Racial and Ethnic Differences in the Population-Attributable Fractions of Alzheimer Disease and Related Dementias

BACKGROUND AND OBJECTIVES

Previous studies estimated that modifiable risk factors explain up to 40% of the dementia cases in the United States and that this population-attributable fraction (PAF) differs by race and ethnicity-estimates of future impact based on the risk factor prevalence in contemporary surveys. The aim of this study was to determine the race-specific and ethnicity-specific PAF of late-onset Alzheimer disease and related dementias (ADRDs) based on the risk factor prevalence and associations observed on the same individuals within a prospective cohort.

METHODS

Data were from Multiethnic Cohort Study participants (African American, Japanese American, Latino, Native Hawaiian, and White) enrolled in Medicare Fee-for-Service. We estimated the PAF based on the prevalence of risk factors at cohort baseline and their mutually adjusted association with subsequent ADRD incidence. Risk factors included low educational attainment and midlife exposures to low neighborhood socioeconomic status, unmarried status, history of hypertension, stroke, diabetes or heart disease, smoking, physical inactivity, short or long sleep duration, obesity, and low-quality diet, as well as APOE ε4 for a subset.

RESULTS

Among 91,881 participants (mean age 59.3 at baseline, 55.0% female participants), 16,507 incident ADRD cases were identified from Medicare claims (1999-2016, mean follow-up 9.3 years). The PAF for nongenetic factors combined was similar in men (24.0% [95% CI 21.3-26.6]) and women (22.8% [20.3-25.2]) but varied across Japanese American (14.2% [11.1-17.2]), White (21.9% [19.0-24.7]), African American (27.8% [22.3-33.0]), Native Hawaiian (29.3% [21.0-36.7]), and Latino (33.3% [27.5-38.5]) groups. The combined PAF was attenuated when accounting for competing risk of death, in both men (10.4%) and women (13.9%) and across racial and ethnic groups (4.7%-25.5%). The combined PAF was also different by age at diagnosis and ADRD subtypes, higher for younger (65-74 years: 43.2%) than older (75-84 years: 32.4%; ≥85 years: 11.3%) diagnoses and higher for vascular or unspecified ADRD than for AD or Lewy body dementia. An additional PAF of 11.8% (9.9-13.6) was associated with APOE ε4, which together with nongenetic risk factors accounted for 30.6% (25.8-35.1) of ADRD.

DISCUSSION

Known risk factors explained about a third of the ADRD cases but with unequal distributions across racial and ethnic groups.

Paradigm Shift: Multiple Potential Pathways to Neurodegenerative Dementia

Neurodegenerative dementia can result from multiple underlying abnormalities, including neurotransmitter imbalances, protein aggregation, and other neurotoxic events. A major complication in identifying effective treatment targets is the frequent co-occurrence of multiple neurodegenerative processes, occurring either in parallel or sequentially. The path towards developing effective treatments for Alzheimer's disease (AD) and other dementias has been relatively slow and until recently has focused on disease symptoms. Aducanumab and lecanemab, recently approved by the FDA, are meant to target disease structures but have only modest benefit on symptom progression and remain unproven in reversing or preventing dementia. A third, donanemab, appears more promising but awaits FDA approval. Ongoing trials include potential cognition enhancers, new combinations of known drugs for synergistic effects, prodrugs with less toxicity, and increasing interest in drugs targeting neuroinflammation or microbiome. Scientific and technological advances offer the opportunity to move in new therapy directions, such as modifying microglia to prevent or suppress underlying disease. A major challenge, however, is that underlying comorbidities likely influence the effectiveness of therapies. Indeed, the full range of comorbidity, today only definitively identified postmortem, likely contributes to failed clinical trials and overmedication of older adults, since it is difficult to exclude (during life) people unlikely to respond. Our current knowledge thus signals that a paradigm shift towards individualized and multimodal treatments is necessary to effectively advance the field of dementia therapeutics.

If Midlife Brain Injury Is a Risk Factor for Alzheimer's Disease and Related Dementias, What Is the Neuropathologic Mechanism?

While we know that brain injuries related to sport and military activities sometimes lead to cognitive impairment or early onset dementia, it is unclear if and how they might influence the development of Alzheimer's Disease and Related Dementias (ADRD). Published analytic conclusions have been mixed. Two reports in the Journal of Alzheimer's Disease reach the same answer: a history of brain injury appears to be a risk factor for generalized brain atrophy, which would likely increase vulnerability to the subsequent development of any variety of ADRD, or to dementia directly attributable to reduced brain mass.

Modifying effects of race and ethnicity and APOE on the association of physical activity with risk of Alzheimer's disease and related dementias

INTRODUCTION

We investigated whether the protective association of physical activity with risk of Alzheimer's disease and related dementias (ADRD) has genetic or behavioral variations.

METHODS

In the Multiethnic Cohort, we analyzed moderate or vigorous physical activity (MVPA) reported at ages 45 to 75 among 88,047 participants in relation to 13,039 incident diagnoses of late-onset ADRD identified in Medicare claims (1999 to 2014), by five racial and ethnic groups, hours sitting, and in a subset (16%), apolipoprotein E (APOE) genotype.

RESULTS

MVPA was inversely associated with ADRD (hazard ratio for ≥14 vs <2.5 hours/week: 0.83, 95% confidence interval [CI]: 0.76 to 0.90 in men; 0.88, 5% CI: 0.81 to 0.95 in women). The association was inverse in all racial and ethnic groups except Black participants (P-heterogeneity = 0.52), but stronger in individuals with lower levels of sitting duration or those who do not carry the APOE e4 risk allele.

DISCUSSION

The different effects of physical activity by sitting duration and APOE genotype warrant further research.

Neuropathologic Changes of Alzheimer's Disease and Related Dementias: Relevance to Future Prevention

BACKGROUND

Decedents with late-life dementia are often found at autopsy to have vascular pathology, cortical Lewy bodies, hippocampal sclerosis, and/or TDP-43 encephalopathy alone or with concurrent Alzheimer's disease (AD) lesions. Nonetheless, it is commonly believed that AD neuropathologic changes (NC) are the dominant or exclusive drivers of late-life dementia.

OBJECTIVE

Assess associations of end-of-life cognitive impairment with any one or any combination of five distinct NC. Assess impairment prevalence among subjects having natural resistance to each type of NC.

METHODS

Brains from 1,040 autopsied participants of the Honolulu-Asia Study, the Nun Study, and the 90 + Study were examined for NC of AD, Lewy body dementia, microvascular brain injury, hippocampal sclerosis, and limbic predominate TDP-43 encephalopathy. Associations with impairment were assessed for each NC and for NC polymorbidity (variable combinations of 2-5 concurrent NC).

RESULTS

Among 387 autopsied decedents with severe cognitive impairment, 20.4% had only AD lesions (ADNC), 25.3% had ADNC plus 1 other NC, 11.1% had ADNC plus 2 or more other NC, 28.7% had no ADNC but 1-4 other NC, and 14.5% had no/negligible NC. Combinations of any two, three, or four NC were highly frequent among the impaired. Natural resistance to ADNC or any other single NC had a modest impact on overall cohort impairment levels.

CONCLUSION

Polymorbidity involving 1-5 types of concurrent NC is a dominant neuropathologic feature of AD and related dementias. This represents a daunting challenge to future prevention and could explain failures of prior preventive intervention trials and of efforts to identify risk factors.

Mid- and later-life risk factors for predicting neuropathological brain changes associated with Alzheimer's and vascular dementia: The Honolulu Asia Aging Study and the Age, Gene/Environment Susceptibility-Reykjavik Study

INTRODUCTION

Dementia prediction models are necessary to inform the development of dementia risk reduction strategies. Here, we examine the utility of neuropathological-based risk scores to predict clinical dementia.

METHODS

Models were developed for predicting Alzheimer's disease (AD) and non-AD neuropathologies using the Honolulu Asia Aging neuropathological sub-study (HAAS; n = 852). Model accuracy for predicting clinical dementia, over 30 years, was tested in the non-autopsied HAAS sample (n = 2960) and the Age, Gene/Environment Susceptibility-Reykjavik Study (n = 4614).

RESULTS

Different models were identified for predicting neurodegenerative and vascular neuropathology (c-statistic range: 0.62 to 0.72). These typically included age, APOE, and a blood pressure-related measure. The neurofibrillary tangle and micro-vascular lesion models showed good accuracy for predicting clinical vascular dementia.

DISCUSSION

There may be shared risk factors across dementia-related lesions, suggesting common pathways. Strategies targeting these models may reduce risk or postpone clinical symptoms of dementia as well as reduce neuropathological burden associated with AD and vascular lesions.

Association of Cognition and Dementia With Neuropathologic Changes of Alzheimer Disease and Other Conditions in the Oldest Old

BACKGROUND AND OBJECTIVES

Age is the largest risk factor for dementia. However, dementia is not universal, even among the oldest-old age groups. Following contemporary neuropathologic guidelines, our objectives were to describe the key neuropathologic lesions and their associations with antemortem cognition in oldest-old individuals.

METHODS

Participants were those enrolled in The 90+ Study, a longitudinal, population-based study of aging/dementia in the oldest old, who agreed to postmortem brain examination. All autopsied brains as of December 2020 were evaluated for the prevalence of Alzheimer disease neuropathologic change (ADNC) and non-ADNC neuropathologic comorbidities. Associations between neuropathologic lesions or the total neuropathologic burden score (sum of the individual scores) and cognition were assessed using multinomial logistic regression and multiple linear regression. Separate regression analyses evaluated relationships between limbic-predominant age-related TDP-43 encephalopathy (LATE-NC) and hippocampal sclerosis (HS) or ADNC/primary age-related tauopathy (PART). Resistance, or failure to develop ADNC/PART, and resilience, inferred from higher-than-expected cognitive functioning, were evaluated in the presence or absence of non-ADNC neuropathologic features.

RESULTS

The most common neuropathologic features in the sample (n = 367) were ADNC/PART related. Increased dementia odds were associated with elevated total neuropathologic burden (odds ratio [OR] 1.5, 95% CI 1.3-1.7, p < 0.0001), β-amyloid (OR 1.6, 95% CI 1.2-2.0, p < 0.0001), neurofibrillary tangles (OR 2.6, 95% CI 1.7-4.1, p < 0.0001), and LATE-NC (OR 2.3, 95% CI 1.7-3.1, p < 0.0001), correcting for multiple comparisons. LATE-NC was associated with dementia with (OR 6.1, 95% CI 2.0-18.7, p = 0.002) and without (OR 5.0, 95% CI 2.6-9.7, p < 0.0001) co-occurring HS and increased the odds of dementia among participants with ADNC (OR 5.0, 95% CI 2.7-9.2, p < 0.0001). Resistance to moderate/severe ADNC/PART was rare (3%), but resilience to ADNC/PART was not (55%). Resilience was rarer in the presence of non-ADNC comorbid lesions, particularly LATE-NC. Among those with moderate/severe ADNC/PART, dementia odds increased with each non-ADNC comorbid lesion (e.g., 1 lesion: OR 2.4, 95% CI 1.3-4.5, p < 0.005; 2 lesions: OR 5.9, 95% CI 2.8-12.3, p < 0.0001).

DISCUSSION

These results highlight the importance of non-ADNC neuropathologic comorbidity, predominantly LATE-NC, to cognition in the oldest old. Given the cumulative effects of non-ADNC comorbid neuropathologic abnormalities, reducing their prevalence, especially LATE-NC, will be vital to the ultimate goal of reducing dementia burden in the oldest-old individuals.

Midlife alcohol consumption and later life cognitive impairment: Light drinking is not protective and APOE genotype does not change this relationship

Introduction

Much debate exists about the role of light to moderate alcohol intake and subsequent cognitive function. The apolipoprotein E genotype may modify the relationship.

Methods

Using data from the Honolulu-Asia Aging Study, a longitudinal population-based cohort (n = 2,416), Cox proportional hazards regression analyses were performed to measure midlife alcohol intake (average age = 52 years) and later life cognitive function (average age = 87 years) and to explore the role of apolipoprotein E genotype.

Results

No protective effect of light drinking (>1 drink/month– 1 drink/day) or moderate drinking (>1–2 drinks/day) was observed in the cohort in adjusted models (HR = 1.013, CI:0.88–1.16; HR = 1.104, CI:0.91–1.34, respectively). Heavy drinking (>2–4 drinks/day) and very heavy drinking (>4 drinks/day) increased the risk for incident moderate cognitive impairment (HR = 1.355, CI:1.09–1.68; HR = 1.462, CI:1.04–2.05, respectively). When examining the relationship by apolipoprotein E ε4 carrier status, a similar dose-response pattern was observed in both groups with higher hazard ratios for those carrying at least one copy of the apolipoprotein E ℇ4 allele. As alcohol level increased, the age at incident moderate cognitive impairment decreased, especially among those with at least one apolipoprotein E ℇ4 allele.

Discussion

We did not observe a significant protective effect for light to moderate drinking in midlife and subsequent cognitive impairment in this cohort. Heavy drinking increased the risk for moderate cognitive impairment and decreased the age at incidence, as did carrying at least one allele of the apolipoprotein E ℇ4 gene.

Brain Injury and Later-Life Cognitive Impairment and Neuropathology: The Honolulu-Asia Aging Study

BACKGROUND

Findings are inconsistent regarding the role of traumatic head injury in the subsequent development of neurologic outcomes.

OBJECTIVE

Examine the relationship between head injury and later cognitive impairment.

METHODS

A sample of 3,123 Japanese-American men was assessed for history of head injury and evaluated for cognitive impairment using the Cognitive Abilities Screening Instrument (CASI). For a subsample of 676 respondents, neuropathologic results from those with and without head injury were compared.

RESULTS

Although the crude model showed an association between history of head injury and later severe cognitive impairment, the relationship lost significance in the adjusted model (OR = 1.320, CI: 0.90-1.93), regardless of time between injury and impairment. Similar to cognitive impairment, hippocampal sclerosis was observed significantly more in the brains of respondents with a history of head injury in the crude model, but the relationship weakened in the adjusted model (OR = 1.462, CI: 0.68-3.12). After adjustment, decedents with a head injury demonstrated marginally higher brain weight (OR = 1.003, CI: 1.00-1.01).

CONCLUSION

We did not find a relationship between head injury and subsequent cognitive decline in this cohort. The neuropathology results also displayed no strong association between history of head injury and specific brain lesions and characteristics. These results support other findings in prospective cohorts. However, they could be influenced by the demographic make-up of the sample (male Japanese-Americans) or by the observation that the majority reported only a single head injury.

Cognitive Impairment in Older Adults and Therapeutic Strategies

Cognitive impairment and its severe form dementia are increasingly prevalent in older adults and loom as a public health disaster unless effective interventions are developed. Cognitive impairment is a convergent trait caused by damage from an idiosyncratic mix of four prevalent diseases (Alzheimer disease; vascular brain injury; Lewy body diseases, such as Parkinson disease and dementia with Lewy bodies; and limbic-predominant age-related transactive response DNA-binding protein 43 encephalopathy) that is counterbalanced by individually varying resilience, which is comprised of reserve and compensation. Brain regional damage from each of these four prevalent diseases is generated by the net effect of injury and (mal)adaptive response and is accompanied by characteristic lesions. Existing therapeutics enhance resilience, whereas most agents under development target mechanisms of damage with only suppression of vascular brain injury yet to show therapeutic promise. We hope to anticipate future tailored interventions that target mechanisms of damage and thereby avert the oncoming surge of cognitive impairment and dementia in older adults. SIGNIFICANCE STATEMENT: Brain regional damage is generated by the net effect of injury and (mal)adaptive response. The extent to which signs and symptoms of such damage occur is influenced by an underlying resilience comprising reserve and compensation. Finding tailored interventions that target specific mechanisms of damage likely yields the most effective therapies.

Military-related experiences and late-life depressive symptomatology among Japanese-American world war II veterans

Objectives: To examine military service-related variables and late-life depressive symptomatology among older Japanese-American males.Method: This study is a secondary data analysis of a longitudinal, community-based study. A sample of 2669 participants (771 World War II veterans, 1898 civilians) was drawn from the Honolulu-Asia Aging Study. Depressive symptoms were assessed twice across a 9-year period with the Center for Epidemiologic Studies-Depression scale. Covariates included sociodemographic, physical health, health behavior, and psychosocial variables. Combat exposure and symptomatology were examined among a subset of 426 veterans. Cross-sectional and longitudinal designs were analyzed with linear regression.Results: Veterans and civilians did not differ in depression scores. Baseline depression scores significantly predicted follow-up depression scores. For the full sample, lower ratings of quality of life satisfaction, daily activity control and general health were associated with higher depression scores both cross-sectionally and longitudinally. Among veterans, light combat exposure was marginally associated with lower depression scores and longitudinally, previous depression scores and poorer health ratings were significant predictors of depression scores.Conclusion: Results suggest that military service does not affect late-life depressive symptomatology. However, combat exposure may play a marginal role in increased symptoms. Reasons for results include the possibility that other factors are more relevant to late-life depression, symptomatology naturally decreasing over time, or type of combat exposure measurement. Results expand literature by examination of an ethnoracial group not studied often and longitudinal examination of late-life depressive symptoms within a military-related context. Stakeholders should be knowledgeable of the distinct issues presented when serving aging veterans.

Incident prolonged QT interval in midlife and late-life cognitive performance

BACKGROUND

Measures of cardiac ventricular electrophysiology have been associated with cognitive performance in cross-sectional studies. We sought to evaluate the association of worsening ventricular repolarization in midlife, as measured by incident prolonged QT interval, with cognitive decline in late life.

METHODS

Midlife QT interval was assessed by electrocardiography during three study visits from 1965/68 to 1971/74 in a cohort of Japanese American men aged 46-68 at Exam 1 from the Honolulu Heart Study. We defined incident prolonged QT as the QT interval in the upper quartile at Exam 2 or 3 after QT interval in lower three quartiles at Exam 1. Cognitive performance was assessed at least once using the Cognitive Abilities Screening Instrument (CASI), scored using item response theory (CASI-IRT), during four subsequent visits from 1991/93 to 1999/2000 among 2,511 of the 4,737 men in the Honolulu-Asia Aging Study otherwise eligible for inclusion in analyses. We used marginal structural modeling to determine the association of incident prolonged QT with cognitive decline, using weighting to account for confounding and attrition.

RESULTS

Incident prolonged QT interval in midlife was not associated with late-life CASI-IRT at cognitive baseline (estimated difference in CASI-IRT: 0.04; 95% CI: -0.28, 0.35; p = 0.81), or change in CASI-IRT over time (estimated difference in annual change in CASI-IRT: -0.002; 95%CI: -0.013, 0.010; p = 0.79). Findings were consistent across sensitivity analyses.

CONCLUSIONS

Although many midlife cardiovascular risk factors and cardiac structure and function measures are associated with late-life cognitive decline, incident prolonged QT interval in midlife was not associated with late-life cognitive performance or cognitive decline.

TDP-43 Neuropathologic Associations in the Nun Study and the Honolulu-Asia Aging Study

Transactive response binding protein-43 (TDP-43) cytoplasmic neuronal and glial aggregates (pathologic TDP-43) have been described in multiple brain diseases. We describe the associations between neuropathologically confirmed TDP-43 and cognition in two population-based cohorts: the Nun Study (NS) and the Honolulu-Asia Aging Study (HAAS). In the HAAS, there was a significant association between hippocampal sclerosis (HS) and TDP-43 (OR = 11.04, p < 0.0001, 95% CI 3.57-34.13). In the NS, there were significant associations between TDP-43 and HS (OR = 16.44, p > 0.001 95%, CI 7.10-38.00) and Alzheimer's disease (AD) severity (OR = 1.74, p = 0.009, 95% CI 1.15-2.64). When cognitive scores were added to the model, HS remained significant but the other variables were not. When HS was removed from the model, the overall model remained significant and the associations between cognitive performance and TDP-43 (OR = 2.11, p = 0.022, 95% CI 1.11-4.02) were significant. In the NS, there was a significant association between cognitive performance and TDP-43 (OR 1.94 p = 0.005, 95% CI 1.22-3.09) (HS remained significant, but AD did not). When HS was removed from the model, only CERAD was significant (OR = 2.43 p < 0.001, 95% CI 1.58-3.74). These results support a consistent association between pathologic TDP-43, HS, and the development of cognitive impairment in two large studies of brain aging, while the relationship between AD pathology and TDP-43 may vary according to cohort-specific features.

How do we validate approaches that aim to harness reserve to improve the aging brain?

An accurate assessment of the impact of reserve on cognitive functioning in older individuals with brain pathology requires careful measurement of each and an assessment of the extent to which each influences the other. Studies to integrate information about molecular biology, neuropathology, behavioral aspects of cognitive decline, and cognitive resilience will be of particular importance. In addition, more work is needed to improve our understanding of the effect of systemic factors on brain health and function. It seems likely that, even in later life, the brain's plasticity may allow for a positive response to stimulation. The ultimate goal of this research is to create a validated set of variables and interventions-and to understand the biology underlying them-that are useful not only in describing an individual's cognitive state but also in identifying promising paths for treatment and prevention of cognitive decline.

Excessive daytime sleepiness and topographic expansion of Lewy pathology

OBJECTIVE

While excessive daytime sleepiness (EDS) can predate the clinical diagnosis of Parkinson disease (PD), associations with underlying PD pathogenesis are unknown. Our objective is to determine if EDS is related to brain Lewy pathology (LP), a marker of PD pathogenesis, using clinical assessments of EDS with postmortem follow-up.

METHODS

Identification of LP was based on staining for α-synuclein in multiple brain regions in a sample of 211 men. Data on EDS were collected at clinical examinations from 1991 to 1999 when participants were aged 72-97 years.

RESULTS

Although EDS was more common in the presence vs absence of LP (p = 0.034), the association became stronger in neocortical regions. When LP was limited to the olfactory bulb, brainstem, and basal forebrain (Braak stages 1-4), frequency of EDS was 10% (4/40) vs 17.5% (20/114) in decedents without LP (p = 0.258). In contrast, compared to the absence of LP, EDS frequency doubled (36.7% [11/30], p = 0.023) when LP reached the anterior cingulate gyrus, insula mesocortex, and midfrontal, midtemporal, and inferior parietal neocortex (Braak stage 5). With further infiltration into the primary motor and sensory neocortices (Braak stage 6), EDS frequency increased threefold (51.9% [14/27], p < 0.001). Findings were similar across sleep-related features and persisted after adjustment for age and other covariates, including the removal of PD and dementia with Lewy bodies.

CONCLUSIONS

The association between EDS and PD includes relationships with extensive topographic LP expansion. The neocortex could be especially vulnerable to adverse relationships between sleep disorders and aggregation of misfolded α-synuclein and LP formation.

Most cases with Lewy pathology in a population-based cohort adhere to the Braak progression pattern but 'failure to fit' is highly dependent on staging system applied

Braak et al.'s 2003 paper detailing the caudo-rostral progression of Lewy body pathology (LP) formed the foundation of current understanding of disease spread in Parkinson's disease (PD); however, its methods are difficult to recreate and consequently multiple new staging systems emerged to recapitulate Braak's staging system using standard neuropathological methods and to account for other patterns of LP. Studies using these systems have documented widely variable rates of cases that 'fail to fit' expected patterns of LP spread. This could be due to population differences, features of individual systems, or may constitute under-recognized patterns of disease. We examined 324 neuropathological cases from the Honolulu Asia Aging Study and applied four different LP staging systems to determine the proportion of cases adhering to different staging methodologies and those that 'fail to fit' expected patterns of LP. Of 141 cases with LP (24: PD, 8: Dementia with Lewy bodies (DLB), 109: Incidental Lewy body disease (ILBD)), our application of Braak et al., 2003 classified 83.7%, Müller et al., 2005 classified 87.9%, Beach et al., 2009 classified 100%, and Leverenz et al., 2008 classified 98.6%. There were significant differences in the cases classifiable by the Leverenz and Beach systems versus the Braak and Müller systems (p < 0.001 for each). In this population-based autopsy cohort with a high prevalence of ILBD, the majority of cases were consistent with the progression characterized by the Braak et al. however, the determination of cases as atypical is highly dependent on the staging system applied.

The CAIDE Dementia Risk Score and the Honolulu-Asia Aging Study

INTRODUCTION

The CAIDE (Cardiovascular Risk Factors, Aging, and Incidence of Dementia) dementia risk score is based on demographic, genetic, and modifiable risk factors in midlife and has been shown to be predictive of later-life dementia.

OBJECTIVE

To test the predictive capacity of the CAIDE dementia risk score among a cohort of Japanese-American men.

METHODS

Midlife measures were obtained from a sample of 3,582 Japanese-American men in the Honolulu Heart Program (1965-1968, average age = 53.1 years). A follow-up exam in 1991 (average age = 77.8 years) assessed cognitive impairment using the Cognitive Abilities Screening Instrument (CASI). Severe cognitive impairment was defined as a CASI score <60.

RESULTS

In this cohort, the CAIDE dementia risk score demonstrates significant association with later-life severe cognitive impairment (OR = 1.477, 95% CI: 1.39-1.58). However, the area under the receiver-operating characteristic curve c-statistics suggests poor predictive ability (c = 0.645, 95% CI: 0.62-0.67). Using a score cut-point of 10, the accuracy is acceptable (0.82), but the sensitivity is low (0.50).

CONCLUSION

While the CAIDE dementia risk score at midlife is associated with later development of cognitive impairment in Japanese-American men, its predictive capacity in this population is weak.

Association of brain heptachlor epoxide and other organochlorine compounds with lewy pathology

BACKGROUND

Organochlorine pesticides are associated with an increased risk of Parkinson's disease. A preliminary analysis from the Honolulu-Asia Aging Study suggested that heptachlor epoxide, a metabolite from an organochlorine pesticide extensively used in Hawaii, may be especially important. This was a cross sectional analysis to evaluate the association of heptachlor epoxide and other organochlorine compounds with Lewy pathology in an expanded survey of brain organochlorine residues from the longitudinal Honolulu-Asia Aging Study.

METHODS

Organochlorines were measured in frozen occipital or temporal lobes in 705 brains using gas chromatography with mass spectrometry. Lewy pathology was identified using hematoxylin and eosin- and α-synuclein immunochemistry-stained sections from multiple brain regions.

RESULTS

The prevalence of Lewy pathology was nearly doubled in the presence versus the absence of heptachlor epoxide (30.1% versus 16.3%, P < 0.001). Although associations with other compounds were weaker, hexachlorobenzene (P = 0.003) and α-chlordane (P = 0.007) were also related to Lewy pathology. Most of the latter associations, however, were a result of confounding from heptachlor epoxide. Neither compound was significantly related to Lewy pathology after adjustment for heptachlor epoxide. In contrast, the association of heptachlor epoxide with Lewy pathology remained significant after adjustments for hexachlorobenzene (P = 0.013) or α-chlordane (P = 0.005). Findings were unchanged after removal of cases of PD and adjustment for age and other characteristics.

CONCLUSIONS

Organochlorine pesticides are associated with the presence of Lewy pathology in the brain, even after exclusion of PD cases. Although most of the association is through heptachlor epoxide, the role of other organochlorine compounds is in need of clarification. © 2018 International Parkinson and Movement Disorder Society.

Effects of Military Service on Marital Stability Among World War II U.S. Veterans of Japanese Descent

INTRODUCTION

This study had two goals. First, we investigated how World War II (WW II) military service impacted marital stability during men's young and middle adulthood in a large community sample of American men of Japanese descent. Second, within a subgroup of WW II veterans, we assessed how the level of combat exposure affected marital stability.

MATERIAL AND METHODS

The Honolulu Heart Program and later Honolulu-Asia Aging Project were longitudinal, community-based studies of Japanese-American men living in Hawai'i. This study is a secondary data analysis of 1,249 male WW II veterans and 3,489 men of Japanese descent who were civilians during WW II, born 1910-1919, who completed interviews at the first (1965-1968) and third (1971-1975) exams. Data from a subsample of veterans who completed a military service interview during the sixth exam (1997-1999) also were used. In the first set of analyses, we compared veterans to civilians on three marital outcomes for ages 15-59: (1) likelihood of never marrying, (2) age at first marriage, and (3) likelihood of divorce. Next, we investigated the negative consequences of increasing combat exposure on the same marital outcomes. All analyses controlled for age in 1941 and occupation.

RESULTS

Overall, 88% of the sample remained in their first marriage with no differences between veterans and civilians. We found no effects of military service on the timing of first marriages on the likelihood of divorce during young and middle adulthood. However, among those who had not married before WW II, veterans were significantly more likely to remain unmarried compared with civilians; odds ratio = 1.52 (1.10, 2.09). The level of combat exposure did not predict any of the three marital outcomes among WW II veterans. In fact, none of the other military service characteristics assessed (i.e., age of military induction, years of service, and service-connected disability) predicted marital outcomes. We found that age at the beginning of WW II impacted the timing and stability of marriage in both veterans and civilians. Finally, we identified cultural effects on the likelihood of marriage between Nisei and Kibei groups with Nisei men being less likely to marry.

CONCLUSION

Similar to other groups in this era, long-term marriage with one partner was the norm for both veterans and civilians. For a small portion of American men of Japanese descent, military service seemed to impact the transition into marriage. However, we found no differences in the timing of marriage or the likelihood of divorce based on military service or level of combat exposure. While our findings are inconsistent with previous research on the impact of military service and combat exposure, much of that research was conducted with mainland veterans, usually of European descent. There appears to be little long-term disruption of life course events. Results highlight the importance of studying diverse groups of veterans to understand how experiences in the military interact with pre-military factors in defining long-term responses to military service.

Selenoprotein S Reduces Endoplasmic Reticulum Stress-Induced Phosphorylation of Tau: Potential Role in Selenate Mitigation of Tau Pathology

Previous studies demonstrated that selenium in the form of sodium selenate reduces neurofibrillary tangle formation in Alzheimer's disease models. Hyperphosphorylation of tau, which leads to formation of neurofibrillary tangles in Alzheimer's disease, is increased by endoplasmic reticulum (ER) stress. Selenoprotein S (SelS) is part of an ER membrane complex that removes misfolded proteins from the ER as a means to reduce ER stress. Selenate, as with other forms of selenium, will increase selenoprotein expression. We therefore proposed that increased SelS expression by selenate would contribute to the beneficial actions of selenate in Alzheimer's disease. SelS expression increased with ER stress and decreased under conditions of elevated glucose concentrations in the SH-SY5Y neuronal cell line. Reducing expression of SelS with siRNA promoted cell death in response to ER stress. Selenate increased SelS expression, which significantly correlated with decreased tau phosphorylation. Restricting SelS expression during ER stress conditions increased tau phosphorylation, and also promoted aggregation of phosphorylated tau in neurites and soma. In human postmortem brain, SelS expression coincided with neurofibrillary tangles, but not with amyloid-β plaques. These results indicate that selenate can alter phosphorylation of tau by increasing expression of SelS in Alzheimer's disease and potentially other neurodegenerative disorders.

Resistance to Alzheimer Disease Neuropathologic Changes and Apparent Cognitive Resilience in the Nun and Honolulu-Asia Aging Studies

Two population-based studies key to advancing knowledge of brain aging are the Honolulu-Asia Aging Study (HAAS) and the Nun Study. Harmonization of their neuropathologic data allows cross comparison, with findings common to both studies likely generalizable, while distinct observations may point to aging brain changes that are dependent on sex, ethnicity, environment, or lifestyle factors. Here, we expanded the neuropathologic evaluation of these 2 studies using revised NIA-Alzheimer's Association guidelines and compared directly the neuropathologic features of resistance and apparent cognitive resilience. There were significant differences in prevalence of Alzheimer disease neuropathologic change, small vessel vascular brain injury, and Lewy body disease between these 2 studies, suggesting that sex, ethnicity, and lifestyle factors may significantly influence resistance to developing brain injury with age. In contrast, hippocampal sclerosis prevalence was very similar, but skewed to poorer cognitive performance, suggesting that hippocampal sclerosis could act sequentially with other diseases to impair cognitive function. Strikingly, despite these observed differences, the proportion of individuals resistant to all 4 diseases of brain or displaying apparent cognitive resilience was virtually identical between HAAS and Nun Study participants. Future in vivo validation of these results awaits comprehensive biomarkers of these 4 brain diseases.

Marinesco bodies and substantia nigra neuron density in Parkinson's disease

AIM

Marinesco bodies (MB) are intranuclear inclusions in pigmented neurons of the substantia nigra (SN). While rare in children, frequency increases with normal ageing and is high in Alzheimer's disease, dementia with Lewy bodies and other neurodegenerative disorders. Coinciding with the age-related rise in MB frequency is initiation of cell death among SN neurons. Whether MB have a role in this process is unknown. Our aim is to examine the association of MB with SN neuron density in Parkinson's disease (PD) in the Honolulu-Asia Aging Study.

METHODS

Data on MB and neuron density were measured in SN transverse sections in 131 autopsied men aged 73-99 years at the time of death from 1992 to 2007.

RESULTS

Marinesco body frequency was low in the presence vs. absence of PD (2.3% vs. 6.6%, P < 0.001). After PD onset, MB frequency declined as duration of PD increased (P = 0.006). Similar patterns were observed for SN neuron density. When MB frequency was low, neuron density was noticeably reduced in the SN ventrolateral quadrant, the region most vulnerable to PD neurodegeneration. Low MB frequency was unique to PD as its high frequency in non-PD cases was unrelated to parkinsonian signs and incidental Lewy bodies. Frequency was high in the presence of Alzheimer's disease and apolipoprotein ε4 alleles.

CONCLUSIONS

While findings confirm that MB frequency is low in PD, declines in MB frequency continue with PD duration. The extent to which MB have a distinct relationship with PD warrants clarification. Further studies of MB could be important in understanding PD processes.

JC Virus Infects Neurons and Glial Cells in the Hippocampus

The human polyomavirus JC (JCV) infects glial cells and is the etiologic agent of the CNS demyelinating disease progressive multifocal leukoencephalopathy. JCV can infect granule cell neurons of the cerebellum, causing JCV granule cell neuronopathy and cortical pyramidal neurons in JCV encephalopathy. Whether JCV also infects neurons in other areas of the CNS is unclear. We determined the prevalence and pattern of JCV infection of the hippocampus in archival samples from 28 patients with known JCV infection of the CNS and 66 control subjects. Among 28 patients, 11 (39.3%) had JCV infection of hippocampus structures demonstrated by immunohistochemistry. Those included gray matter (dentate gyrus and cornu ammonis, subiculum) in 11/11 and afferent or efferent white matter tracts (perforant path, alveus, fimbria) in 10/11. In the hippocampus, JCV infected granule cell and pyramidal neurons, astrocytes, and oligodendrocytes. Although glial cells expressed either JCV regulatory T Antigen or JCV VP1 capsid protein, infected neurons expressed JCV T Antigen only, suggesting an abortive/restrictive infection. None of the 66 control subjects had evidence of hippocampal JCV protein expression by immunohistochemistry or JCV DNA by in situ hybridization. These results greatly expand our understanding of JCV pathogenesis in the CNS.

Changes in Frailty Predict Changes in Cognition in Older Men: The Honolulu-Asia Aging Study

BACKGROUND

As cognitive decline mostly occurs in late life, where typically it co-exists with many other ailments, it is important to consider frailty in understanding cognitive change.

OBJECTIVE

Here, we examined the association of change in frailty status with cognitive trajectories in a well-studied cohort of older Japanese-American men.

METHODS

Using the prospective Honolulu-Asia Aging Study (HAAS), 2,817 men of Japanese descent were followed (aged 71-93 at baseline). Starting in 1991 with follow-up health assessments every two to three years, cognition was measured using the Cognitive Abilities Screening Instrument (CASI). For this study, health data was used to construct an accumulation of deficits frailty index (FI). Using six waves of data, multilevel growth curve analyses were constructed to examine simultaneous changes in cognition in relation to changes in FI, controlling for baseline frailty, age, education, and APOE-ɛ4 status.

RESULTS

On average, CASI scores declined by 2.0 points per year (95% confidence interval 1.9-2.1). Across six waves, each 10% within-person increase in frailty from baseline was associated with a 5.0 point reduction in CASI scores (95% confidence interval 4.7-5.2). Baseline frailty and age were associated both with lower initial CASI scores and with greater decline across the five follow-up assessments (p < 0.01).

DISCUSSION

Cognition is adversely affected by impaired health status in old age. Using a multidimensional measure of frailty, both baseline status and within-person changes in frailty were predictive of cognitive trajectories.

Phytoestrogen consumption and risk for cognitive decline and dementia: With consideration of thyroid status and other possible mediators

It is predicted that around 20% of the worlds population will be age 60 or above by 2050. Prevalence of cognitive decline and dementia is high in older adults and modifiable dietary factors may be able to reduce risk for these conditions. Phytoestrogens are bioactive plant chemicals found in soy, which have a similarity in structure to natural estradiol (the most abundant circulating estrogen). This structural likeness enables phytoestrogens to interact with estrogen receptors in the brain, potentially affecting cognition. However, findings in this domain are largely inconsistent, with approximately 50% of studies showing positive effects of phytoestrogens on cognition and the other half resulting in null/negative findings. This paper provides an updated review of the relationship between consumption of phytoestrogens and risk for cognitive decline and/or dementia. In particular, possible mediators were identified to explain discrepant findings and for consideration in future research. A case can be made for a link between phytoestrogen consumption, thyroid status and cognition in older age, although current findings in this area are very limited. Evidence suggests that inter-individual variants that can affect phytoestrogen bioavailability (and thus cognitive outcome) include age and ability to breakdown ingested phytoestrogens into their bioactive metabolites. Factors of the study design that must be taken into account are type of soy product, dosage, frequency of dietary intake and type of cognitive test used. Guidelines regarding optimal phytoestrogen dosage and frequency of intake are yet to be determined.

Neuropathologic comorbidity and cognitive impairment in the Nun and Honolulu-Asia Aging Studies

OBJECTIVE

To examine frequencies and relationships of 5 common neuropathologic abnormalities identified at autopsy with late-life cognitive impairment and dementia in 2 different autopsy panels.

METHODS

The Nun Study (NS) and the Honolulu-Asia Aging Study (HAAS) are population-based investigations of brain aging that included repeated cognitive assessments and comprehensive brain autopsies. The neuropathologic abnormalities assessed were Alzheimer disease (AD) neuropathologic changes, neocortical Lewy bodies (LBs), hippocampal sclerosis, microinfarcts, and low brain weight. Associations with screening tests for cognitive impairment were examined.

RESULTS

Neuropathologic abnormalities occurred at levels ranging from 9.7% to 43%, and were independently associated with cognitive impairment in both studies. Neocortical LBs and AD changes were more frequent among the predominantly Caucasian NS women, while microinfarcts were more common in the Japanese American HAAS men. Comorbidity was usual and very strongly associated with cognitive impairment. Apparent cognitive resilience (no cognitive impairment despite Braak stage V) was strongly associated with minimal or no comorbid abnormalities, with fewer neocortical AD lesions, and weakly with longer interval between final testing and autopsy.

CONCLUSIONS

Total burden of comorbid neuropathologic abnormalities, rather than any single lesion type, was the most relevant determinant of cognitive impairment in both cohorts, often despite clinical diagnosis of only AD. These findings emphasize challenges to dementia pathogenesis and intervention research and to accurate diagnoses during life.

Midlife milk consumption and substantia nigra neuron density at death

OBJECTIVE

To examine the relationship between midlife milk intake and Parkinson disease (PD) incidence through associations with substantia nigra (SN) neuron density and organochlorine pesticide exposure in decedent brains from the Honolulu-Asia Aging Study.

METHODS

Milk intake data were collected from 1965 to 1968 in 449 men aged 45-68 years with postmortem examinations from 1992 to 2004. Neuron density (count/mm(2)) was measured in quadrants from a transverse section of the SN. Additional measures included brain residues of heptachlor epoxide, an organochlorine pesticide found at excessively high levels in the milk supply in Hawaii in the early 1980s.

RESULTS

Neuron density was lowest in nonsmoking decedents who consumed high amounts of milk (>16 oz/d). After removing cases of PD and dementia with Lewy bodies, adjusted neuron density in all but the dorsomedial quadrant was 41.5% lower for milk intake >16 oz/d vs intake that was less (95% confidence interval 22.7%-55.7%, p < 0.001). Among those who drank the most milk, residues of heptachlor epoxide were found in 9 of 10 brains as compared to 63.4% (26/41) for those who consumed no milk (p = 0.017). For those who were ever smokers, an association between milk intake and neuron density was absent.

CONCLUSIONS

Milk intake is associated with SN neuron loss in decedent brains unaffected by PD. Whether contamination of milk with organochlorine pesticides has a role in SN neurodegeneration warrants further study.

Increased selenoprotein P in choroid plexus and cerebrospinal fluid in Alzheimer's disease brain

Subjects with Alzheimer's disease (AD) have elevated brain levels of the selenium transporter selenoprotein P (Sepp1). We investigated if this elevation results from increased release of Sepp1 from the choroid plexus (CP). Sepp1 is significantly increased in CP from AD brains in comparison to non-AD brains. Sepp1 localizes to the trans-Golgi network within CP epithelia, where it is processed for secretion. The cerebrospinal fluid from AD subjects also contains increased levels Sepp1 in comparison to non-AD subjects. These findings suggest that AD pathology induces increased levels of Sepp1 within CP epithelia for release into the cerebrospinal fluid to ultimately increase brain selenium.

Clinical-pathologic correlations in vascular cognitive impairment and dementia

The most common causes of cognitive impairment and dementia are Alzheimer's disease (AD) and vascular brain injury (VBI), either independently, in combination, or in conjunction with other neurodegenerative disorders. The contribution of VBI to cognitive impairment and dementia, particularly in the context of AD pathology, has been examined extensively yet remains difficult to characterize due to conflicting results. Describing the relative contribution and mechanisms of VBI in dementia is important because of the profound impact of dementia on individuals, caregivers, families, and society, particularly the stability of health care systems with the rapidly increasing age of our population. Here we discuss relationships between pathologic processes of VBI and clinical expression of dementia, specific subtypes of VBI including microvascular brain injury, and what is currently known regarding contributions of VBI to the development and pathogenesis of the dementia syndrome. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

Social vulnerability and survival across levels of frailty in the Honolulu-Asia Aging Study

PURPOSE

we evaluated mortality risk in relation to social vulnerability across levels of frailty among a cohort of older Japanese-American men.

METHODS

in secondary analysis of the Honolulu-Asia Aging Study (HAAS), participants (n = 3,271) were aged 72-93 years at baseline. A frailty index (FI) created using 58 potential health deficits to quantify participants' frailty level at baseline, with four frailty strata: 0.0 < FI ≤ 0.1 (n = 1,074); 0.1 < FI ≤ 0.20 (n = 1,549); 0.2 < FI ≤ 0.30 (n = 472); FI > 0.3 (n = 176). Similarly, a social vulnerability index was created using 19 self-reported social deficits. Cox proportional hazard modelling was employed to estimate the impact of social vulnerability across the four levels of frailty, accounting for age, smoking, alcohol use and variation in health deficits within each frailty level.

RESULTS

for the fittest participants, social vulnerability was associated with mortality (hazards ratio (HR) = 1.04, 95% confidence interval (CI) = 1.01, 1.07; P value = 0.008). Similarly, for those considered at risk for frailty, each social deficit was associated with a 5% increased risk of mortality. For frail individuals, the Cox regression analyses indicated that social vulnerability was not significantly associated with mortality (0.2 < FI ≤ 0.3: HR = 1.016, 95% CI = 0.98, 1.06; P value = 0.442; FI > 0.3: HR = 0.98, 95% CI = 0.93, 1.04).

CONCLUSIONS

for the fittest and at-risk HAAS participants, the accumulation of social deficits was associated with significant increases in mortality risk. For frail individuals (FI > 0.20), the estimation of mortality risk may depend more so on intrinsic factors related to their health.

Cumulative impact of health deficits, social vulnerabilities, and protective factors on cognitive dynamics in late life: a multistate modeling approach

Introduction

Many factors influence late-life cognitive changes, and evaluating their joint impact is challenging. Typical approaches focus on average decline and a small number of factors. We used multistate transition models and index variables to look at changes in cognition in relation to frailty (accumulation of health deficits), social vulnerability, and protective factors in the Honolulu-Asia Aging Study (HAAS).

Methods

The HAAS is a prospective cohort study of 3,845 men of Japanese descent, aged 71 to 93 years at baseline. Cognitive function was measured using the Cognitive Abilities Screening Instrument (CASI). Baseline index variables were constructed of health deficits (frailty), social vulnerabilities, and protective factors. The chances of improvement/stability/decline in cognitive function and death were simultaneously estimated using multistate transition modeling for 3- and 6-year transitions from baseline.

Results

On average, CASI scores declined by 5.3 points (standard deviation (SD) = 10.0) over 3 years and 9.5 points (SD = 13.9) over 6 years. After adjusting for education and age, baseline frailty was associated with an increased risk of cognitive decline at 3 years (β = 0.18, 95% confidence interval (CI), 0.08 to 0.29) and 6 years (β = 0.40, 95% CI, 0.27 to 0.54). The social vulnerability index was associated with 3-year changes (β = 0.16, 95% CI, 0.09 to 0.23) and 6-year changes (β = 0.14, 95% CI, 0.05 to 0.24) in CASI scores. The protective index was associated with reductions in cognitive decline over the two intervals (3-year: β = −0.16, 95% CI, −0.24 to −0.09; 6-year: β = −0.21, 95% CI, −0.31 to –0.11,).

Conclusions

Research on cognition in late life needs to consider overall health, the accumulation of protective factors, and the dynamics of cognitive change. Index variables and multistate transition models can enhance understanding of the multifactorial nature of late-life changes in cognition.

Electronic supplementary material

The online version of this article (doi:10.1186/s13195-015-0120-7) contains supplementary material, which is available to authorized users.

Associations of brain lesions at autopsy with polysomnography features before death

OBJECTIVE

To determine how sleep-disordered breathing, nocturnal hypoxia, and changes in sleep architecture in the elderly may be related to the development of the neuropathologic correlates of dementia.

METHODS

The Honolulu-Asia Aging Study is a prospective cohort study of Japanese American men in Honolulu, HI. We examined brain lesions at autopsy (Braak stage, neurofibrillary tangle and neuritic plaque counts, microinfarcts, generalized brain atrophy, lacunar infarcts, Lewy bodies [LBs], neuronal loss and gliosis in the locus ceruleus) in 167 participants who underwent polysomnography in 1999-2000 (mean age, 84 years) and died through 2010 (mean 6.4 years to death). Polysomnography measures included the apnea-hypopnea index, duration of apnea or hypopnea, duration of hypoxemia, minimum oxygen saturation (SpO₂), duration of slow-wave sleep (SWS, non-REM stage N3), and arousals.

RESULTS

Sleep duration with SpO₂ <95% was associated with higher levels of microinfarcts (adjusted odds ratio [OR] 3.88, 95% confidence interval [CI] 1.10-13.76, comparing the highest to lowest quartiles of %sleep with SpO₂ <95%). Greater SWS duration was associated with less generalized atrophy (adjusted OR 0.32, 95% CI 0.10-1.03, comparing highest to lowest quartiles of %sleep in SWS). LBs were less common with greater %sleep with SpO₂ <95% (adjusted OR 0.17, 95% CI 0.04-0.78, comparing highest to lowest quartiles). Higher minimum SpO₂ during REM sleep was associated with less gliosis and neuronal loss in the locus ceruleus. Cognitive scores declined less among men with greater SWS duration.

CONCLUSIONS

The findings support a role for lower nocturnal oxygenation and SWS in the development of microinfarcts and brain atrophy, but not Alzheimer lesions or LBs.

Frailty in the Honolulu-Asia Aging Study: deficit accumulation in a male cohort followed to 90% mortality

BACKGROUND

A frailty index (FI) based on the accumulation of deficits typically has a submaximal limit at about 0.70. The objectives of this study were to examine how population characteristics of the FI change in the Honolulu-Asia Aging Study cohort, which has been followed to near-complete mortality. In particular, we were interested to see if the limit was exceeded.

METHODS

Secondary analysis of six waves of the Honolulu-Asia Aging Study. Men (n = 3,801) aged 71-93 years at baseline (1991) were followed until death (N = 3,455; 90.9%) or July 2012. FIs were calculated across six waves and the distribution at each wave was evaluated. Kaplan-Meier analyses and Cox proportional hazard models were performed to examine the relationship of frailty with mortality.

RESULTS

At each wave, frailty was nonlinearly associated with age, with acceleration in later years. The distributions of the FIs were skewed with long right tails. Despite the increasing mortality in each successive wave, the 99% submaximal limit never exceeded 0.65. The risk of death increased with increasing values of the FI (eg, the hazard rate increased by 1.44 [95% CI = 1.39-1.49] with each increment in the baseline FI grouping). Depending on the wave, the median survival of people with FI more than 0.5 ranged 0.84-2.04 years.

CONCLUSIONS

Even in a study population followed to almost complete mortality, the limit to deficit accumulation did not exceed 0.65, confirming a quantifiable, maximum number of health deficits that older men can tolerate.

Changes in selenoprotein P in substantia nigra and putamen in Parkinson's disease

Oxidative stress and oxidized dopamine contribute to the degeneration of the nigrostriatal pathway in Parkinson's disease (PD). Selenoproteins are a family of proteins containing the element selenium in the form of the amino acid selenocysteine, and many of these proteins have antioxidant functions. We recently reported changes in expression of the selenoprotein, phospholipid hydroperoxide glutathione peroxidase GPX4 and its co-localization with neuromelanin in PD brain. To further understand the changes in GPX4 in PD, we examine here the expression of the selenium transport protein selenoprotein P (Sepp1) in postmortem Parkinson's brain tissue. Sepp1 in midbrain was expressed in neurons of the substantia nigra (SN), and expression was concentrated within the centers of Lewy bodies, the pathological hallmark of PD. As with GPX4, Sepp1 expression was significantly reduced in SN from PD subjects compared with controls, but increased relative to cell density. In putamen, Sepp1 was found in cell bodies and in dopaminergic axons and terminals, although levels of Sepp1 were not altered in PD subjects compared to controls. Expression levels of Sepp1 and GPX4 correlated strongly in the putamen of control subjects but not in the putamen of PD subjects. These findings indicate a role for Sepp1 in the nigrostriatal pathway, and suggest that local release of Sepp1 in striatum may be important for signaling and/or synthesis of other selenoproteins such as GPX4.

Antihypertensive medication use and risk of cognitive impairment: the Honolulu-Asia Aging Study

OBJECTIVE

To determine the associations between classes of antihypertensive medication use and the risk of cognitive impairment among elderly hypertensive men.

METHODS

The Honolulu-Asia Aging Study is a prospective, community-based cohort study of Japanese American men conducted in Honolulu, Hawaii. We examined 2,197 participants (mean age 77 years at cohort entry, 1991-1993, followed through September 2010) with hypertension and without dementia or cognitive impairment at baseline, who provided information on medication use. Cognitive function was assessed at 7 standardized examinations using the Cognitive Abilities Screening Instrument (CASI). Cognitive impairment was defined as a CASI score <74.

RESULTS

A total of 854 men developed cognitive impairment (median follow-up, 5.8 years). β-Blocker use as the sole antihypertensive drug at baseline was consistently associated with a lower risk of cognitive impairment (incidence rate ratio [IRR] 0.69; 95% confidence interval [CI] 0.50-0.94), as compared with men not taking any antihypertensive medications, adjusting for multiple potential confounders. The use of diuretics, calcium channel blockers, angiotensin-converting enzyme inhibitors, or vasodilators alone was not significantly associated with cognitive impairment. Results were similar excluding those with cardiovascular disease or <1 year of follow-up, and additionally adjusting for pulse pressure, heart rate, baseline and midlife systolic blood pressure, and midlife antihypertensive treatment (IRR 0.65; 95% CI 0.45-0.94). The association between β-blocker use and cognitive impairment was stronger among men with diabetes, men aged >75 years, and those with pulse pressure ≥70 mm Hg.

CONCLUSIONS

β-blocker use is associated with a lower risk of developing cognitive impairment in elderly Japanese American men.

Brain organochlorines and Lewy pathology: the Honolulu-Asia Aging Study

Although organochlorines have been reported more frequently in Parkinson's disease (PD) brains than in controls, the association with brain Lewy pathology is unknown. Honolulu-Asia Aging Study (HAAS) participants, exposed to organochlorines from a variety of sources during midlife, represent a population well suited to determining the relationship of brain organochlorines with Lewy pathology in decedents from the longitudinal HAAS. The study design included the measurement of 21 organochlorine levels in frozen occipital lobe samples from HAAS decedents. Alpha-synuclein immunostaining performed on 225 brains was used to identify Lewy bodies and Lewy neurites. With the potential for spurious associations to appear between Lewy pathology and 17 organochlorine compounds found in at least 1 brain, initial assessments identified heptachlor epoxide isomer b, methoxychlor, and benzene hexachloride b as being most important. The prevalence of Lewy pathology was 75% (6 of 8) among brains with any 2 of the 3 compounds, 48.8% (79 of 162) among those with 1, and 32.7% (18 of 55) for those with neither (P = .007 test for trend). Although findings persisted after removing cases with PD and dementia with Lewy bodies and after adjustment for age at death, body mass index, pack-years of cigarette smoking, and coffee intake (P = .013), the results were insignificant when correcting for multiple testing. Although consistent with earlier accounts of an association between organochlorines and clinical PD, associations with Lewy pathology warrant further study.

Coffee intake in midlife and risk of dementia and its neuropathologic correlates

While animal data suggest a protective effect of caffeine on cognition, studies in humans remain inconsistent. We examined associations of coffee and caffeine intake in midlife with risk of dementia, its neuropathologic correlates, and cognitive impairment among 3494 men in the Honolulu-Asia Aging Study (mean age 52 at cohort entry, 1965-1968) examined for dementia in 1991-1993, including 418 decedents (1992-2004) who underwent brain autopsy. Caffeine intake was determined according to self-reported coffee, tea, and cola consumption at baseline. Logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI) for overall dementia, Alzheimer's disease (AD), vascular dementia (VaD), cognitive impairment (Cognitive Abilities Screening Instrument score <74), and neuropathologic lesions at death (Alzheimer lesions, microvascular ischemic lesions, cortical Lewy bodies, hippocampal sclerosis, generalized atrophy), according to coffee and caffeine intake. Dementia was diagnosed in 226 men (including 118 AD, 80 VaD), and cognitive impairment in 347. There were no significant associations between coffee or caffeine intake and risk of cognitive impairment, overall dementia, AD, VaD, or moderate/high levels of the individual neuropathologic lesion types. However, men in the highest quartile of caffeine intake (>/=411.0 mg/d) [corrected] were less likely than men in the lowest quartile (</=137.0 mg) [corrected] to have any of the lesion types (adjusted-OR, 0.45; 95% CI, 0.23-0.89; p, trend = 0.04). Coffee and caffeine intake in midlife were not associated with cognitive impairment, dementia, or individual neuropathologic lesions, although higher caffeine intake was associated with a lower odds of having any of the lesion types at autopsy.

Midlife blood pressure, plasma β-amyloid, and the risk for Alzheimer disease: the Honolulu Asia Aging Study

β-Amyloid (Aβ), a vasoactive protein, and elevated blood pressure (BP) levels are associated with Alzheimer disease (AD) and possibly vascular dementia. We investigated the joint association of midlife BP and Aβ peptide levels with the risk for late-life AD and vascular dementia. Subjects were 667 Japanese-American men (including 73 with a brain autopsy), from the prospective Honolulu Heart Program/Honolulu Asia Aging Study (1965-2000). Midlife BP was measured starting in 1971 in participants with a mean age of 58 years; Aβ was measured in specimens collected in 1980-1982, and assessment of dementia and autopsy collection started in 1991-1993. The outcome measures were prevalent (present in 1991-1993) and incident AD (n=53, including 38 with no contributing cardiovascular disease) and vascular dementia (n=24). Cerebral amyloid angiopathy, β-amyloid neuritic plaques, and neurofibrillary tangles were evaluated in postmortem tissue. The risk for AD significantly increased with lower levels of plasma Aβ (Aβ1-40 hazard ratio: 2.1 [95% CI: 1.4 to 3.1]; Aβ1-42 hazard ratio: 1.6 [95% CI: 1.1 to 2.3]). Evidence of interaction between diastolic BP and plasma Aβ (1-40 P(interaction)<0.05; 1-42 P(interaction)<0.07) levels indicated that the Aβ-related risk for AD was higher when BP was higher. Low plasma Aβ was associated with the presence of cerebral amyloid angiopathy (P(trend)<0.05) but not the other neuropathologies. Aβ plasma levels start decreasing ≥15 years before AD is diagnosed, and the association of Aβ to AD is modulated by midlife diastolic BP. Elevated BP may compromise vascular integrity leading to cerebral amyloid angiopathy and impaired Aβ clearance from the brain.

Microinfarcts, brain atrophy, and cognitive function: the Honolulu Asia Aging Study Autopsy Study

OBJECTIVE

This study was untaken to investigate the association of micro brain infarcts (MBIs) with antemortem global cognitive function (CF), and whether brain weight (BW) and Alzheimer lesions (neurofibrillary tangles [NFTs] or neuritic plaques [NPs]) mediate the association.

METHODS

Subjects were 436 well-characterized male decedents from the Honolulu Asia Aging Autopsy Study. Brain pathology was ascertained with standardized methods, CF was measured by the Cognitive Abilities Screening Instrument, and data were analyzed using formal mediation analyses, adjusted for age at death, time between last CF measure and death, education, and head size. Based on antemortem diagnoses, demented and nondemented subjects were examined together and separately.

RESULTS

In those with no dementia, MBIs were strongly associated with the last antemortem CF score; this was significantly mediated by BW, and not NFTs or NPs. In contrast, among those with an antemortem diagnosis of dementia, NFTs had the strongest associations with BW and with CF, and MBIs were modestly associated with CF.

INTERPRETATION

This suggests that microinfarct pathology is a significant and independent factor contributing to brain atrophy and cognitive impairment, particularly before dementia is clinically evident. The role of vascular damage as initiator, stimulator, or additive contributor to neurodegeneration may differ depending on when in the trajectory toward dementia the lesions develop.