeconomic status (SES) in childhood and adulthood with late-life cognitive domains (verbal episodic memory, executive function, and semantic memory) and cognitive decline in the Kaiser Healthy Aging and Diverse Life Experiences cohort was estimated using marginal structural models with stabilized inverse probability weights.

Results

After adjusting for time-varying SES, the estimated marginal effect of rural residence in childhood was harmful for both executive function (β = -0.19, 95% confidence interval [CI] = -0.32, -0.06) and verbal episodic memory (β = -0.22, 95% CI = -0.35, -0.08). Effects of adult rural residence were imprecisely estimated with beneficial point estimates for both executive function (β = 0.19; 95% CI = -0.07, 0.44) and verbal episodic memory (β = 0.24, 95% CI = -0.07, 0.55).

Conclusions

Childhood rurality is associated with poorer late-life cognition independent of SES.

Associations between social determinants of health and 10-year change in everyday functioning within Black/African American and White older adults enrolled in ACTIVE

Introduction

Given prior work showing racial differences on baseline social determinants of health (SDoH) and 10-year trajectories of everyday functioning, we examined associations between SDoH and longitudinal everyday functioning performance in Black/African American and White older adults.

Methods

Participants were 2505 older adults (Mage = 73.5; 28% Black/African American) without dementia. SDoH included economic stability/status, education access/quality, health-care access, neighborhood/built environment, and social/community contexts. The Observed Tasks of Daily Living (OTDL) measured everyday functioning and was administered at baseline and 1-, 2-, 3-, 5-, and 10-year visits.

Results

Across the sample, social and community context and economic stability/status were associated with steeper age-related OTDL declines (βs = 0.05 to 0.07, Ps < 0.001). Lower levels of social and community context (β = 0.08, P = 0.002) and economic stability/status (β = 0.07, P = 0.04) were associated with OTDL linear age declines in Black/African American participants, but not in White participants (Ps > 0.30).

Discussion

Inequities across SDoH accelerate age-related declines in everyday functioning among Black/African American older adults.

Longitudinal associations between the neighborhood social, natural, and built environment and mental health: A systematic review with meta-analyses

This review aimed to assess the longitudinal associations between neighborhood social, natural, and built environments, and multiple mental health outcomes (i.e., depression, anxiety, common mental disorder, and pooled mental disorders). Of 6,785 records retrieved, 30 studies fulfilled the inclusion criteria. Meta-analytical results primarily obtained from developed country studies showed that composite neighborhood socioeconomic status was negatively associated with depression (p = 0.007) and pooled mental disorders (p = 0.002), while neighborhood urbanicity was positively associated with depression (p = 0.012) and pooled mental disorders (p = 0.005). Future longitudinal studies with similar designs and standardized exposure assessments are warranted.

Periodontal health, cognitive decline, and dementia: A systematic review and meta-analysis of longitudinal studies

BACKGROUND

Emerging evidence indicates that poor periodontal health adversely impacts cognition. This review examined the available longitudinal evidence concerning the effect of poor periodontal health on cognitive decline and dementia.

METHODS

Comprehensive literature search was conducted on five electronic databases for relevant studies published until April 2022. Longitudinal studies having periodontal health as exposure and cognitive decline and/or dementia as outcomes were considered. Random effects pooled estimates and 95% confidence intervals were generated (pooled odds ratio for cognitive decline and hazards ratio for dementia) to assess whether poor periodontal health increases the risk of cognitive decline and dementia. Heterogeneity between studies was estimated by I2 and the quality of available evidence was assessed through quality assessment criteria.

RESULTS

Adopted search strategy produced 2132 studies for cognitive decline and 2023 for dementia, from which 47 studies (24 for cognitive decline and 23 for dementia) were included in this review. Poor periodontal health (reflected by having periodontitis, tooth loss, deep periodontal pockets, or alveolar bone loss) was associated with both cognitive decline (OR = 1.23; 1.05-1.44) and dementia (HR = 1.21; 1.07-1.38). Further analysis, based on measures of periodontal assessment, found tooth loss to independently increase the risk of both cognitive decline (OR = 1.23; 1.09-1.39) and dementia (HR = 1.13; 1.04-1.23). Stratified analysis based on the extent of tooth loss indicated partial tooth loss to be important for cognitive decline (OR = 1.50; 1.02-2.23) and complete tooth loss for dementia (HR = 1.23; 1.05-1.45). However, the overall quality of evidence was low, and associations were at least partly due to reverse causality.

CONCLUSIONS

Poor periodontal health and tooth loss appear to increase the risk of both cognitive decline and dementia. However, the available evidence is limited (e.g., highly heterogenous, lacking robust methodology) to draw firm conclusions. Further well-designed studies involving standardized periodontal and cognitive health assessment and addressing reverse causality are highly warranted.

Green areas and students' academic performance in the Federal District, Brazil: An assessment of three greenness metrics

Most of the epidemiological investigations looking at the health benefits of green spaces have measured the level of green areas by using only one approach, mainly the Normalized Difference Index - NDVI (a satellite-derived indicator). We hypothesized a difference in the association between health and green space depending on the metric used to measure green exposure. This study considers students' academic performance as a proxy of cognitive abilities (a health indicator). We estimated the relationship between green areas and students' academic performance in the Federal District (FD), Brazil, with three different greenness metrics: NDVI, distance to green spaces (m) - obtained from land use data, and quantity of green spaces (m²) - also from land use data. We assessed student-level academic performance data provided by the Department of the Education in the FD. The data includes students from the public schools in the FD for 256 schools (all the public schools in the FD) and 344,175 students (all the students enrolled in the public schools in the FD in 2017-2020).). For the first metric represented by the distance to green spaces, we estimated the straight-line distance between each school and the nearest green area. For NDVI and quantity of green spaces, we estimated the area of all green spaces within buffers of 500 m, 750 m, and 1 km around the schools. We applied a cross-sectional study design using mixed-effects regression models to analyze the association exposure to green areas around schools and student-level academic performance. Our results confirmed our hypothesis showing that the impact of green areas on students' performance varied significantly depending on the type of green metric. After adjustments for the covariates, we estimated that NDVI is positively associated with school-level academic performance, with an estimated coefficient of 0.91 (95%CI: 0.83; 0.99) for NDVI values at a school's centroid. Distance to green areas was negatively associated with academic performance [-2.09 × 10^-5 (95CI: 3.91 × 10^-5; -2.84 × 10^-6]. The quantity of green areas was estimated with mixed results (direction of the association), depending on the buffer size. Results from this paper suggest that epidemiological investigations must consider the different effects of greenness measures when looking at the association between green space and academic performance. More studies on residual confounding from this association with a different study design are needed to promote public health by making schools healthier.

Causal Effect of Age at Menarche on the Risk for Depression: Results From a Two-Sample Multivariable Mendelian Randomization Study

A fair number of epidemiological studies suggest that age at menarche (AAM) is associated with depression, but the reported effect sizes are small, and there is evidence of residual confounding. Moreover, previous Mendelian randomization (MR) studies to avoid inferential problems inherent to epidemiological studies have provided mixed findings. To clarify the causal relationship between age at menarche and broadly defined depression risk, we used 360 genome-wide significantly AAM-related single-nucleotide polymorphisms (SNPs) as instrumental variable and data from the latest GWAS for the broadly defined depression risk on 807,553 individuals (246,363 cases and 561,190 controls). Multiple methods to account for heterogeneity of the instrumental variable (penalized weighted median, MR Lasso, and contamination mixture method), systematic and idiosyncratic pleiotropy (MR RAPS), and horizontal pleiotropy (MR PRESSO and multivariable MR using three methods) were used. Body mass index, education attainment, and total white blood count were considered pleiotropic phenotypes in the multivariable MR analysis. In the univariable [inverse-variance weighted (IVW): OR = 0.96, 95% confidence interval = 0.94–0.98, p = 0.0003] and multivariable MR analysis (IVW: OR = 0.96, 95% confidence interval = 0.94–0.99, p = 0.007), there was a significant causal effect of AAM on depression risk. Thus, the present study supports conclusions from previous epidemiological studies implicating AAM in depression without the pitfalls of residual confounding and reverse causation. Considering the adverse consequences of an earlier AAM on mental health, this finding should foster efforts to address risk factors that promote an earlier AAM.

Geographic ecological momentary assessment methods to examine spatio-temporal exposures associated with marijuana use among young adults: A pilot study

BACKGROUND

This study demonstrates the use of geographic ecological momentary assessment (GEMA) methods among young adult marijuana users.

METHOD

Participants were 14 current marijuana users ages 21-27 living in Greater Seattle, Washington. They completed brief surveys four times per day for 14 consecutive days, including measures of marijuana use and desire to use. They also carried a GPS data logger that tracked their spatial movements over time.

RESULTS

Participants completed 80.1% of possible EMA surveys. Using the GPS data, we calculated daily number of exposures to (i.e., within 100-m of) marijuana retail outlets (mean = 3.9 times per day; SD = 4.4) and time spent per day in high poverty census tracts (mean = 7.3 h per day in high poverty census tracts; SD = 5.1).

CONCLUSIONS

GEMA may be a promising approach for studying the role spatio-temporal factors play in marijuana use and related factors.