Bryan K. Woodruff

Longitudinal Modeling of Age-Related Memory Decline and the APOE ε4 Effect

BACKGROUND The APOE epsilon4 allele is associated with the risk of late-onset Alzheimers disease. The age at which memory decline diverges among persons who are homozygous for the APOE epsilon4 allele, those who are heterozygous for the allele, and noncarriers is unknown. METHODS Using local advertisements, we recruited cognitively normal subjects between the ages of 21 and 97 years, who were grouped according to their APOE epsilon4 status. We then followed the subjects with longitudinal neuropsychological testing. Anyone in whom mild cognitive impairment or dementia developed during follow-up was excluded. We compared the rates of decline in predetermined cognitive measures between carriers and noncarriers of the APOE epsilon4 allele, using a mixed model for longitudinal change with age. RESULTS We analyzed 815 subjects: 317 APOE epsilon4 carriers (79 who were homozygous for the APOE epsilon4 allele and 238 who were heterozygous) and 498 noncarriers. Carriers, as compared with noncarriers, were generally younger (mean age, 58.0 vs. 61.4 years; P<0.001) and were followed for a longer period (5.3 vs. 4.7 years, P=0.01), with an equivalent duration of formal education (15.4 years) and proportion of women (69%). Longitudinal decline in memory in carriers began before the age of 60 years and showed greater acceleration than in noncarriers (P=0.03), with a possible allele-dose effect (P=0.008). We observed similar although weaker effects on measures of visuospatial awareness and general mental status. CONCLUSIONS Age-related memory decline in APOE epsilon4 carriers diverges from that of noncarriers before the age of 60 years, despite ongoing normal clinical status.

Common variants at 7p21 are associated with frontotemporal lobar degeneration with TDP-43 inclusions

Frontotemporal lobar degeneration (FTLD) is the second most common cause of presenile dementia. The predominant neuropathology is FTLD with TAR DNA-binding protein (TDP-43) inclusions (FTLD-TDP). FTLD-TDP is frequently familial, resulting from mutations in GRN (which encodes progranulin). We assembled an international collaboration to identify susceptibility loci for FTLD-TDP through a genome-wide association study of 515 individuals with FTLD-TDP. We found that FTLD-TDP associates with multiple SNPs mapping to a single linkage disequilibrium block on 7p21 that contains TMEM106B. Three SNPs retained genome-wide significance following Bonferroni correction (top SNP rs1990622, P = 1.08 × 10−11; odds ratio, minor allele (C) 0.61, 95% CI 0.53–0.71). The association replicated in 89 FTLD-TDP cases (rs1990622; P = 2 × 10−4). TMEM106B variants may confer risk of FTLD-TDP by increasing TMEM106B expression. TMEM106B variants also contribute to genetic risk for FTLD-TDP in individuals with mutations in GRN. Our data implicate variants in TMEM106B as a strong risk factor for FTLD-TDP, suggesting an underlying pathogenic mechanism.

Clinicopathologic correlations in 172 cases of rapid eye movement sleep behavior disorder with or without a coexisting neurologic disorder.

OBJECTIVE To determine the pathologic substrates in patients with rapid eye movement (REM) sleep behavior disorder (RBD) with or without a coexisting neurologic disorder. METHODS The clinical and neuropathologic findings were analyzed on all autopsied cases from one of the collaborating sites in North America and Europe, were evaluated from January 1990 to March 2012, and were diagnosed with polysomnogram (PSG)-proven or probable RBD with or without a coexisting neurologic disorder. The clinical and neuropathologic diagnoses were based on published criteria. RESULTS 172 cases were identified, of whom 143 (83%) were men. The mean±SD age of onset in years for the core features were as follows - RBD, 62±14 (range, 20-93), cognitive impairment (n=147); 69±10 (range, 22-90), parkinsonism (n=151); 68±9 (range, 20-92), and autonomic dysfunction (n=42); 62±12 (range, 23-81). Death age was 75±9 years (range, 24-96). Eighty-two (48%) had RBD confirmed by PSG, 64 (37%) had a classic history of recurrent dream enactment behavior, and 26 (15%) screened positive for RBD by questionnaire. RBD preceded the onset of cognitive impairment, parkinsonism, or autonomic dysfunction in 87 (51%) patients by 10±12 (range, 1-61) years. The primary clinical diagnoses among those with a coexisting neurologic disorder were dementia with Lewy bodies (n=97), Parkinsons disease with or without mild cognitive impairment or dementia (n=32), multiple system atrophy (MSA) (n=19), Alzheimers disease (AD)(n=9) and other various disorders including secondary narcolepsy (n=2) and neurodegeneration with brain iron accumulation-type 1 (NBAI-1) (n=1). The neuropathologic diagnoses were Lewy body disease (LBD)(n=77, including 1 case with a duplication in the gene encoding α-synuclein), combined LBD and AD (n=59), MSA (n=19), AD (n=6), progressive supranulear palsy (PSP) (n=2), other mixed neurodegenerative pathologies (n=6), NBIA-1/LBD/tauopathy (n=1), and hypothalamic structural lesions (n=2). Among the neurodegenerative disorders associated with RBD (n=170), 160 (94%) were synucleinopathies. The RBD-synucleinopathy association was particularly high when RBD preceded the onset of other neurodegenerative syndrome features. CONCLUSIONS In this large series of PSG-confirmed and probable RBD cases that underwent autopsy, the strong association of RBD with the synucleinopathies was further substantiated and a wider spectrum of disorders which can underlie RBD now are more apparent.

Ataxin-2 repeat-length variation and neurodegeneration

Expanded glutamine repeats of the ataxin-2 (ATXN2) protein cause spinocerebellar ataxia type 2 (SCA2), a rare neurodegenerative disorder. More recent studies have suggested that expanded ATXN2 repeats are a genetic risk factor for amyotrophic lateral sclerosis (ALS) via an RNA-dependent interaction with TDP-43. Given the phenotypic diversity observed in SCA2 patients, we set out to determine the polymorphic nature of the ATXN2 repeat length across a spectrum of neurodegenerative disorders. In this study, we genotyped the ATXN2 repeat in 3919 neurodegenerative disease patients and 4877 healthy controls and performed logistic regression analysis to determine the association of repeat length with the risk of disease. We confirmed the presence of a significantly higher number of expanded ATXN2 repeat carriers in ALS patients compared with healthy controls (OR = 5.57; P= 0.001; repeat length >30 units). Furthermore, we observed significant association of expanded ATXN2 repeats with the development of progressive supranuclear palsy (OR = 5.83; P= 0.004; repeat length >30 units). Although expanded repeat carriers were also identified in frontotemporal lobar degeneration, Alzheimers and Parkinsons disease patients, these were not significantly more frequent than in controls. Of note, our study identified a number of healthy control individuals who harbor expanded repeat alleles (31-33 units), which suggests caution should be taken when attributing specific disease phenotypes to these repeat lengths. In conclusion, our findings confirm the role of ATXN2 as an important risk factor for ALS and support the hypothesis that expanded ATXN2 repeats may predispose to other neurodegenerative diseases, including progressive supranuclear palsy.

Arizona Study of Aging and Neurodegenerative Disorders and Brain and Body Donation Program

The Brain and Body Donation Program (BBDP) at Banner Sun Health Research Institute (http://www.brainandbodydonationprogram.org) started in 1987 with brain‐only donations and currently has banked more than 1600 brains. More than 430 whole‐body donations have been received since this service was commenced in 2005. The collective academic output of the BBDP is now described as the Arizona Study of Aging and Neurodegenerative Disorders (AZSAND). Most BBDP subjects are enrolled as cognitively normal volunteers residing in the retirement communities of metropolitan Phoenix, Arizona. Specific recruitment efforts are also directed at subjects with Alzheimers disease, Parkinsons disease and cancer. The median age at death is 82. Subjects receive standardized general medical, neurological, neuropsychological and movement disorders assessments during life and more than 90% receive full pathological examinations by medically licensed pathologists after death. The Program has been funded through a combination of internal, federal and state of Arizona grants as well as user fees and pharmaceutical industry collaborations. Subsets of the Program are utilized by the US National Institute on Aging Arizona Alzheimers Disease Core Center and the US National Institute of Neurological Disorders and Stroke National Brain and Tissue Resource for Parkinsons Disease and Related Disorders. Substantial funding has also been received from the Michael J. Fox Foundation for Parkinsons Research. The Program has made rapid autopsy a priority, with a 3.0‐hour median post‐mortem interval for the entire collection. The median RNA Integrity Number (RIN) for frozen brain and body tissue is 8.9 and 7.4, respectively. More than 2500 tissue requests have been served and currently about 200 are served annually. These requests have been made by more than 400 investigators located in 32 US states and 15 countries. Tissue from the BBDP has contributed to more than 350 publications and more than 200 grant‐funded projects.

Reversible metronidazole-induced lesions of the cerebellar dentate nuclei

To the Editor: The toxic effects of metronidazole include ataxia, peripheral neuropathy, and seizures.1 There have been two reported cases in which abnormalities of the dentate nucleus on magnetic ...

Cerebrovascular risk factors and preclinical memory decline in healthy APOE ε4 homozygotes

Objective: To characterize the effects of cerebrovascular (CV) risk factors on preclinical memory decline in cognitively normal individuals at 3 levels of genetic risk for Alzheimer disease (AD) based on APOE genotype. Methods: We performed longitudinal neuropsychological testing on an APOE ε4 enriched cohort, ages 21–97. The long-term memory (LTM) score of the Auditory Verbal Learning Test (AVLT) was the primary outcome measure. Any of 4 CV risk factors (CVany), including hypercholesterolemia (CHOL), prior cigarette use (CIG), diabetes mellitus (DM), and hypertension (HTN), was treated as a dichotomized variable. We estimated the longitudinal effect of age using statistical models that simultaneously modeled the cross-sectional and longitudinal effects of age on AVLT LTM by APOE genotype, CVany, and the interaction between the two. Results: A total of 74 APOE ε4 homozygotes (HMZ), 239 ε4 heterozygotes (HTZ), and 494 ε4 noncarriers were included. APOE ε4 carrier status showed a significant quadratic effect with age-related LTM decline in all models as previously reported. CVany was associated with further longitudinal AVLT LTM decline in APOE ε4 carriers (p = 0.02), but had no effect in noncarriers. When ε4 HTZ and HMZ were considered separately, there was a striking effect in HMZ (p < 0.001) but not in HTZ. In exploratory analyses, significant deleterious effects were found for CIG (p = 0.001), DM (p = 0.03), and HTN (p = 0.05) in APOE ε4 carriers only that remained significant only for CIG after correction for multiple comparisons. Conclusion: CV risk factors influence age-related memory decline in APOE ε4 HMZ.

Longitudinal modeling of frontal cognition in APOE ε4 homozygotes, heterozygotes, and noncarriers

Background: Fibrillar amyloid deposition preferentially affects the frontal lobes, temporal pole/neocortex, and posterior cingulate by age 65 years in APOE ε4 carriers prior to the diagnosis of mild cognitive impairment (MCI) and Alzheimer disease (AD), but is it impairing frontally mediated neuropsychological performance? Methods: A total of 71 ε4 homozygotes (HMZ), 194 ε4 heterozygotes (HTZ), and 356 ε4 noncarriers (NC) who did not differ significantly in mean age (56.6 years), years of education (15.6), gender (70% women), or follow-up duration (6.3 years) had neuropsychological testing every 2 years including the Auditory Verbal Learning Test (AVLT) and frontal/executive tasks sensitive to psychomotor speed, working memory, problem solving, and activity. A subset also received the Iowa Gambling Task (IGT). Findings were then tested in a clinical sample of 27 patients with incident MCI and AD. Results: APOE ε4 carriers had greater acceleration of decline (quadratic effect) than NC on the AVLT (p = 0.04) but not on any frontal test. APOE ε4 HMZ had greater velocity of decline (linear effects) than NC on all mental arithmetic tests: paced auditory serial attention task (PASAT) 3 second (p = 0.01) and 2 second (p = 0.004) versions; and Wechsler Adult Intelligence Scale–Revised arithmetic (p = 0.048). IGT performance did not differ between 12 ε4 HMZ, 27 ε4 HTZ, and 44 NC. Among 27 patients with incident MCI and AD, the PASAT showed progressive decline preceding diagnosis in 50%. Conclusions: No frontal cognitive effects were as robust as memory decline. APOE ε4 HMZ declined more quickly than NC on mental arithmetic tests related to frontal lobe–mediated working memory ability.

The neuropsychology of normal aging and preclinical Alzheimer's disease.

A National Institute on Aging–sponsored work group on preclinical Alzheimers disease (AD) articulated the need to characterize cognitive differences between normal aging and preclinical AD.

Adjunctive haloperidol prophylaxis reduces postoperative delirium severity and duration in at-risk elderly patients.

Background:Delirium is a potentially life-threatening syndrome that is particularly common in elderly hospitalized patients, especially those with preexisting neurologic disorders. Nonpharmacological tactics can reduce the incidence and severity of delirium in acute care settings and antipsychotic drugs are widely used to treat established delirium. More effective preventive strategies could notably impact morbidity, mortality, and health care costs. Objective:To determine whether antipsychotic drug prophylaxis reduces the incidence and severity of postoperative delirium in at-risk elderly patients. Methods:We addressed the objective through development of a structured critically appraised topic that included a clinical scenario, structured question, search strategy, critical appraisal, results, evidence summary, commentary, and conclusions. Participants included consultant and resident neurologists, a medical librarian, clinical epidemiologists, and content experts in the field of cognitive disorders. Results:One randomized controlled trial addressed the question. In at-risk patients aged >70 years, oral haloperidol 0.5 mg TID, administered from up to 72 hours preoperatively until the third postoperative day, did not alter the incidence of postoperative delirium (15.1%) compared with placebo (16.5%; relative risk 0.91; 95% confidence interval 0.59–1.44). However, the study was underpowered for this primary outcome, possibly because both groups received nonpharmacological delirium prevention strategies. Haloperidol significantly reduced delirium severity ratings, delirium duration (from a mean of 11.8 to 5.4 days), and length of hospital stay in affected participants (from 22.6 to 17.1 day). Conclusion:Adjunctive low-dose haloperidol prophylaxis reduces delirium severity, duration, and subsequent hospitalization length in elderly at-risk patients. Further study is needed to determine the optimal pharmacological approach, combination with nonpharmacological strategies, and generalizability to other settings.