Dementia is a highly prevalent condition characterized by cognitive difficulties that typically begin in adulthood and affect a person’s ability to independently perform everyday activities. Alzheimer disease is the most common cause of dementia, accounting for approximately 60% to 80% of all dementia cases.^1,2 Mild cognitive impairment (MCI) is a clinical classification assigned to people who are thought to be transitioning between normal aging and dementia.^3-5 Because age is the most potent risk factor for dementia and MCI, the number of adults with these conditions is projected to rise dramatically in the US and around the world due to demographic trends that have transformed populations from mostly young adults to mostly older adults.² As dementia progresses, individuals need increased supervision and help making decisions and may ultimately require full-time long-term care. The impact of dementia and MCI on older adults and their families, health care capacity and costs, and care and services for people with dementia and their caregivers poses a considerable challenge to future social and financial well-being across the globe. The economic impact of dementia, including the large burden of unpaid family caregiving, has been estimated at $257 billion per year in the US² and $800 billion worldwide.⁶

Objective To evaluate the association between long-term exposure to ambient air pollution and cognitive decline in older adults residing in an urban area. Methods Data for this study were obtained from 2 prospective cohorts of residents in the northern Manhattan area of New York City: the Washington Heights–Inwood Community Aging Project (WHICAP) and the Northern Manhattan Study (NOMAS). Participants of both cohorts received in-depth neuropsychological testing at enrollment and during follow-up. In each cohort, we used inverse probability weighted linear mixed models to evaluate the cross-sectional and longitudinal associations between markers of average residential ambient air pollution (nitrogen dioxide [NO₂], fine particulate matter [PM_2.5], and respirable particulate matter [PM₁₀]) levels in the year prior to enrollment and measures of global and domain-specific cognition, adjusting for sociodemographic factors, temporal trends, and censoring. Results Among 5,330 participants in WHICAP, an increase in NO₂ was associated with a 0.22 SD lower global cognitive score at enrollment (95% confidence interval [CI], −0.30, −0.14) and 0.06 SD (95% CI, −0.08, −0.04) more rapid decline in cognitive scores between visits. Results were similar for PM_2.5 and PM₁₀ and across functional cognitive domains. We found no evidence of an association between pollution and cognitive function in NOMAS. Conclusion WHICAP participants living in areas with higher levels of ambient air pollutants have lower cognitive scores at enrollment and more rapid rates of cognitive decline over time. In NOMAS, a smaller cohort with fewer repeat measurements, we found no statistically significant associations. These results add to the evidence regarding the adverse effect of air pollution on cognitive aging and brain health.

Objective To investigate whether illiteracy was associated with greater risk of prevalent and incident dementia and more rapid cognitive decline among older adults with low education. Methods Analyses included 983 adults (≥65 years old, ≤4 years of schooling) who participated in a longitudinal community aging study. Literacy was self-reported (“Did you ever learn to read or write?”). Neuropsychological measures of memory, language, and visuospatial abilities were administered at baseline and at follow-ups (median [range] 3.49 years [0–23]). At each visit, functional, cognitive, and medical data were reviewed and a dementia diagnosis was made using standard criteria. Logistic regression and Cox proportional hazards models evaluated the association of literacy with prevalent and incident dementia, respectively, while latent growth curve models evaluated the effect of literacy on cognitive trajectories, adjusting for relevant demographic and medical covariates. Results Illiterate participants were almost 3 times as likely to have dementia at baseline compared to literate participants. Among those who did not have dementia at baseline, illiterate participants were twice as likely to develop dementia. While illiterate participants showed worse memory, language, and visuospatial functioning at baseline than literate participants, literacy was not associated with rate of cognitive decline. Conclusion We found that illiteracy was independently associated with higher risk of prevalent and incident dementia, but not with a more rapid rate of cognitive decline. The independent effect of illiteracy on dementia risk may be through a lower range of cognitive function, which is closer to diagnostic thresholds for dementia than the range of literate participants.

Racial/ethnic disparities in cognitive aging are only partly attributable to socioeconomic indicators. Psychosocial factors, such as discrimination and perceived control, also differ across racial/ethnic groups, and emerging literature highlights their potential role in contributing to cognitive disparities in addition to socioeconomic status. 1,463 older adults (51% Hispanic, 27% non-Hispanic Black, 22% non-Hispanic White) in the Washington Heights-Inwood Columbia Aging Project completed cognitive and psychosocial measures, including a comprehensive neuropsychological battery, Everyday and Major Experiences of Lifetime Discrimination scales, and the Perceived Control scale. Mediation models quantified separate indirect effects of Black race and Hispanic ethnicity on global cognitive composite scores through education, income, discrimination, and external perceived control. Educational attainment, income, and perceived control each mediated racial/ethnic disparities in global cognition. Socioeconomic indicators (i.e., lower education, lower income) explained approximately 50% of the Black-White and Hispanic-White disparities in global cognition, and more external perceived control explained an additional 5–8%. Hispanics reported the lowest levels of discrimination, while non-Hispanic Blacks reported the highest levels. However, neither everyday nor major lifetime discrimination was associated with global cognition. Significant racial/ethnic disparities in global cognition remained after accounting for the included socioeconomic and psychosocial factors. This study suggests that psychosocial factors may explain racial/ethnic disparities in cognitive aging above and beyond socioeconomic indicators. More external perceived control, which could reflect chronic exposure to interpersonal and institutional marginalization, may be a particularly salient psychosocial risk factor for poorer cognitive aging among non-Hispanic Black and Hispanic older adults.

Hypertension is an established risk factor for cognitive decline and dementia in older adults, highlighting the potential importance of antihypertensive treatments in prevention efforts. Work surrounding antihypertensive treatments has suggested possible salutary effects on cognition and neuropathology. Several studies have specifically highlighted renin-angiotensin system drugs, including AT1-receptor blockers and angiotensin-converting-enzyme inhibitors, as potentially benefiting cognition in later life. A small number of studies have further suggested renin-angiotensin system drugs that cross the blood-brain barrier may be linked to lower dementia risk compared to their nonpenetrant counterparts. The present meta-analysis sought to evaluate the potential cognitive benefits of blood-brain barrier crossing renin-angiotensin system drugs relative to their nonpenetrant counterparts. We harmonized longitudinal participant data from 14 cohorts from 6 countries (Australia, Canada, Germany, Ireland, Japan, United States), for a total of 12 849 individuals at baseline, and assessed for blood-brain barrier crossing potential within antihypertensive medications used by cognitively normal participants. We analyzed 7 cognitive domains (attention, executive function, language, verbal memory learning, recall, mental status, and processing speed) using ANCOVA (adjusted for age, sex, and education) and meta-analyses. Older adults taking blood-brain barrier-crossing renin-angiotensin drugs exhibited better memory recall over up to 3 years of follow-up, relative to those taking nonpenetrant medications, despite their relatively higher vascular risk burden. Conversely, those taking nonblood-brain barrier-penetrant medications showed better attention over the same follow-up period, although their lower vascular risk burden may partially explain this result. Findings suggest links between blood-brain barrier crossing renin-angiotensin drugs and less memory decline.