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Background Understanding the pathological bases underlying the heterogeneity of motor decline in old age may lead to targeted treatments. We examined whether different brain pathologies are related to declining grip strength and gait function. Methods We examined postmortem brains of older adults who underwent annual motor testing. Postmortem exam measured 6 neurodegenerative and 5 cerebrovascular disease (CVD) pathologies. Grip strength was measured twice bilaterally using a hand-held dynamometer, and gait function was a composite measure based on time and steps taken to walk 8 ft and perform a 360° turn twice. Results In separate linear mixed-effects models including all autopsied adults (N = 1 217), neurodegenerative pathologies including tau tangles, TDP-43, and nigral neuronal loss were associated with declining grip strength, but not CVD pathologies. In contrast, although both CVD and neurodegenerative pathologies were associated with declining gait function, CVD pathologies accounted for 75% of the variance of declining rate of gait function explained by brain pathologies and neurodegenerative pathologies accounted for 25%. These findings were unchanged in adults (n = 970) without a history of stroke. Restricting analyses to only adults without dementia (n = 661), CVD pathologies continued to account for the majority of the variance of declining gait. However, we failed to detect in this subgroup the variance of declining grip strength explained by neurodegenerative or CVD pathologies. Conclusion Different pathologies accumulating in aging brains may contribute to the phenotypic heterogeneity of motor decline. Larger studies are needed in older adults without dementia to assess differences in the motor consequences of varied brain pathologies.

Approximately 30% of elderly adults are cognitively unimpaired at time of death despite the presence of Alzheimer’s disease neuropathology at autopsy. Studying individuals who are resilient to the cognitive consequences of Alzheimer’s disease neuropathology may uncover novel therapeutic targets to treat Alzheimer’s disease. It is well established that there are sex differences in response to Alzheimer’s disease pathology, and growing evidence suggests that genetic factors may contribute to these differences. Taken together, we sought to elucidate sex-specific genetic drivers of resilience. We extended our recent large scale genomic analysis of resilience in which we harmonized cognitive data across four cohorts of cognitive ageing, in vivo amyloid PET across two cohorts, and autopsy measures of amyloid neuritic plaque burden across two cohorts. These data were leveraged to build robust, continuous resilience phenotypes. With these phenotypes, we performed sex-stratified [n (males) = 2093, n (females) = 2931] and sex-interaction [n (both sexes) = 5024] genome-wide association studies (GWAS), gene and pathway-based tests, and genetic correlation analyses to clarify the variants, genes and molecular pathways that relate to resilience in a sex-specific manner. Estimated among cognitively normal individuals of both sexes, resilience was 20–25% heritable, and when estimated in either sex among cognitively normal individuals, resilience was 15–44% heritable. In our GWAS, we identified a female-specific locus on chromosome 10 [rs827389, β (females) = 0.08, P (females) = 5.76 × 10−09, β (males) = −0.01, P(males) = 0.70, β (interaction) = 0.09, P (interaction) = 1.01 × 10−04] in which the minor allele was associated with higher resilience scores among females. This locus is located within chromatin loops that interact with promoters of genes involved in RNA processing, including GATA3. Finally, our genetic correlation analyses revealed shared genetic architecture between resilience phenotypes and other complex traits, including a female-specific association with frontotemporal dementia and male-specific associations with heart rate variability traits. We also observed opposing associations between sexes for multiple sclerosis, such that more resilient females had a lower genetic susceptibility to multiple sclerosis, and more resilient males had a higher genetic susceptibility to multiple sclerosis. Overall, we identified sex differences in the genetic architecture of resilience, identified a female-specific resilience locus and highlighted numerous sex-specific molecular pathways that may underly resilience to Alzheimer’s disease pathology. This study illustrates the need to conduct sex-aware genomic analyses to identify novel targets that are unidentified in sex-agnostic models. Our findings support the theory that the most successful treatment for an individual with Alzheimer’s disease may be personalized based on their biological sex and genetic context.

Cerebral small vessel disease (SVD) causes lacunar stroke and vascular cognitive impairment in older people. The pathogenic pathways from vessel pathology to parenchymal damage in SVD are unknown. Neurofilaments are axonal structural proteins. Neurofilament-light (NfL) is an emerging biomarker for neurological disease. Here, we examined the high molecular weight form neurofilament-heavy (NfH) and quantified a characteristic pattern of peri-arterial (vasculocentric) NfH labeling. Subcortical frontal and parietal white matter from young adult controls, aged controls, and older people with SVD or severe Alzheimer disease (n = 52) was immunohistochemically labeled for hyperphosphorylated NfH (pNfH). The extent of pNfH immunolabeling and the degree of vasculocentric axonal pNfH were quantified. Axonal pNfH immunolabeling was sparse in young adults but a common finding in older persons (controls, SVD, or AD). Axonal pNfH was often markedly concentrated around small penetrating arteries. This vasculocentric feature was more common in older people with SVD than in those with severe AD (p = 0.004). We conclude that axonal pNfH is a feature of subcortical white matter in aged brains. Vasculocentric axonal pNfH is a novel parenchymal lesion that is co-located with SVD arteriopathy and could be a consequence of vessel pathology.

Background We tested the hypothesis that indices of Alzheimer’s disease and related dementia (ADRD) pathologies may explain associations between change in body mass index (BMI) and cognitive decline in old age. Method We used data from 436 older decedents participating in a prospective longitudinal cohort study who had undergone annual cognitive and BMI assessments and postmortem collection of indices of 12 brain pathologies. We identified ADRD brain pathologies associated with BMI range, a previously published metric of change in BMI. We employed sigmoidal mixed-effect models of cognitive decline to examine the associations of change in BMI and cognitive decline with and without terms for ADRD brain pathologies. Results Average age at baseline was 78.6 years, SD = 6.5 years with 64% female. On average, 9 cognitive assessments were obtained with average age at death 88.4 years (SD = 6.2 years). Change in BMI as measured by BMI range was associated with cognitive decline (θ 2 = 0.260). β-Amyloid, hippocampal sclerosis, and substantia nigra neuronal loss were associated with BMI range. β-Amyloid strongly attenuated the association of BMI range with cognitive decline. Hippocampal sclerosis showed only partial attenuation of the association of BMI range and cognitive decline and nigral neuronal loss did not attenuate this association. Conclusion Changes in BMI and cognitive decline in older adults may be affected by similar mechanisms underlying the accumulation of brain pathologies like β-amyloid in aging brains. Elucidating the molecular mechanisms underlying these associations may provide novel targets for developing interventions that maintain brain health and metabolic homeostasis in old age.

Background Mixed-brain pathologies are the most common cause of progressive parkinsonism in older adults. We tested the hypothesis that the impact of individual pathologies associated with progressive parkinsonism differs among older adults. Methods Data were from 1089 decedents who had undergone annual clinical testing and autopsy. Parkinsonism was based on a modified United Parkinson’s Disease Rating Scale. Linear mixed-effects models were employed, to investigate the combinations of 9 pathologies related to progressive parkinsonism. Then we estimated the person-specific contributions of each pathology for progressive parkinsonism. Results The average participant showed 3 pathologies. Parkinson’s disease (PD) and 4 cerebrovascular pathologies (macroinfarcts, atherosclerosis, arteriolosclerosis, and cerebral amyloid angiopathy [CAA]), but not Alzheimer’s disease, TDP-43, hippocampal sclerosis, and microinfarcts, were independently associated with progressive parkinsonism. These pathologies accounted for 13% of additional variance of progressive parkinsonism. Thirty-one different combinations of these 5 pathologies were observed to be associated with progressive parkinsonism observed. On average, PD and CAA accounted, respectively, for 66% and 65% of person-specific progression of parkinsonism, while macroinfarcts, atherosclerosis, and arteriolosclerosis accounted for 41%–48%. Conclusion There is much greater heterogeneity in the comorbidity and relative impact of individual brain pathologies affecting progressive parkinsonism than previously recognized and this may account in part for its phenotypic heterogeneity in older adults.

Autopsy measures of Alzheimer’s disease neuropathology have been leveraged as endophenotypes in previous genome-wide association studies (GWAS). However, despite evidence of sex differences in Alzheimer’s disease risk, sex-stratified models have not been incorporated into previous GWAS analyses. We looked for sex-specific genetic associations with Alzheimer’s disease endophenotypes from six brain bank data repositories. The pooled dataset included 2701 males and 3275 females, the majority of whom were diagnosed with Alzheimer’s disease at autopsy (70%). Sex-stratified GWAS were performed within each dataset and then meta-analysed. Loci that reached genome-wide significance (P < 5 × 10−8) in stratified models were further assessed for sex interactions. Additional analyses were performed in independent datasets leveraging cognitive, neuroimaging and CSF endophenotypes, along with age-at-onset data. Outside of the APOE region, one locus on chromosome 7 (rs34331204) showed a sex-specific association with neurofibrillary tangles among males (P = 2.5 × 10−8) but not females (P = 0.85, sex-interaction P = 2.9 × 10−4). In follow-up analyses, rs34331204 was also associated with hippocampal volume, executive function, and age-at-onset only among males. These results implicate a novel locus that confers male-specific protection from tau pathology and highlight the value of assessing genetic associations in a sex-specific manner.

Neuropathologic evaluation remains the gold standard for determining the presence and severity of aging-related neurodegenerative diseases. Researchers at U.S. Alzheimer’s Disease Centers (ADCs) have worked for >30 years studying human brains, with the goals of achieving new research breakthroughs. Harmonization and sharing among the 39 current and past ADCs is promoted by the National Alzheimer’s Coordinating Center (NACC), which collects, audits, and disburses ADC-derived data to investigators on request. The past decades have witnessed revised disease definitions paired with dramatic expansion in the granularity and multimodality of the collected data. The NACC database now includes cognitive test scores, comorbidities, drug history, neuroimaging, and links to genomics. Relatively, recent advances in the neuropathologic diagnoses of Alzheimer’s disease, frontotemporal lobar degeneration (FTLD), and vascular contributions to cognitive impairment and dementia catalyzed a 2014 update to the NACC Neuropathology Form completed by all ADCs. New focal points include cerebrovascular disease (including arteriolosclerosis, microbleeds, and microinfarcts), hippocampal sclerosis, TDP-43, and FTLD. Here, we provide summary data and analyses to illustrate the potential for both hypothesis-testing and also generating new hypotheses using the NACC Neuropathology data set, which represents one of the largest multi-center databases of carefully curated neuropathologic information that is freely available to researchers worldwide.

Introduction Many individuals remain free from dementia despite substantial plaque and tangle deposits, the hallmarks of Alzheimer’s disease (AD). Understanding of this cognitive resilience is poor. Evidence suggests that circadian disturbances predict increased risk of incident AD, and that circadian regulation deteriorates as clinical AD progresses. We hypothesize that circadian robustness protects against dementia, and the effect is stronger in individuals with AD pathology than those without. Methods We studied 575 deceased participants (age at death: 91.1□6.2; female: 414) in the Rush Memory and Aging Project who underwent brain autopsy at death, had clinical diagnostic opinion of dementia and motor activity assessments with actigraphy of ~10 days before death. Using actigraphy proximate to death, we calculated four circadian metrics: amplitude, acrophase, interdaily stability, and intradaily variability. Logistic regressions, stratified by postmortem pathologic AD diagnosis, were used to examine associations of circadian metrics with odds of dementia, and separately cognitive impairment (CI, including both dementia and mild cognitive impairment [MCI]), adjusting for age at death, sex, education, and time-lag between actigraphy and death. Results Based on postmortem assessment, 378 participants met the NIA-Reagan criteria for high/intermediate likelihood AD (AD group), including 197 clinically diagnosed with dementia, 86 MCI, and 85 cognitively intact. Non-AD group consisted of the remaining 197 participants, including 36 with clinical dementia, 47 MCI, and 114 cognitively intact. In the AD group, greater amplitude, greater interdaily stability, and lower intradaily variability were associated with lower odds of CI and dementia, i.e., odds ratios [OR] for CI corresponding to 1-SD changes were 0.54 (95% CI: 0.40-0.71), 0.70 (0.54-0.91), and 0.63 (0.47-0.84), and were 0.46 (0.35-0.60), 0.55 (0.43-0.70), and 0.61 (0.48-0.78) for dementia. In the non-AD group, only amplitude was associated with the odds of CI or dementia, i.e., the ORs corresponding to 1-SD increase was 0.61 (0.42-0.88) and 0.50 (0.31-0.82), respectively. Conclusion Better preserved circadian function, as characterized by more pronounced, more stable and less fragmented rest-activity rhythms, links to lower risk of CI or dementia in older people, especially those with pathological AD. Support (if any) NIH RF1AG064312, RF1AG059867, R01AG017917, R01AG56352; and the BrightFocus Foundation A2020886S.

With the Breakthrough Therapy Designation program adding to the tools that the U.S. Food and Drug Administration (FDA) has for expediting drug development, the FDA reassessed the endpoints needed for approval of transformative therapies. Although the demonstration of an improvement in overall survival remains the gold standard for drug approval, innovation in cancer research has led to use of other endpoints in regulatory decision-making. These endpoints include substantially delaying tumor progression or extending progression-free survival, substantially reducing tumor size for a prolonged time, improving objective response rate and duration of response, or improving cancer-related symptoms and patient function.

Hyperphosphorylated transactive response DNA-binding protein 43 (TDP-43, encoded by TARDBP ) proteinopathy has recently been described in ageing and in association with cognitive impairment, especially in the context of Alzheimer's disease pathology. To explore the role of mixed Alzheimer's disease and TDP-43 pathologies in clinical Alzheimer's-type dementia, we performed a comprehensive investigation of TDP-43, mixed pathologies, and clinical Alzheimer's-type dementia in a large cohort of community-dwelling older subjects. We tested the hypotheses that TDP-43 with Alzheimer's disease pathology is a common mixed pathology; is related to increased likelihood of expressing clinical Alzheimer's-type dementia; and that TDP-43 pathologic stage is an important determinant of clinical Alzheimer's-type dementia. Data came from 946 older adults with ( n = 398) and without dementia ( n = 548) from the Rush Memory and Aging Project and Religious Orders Study. TDP-43 proteinopathy (cytoplasmic inclusions) was present in 496 (52%) subjects, and the pattern of deposition was classified as stage 0 (none; 48%), stage 1 (amygdala; 18%), stage 2 (extension to hippocampus/entorhinal; 21%), or stage 3 (extension to neocortex; 14%). TDP-43 pathology combined with a pathologic diagnosis of Alzheimer's disease was a common mixed pathology (37% of all participants), and the proportion of subjects with clinical Alzheimer's-type dementia formerly labelled 'pure pathologic diagnosis of Alzheimer's disease' was halved when TDP-43 was considered. In logistic regression models adjusted for age, sex, and education, TDP-43 pathology was associated with clinical Alzheimer's-type dementia (odds ratio = 1.51, 95% confidence interval = 1.11, 2.05) independent of pathological Alzheimer's disease (odds ratio = 4.30, 95% confidence interval = 3.08, 6.01) or other pathologies (infarcts, arteriolosclerosis, Lewy bodies, and hippocampal sclerosis). Mixed Alzheimer's disease and TDP-43 pathologies were associated with higher odds of clinical Alzheimer's-type dementia (odds ratio = 6.73, 95% confidence interval = 4.18, 10.85) than pathologic Alzheimer's disease alone (odds ratio = 4.62, 95% confidence interval = 2.84, 7.52). In models examining TDP-43 stage, a dose-response relationship with clinical Alzheimer's-type dementia was observed, and a significant association was observed starting at stage 2, extension beyond the amygdala. In this large sample from almost 1000 community participants, we observed that TDP-43 proteinopathy was very common, frequently mixed with pathological Alzheimer's disease, and associated with a higher likelihood of the clinical expression of clinical Alzheimer's-type dementia but only when extended beyond the amygdala.

Vascular risk factors (VRFs) have been associated with clinically diagnosed Alzheimer disease (AD), but few studies have examined the association between VRF and AD neuropathology (ADNP) in cognitively normal individuals. We used longitudinal data from the National Alzheimer's Disease Center's Uniform Data Set and Neuropathology Data Set to examine the association between VRF and ADNP (moderate to frequent neuritic plaques; Braak stage III-VI) in those with normal cognition. Our sample included 53 participants with ADNP and 140 without ADNP. Body mass index (BMI), resting heart rate (HR), and pulse pressure (PP) were measured at each visit; values were averaged across participant visits and examined annual change in BMI, PP, and HR. Hypertension, diabetes, and hypercholesterolemia were self-reported. In the multivariable logistic regression analyses, average BMI and HR were associated with lower odds of ADNP, and annual increases in HR and BMI were associated with higher odds of ADNP. A previously experienced decline in BMI or HR in late-life (therefore, currently low BMI and low HR) as well as a late-life increase in BMI and HR may indicate underlying AD pathology. Additional clinicopathological research is needed to elucidate the role of changes in late-life VRF and AD pathogenesis.

In 2012, florbetapir (F) (Amyvid) received US Food and Drug Administration approval as a diagnostic agent for detecting neuritic (β-amyloid) plaques in living patients. Although such approval is specifically not extended to the use of florbetapir as a single definitive diagnostic test for Alzheimer disease dementia (ADD), it is of considerable importance to examine its potential in this regard. To estimate the ability of florbetapir amyloid imaging to detect specified densities of postmortem-identified neuritic plaques, we used the data of Clark et al [Clark CM, Pontecorvo MJ, Beach TG, et al. Cerebral PET with florbetapir compared with neuropathology at autopsy for detection of neuritic amyloid-beta plaques: A prospective cohort study. Lancet Neurol 2012;11:669-78]. We then used the data of Beach et al [Beach TG, Monsell SE, Phillips LE, et al. Accuracy of the clinical diagnosis of Alzheimer disease at National Institute on Aging Alzheimer Disease Centers, 2005-2010. J Neuropathol Exp Neurol 2012;71:266-73], derived from the National Alzheimer's Coordinating Center, to estimate the fraction of subjects who would have been called florbetapir-positive and, among these, the fraction of subjects who would also meet neuropathologic criteria for the presence of ADD. The accuracy of a positive florbetapir β-amyloid scan for the detection of neuropathologically defined ADD is estimated at between 69% and 95% sensitivity and between 83% and 89% specificity. From the same National Alzheimer's Coordinating Center data set, 144 subjects were recorded as having normal cognition. Among these, 84 (58%) had at least sparse neuritic plaques at autopsy and, among these, florbetapir imaging was estimated to detect 47 (56%). These findings suggest that amyloid imaging may significantly improve the clinical identification of ADD.

Objective. First, we tested the hypothesis that the rate of change of physical frailty and cognitive function in older adults are correlated. Next, we examined if their rates of change are associated with the same brain pathologies. Methods. About 2,167 older adults participating in the Religious Orders Study and the Rush Memory and Aging Project had annual clinical evaluations. Bivariate random coefficient models were used to estimate simultaneously the rates of change in both frailty and cognition, and the correlation of change was characterized by a joint distribution of the random effects. Then, we examined whether postmortem indices from deceased were associated with the rate of change of frailty and cognition. Results. During an a verage follow-up of 6 years, frailty worsened by 0.09 unit/y and cognition declined by 0.08 unit/y. Most individuals showed worsening frailty and cognition (82.8%); 17% showed progressive frailty alone and

Understanding of frontotemporal lobar degeneration, the underlying pathology most often linked to the clinical diagnosis of frontotemporal dementia, is rapidly increasing. Mutations in 7 known genes (MAPT, GRN, C9orf72, VCP, CHMP2B, and, rarely, TARDBP and FUS) are associated with frontotemporal dementia, and the pathologic classification of frontotemporal lobar degeneration has recently been modified to reflect these discoveries. Mutations in one of these genes (GRN), which encodes progranulin, have been implicated in up to a quarter of cases of frontotemporal lobar degeneration with TDP-43 (TAR DNA-binding protein 43)-positive inclusions; currently, there are more than 60 known pathogenic mutations of the gene. We present the clinical, pathologic, and genetic findings on 6 cases from 4 families, 5 of which were shown to have a novel GRN c.708+6_+9delTGAG mutation.

Neuropathologic heterogeneity is often present among Alzheimer disease (AD) patients. We sought to determine whether amyloid imaging measures of AD are affected by concurrent pathologies. Thirty-eight clinically and pathologically defined AD and 17 nondemented patients with quantitative florbetapir F-18 (F-AV-45) positron emission tomography (PET) imaging during life and postmortem histological β-amyloid quantification and neuropathologic examination were assessed. AD patients were divided on the basis of concurrent pathologies, including those with Lewy bodies (LBs) (n = 21), white matter rarefaction (n = 27), severe cerebral amyloid angiopathy (n = 11), argyrophilic grains (n = 5), and TAR DNA binding protein-43 inclusions (n = 18). Many patients exhibited more than 1 type of concurrent pathology. The ratio of cortical to cerebellar amyloid imaging signal (SUVr) and immunohistochemical β-amyloid load were analyzed in 6 cortical regions of interest. All AD subgroups had strong and significant correlations between SUVr and histological β-amyloid measures (p μ 0.001). All AD subgroups had significantly greater amyloid measures versus nondemented patients, and mean amyloid measures did not significantly differ between AD subgroups. When comparing AD cases with and without each pathology, AD cases with LBs had significantly lower SUVr measures versus AD cases without LBs (p = 0.002); there were no other paired comparison differences. These findings indicate that florbetapir-PET imaging is not confounded by neuropathological heterogeneity within AD.

Serum, cerebrospinal fluid (CSF), and cryopreserved lymphocytes from subjects in the Rush Alzheimer's Disease Center Religious Orders Study were analyzed for associations between cytomegalovirus (CMV) infection and clinical and pathological markers of Alzheimer disease. CMV antibody levels were associated with neurofibrillary tangles (NFTs). CSF interferon γ was only detected in seropositive subjects and was significantly associated with NFTs. The percentage of senescent T cells (CD4+ or CD8+CD28−CD57+) was significantly higher for CMV-seropositive as compared to CMV-seronegative subjects and was marginally associated with the pathologic diagnosis of Alzheimer disease (CD4+) or amyloid-β (CD8+). Immunocytochemical analysis showed induction of amyloid-β in human foreskin fibroblasts (HFFs) infected with each of 3 clinical CMV strains. In the same subjects, there was no association of herpes simplex virus type 1 (HSV-1) antibody levels with CMV antibody levels or clinical or pathological markers of Alzheimer disease. HSV-1 infection of HFFs did not induce amyloid-β. These data support an association between CMV and the development of Alzheimer disease.

Alzheimer's disease begins about two decades before the onset of symptoms or neuron death, and is believed to be caused by pathogenic amyloid-β aggregates that initiate a cascade of molecular events culminating in widespread neurodegeneration. The microtubule binding protein tau may mediate the effects of amyloid-β in this cascade. Amyloid plaques comprised of insoluble, fibrillar amyloid-β aggregates are the most characteristic feature of Alzheimer's disease. However, the correspondence between the distribution of plaques and the pattern of neurodegeneration is tenuous. This discrepancy has stimulated the investigation of other amyloid-β aggregates, including soluble amyloid-β oligomers. Different soluble amyloid-β oligomers have been studied in several mouse models, but not systematically in humans. Here, we measured three amyloid-β oligomers previously described in mouse models-amyloid-β trimers, Aβ*56 and amyloid-β dimers-in brain tissue from 75 cognitively intact individuals, ranging from young children to the elderly, and 58 impaired subjects with mild cognitive impairment or probable Alzheimer's disease. As in mouse models, where amyloid-β trimers appear to be the fundamental amyloid-β assembly unit of Aβ*56 and are present in young mice prior to memory decline, amyloid-β trimers in humans were present in children and adolescents; their levels rose gradually with age and were significantly above baseline in subjects in their 70s. Aβ*56 levels were negligible in children and young adults, rose significantly above baseline in subjects in their 40s and increased steadily thereafter. Amyloid-β dimers were undetectable until subjects were in their 60s; their levels then increased sharply and correlated with plaque load. Remarkably, in cognitively intact individuals we found strong positive correlations between Aβ*56 and two pathological forms of soluble tau (tau-CP13 and tau-Alz50), and negative correlations between Aβ*56 and two postsynaptic proteins (drebrin and fyn kinase), but none between amyloid-β dimers or amyloid-β trimers and tau or synaptic proteins. Comparing impaired with age-matched unimpaired subjects, we found the highest levels of amyloid-β dimers, but the lowest levels of Aβ*56 and amyloid-β trimers, in subjects with probable Alzheimer's disease. In conclusion, in cognitively normal adults Aβ*56 increased ahead of amyloid-β dimers or amyloid-β trimers, and pathological tau proteins and postsynaptic proteins correlated with Aβ*56, but not amyloid-β dimers or amyloid-β trimers. We propose that Aβ*56 may play a pathogenic role very early in the pathogenesis of Alzheimer's disease.

Lewy bodies are common in the ageing brain and often co-occur with Alzheimer’s disease pathology. There is little known regarding the independent role of Lewy body pathology in cognition impairment, decline and fluctuations in community-dwelling older persons. We examined the contribution of Lewy body pathology to dementia, global cognition, cognitive domains, cognitive decline and fluctuations in 872 autopsied subjects (mean age = 87.9 years) from the Rush Religious Order Study (n = 491) and Memory and Aging Project (n = 381) longitudinal community-based clinical–pathological studies. Dementia was based on a clinical evaluation; annual cognitive performance tests were used to create a measure of global cognition and five cognitive domains. Lewy body type was determined by using α-synuclein immunostained sections of substantia nigra, limbic and neocortical regions. Statistical models included multiple regression models for dementia and cognition and mixed effects models for decline. Cognitive fluctuations were estimated by comparing standard deviations of individual residuals from mean trajectories of decline in those with and without Lewy bodies. All models controlled for age, sex, education, Alzheimer’s disease pathology and infarcts. One hundred and fifty-seven subjects (18%) exhibited Lewy body pathology (76 neocortical-type, 54 limbic-type and 27 nigra-predominant). One hundred and three (66%) subjects with Lewy body pathology had a pathologic diagnosis of Alzheimer’s disease. Neocortical-type, but not nigral-predominant or limbic-type Lewy body pathology was related to an increased odds of dementia (odds ratio = 3.21; 95% confidence interval = 1.78–5.81) and lower cognition (P < 0.001) including episodic memory function (P < 0.001) proximate to death. Neocortical-type Lewy body pathology was also related to a faster decline in global cognition (P < 0.001), decline in all five specific cognitive domains (all P-values < 0.001), and to fluctuations in decline of working and semantic memory (P-values < 0.001). Limbic-type Lewy body pathology was related to lower and faster decline in visuospatial skills (P = 0.042). The relationship of Lewy body pathology to cognition and dementia was not modified by Alzheimer’s disease pathology. Neocortical-type Lewy body pathology is associated with increased odds of dementia; lower and more rapid decline in all cognitive domains including episodic memory and fluctuations in decline in semantic and working memory. Limbic-type Lewy body pathology is specifically associated with lower and more rapid decline in visuospatial skills. The effect of Lewy body pathology on cognition appears to be independent of Alzheimer’s disease pathology.

There has been considerable recent interest in understanding the way in which recombination rates vary over small physical distances, and the extent of recombination hotspots, in various genomes. Here we adapt, apply, and assess the power of recently developed coalescent-based approaches to estimating recombination rates from sequence polymorphism data. We apply full-likelihood estimation to study rate variation in and around a well-characterized recombination hotspot in humans, in the β-globin gene cluster, and show that it provides similar estimates, consistent with those from sperm studies, from two populations deliberately chosen to have different demographic and selectional histories. We also demonstrate how approximate-likelihood methods can be used to detect local recombination hotspots from genomic-scale SNP data. In a simulation study based on 80 100-kb regions, these methods detect 43 out of 60 hotspots (ranging from 1 to 2 kb in size), with only two false positives out of 2000 subregions that were tested for the presence of a hotspot. Our study suggests that new computational tools for sophisticated analysis of population diversity data are valuable for hotspot detection and fine-scale mapping of local recombination rates.

The objective of this study was to examine whether the effects of age-related neuropathologies on cognition change over time. Participants were 1096 deceased persons from two clinical-pathologic studies. All were without dementia at baseline, completed a detailed battery of cognitive tests annually over up to 21 years, died, and underwent detailed neuropathologic examinations to identify Alzheimer's disease pathology, vascular pathologies (i.e. macro- and microscopic infarcts, atherosclerosis, arteriolar sclerosis, and cerebral amyloid angiopathy), Lewy bodies, transactive response DNA-binding protein 43 (TDP-43) pathology, and hippocampal sclerosis. A time-varying effects model was used to flexibly characterize the trajectory of global cognition and assess whether the effects of demographics and each neuropathologic index on cognition changed over time. Results indicated that the mean trajectory of global cognition was characterized by gradual cognitive decline beginning ∼15 years before death and accelerated decline in the last few years. With the exception of microinfarcts and arteriolar sclerosis, all neuropathologies were associated with the cognitive trajectory. However, the nature of their associations varied. Alzheimer's disease pathology, macroscopic infarcts, Lewy bodies, TDP-43 pathology, and hippocampal sclerosis were associated with progressive cognitive decline, with their deleterious effects increasing over time. By contrast, atherosclerosis and cerebral amyloid angiopathy pathology were associated with a lower level of cognition but their effects were relatively stable over time. These results suggest that age-related neuropathologies are differentially related to late life cognitive trajectories. Whereas some contribute to progressive cognitive deterioration, others lower the level of cognition but exert relatively stable effects over time.

DNA sequence polymorphism and divergence was examined in the vicinity of the human beta-globin gene cluster origin of replication initiation region (IR), a 1.3-kb genomic region located immediately 5' of the adult-expressed beta-globin gene. DNA sequence variation in the replication origin IR and 5 kb of flanking DNA was surveyed in samples drawn from two populations, one African (from the Gambia, West Africa) and the other European (from Oxford, England). In these samples, levels of nucleotide and length polymorphism in the IR were found to be more than two times as high as adjacent non-IR-associated regions (estimates of per-nucleotide heterozygosity were 0.30% and 0.12%, respectively). Most polymorphic positions identified in the origin IR fall within or just adjacent to a 52-bp alternating purine-pyrimidine ((RY)n) sequence repeat. Within- and between-populations divergence is highest in this portion of the IR, and interspecific divergence in the same region, determined by comparison with an orthologous sequence from the chimpanzee, is also pronounced. Higher levels of diversity in this subregion are not, however, primarily attributable to slippage-mediated repeat unit changes, as nucleotide substitution contributes disproportionately to allelic heterogeneity. An estimate of helical stability in the sequenced region suggests that the hypervariable (RY)n constitutes the major DNA unwinding element (DUE) of the replication origin IR, the location at which the DNA duplex first unwinds and new strand synthesis begins. These findings suggest that the beta-globin IR experiences a higher underlying rate of neutral mutation than do adjacent genomic regions and that enzyme fidelity associated with the initiation of DNA replication at this origin may be compromised. The significance of these findings for our understanding of eukaryotic replication origin biology is discussed.

Characteristics of pyrroline-5-carboxylate reductase (P5CR) from Bradyrhizobium japonicum bacteroids and cultured rhizobia were compared with those of the enzyme in soybean nodule host cytosol. Reductase from host cytosol differed from that in bacteroids in: (a) the effect of pH on enzymic activity, (b) the capacity to catalyze both reduction of pyrroline-5-carboxylic acid and NAD(+)-dependent proline oxidation, (c) apparent affinities for pyrroline-5-carboxylic acid, and (d) sensitivities to inhibition by NADP(+) and proline. The K(1) for proline inhibition of P5CR in bacteroid cytosol was 1.8 millimolar. The properties of P5CR in B. japonicum and bacteroid cytosol were similar. The specific activities of P5CR in the cytosolic fractions of the nodule host and the bacteroid compartment were also comparable.