The relation of cigarette smoking to incident Alzheimer's disease in a biracial urban community population

External validation of dementia prediction models in Black or African American and White older adults: A longitudinal population-based study in the United States

INTRODUCTION

Identifying people at high risk of Alzheimer's disease (AD) dementia allows for timely intervention, which, if successful, will result in preventing or delaying the onset of the disease.

METHODS

Utilizing data from the Chicago Health and Aging Project (CHAP; n = 2130), we externally evaluated four risk-prediction models for AD dementia, including Cardiovascular Risk Factors, Aging, and Dementia (CAIDE), Australian National University Alzheimer's Disease Risk Index (ANU-ADRI), Brief Dementia Screening Indicator (BDSI), and Dementia Risk Score (DRS), in Black or African American and White adults.

RESULTS

BDSI had the highest discriminate abilities for AD dementia (c-statistics of 0.79 in Black and 0.77 in White adults), followed by ANU-ADRI, within the age range and follow-up period of the original development cohort. CAIDE had the lowest discriminating power (c-statistic ≤0.55). With increasing follow-up periods (i.e., 10-15 years), the discrimination abilities for all models declined.

DISCUSSION

Because of racial disparities in AD dementia and longer preclinical and prodromal stages of disease development, race-specific models are needed to predict AD risk over 10 years.

HIGHLIGHTS

Utilizing risk-prediction models to identify individuals at higher risk of Alzheimer's disease (AD) dementia could benefit clinicians, patients, and policymakers. Clinicians could enroll high-risk individuals in clinical trials to test new risk-modifiable treatments or initiate lifestyle modifications, which, if successful, would slow cognitive decline and delay the onset of the disease. Current risk-prediction models had good discriminative power during the first 6 years of follow-up but decreased with longer follow-up time. Acknowledging the longer preclinical phase of AD dementia development and racial differences in dementia risk, there is a need to develop race-specific risk-prediction models that can predict 10 or 20 years of risk for AD and related dementias.

Pilot implementation of the revised criteria for staging of Alzheimer's disease by the Alzheimer's Association Workgroup in a tertiary memory clinic

INTRODUCTION

We aimed to evaluate the feasibility of the 2024 Alzheimer's Association Workgroup's integrated clinical-biological staging scheme in outpatient settings within a tertiary memory clinic.

METHODS

The 2018 syndromal cognitive staging system, coupled with a binary biomarker classification, was implemented for 236 outpatients with cognitive concerns. The 2024 numeric clinical staging framework, incorporating biomarker staging, was specifically applied to 154 individuals within the Alzheimer's disease (AD) continuum.

RESULTS

The 2024 staging scheme accurately classified 95.5% AD. Among these, 56.5% exhibited concordant clinical and biological stages (canonical), 34.7% demonstrated more advanced clinical stages than biologically expected (susceptible), and 8.8% displayed the inverse pattern (resilient). The susceptible group was characterized by a higher burden of neurodegeneration and inflammation than anticipated from tau, whereas the resilient group showed the opposite.

DISCUSSION

The 2024 staging scheme is generally feasible. A discrepancy between clinical and biological stages is relatively frequent among symptomatic patients with AD.

HIGHLIGHTS

The 2024 AA staging scheme is generally feasible in a tertiary memory clinic. A discrepancy between clinical and biological stages is relatively frequent in AD. The mismatch may be influenced by a non-specific pathological process involved in AD. Individual profiles like aging and lifestyles may contribute to such a mismatch. Matched and mismatched cases converge toward similar clinical outcomes.

Time trends in Alzheimer's disease mortality attributable to metabolic risks and smoking in China from 1990 to 2019: an age-period-cohort analysis

Background

With the increase in the aging population worldwide, Alzheimer's disease has become a rapidly increasing public health concern. In the Global Burden of Disease Study 2019, there are three risk factors judged to have evidence for a causal link to Alzheimer's disease and other dementias: smoking, high body-mass index (HBMI), and high fasting plasma glucose (HFPG).

Objective

This study aimed to analyze trends in AD mortality and the relevant burden across China from 1990 to 2019, as well as their correlation with age, period, and birth cohort.

Methods

The data were extracted from the GBD 2019. Trends in AD mortality attributable to metabolic risks (HFPG and HBMI) and smoking were analyzed using Joinpoint regression. The age-period-cohort (APC) model was used to evaluate cohort and period effects.

Results

From 1990 to 2019, the overall age-standardized mortality rate of AD increased, especially in women. There was an increase in AD mortality due to smoking in the net drift, and it was more significant in women (0.46, 95%CI = [0.09, 0.82]) than men (-0.03, 95%CI = [-0.11, 0.05]). For the cause of HFPG, the net drift values for men and women were 0.82% and 0.43%. For HBMI, the values were 3.14% and 2.76%, respectively, reflecting substantial increases in AD mortality.

Conclusion

Time trends in AD mortality caused by metabolic risks and smoking in China from 1990 to 2019 have consistently increased. Therefore, it is necessary to prevent excessive weight gain and obesity during the later stages of life, especially for females.

Socioeconomic status, lifestyle and risk of incident dementia: a prospective cohort study of 276730 participants

Healthy lifestyle might alleviate the socioeconomic inequities in health, but the extent of the joint and interactive effects of these two factors on dementia are unclear. This study aimed to detect the joint and interactive associations of socioeconomic status (SES) and lifestyle factors with incident dementia risk, and the underlying brain imaging alterations. Cox proportional hazards analysis was performed to test the joint and interactive associations. Partial correlation analysis was performed to reflect the brain imaging alterations. A total of 276,730 participants with a mean age of 55.9 (±8.0) years old from UK biobank were included. Over 8.5 (±2.6) years of follow-up, 3013 participants were diagnosed with dementia. Participants with high SES and most healthy lifestyle had a significantly lower risk of incident dementia (HR=0.19, 95% CI=0.14 to 0.26, P<2×10-16), Alzheimer's disease (AD, HR=0.19, 95% CI=0.13 to 0.29, P=8.94×10-15), and vascular dementia (HR=0.24, 95% CI=0.12 to 0.48, P=7.57×10-05) compared with participants with low SES and an unhealthy lifestyle. Significant interactions were found between SES and lifestyle on dementia (P=0.002) and AD (P=0.001) risks; the association between lifestyle and dementia was stronger among those of high SES. The combination of high SES and healthy lifestyle was positively associated with higher volumes in brain regions vulnerable to dementia-related atrophy. These findings suggest that SES and lifestyle significantly interact and influence dementia with its related brain structure phenotypes.

Healthy Lifestyle and Cognition in Older Adults With Common Neuropathologies of Dementia

Importance

A healthy lifestyle is associated with better cognitive functioning in older adults, but whether this association is independent of the accumulation of dementia-related pathologies in the brain is uncertain.

Objective

To determine the role of postmortem brain pathology, including β-amyloid load, phosphorylated tau tangles, cerebrovascular pathology, and other brain pathologies, in the association between lifestyle and cognition proximate to death.

Design, Setting, and Participants

This cohort study used data from the Rush Memory and Aging Project, a longitudinal clinical-pathologic study with autopsy data from 1997 to 2022 and up to 24 years of follow-up. Participants included 754 deceased individuals with data on lifestyle factors, cognitive testing proximate to death, and a complete neuropathologic evaluation at the time of these analyses. Data were analyzed from January 2023 to June 2023.

Exposures

A healthy lifestyle score was developed based on self-reported factors, including noncurrent smoking, at least 150 minutes of physical activity per week, limiting alcohol consumption, a Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet score higher than 7.5, and a late-life cognitive activity score higher than 3.2. The lifestyle score ranges from 0 to 5, with higher scores reflecting a healthier lifestyle.

Main Outcomes and Measures

The global cognitive score was derived from a battery of nineteen standardized tests. Brain pathology measures included β-amyloid load, phosphorylated tau tangles, global Alzheimer disease pathology, vascular brain pathologies, Lewy body, hippocampal sclerosis, and TAR DNA-binding protein 43.

Results

Of 586 included decedents, 415 (70.8%) were female, 171 (29.2%) were male, and the mean (SD) age at death was 90.9 (6.0) years. Higher lifestyle score was associated with better global cognitive functioning proximate to death. In the multivariable-adjusted model, a 1-point increase in lifestyle score was associated with 0.216 (SE = 0.036, P < .001) units higher in global cognitive scores. Neither the strength nor the significance of the association changed substantially when common dementia-related brain pathologies were included in the multivariable-adjusted models. The β estimate after controlling for the β-amyloid load was 0.191 (SE = 0.035; P < .001). A higher lifestyle score was associated with lower β-amyloid load in the brain (β = -0.120; SE = 0.041; P = .003), and 11.6% of the lifestyle-cognition association was estimated through β-amyloid load.

Conclusions and Relevance

This study found that in older adults, a healthy lifestyle may provide a cognitive reserve to maintain cognitive abilities independently of common neuropathologies of dementia.

Associations of Nativity and the Role of the Hispanic Paradox on the Cognitive Health of Older Latinos Living in the United States

Background

US-based Latinos have lower education and income combined with higher health risks than non-Latino whites, but often 'paradoxically' evidence better health-related outcomes. Less work has investigated this paradox for cognitive-related outcomes despite nativity diversity.

Objective

We evaluated cognitive aging within older Latinos of diverse nativity currently living in the US and participating in Rush Alzheimer's Disease Center studies.

Methods

Participants without baseline dementia, who completed annual neuropsychological assessments (in English or Spanish) were grouped by US-born (n = 117), Mexico-born (n = 173), and born in other Latin American regions (LAr-born = 128). Separate regression models examined associations between nativity and levels of (N = 418) or change in (n = 371; maximum follow-up ∼16 years) global and domain-specific cognition.

Results

Demographically-adjusted linear regression models indicated that foreign-born nativity was associated with lower levels of global cognition and select cognitive domains compared to US-born Latinos. No associations of nativity with cognitive decline emerged from demographically-adjusted mixed-effects models; however, Mexico-born nativity appeared associated with slower declines in working memory compared to other nativity groups (p-values ≥ 0.051). Mexico-born Latinos had relatively higher vascular burden and lower education levels than other nativity groups; however, this did not alter results.

Conclusions

Nativity differences in baseline cognition may be due, in part, to accumulated stressors related to immigration and acculturation experienced by foreign-born Latinos which may hasten meeting criteria for dementia later in life. In contrast, Mexico-born participants' slower working memory declines, taken in the context of other participant characteristics including vascular burden, suggests the Hispanic Paradox may relate to factors with the potential to affect cognition.

Circadian disturbances and frailty risk in older adults

Frailty is characterized by diminished resilience to stressor events. It is associated with adverse future health outcomes and impedes healthy aging. The circadian system orchestrates ~24-h rhythms in bodily functions in synchrony with the day-night cycle, and disturbed circadian regulation plays an important role in many age-related health consequences. We investigated prospective associations of circadian disturbances with incident frailty in over 1000 older adults who had been followed annually for up to 16 years. We found that decreased rhythm strength, reduced stability, or increased variation were associated with a higher risk of incident frailty and faster progress of frailty over time. Perturbed circadian rest-activity rhythms may be an early sign or risk factor for frailty in older adults.

Blood pressure variability, dementia, and role of antihypertensive medications in older adults

INTRODUCTION

We assessed the association between visit-to-visit blood pressure variability (BPV) up to 12 years and subsequent dementia risk, and tested the modifying effect of antihypertensive medications.

METHODS

We studied 2234 participants from two community-based cohorts of older adults with normal cognition or mild cognitive impairment. Participants were followed through annual assessments for up to 27 years. Visit-to-visit BPV was quantified over 3, 6, 9, and 12 years, respectively.

RESULTS

Higher systolic BPV (SBPV) during 3, 6, 9, and 12 years was associated with a subsequent increased risk of dementia, with hazard ratios ranging from 1.02 (95% confidence interval [CI]: 1.01-1.04) to 1.10 (95% CI: 1.05-1.16). The association between SBPV and dementia risk was stronger among participants not taking calcium channel blockers (p-for interaction < 0.05).

DISCUSSION

Among older adults, long-term exposure to higher visit-to-visit SBPV is associated with an increased risk of dementia later in life, and calcium channel blockers may modify this association.

HIGHLIGHTS

Among adults aged >65, higher systolic blood pressure variability spanning 3-12 years is associated with an increased risk of dementia later in life. Single blood pressure measurement or mean blood pressure levels does not seem to associate with dementia risk among older adults. The association between systolic blood pressure variability and dementia risk is stronger among those not taking calcium channel blocker medications.

Association of Mediterranean-DASH Intervention for Neurodegenerative Delay and Mediterranean Diets With Alzheimer Disease Pathology

BACKGROUND AND OBJECTIVES

Diet may reduce Alzheimer dementia risk and slow cognitive decline, but the understanding of the relevant neuropathologic mechanisms remains limited. The association of dietary patterns with Alzheimer disease (AD) pathology has been suggested using neuroimaging biomarkers. This study examined the association of Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) and Mediterranean dietary patterns with β-amyloid load, phosphorylated tau tangles, and global AD pathology in postmortem brain tissue of older adults.

METHODS

Autopsied participants of the Rush Memory and Aging Project with complete dietary information (collected through a validated food frequency questionnaire) and AD pathology data (β-amyloid load, phosphorylated tau tangles, and global AD pathology [summarized neurofibrillary tangles and neuritic and diffuse plaques]) were included in this study. Linear regression models controlled for age at death, sex, education, APOE-ε4 status, and total calories were used to investigate the dietary patterns (MIND and Mediterranean diets) and dietary components associated with AD pathology. Further effect modification was tested for APOE-ε4 status and sex.

RESULTS

Among our study participants (N = 581, age at death: 91.0 ± 6.3 years; mean age at first dietary assessment: 84.2 ± 5.8 years; 73% female; 6.8 ± 3.9 years of follow-up), dietary patterns were associated with lower global AD pathology (MIND: β = -0.022, p = 0.034, standardized β = -2.0; Mediterranean: β = -0.007, p = 0.039, standardized β = -2.3) and specifically less β-amyloid load (MIND: β = -0.068, p = 0.050, standardized β = -2.0; Mediterranean: β = -0.040, p = 0.004, standardized β = -2.9). The findings persisted when further adjusted for physical activity, smoking, and vascular disease burden. The associations were also retained when participants with mild cognitive impairment or dementia at the baseline dietary assessment were excluded. Those in the highest tertile of green leafy vegetables intake had less global AD pathology when compared with those in the lowest tertile (tertile 3 vs tertile 1: β = -0.115, p = 0.0038).

DISCUSSION

The MIND and Mediterranean diets are associated with less postmortem AD pathology, primarily β-amyloid load. Among dietary components, higher green leafy vegetable intake was associated with less AD pathology.

Plasma Extracellular Vesicle MicroRNA Analysis of Alzheimer's Disease Reveals Dysfunction of a Neural Correlation Network

Small extracellular vesicle (sEV) is an emerging source of potential biomarkers of Alzheimer's disease (AD), but the role of microRNAs (miRNAs) in sEV is not well understood. In this study, we conducted a comprehensive analysis of sEV-derived miRNAs in AD using small RNA sequencing and coexpression network analysis. We examined a total of 158 samples, including 48 from AD patients, 48 from patients with mild cognitive impairment (MCI), and 62 from healthy controls. We identified an miRNA network module (M1) that was strongly linked to neural function and showed the strongest association with AD diagnosis and cognitive impairment. The expression of miRNAs in the module was decreased in both AD and MCI patients compared to controls. Conservation analysis revealed that M1 was highly preserved in the healthy control group but dysfunctional in the AD and MCI groups, suggesting that changes in the expression of miRNAs in this module may be an early response to cognitive decline prior to the appearance of AD pathology. We further validated the expression levels of the hub miRNAs in M1 in an independent population. The functional enrichment analysis showed that 4 hub miRNAs might interact with a GDF11-centered network and play a critical role in the neuropathology of AD. In summary, our study provides new insights into the role of sEV-derived miRNAs in AD and suggests that M1 miRNAs may serve as potential biomarkers for the early diagnosis and monitoring of AD.

Circadian disturbances and frailty risk in older adults: a prospective cohort study

Frailty is characterized by diminished resilience to stressor events. It associates with adverse future health outcomes and impedes healthy aging. The circadian system orchestrates a ~24-h rhythm in bodily functions in synchrony with the day-night cycle, and disturbed circadian regulation plays an important role in many age-related health consequences. We investigated prospective associations of circadian disturbances with incident frailty in over 1,000 older adults who had been followed annually for up to 16 years. We found that decreased rhythm strength, reduced stability, or increased variation, were associated with a higher risk of incident frailty, and faster worsening of the overall frailty symptoms over time. Perturbed circadian rest-activity rhythms may be an early sign or risk factor for frailty in older adults.

A Longitudinal Study of Acculturation in Context and Cardiovascular Health and Their Effects on Cognition Among Older Latino Adults

Background We previously outlined the importance of considering acculturation within the context of older Latino adults' lived experience (ie, acculturation in context) to better capture contributors to cognitive aging. We now examine this conceptual framework as related to level of and change in cardiovascular health, and whether cardiovascular health modifies previously documented associations of acculturation in context with cognition. Methods and Results Acculturation in context data from 192 Latino participants without dementia at baseline (age ~70 years) were compiled into 3 separate composite scores: acculturation-related (nativity, language-, and social-based preferences), contextually related socioenvironmental (experiences of discrimination, social isolation, social networks), and familism-related (Latino-centric family ethos). A modified American Heart Association's Life's Simple 7 (mLS7; ie, smoking, physical activity, body mass index, blood pressure, total cholesterol, blood glucose) was used to measure cardiovascular health. Mixed effects regressions simultaneously tested the association of all 3 composite scores with total mLS7 adjusting for confounders. Separate models tested whether mLS7 modified associations of the 3 composite scores and cognition. The contextually related socioenvironmental composite score reflecting higher discrimination, higher social isolation, and smaller social networks (estimate=0.22, SE=0.10, P=0.02) and the familism score (estimate=0.16, SE=0.07, P=0.02) both significantly associated with change in total mLS7. The acculturation-related composite was not significantly associated with change in mLS7. No composite was significantly associated with level of mLS7. Total mLS7, however, significantly modified associations between the acculturation-related composite and change in working memory (estimate=-0.02, SE=0.01, P=0.043). Conclusions Acculturation within the context of older Latino adults' lived experience is important for maintaining cardiovascular health, relationships that also affect domain-specific cognitive decline.

Association of Dietary Intake of Flavonols With Changes in Global Cognition and Several Cognitive Abilities

BACKGROUND AND OBJECTIVES

Previous research has examined the association between cognition and flavonoids: bioactives found in foods, known to possess anti-inflammatory and antioxidant properties. We extend this research by investigating associations of dietary intakes of total flavonols and constituents (kaempferol, quercetin, myricetin, and isorhamnetin) on the change in cognitive performance in global cognition, episodic memory, semantic memory, visuospatial ability, perceptual speed, and working memory.

METHODS

The study was conducted using 961 participants (aged 60-100 years) of the Rush Memory and Aging Project, a prospective cohort of community-dwelling Chicagoans who were followed for an average of 6.9 years. Diet was assessed using a validated semiquantitative food frequency questionnaire. Cognitive performance was assessed annually with a battery of 19 standardized tests. Flavonol intake was analyzed as a continuous variable using linear mixed-effects models. Cognitive domain scores were regressed on baseline calorie-adjusted flavonol variables.

RESULTS

Higher dietary intakes of total flavonols and flavonol constituents were associated with a slower rate of decline in global cognition and multiple cognitive domains. In continuous models adjusted for age, sex, education, APOE ɛ4, late-life cognitive activity, physical activity, and smoking, total flavonol intake was associated with slower decline in global cognition β estimate = 0.004 (95% CI 0.001-0.006), episodic memory β = 0.004 (95% CI 0.002-0.006), semantic memory β = 0.003 (95% CI 0.001-0.007), perceptual speed β = 0.003 (95% CI 0.001-0.004), and working memory β = 0.003 (95% CI 0.001-0.005) and marginally associated with visuospatial ability β = 0.001 (95% CI -0.001 to 0.003). Analyses of individual flavonol constituents demonstrated that intakes of kaempferol and quercetin were associated with slower global cognitive decline (β = 0.01 [95% CI 0.006-0.02] and β = 0.004 [95% CI 0.0005-0.007]), respectively. Myricetin and isorhamnetin were not associated with global cognition.

DISCUSSION

Results suggest that dietary intakes of total flavonols and several flavonol constituents may be associated with slower decline in global cognition and multiple cognitive abilities with older age.

Thwarting Alzheimer's Disease through Healthy Lifestyle Habits: Hope for the Future

Alzheimer's disease (AD) is a neurodegenerative disorder that slowly disintegrates memory and thinking skills. Age is known to be the major risk factor in AD, but there are several nonmodifiable and modifiable causes. The nonmodifiable risk factors such as family history, high cholesterol, head injuries, gender, pollution, and genetic aberrations are reported to expediate disease progression. The modifiable risk factors of AD that may help prevent or delay the onset of AD in liable people, which this review focuses on, includes lifestyle, diet, substance use, lack of physical and mental activity, social life, sleep, among other causes. We also discuss how mitigating underlying conditions such as hearing loss and cardiovascular complications could be beneficial in preventing cognitive decline. As the current medications can only treat the manifestations of AD and not the underlying process, healthy lifestyle choices associated with modifiable factors is the best alternative strategy to combat the disease.

Biological and Clinical Implications of Sex-Specific Differences in Alzheimer's Disease

Mounting evidence indicates that the female sex is a risk factor for Alzheimer's disease (AD), the most common cause of dementia worldwide. Decades of research suggest that sex-specific differences in genetics, environmental factors, hormones, comorbidities, and brain structure and function may contribute to AD development. However, although significant progress has been made in uncovering specific genetic factors and biological pathways, the precise mechanisms underlying sex-biased differences are not fully characterized. Here, we review several lines of evidence, including epidemiological, clinical, and molecular studies addressing sex differences in AD. In addition, we discuss the challenges and future directions in advancing personalized treatments for AD.

Social Engagement and All-Cause Mortality: A Focus on Participants of the Minority Aging Research Study

INTRODUCTION

Social engagement is known to improve health; less is known about whether social activities at the core of African American life decrease mortality risk in this minoritized population. This study investigated whether and which aspects of social engagement predict mortality risk in older African Americans.

METHODS

Data from 768 African Americans (aged ∼73 years; nondemented at baseline) participating in the Minority Aging Research Study, a longitudinal community-based, cohort study of aging, was collected between 2004 and 2020 and analyzed in 2020. Participants self-reported late-life social activity, social network size, life space, and purpose in life at baseline and completed approximately 6.5 years of annual follow-up (range=15.70). Cox models included time from baseline to death or censoring and an indicator for death versus censored with age, sex, education, cardiovascular disease risk factor burden, depressive symptomatology, and motor gait performance as covariates.

RESULTS

As of March 2020, 25% of participants died (n=192; age at death ∼83 years). In fully adjusted Cox models, mortality risk decreased by 34% (hazard ratio=0.66; 95% CI=0.48, 0.91; p=0.012) for those with higher compared with that for those with lower social activity generally, with community/volunteer-, group-, and socially-related activities specifically driving these results.

CONCLUSIONS

Engaging in late-life social activity, especially group- and socially-based activities, was most consistently and robustly associated with reduced mortality risk in African Americans regardless of health. These results lay the foundation for considering community-based approaches to increase and/or maintain social participation in older African Americans as a potential means by which to increase longevity in this population.

Sex-specific transcriptional rewiring in the brain of Alzheimer’s disease patients

Sex-specific differences may contribute to Alzheimer’s disease (AD) development. AD is more prevalent in women worldwide, and female sex has been suggested as a disease risk factor. Nevertheless, the molecular mechanisms underlying sex-biased differences in AD remain poorly characterized. To this end, we analyzed the transcriptional changes in the entorhinal cortex of symptomatic and asymptomatic AD patients stratified by sex. Co-expression network analysis implemented by SWItchMiner software identified sex-specific signatures of switch genes responsible for drastic transcriptional changes in the brain of AD and asymptomatic AD individuals. Pathway analysis of the switch genes revealed that morphine addiction, retrograde endocannabinoid signaling, and autophagy are associated with both females with AD (F-AD) and males with (M-AD). In contrast, nicotine addiction, cell adhesion molecules, oxytocin signaling, adipocytokine signaling, prolactin signaling, and alcoholism are uniquely associated with M-AD. Similarly, some of the unique pathways associated with F-AD switch genes are viral myocarditis, Hippo signaling pathway, endometrial cancer, insulin signaling, and PI3K-AKT signaling. Together these results reveal that there are many sex-specific pathways that may lead to AD. Approximately 20–30% of the elderly have an accumulation of amyloid beta in the brain, but show no cognitive deficit. Asymptomatic females (F-asymAD) and males (M-asymAD) both shared dysregulation of endocytosis. In contrast, pathways uniquely associated with F-asymAD switch genes are insulin secretion, progesterone-mediated oocyte maturation, axon guidance, renal cell carcinoma, and ErbB signaling pathway. Similarly, pathways uniquely associated with M-asymAD switch genes are fluid shear stress and atherosclerosis, FcγR mediated phagocytosis, and proteoglycans in cancer. These results reveal for the first time unique pathways associated with either disease progression or cognitive resilience in asymptomatic individuals. Additionally, we identified numerous sex-specific transcription factors and potential neurotoxic chemicals that may be involved in the pathogenesis of AD. Together these results reveal likely molecular drivers of sex differences in the brain of AD patients. Future molecular studies dissecting the functional role of these switch genes in driving sex differences in AD are warranted.

Olfactory Dysfunction and Incidence of Motoric Cognitive Risk Syndrome: A Prospective Clinical-Pathologic Study

BACKGROUND AND OBJECTIVES

To examine associations between olfactory dysfunction, Alzheimer disease (AD) pathology, and motoric cognitive risk syndrome (MCR), a predementia syndrome characterized by cognitive complaints and slow gait that is associated with risk for AD and other dementias.

METHODS

We conducted a retrospective analysis of a prospective cohort study to examine whether baseline olfactory function was associated with the risk of incident MCR in 1,119 adults aged 60 years and older (75.1% female). The association between performance on the Brief Smell Identification Test (BSIT) and incident MCR risk was computed using Cox models and reported as the hazard ratio (HR) with 95% CIs adjusted for demographic, comorbidity, and cognitive factors. Furthermore, we assessed the relationship between postmortem AD pathology and non-AD pathology and olfactory function at the time of MCR diagnosis using linear regression models adjusted for sex, education, age at death, and time from diagnosis to death.

RESULTS

There were 544 (48.6%) incident cases of MCR over a median follow-up of 3.94 years. Lower BSIT scores (poor olfaction) at baseline were associated with an increased risk of incident MCR (HR for a 1-point increase in BSIT score 0.92; 95% CI 0.88-0.96) in fully adjusted models. Those with hyposmia (scores of ≤8 on the BSIT) at baseline (26.6%) were at an increased risk of MCR (HR 1.44; 95% CI 1.19-1.74) compared with those with normal olfactory function. Higher levels of the composite measure of global AD pathology and presence of Lewy body pathology were associated with lower BSIT scores at the time of incident MCR diagnosis (n = 118). τ tangle density, a specific component of AD pathology, was inversely associated with olfactory function, and the correlation remained after controlling for mild cognitive impairment syndrome and the presence of Lewy body pathology.

DISCUSSION

The results provide evidence that olfactory dysfunction precedes MCR incidence and is related to Alzheimer pathology, providing a clinical approach to risk stratify and subtype MCR.

Lifestyle and Cognitive Decline in Community-Dwelling Stroke Survivors

Background: Patients with stroke are at a higher risk of cognitive impairment and Alzheimer’s disease dementia. Objective: To quantify the role of lifestyle pre-stroke, post-stroke, and changes in lifestyle before and after stroke with cognitive decline in community-dwelling stroke survivors. Methods: Utilizing data from the Chicago Health and Aging Project, a population-based cohort study, we studied 1,078 individuals with stroke (662 incident and 416 prevalent) who underwent cognitive testing during the study period. A healthy lifestyle score was defined by scoring four behaviors: non-smoking, exercising, being cognitively active, and having a high-quality diet. The global cognitive score was derived from a comprehensive battery of 4 standardized tests. Results: The mean age at incident stroke was 78.2 years, and 60.1% were women. A healthy lifestyle pre-incident stroke was associated with a slower rate of cognitive decline after stroke. Participants with 3–4 healthy lifestyle factors pre-incident stroke had a slower cognitive decline after stroke by 0.046 units/year (95% CI 0.010, 0.083), or 47.7% slower, than participants with 0–1 healthy lifestyle factor. Lifestyle score post-prevalent stroke was not associated with cognitive decline. Changes in lifestyle behaviors from pre- to post-incident stroke were related to cognitive decline after stroke. Individuals who deteriorated their lifestyle quality after stroke had a faster cognitive decline by 0.051 units/year (β –0.051, 95% CI –0.090, –0.012) than participants with no change in lifestyle score. Conclusion: A healthy lifestyle pre-stroke was associated with a slower rate of cognitive decline in stroke survivors, highlighting the importance of primary prevention. After the stroke, changes in lifestyle behaviors may influence the cognitive abilities of older adults as they age.

Association Between Various Types or Statuses of Smoking and Subjective Cognitive Decline Based on a Community Health Survey of Korean Adults

Objectives

The relationship between smoking and subjective cognitive decline (SCD), which is defined as the subjective perception of cognitive decline, is not well known. This study aimed to investigate the relationship of various types of smoking, including E-cigarette smoking and the use of E-liquid, with the incidence of SCD among Korean adults.

Methods

We evaluated the 2018 Korean Community Health Survey data collected from community-dwelling people in Korea. A total of 104,453 non-smokers, 38,607 past smokers, and 26,776 current smokers with eligible data were included in the study. SCD was assessed using the Behavioral Risk Factor Surveillance System. The past or current smoking pack-years throughout each participant's entire life were calculated. Multiple regression analyses were carried out to estimate the adjusted odds ratios (ORs) as measures of the association between each type of smoking and SCD after adjustment for potential confounders.

Results

Compared to no exposure, passive smoking was associated with higher odds of SCD. Compared to non-smokers, past smokers had a higher OR for SCD; however, current smokers did not. There were no significant associations between passive smoking and SCD in the non-smoker and past smoker groups, but there was a significant relationship between them in the current smoker group. While the cumulative dose of smoking was correlated with an increased OR of SCD in each group of current smokers and past smokers, E-cigarette smoking and the use of E-liquid were not associated with higher ORs in the current smoker group.

Conclusion

Our findings support that passive smoking and past smoking are significantly associated with SCD and that more cumulative exposure to smoking is correlated with a higher OR of SCD.

Healthy lifestyle and life expectancy with and without Alzheimer's dementia: population based cohort study

OBJECTIVE

To determine the impact of lifestyle factors on life expectancy lived with and without Alzheimer's dementia.

DESIGN

Prospective cohort study.

SETTING

The Chicago Health and Aging Project, a population based cohort study in the United States.

PARTICIPANTS

2449 men and women aged 65 years and older.

MAIN EXPOSURE

A healthy lifestyle score was developed based on five modifiable lifestyle factors: a diet for brain health (Mediterranean-DASH Diet Intervention for Neurodegenerative Delay-MIND diet score in upper 40% of cohort distribution), late life cognitive activities (composite score in upper 40%), moderate or vigorous physical activity (≥150 min/week), no smoking, and light to moderate alcohol consumption (women 1-15 g/day; men 1-30 g/day).

MAIN OUTCOME

Life expectancy with and without Alzheimer's dementia in women and men.

RESULTS

Women aged 65 with four or five healthy factors had a life expectancy of 24.2 years (95% confidence interval 22.8 to 25.5) and lived 3.1 years longer than women aged 65 with zero or one healthy factor (life expectancy 21.1 years, 19.5 to 22.4). Of the total life expectancy at age 65, women with four or five healthy factors spent 10.8% (2.6 years, 2.0 to 3.3) of their remaining years with Alzheimer's dementia, whereas women with zero or one healthy factor spent 19.3% (4.1 years, 3.2 to 5.1) with the disease. Life expectancy for women aged 65 without Alzheimer's dementia and four or five healthy factors was 21.5 years (20.0 to 22.7), and for those with zero or one healthy factor it was 17.0 years (15.5 to 18.3). Men aged 65 with four or five healthy factors had a total life expectancy of 23.1 years (21.4 to 25.6), which is 5.7 years longer than men aged 65 with zero or one healthy factor (life expectancy 17.4 years, 15.8 to 20.1). Of the total life expectancy at age 65, men with four or five healthy factors spent 6.1% (1.4 years, 0.3 to 2.0) of their remaining years with Alzheimer's dementia, and those with zero or one healthy factor spent 12.0% (2.1 years, 0.2 to 3.0) with the disease. Life expectancy for men aged 65 without Alzheimer's dementia and four or five healthy factors was 21.7 years (19.7 to 24.9), and for those with zero or one healthy factor life expectancy was 15.3 years (13.4 to 19.1).

CONCLUSION

A healthy lifestyle was associated with a longer life expectancy among men and women, and they lived a larger proportion of their remaining years without Alzheimer's dementia. The life expectancy estimates might help health professionals, policy makers, and stakeholders to plan future healthcare services, costs, and needs.

APOE Genotype and Alzheimer's Disease: The Influence of Lifestyle and Environmental Factors

Alzheimer's disease (AD) is the most common neurodegenerative disorder with obscure pathogenesis and no disease-modifying therapy to date. AD is multifactorial disease that develops from the complex interplay of genetic factors and environmental exposures. The E4 allele of the gene encoding apolipoprotein E (APOE) is the most common genetic risk factor for AD, whereas the E2 allele acts in a protective manner. A growing amount of epidemiological evidence suggests that several lifestyle habits and environmental factors may interact with APOE alleles to synergistically affect the risk of AD development. Among them, physical exercise, dietary habits including fat intake and ketogenic diet, higher education, traumatic brain injury, cigarette smoking, coffee consumption, alcohol intake, and exposure to pesticides and sunlight have gained increasing attention. Although the current evidence is inconsistent, it seems that younger APOE4 carriers in preclinical stages may benefit mostly from preventive lifestyle interventions, whereas older APOE4 noncarriers with dementia may show the most pronounced effects. The large discrepancies between the epidemiological studies may be attributed to differences in the sample sizes, the demographic characteristics of the participants, including age and sex, the methodological design, and potential related exposures and comorbidities as possible cofounding factors. In this Review, we aim to discuss available evidence of the prominent APOE genotype-environment interactions in regard to cognitive decline with a focus on AD, providing an overview of the current landscape in this field and suggesting future directions.

Genetic risk, adherence to a healthy lifestyle, and cognitive decline in African Americans and European Americans

INTRODUCTION

We investigated the role of genetic risk and adherence to lifestyle factors on cognitive decline in African Americans and European Americans.

METHODS

Using data from the Chicago Health and Aging Project (1993-2012; n = 3874), we defined the genetic risk based on presence of apolipoprotein E (APOE) ε 4 allele and determined a healthy lifestyle using a scoring of five factors: non-smoking, exercising, being cognitively active, having a high-quality diet, and limiting alcohol use. We used linear mixed-effects models to estimate cognitive decline by genetic risk and lifestyle score.

RESULTS

APOE  ε 4 allele was associated with faster cognitive decline in both races. However, within APOE  ε 4 carriers, adherence to a healthy lifestyle (eg., 4 to 5 healthy factors) was associated with a slower cognitive decline by 0.023 (95% confidence interval [CI] 0.004, 0.042) units/year in African Americans and 0.044 (95% CI 0.008, 0.080) units/year in European Americans.

DISCUSSION

A healthy lifestyle was associated with a slower cognitive decline in African and European Americans.

Impact of the Apolipoprotein E ε4 Allele on the Relationship Between Healthy Lifestyle and Cognitive Decline: A Population-Based Study

Adherence to a healthy lifestyle-characterized by abstaining from smoking, being physically and cognitively active, having a high-quality diet, and limiting alcohol use-is associated with slower cognitive decline in older adults, but whether this relationship extends to persons with a genetic predisposition (e.g., carriers of the ε4 allele of the apolipoprotein E gene (APOE*E4)) remains uncertain. Using data from a population-based study, the Chicago Health and Aging Project (Chicago, Illinois), we followed 3,886 individuals who underwent regular clinical and cognitive assessments from 1993 to 2012. Of 3,886 older adults, 1,269 (32.7%) were APOE*E4 carriers. Compared with noncarriers, APOE*E4 carriers had faster cognitive decline (β = -0.027 units/year, 95% confidence interval (CI): -0.032, -0.023). In contrast, persons with 2-3 and 4-5 healthy lifestyle factors had slower cognitive decline (β = 0.008 units/year (95% CI: 0.002, 0.014) and β = 0.019 units/year (95% CI: 0.011, 0.026), respectively) compared with those with 0-1 factor. In analyses stratified by APOE*E4 status, adherence to a healthy lifestyle (e.g., 4-5 factors vs. 0-1 factors) was associated with a slower rate of cognitive decline in both APOE*E4 carriers (β = 0.029, 95% CI: 0.013, 0.045) and noncarriers (β = 0.013, 95% CI: 0.005, 0.022). These results underscore the impact of a healthy lifestyle on cognition, particularly among persons with a genetic predisposition, who are more vulnerable to cognitive decline as they age.

Smoking is associated with impaired verbal learning and memory performance in women more than men

Vascular contributions to cognitive impairment and dementia (VCID) include structural and functional blood vessel injuries linked to poor neurocognitive outcomes. Smoking might indirectly increase the likelihood of cognitive impairment by exacerbating vascular disease risks. Sex disparities in VCID have been reported, however, few studies have assessed the sex-specific relationships between smoking and memory performance and with contradictory results. We investigated the associations between sex, smoking, and cardiovascular disease with verbal learning and memory function. Using MindCrowd, an observational web-based cohort of ~ 70,000 people aged 18-85, we investigated whether sex modifies the relationship between smoking and cardiovascular disease with verbal memory performance. We found significant interactions in that smoking is associated with verbal learning performance more in women and cardiovascular disease more in men across a wide age range. These results suggest that smoking and cardiovascular disease may impact verbal learning and memory throughout adulthood differently for men and women.

Effects of Smoking on Regional Homogeneity in Mild Cognitive Impairment: A Resting-State Functional MRI Study

Background

Smoking is a modifiable risk factor for Alzheimer’s disease (AD). However, smoking-related effects on intrinsic brain activity in high-risk AD population are still unclear.

Objective

We aimed to explore differences in smoking effects on brain function between healthy elderly and amnestic mild cognitive impairment (aMCI) patients using ReHo mapping.

Methods

We identified 64 healthy elderly controls and 116 aMCI patients, including 98 non-smoking and 18 smoking aMCI. Each subject underwent structural and resting-state functional MRI scanning and neuropsychological evaluations. Regional homogeneity (ReHo) mapping was used to assess regional brain synchronization. After correction for age, gender, education, and gray matter volume, we explored the difference of ReHo among groups in a voxel-wise way based on analysis of covariance (ANCOVA), followed by post hoc two-sample analyses (p < 0.05, corrected). Further, we correlated the mean ReHo with neuropsychological scales.

Results

Three groups were well-matched in age, gender, and education. Significant ReHo differences were found among three groups, located in the left supramarginal gyrus (SMG) and left angular gyrus (AG). Specifically, non-smoking aMCI had lower ReHo in SMG and AG than smoking aMCI and controls. By contrast, smoking aMCI had greater AG ReHo than healthy controls (p < 0.05). Across groups, correlation analyses showed that left AG ReHo correlated with MMSE (r = 0.18, p = 0.015), clock drawing test (r = 0.20, p = 0.007), immediate recall (r = 0.36, p < 0.001), delayed recall (r = 0.34, p < 0.001), and auditory verbal learning test (r = 0.20, p = 0.007).

Conclusion

Smoking might pose compensatory or protective effects on intrinsic brain activity in aMCI patients.

Adverse Vascular Risk Relates to Cerebrospinal Fluid Biomarker Evidence of Axonal Injury in the Presence of Alzheimer's Disease Pathology

BACKGROUND

Vascular risk factors promote cerebral small vessel disease and neuropathological changes, particularly in white matter where large-caliber axons are located. How Alzheimer's disease pathology influences the brain's vulnerability in this regard is not well understood.

OBJECTIVE

Systemic vascular risk was assessed in relation to cerebrospinal fluid concentrations of neurofilament light, a biomarker of large-caliber axonal injury, evaluating for interactions by clinical and protein markers of Alzheimer's disease.

METHODS

Among Alzheimer's Disease Neuroimaging Initiative participants with normal cognition (n = 117), mild cognitive impairment (n = 190), and Alzheimer's disease (n = 95), linear regression related vascular risk (as measured by the modified Framingham Stroke Risk Profile) to neurofilament light, adjusting for age, sex, education, and cognitive diagnosis. Interactions were assessed by cognitive diagnosis, and by cerebrospinal fluid markers of Aβ42, hyperphosphorylated tau, and total tau.

RESULTS

Vascular risk and neurofilament light were not related in the main effect model (p = 0.08). However, interactions emerged for total tau (p = 0.01) and hyperphosphorylated tau (p = 0.002) reflecting vascular risk becoming more associated with cerebrospinal fluid neurofilament light in the context of greater concentrations of tau biomarkers. An interaction also emerged for the Alzheimer's disease biomarker profiles (p = 0.046) where in comparison to the referent 'normal' biomarker group, individuals with abnormal levels of both Aβ42 and total tau showed stronger associations between vascular risk and neurofilament light.

CONCLUSION

Older adults may be more vulnerable to axonal injury in response to higher vascular risk burdens in the context of concomitant Alzheimer's disease pathology.

Factors Predicting the Onset of Amnestic Mild Cognitive Impairment or Alzheimer's Dementia in Persons With Subjective Cognitive Decline

The objective of the current retrospective cohort study was to identify vascular and/or neuropsychiatric risk factors predicting clinical progression in persons with subjective cognitive decline (SCD). Information on 1,525 persons with SCD (mean age = 73.8 [SD = 8.1] years) was obtained from the National Alzheimer's Coordinating Center. Clinical progression occurred from SCD to either amnestic mild cognitive impairment or Alzheimer's dementia over an average of 4.7 (SD = 2.9) years. Stepwise Cox regression was used. Compared to obesity (hazard ratio [HR] = 0.59) in the univariate unadjusted model, obesity (HR = 0.64), current smoking (HR = 2.02), and depressive symptoms (HR = 1.35) were significant after adjusting for covariates in the univariate model. In the multivariate adjusted model, obesity (HR = 0.64), current smoking (HR = 2.04), and depressive symptoms (HR = 1.36) remained significant predictors. Interventions should be designed to minimize transition by managing smoking and depressive symptoms. Further research is required for associations between obesity and clinical progression to test the hypothesis of obesity paradox. [Journal of Gerontological Nursing, 46(8), 28-36.].

Healthy lifestyle and the risk of Alzheimer dementia: Findings from 2 longitudinal studies

OBJECTIVE

To quantify the impact of a healthy lifestyle on the risk of Alzheimer dementia.

METHODS

Using data from the Chicago Health and Aging Project (CHAP; n = 1,845) and the Rush Memory and Aging Project (MAP; n = 920), we defined a healthy lifestyle score on the basis of nonsmoking, ≥150 min/wk moderate/vigorous-intensity physical activity, light to moderate alcohol consumption, high-quality Mediterranean-DASH Diet Intervention for Neurodegenerative Delay diet (upper 40%), and engagement in late-life cognitive activities (upper 40%), giving an overall score ranging from 0 to 5. Cox proportional hazard models were used for each cohort to estimate the hazard ratio (HR) and 95% confidence interval (CI) of the lifestyle score with Alzheimer dementia, and a random-effect meta-analysis was used to pool the results.

RESULTS

During a median follow-up of 5.8 years in CHAP and 6.0 years in MAP, 379 and 229 participants, respectively, had incident Alzheimer dementia. In multivariable-adjusted models, the pooled HR (95% CI) of Alzheimer dementia across 2 cohorts was 0.73 (95% CI 0.66-0.80) per each additional healthy lifestyle factor. Compared to participants with 0 to 1 healthy lifestyle factor, the risk of Alzheimer dementia was 37% lower (pooled HR 0.63, 95% CI 0.47-0.84) in those with 2 to 3 healthy lifestyle factors and 60% lower (pooled HR 0.40, 95% CI 0.28-0.56) in those with 4 to 5 healthy lifestyle factors.

CONCLUSION

A healthy lifestyle as a composite score is associated with a substantially lower risk of Alzheimer's dementia.

Smoking cessation and incident dementia in elderly Japanese: the Ohsaki Cohort 2006 Study

To investigate the association of smoking status and years since smoking cessation with the risk of incident dementia among elderly Japanese. We conducted a longitudinal analysis of smoking status and smoking cessation with dementia in prospective cohort study of 12,489 Japanese individuals aged ≥ 65 years who were followed up for 5.7 years. Information on smoking status and other lifestyle factors was collected via a questionnaire in 2006. Data on incident dementia were retrieved from the public Long-term Care Insurance Database. The Cox proportional hazards model was used to estimate the multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (95% CIs) for incident dementia. During 61,613 person-years of follow-up, 1110 cases (8.9%) of incident dementia were documented. Compared with individuals who had never smoked, current smokers showed a higher risk of dementia (HR 1.46, 95% CI 1.17, 1.80). Among ex-smokers, the risk for those who had stopped smoking for ≤ 2 years was still high (HR 1.39, 95% CI 0.96, 2.01), however, quitting smoking for 3 years or longer mitigated the increased risk incurred by smokers; the multivariable HRs (95% CIs) were 1.03 (0.70, 1.53) for those who had stopped smoking for 3–5 years, 1.04 (0.74, 1.45) for 6–10 years, 1.19 (0.84, 1.69) for 11–15 years, and 0.92 (0.73, 1.15) for > 15 years. Our study suggests that the risk of incident dementia among ex-smokers becomes the same level as that of never smokers if they maintain abstinence from smoking for at least 3 years.

Associations of cigarette smoking with memory decline and neurodegeneration among cognitively normal older individuals

Cigarette smoking is associated with a higher risk of Alzheimer's disease (AD), but the underlying mechanisms remain to be clarified. In this study, we aimed to examine the effects of cigarette smoking on multiple AD biomarkers among older individuals with normal cognition (NC). Among 415 older individuals with NC from the Alzheimer's disease Neuroimaging Initiative (ADNI) cohort, we examined the associations between smoking status (non-smokers vs smokers) and global cognition, verbal memory, hippocampal volumes, cerebral glucose metabolism and CSF AD pathologies. The primary findings of this study were: (1) In NC, smokers showed worse performance on verbal memory tests [Rey Auditory Verbal Learning Test (RAVLT) total learning score and delayed recall] than non-smokers; (2) Compared with non-smokers, smokers had significantly lower HpVR; (3) Smokers, relative to non-smokers, demonstrated lower levels of cerebral glucose metabolism as measured by FDG-PET; and (4) there were no significant differences in CSF AD pathologies (CSF Aβ42, t-tau or p-tau) between non-smokers and smokers. Longitudinal studies are needed to investigate the relationship between cigarettes smoking and changes in AD-related markers over time. Further, ADNI participants were highly educated and predominantly white. This may limit the generalizability of our results. In summary, among individuals with NC, cigarette smoking was associated with memory impairment, hippocampal atrophy and cerebral glucose hypometabolism, but not CSF AD pathologies.

Interactive Effects of Physical Activity and Cognitive Activity on Cognition in Older Adults Without Mild Cognitive Impairment or Dementia

Objective: The purpose of this secondary analysis was to test effects of interactions between accelerometer-measured physical activity and self-reported cognitive activity on cognition in older adults without cognitive impairment. Method: Participants were 742 older adults from the Rush Memory and Aging Project who completed annual clinical evaluations. A series of parallel growth models tested effects of interactions between physical activity and cognitive activity on cognition (global index, five domains) at Year 5, controlling for demographics, health factors, and corresponding cognition measures at Year 1. Results: Results were mixed, with significant physical and cognitive activity interactive effects for working and semantic memory. In models without interactions, higher physical and cognitive activities at Year 1 and less decline in cognitive activity over time were independently associated with better cognition at Year 5. Discussion: These findings may inform interventions that enhance physical and cognitive activities to prevent cognitive impairment in older adults.

Brain Banks Spur New Frontiers in Neuropsychiatric Research and Strategies for Analysis and Validation

Neuropsychiatric disorders affect hundreds of millions of patients and families worldwide. To decode the molecular framework of these diseases, many studies use human postmortem brain samples. These studies reveal brain-specific genetic and epigenetic patterns via high-throughput sequencing technologies. Identifying best practices for the collection of postmortem brain samples, analyzing such large amounts of sequencing data, and interpreting these results are critical to advance neuropsychiatry. We provide an overview of human brain banks worldwide, including progress in China, highlighting some well-known projects using human postmortem brain samples to understand molecular regulation in both normal brains and those with neuropsychiatric disorders. Finally, we discuss future research strategies, as well as state-of-the-art statistical and experimental methods that are drawn upon brain bank resources to improve our understanding of the agents of neuropsychiatric disorders.

The 20-Year Voyage Aboard the Journal of Alzheimer's Disease: Docking at 'Type 3 Diabetes', Environmental/Exposure Factors, Pathogenic Mechanisms, and Potential Treatments

The Journal of Alzheimer’s Disease (JAD), founded in 1998, played a pivotal role in broadening the field of research on Alzheimer’s disease (AD) by publishing a diverse range of clinical, pathological, molecular, biochemical, epidemiological, experimental, and review articles from its birth. This article recounts my own journey as an author who contributed articles to JAD over the 20 years of the journal’s existence. In retrospect, it seems remarkable that a considerable body of work that originated from our group marks a trail that began with studies of vascular, stress, and mitochondrial factors in AD pathogenesis, exploded into the concept of ‘Type 3 Diabetes’, and continued with the characterization of how environmental, exposure, and lifestyle factors promote neurodegeneration and which therapeutic strategies could reverse the neurodegeneration cascade.

Expanding instrumented gait testing in the community setting: A portable, depth-sensing camera captures joint motion in older adults

BACKGROUND

Currently, it is not feasible to obtain laboratory-based measures of joint motion in large numbers of older adults. We assessed the utility of a portable depth-sensing camera for quantifying hip and knee joint motion of older adults during mobility testing in the community.

METHODS

Participants were 52 older adults enrolled in the Rush Memory and Aging Project, a community-based cohort study of aging. In a subset, we compared dynamic hip and knee flexion/extension obtained via the depth-sensing camera with that obtained concurrently using a laboratory-based optoelectronic motion capture system. Then we recorded participants' annual instrumented gait assessment in the community setting with the depth-sensing camera and examined the inter-relationships of hip and knee range of motion (ROM) with mobility metrics derived from a wearable sensor and other mobility-related health measures.

RESULTS

In the community, we successfully acquired joint motion from 49/52 participants using the depth-sensing camera. Hip and knee ROMs were related to diverse sensor-derived metrics of mobility performance (hip: Pearson's r = 0.31 to 0.58; knee: Pearson's r = 0.29 to 0.51), as well as daily physical activity, conventional motor measures, self-report hip and knee pain and dysfunction, mobility disability, and falls.

CONCLUSIONS

The depth-sensing camera's high rate of successful data acquisition and correlations of its hip and knee ROMs with other mobility measures suggest that this device can provide a cost-efficient means of quantifying joint motion in large numbers of community-dwelling older adults who span the health spectrum.

Is Alzheimer's Disease Risk Modifiable?

Population-based clinic-pathological studies have established that the most common pathological substrate of dementia in community-dwelling elderly people is mixed, especially Alzheimer's disease (AD) and cerebrovascular ischemic disease (CVID), rather than pure AD. While these could be just two frequent unrelated comorbidities in the elderly, epidemiological research has reinforced the idea that mid-life (age <65 years) vascular risk factors increase the risk of late-onset (age ≥ 65 years) dementia, and specifically AD. By contrast, healthy lifestyle choices such as leisure activities, physical exercise, and Mediterranean diet are considered protective against AD. Remarkably, several large population-based longitudinal epidemiological studies have recently indicated that the incidence and prevalence of dementia might be decreasing in Western countries. Although it remains unclear whether these positive trends are attributable to neuropathologically definite AD versus CVID, based on these epidemiological data it has been estimated that a sizable proportion of AD cases could be preventable. In this review, we discuss the current evidence about modifiable risk factors for AD derived from epidemiological, preclinical, and interventional studies, and analyze the opportunities for therapeutic and preventative interventions.

Smoking and Risk for Alzheimer Disease: A Meta-Analysis Based on Both Case-Control and Cohort Study

This study was performed to identify the association between smoking and Alzheimer's disease (AD). To perform this meta-analysis based on case-control and cohort studies, PubMed, Google Scholar, and the CNKI electronic databases were searched through April 30, 2017. Our meta-analysis included 27 studies, including 16 that reported odds ratios (ORs) and 11 that reported hazard ratios (HRs) or ratio risks. No significant association was found between smoking and AD among the studies that reported ORs (1.020, 95% confidence interval [CI] = 0.812-1.281, I = 67.9%, random model, p < 0.001). A subgroup analysis revealed no significant difference between different smoking statuses. The pooled HRs revealed a significant association between smoking and AD (HR = 1.520, 95% CI = 1.194-1.934, I = 83.6%, random model, p < 0.001). Cumulative meta-analysis of the HRs revealed that the effect of smoking on AD tended to be stable over time. Smoking may confer an increased risk of AD, and this effect has tended to be stable over time.

Targeting Neuroinflammation to Treat Alzheimer's Disease

Over the past few decades, research on Alzheimer's disease (AD) has focused on pathomechanisms linked to two of the major pathological hallmarks of extracellular deposition of beta-amyloid peptides and intra-neuronal formation of neurofibrils. Recently, a third disease component, the neuroinflammatory reaction mediated by cerebral innate immune cells, has entered the spotlight, prompted by findings from genetic, pre-clinical, and clinical studies. Various proteins that arise during neurodegeneration, including beta-amyloid, tau, heat shock proteins, and chromogranin, among others, act as danger-associated molecular patterns, that-upon engagement of pattern recognition receptors-induce inflammatory signaling pathways and ultimately lead to the production and release of immune mediators. These may have beneficial effects but ultimately compromise neuronal function and cause cell death. The current review, assembled by participants of the Chiclana Summer School on Neuroinflammation 2016, provides an overview of our current understanding of AD-related immune processes. We describe the principal cellular and molecular players in inflammation as they pertain to AD, examine modifying factors, and discuss potential future therapeutic targets.

Tobacco Smoke Exposure Impairs Brain Insulin/IGF Signaling: Potential Co-Factor Role in Neurodegeneration

BACKGROUND

Human studies suggest tobacco smoking is a risk factor for cognitive impairment and neurodegeneration, including Alzheimer's disease (AD). However, experimental data linking tobacco smoke exposures to underlying mediators of neurodegeneration, including impairments in brain insulin and insulin-like growth factor (IGF) signaling in AD are lacking.

OBJECTIVE

This study tests the hypothesis that cigarette smoke (CS) exposures can impair brain insulin/IGF signaling and alter expression of AD-associated proteins.

METHODS

Adult male A/J mice were exposed to air for 8 weeks (A8), CS for 4 or 8 weeks (CS4, CS8), or CS8 followed by 2 weeks recovery (CS8+R). Gene expression was measured by qRT-PCR analysis and proteins were measured by multiplex bead-based or direct binding duplex ELISAs.

RESULTS

CS exposure effects on insulin/IGF and insulin receptor substrate (IRS) proteins and phosphorylated proteins were striking compared with the mRNA. The main consequences of CS4 or CS8 exposures were to significantly reduce insulin R, IGF-1R, IRS-1, and tyrosine phosphorylated insulin R and IGF-1R proteins. Paradoxically, these effects were even greater in the CS8+R group. In addition, relative levels of S312-IRS-1, which inhibits downstream signaling, were increased in the CS4, CS8, and CS8+R groups. Correspondingly, CS and CS8+R exposures inhibited expression of proteins and phosphoproteins required for signaling through Akt, PRAS40, and/or p70S6K, increased AβPP-Aβ, and reduced ASPH protein, which is a target of insulin/IGF-1 signaling.

CONCLUSION

Secondhand CS exposures caused molecular and biochemical abnormalities in brain that overlap with the findings in AD, and many of these effects were sustained or worsened despite short-term CS withdrawal.

Analysis of genetics and risk factors of Alzheimer's Disease

Alzheimer's Disease is the leading neurodegenerative cause of dementia. The pathogenesis is not clearly understood yet, is believed to be the complex interaction between genetic and environmental factors. Consequently vascular risk factors and Apolipoprotein E genotyping are increasingly gaining importance. This study aimed at assessing the relationships between Alzheimer's Disease and Apolipoprotein E phenotype and vascular risk factors. Patients diagnosed with "possible Alzheimer's Disease" in the Gazi University, Department of Neurology, were included in the study and age-matched volunteer patients who attended the polyclinic were included as a control group. In this study, the risk factors including low education level, smoking, hyperlipidemia, higher serum total cholesterol levels, and hyperhomocysteinemia were found to be statistically significantly more common in the Alzheimer's Disease group in comparison to the Control Group, while all Apolipoprotein E ε4/ε4 genotypes were found in the Alzheimer's Disease group. The presence of the Apolipoprotein E ε4 allele is believed to increase vascular risk factors as well as to affect Alzheimer's Disease directly. The biological indicators which are used in identifying the patients' genes will be probably used in the treatment plan of the patients in the future.

Relationship between metabolic and vascular conditions and cognitive decline among older Mexican Americans

OBJECTIVE

Metabolic and vascular conditions have been independently associated with dementia and cognitive decline among older adults, but research on the combined effects that these conditions have on cognitive decline, especially among older Mexican Americans, is lacking. The purpose of this study was to examine the relationship between metabolic and vascular conditions and cognitive decline among older Mexican Americans.

METHODS

The final sample included 2767 participants of the Hispanic Established Populations for the Epidemiologic Study of the Elderly. Linear mixed-effects regression was used to model cognitive decline across six examinations (1993-2007) according to the number (zero, one, two, and three to four) of metabolic and vascular conditions (hypertension, diabetes, stroke, and heart attack).

RESULTS

Of the 2767 participants included in the final sample, 777 had zero conditions, 1314 had one condition, 553 had two conditions, and 123 had three to four conditions. Participants with two or three to four conditions had significantly greater cognitive decline compared with participants with zero or one condition. Stroke had the largest effect size on cognitive decline based on the proportion of variance that stroke accounted for in the linear mixed-effects model.

CONCLUSION

Mexican American older adults with multiple metabolic and vascular conditions exhibit greater cognitive decline than those with zero or one condition. Public health interventions designed to reduce the prevalence of chronic metabolic and vascular conditions, in particular stroke, may limit the severity of cognitive decline among older Mexican Americans.

Dementias

This chapter will focus on the descriptive, analytic, and intervention-oriented epidemiology of dementia and its most frequent etiologic type due to Alzheimer's disease. The chapter opens with a brief presentation of the concept of dementia, followed by the presentation of dementia of the Alzheimer type (DAT), including natural history, clinical manifestation, neuropathology, medical prognosis, and management. Further, the chapter presents the prevalence and incidence of dementia, with special consideration of secular trends in prevalence and incidence of DAT, and prognosis of the socioeconomic impact of dementia. Thereafter the main risk factors for DAT are covered. The chapter also addresses the results of ongoing therapeutic and preventive intervention trials for DAT. Finally, the future challenges of the epidemiology of dementia with a focus on the impact of the new diagnostic criteria for neurocognitive disorders, as well as the development of biomarkers for DAT and other types of dementia, will be briefly discussed.

Impact of smoking on neurodegeneration and cerebrovascular disease markers in cognitively normal men

BACKGROUND AND PURPOSE

Smoking is a major risk factor for cognitive decline and dementia. However, the exact pathobiology of smoking remains unknown. The effects of smoking on cortical thickness as a biomarker of neurodegeneration or white matter hyperintensities and lacunes as biomarkers of cerebrovascular burden were concurrently evaluated.

METHODS

Our study included 977 cognitively normal men who visited a health promotion centre and underwent medical check-ups, including 3.0 T magnetic resonance imaging. Participants were categorized into never smoker, past smoker or current smoker groups and pack-years and the years of smoking cessation were used as continuous variables.

RESULTS

The current smoker group exhibited cortical thinning in frontal and temporo-parietal regions compared with the never smoker group. These effects were particularly prominent in smokers with a high cumulative exposure to smoking in the current smoker group. However, there was no association between smoking and the severity of white matter hyperintensity or number of lacunes.

CONCLUSION

Our findings indicate that smoking might impact on neurodegeneration rather than cerebrovascular burdens in cognitively normal men, suggesting that smoking might be an important modifiable risk factor for the development of Alzheimer's disease.

Smoking is associated with an increased risk of dementia: a meta-analysis of prospective cohort studies with investigation of potential effect modifiers

Background

Previous studies showed inconsistent results on the association of smoking with all-cause dementia and vascular dementia (VaD), and are limited by inclusion of a small number of studies and unexplained heterogeneity. Our review aimed to assess the risk of all-cause dementia, Alzheimer’s disease (AD) and VaD associated with smoking, and to identify potential effect modifiers.

Methods and Findings

The PubMed, Embase, Cochrane Library and Psychinfo databases were searched to identify studies that provided risk estimates on smoking and incidence of dementia. A random-effects model was used to yield pooled results. Thirty-seven studies were included. Compared with never smokers, current smokers showed an increased risk of all-cause dementia (risk ratio (RR) 1.30, 95% confidence interval (CI) 1.18–1.45), AD (RR 1.40, 95% CI 1.13–1.73) and VaD (RR 1.38, 95% CI 1.15–1.66). For all-cause dementia, the risk increased by 34% for every 20 cigarettes per day (RR 1.34, 95% CI 1.25–1.43). Former smokers did not show an increased risk of all-cause dementia (RR 1.01, 95% CI 0.96–1.06), AD (RR 1.04, 95% CI 0.96–1.13) and VaD (RR 0.97, 95% CI 0.83–1.13). Subgroup analyses indicated that (1) the significantly increased risk of AD from current smoking was seen only in apolipoprotein E ε4 noncarriers; (2) current smokers aged 65 to 75 years at baseline showed increased risk of all-cause dementia and AD compared to those aged over 75 or under 65 years; and (3) sex, race, study location and diagnostic criteria difference in risk of dementia was not found.

Conclusions

Smokers show an increased risk of dementia, and smoking cessation decreases the risk to that of never smokers. The increased risk of AD from smoking is more pronounced in apolipoprotein E ε4 noncarriers. Survival bias and competing risk reduce the risk of dementia from smoking at extreme age.

Smoking and increased Alzheimer's disease risk: a review of potential mechanisms

BACKGROUND

Cigarette smoking has been linked with both increased and decreased risk for Alzheimer's disease (AD). This is relevant for the US military because the prevalence of smoking in the military is approximately 11% higher than in civilians.

METHODS

A systematic review of published studies on the association between smoking and increased risk for AD and preclinical and human literature on the relationships between smoking, nicotine exposure, and AD-related neuropathology was conducted. Original data from comparisons of smoking and never-smoking cognitively normal elders on in vivo amyloid imaging are also presented.

RESULTS

Overall, literature indicates that former/active smoking is related to a significantly increased risk for AD. Cigarette smoke/smoking is associated with AD neuropathology in preclinical models and humans. Smoking-related cerebral oxidative stress is a potential mechanism promoting AD pathology and increased risk for AD.

CONCLUSIONS

A reduction in the incidence of smoking will likely reduce the future prevalence of AD.

Poor oral health as a chronic, potentially modifiable dementia risk factor: review of the literature

Poor oral health, including caries, tooth loss, and periodontitis, is ubiquitous worldwide, and is potentially treatable and preventable. Like adverse oral health conditions, Alzheimer disease and related disorders are also very common among aging populations. Established risk factors for Alzheimer disease include cerebrovascular disease and its vascular risk factors, many of which share associations with evidence of systemic inflammation also identified in periodontitis and other poor oral health states. In this review, we present epidemiologic evidence of links between poor oral health and both prevalent and incident cognitive impairment, and review plausible mechanisms linking these conditions, including evidence from compelling animal models. Considering that a large etiologic fraction of dementia remains unexplained, these studies argue for further multidisciplinary research between oral health conditions, including translational, epidemiologic, and possibly clinical treatment studies.

Alzheimer’s disease, cerebrovascular disease, and the β-amyloid cascade

Alzheimer’s disease (AD), considered the commonest neurodegenerative cause of dementia, is associated with hallmark pathologies including extracellular amyloid-β protein (Aβ) deposition in extracellular senile plaques and vessels, and intraneuronal tau deposition as neurofibrillary tangles. Although AD is usually categorized as neurodegeneration distinct from cerebrovascular disease (CVD), studies have shown strong links between AD and CVD. There is evidence that vascular risk factors and CVD may accelerate Aβ 40-42 production/ aggregation/deposition and contribute to the pathology and symptomatology of AD. Aβ deposited along vessels also causes cerebral amyloid angiopathy. Amyloid imaging allows in vivo detection of AD pathology, opening the way for prevention and early treatment, if disease-modifying therapies in the pipeline show safety and efficacy. In this review, we review the role of vascular factors and Aβ, underlining that vascular risk factor management may be important for AD prevention and treatment.