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Approximately 30% of healthy persons aged over 75 years show A[beta] deposition at autopsy. It is postulated that this represents preclinical Alzheimer's disease (AD). We evaluated the relationship between A[beta] burden as assessed by PiB PET and cognitive decline in a well-characterized, non-demented, elderly cohort. PiB PET studies and cognitive tests were performed on 34 elderly participants (age 73 [plus or minus] 6) from the longitudinal Melbourne Healthy Aging Study (MHAS). Subjects were classified as being cognitively "stable" or "declining" by an independent behavioural neurologist based on clinical assessment and serial word-list recall scores from the preceding 6-10 years. Decline was calculated from the slope of the word-list recall scores. A[beta] burden was quantified using Standardized Uptake Value normalized to cerebellar cortex. Ten subjects were clinically classified as declining. At the time of the PET scans, three of the declining subjects had mild cognitive impairment, one had AD, and six were declining but remained within the normal range for age on cognitive tests. Declining subjects were much more likely to show cortical PiB binding than stable subjects (70% vs. 17%, respectively). Neocortical A[beta] burden correlated with word-list recall slopes (r = -0.78) and memory function (r = -0.85) in the declining group. No correlations were observed in the stable group. A[beta] burden correlated with incident memory impairment and the rate of memory decline in the non-demented ageing population. These observations suggest that neither memory decline nor A[beta] deposition are part of normal ageing and likely represent preclinical AD. Further longitudinal observations are required to confirm this hypothesis. (Contains 4 tables and 4 figures.)

Background: Plasma p217+tau has shown high concordance with cerebrospinal fluid (CSF) and positron emission tomography (PET) measures of amyloid-β (Aβ) and tau in Alzheimer's Disease (AD). However, its association with longitudinal cognition and comparative performance to PET Aβ and tau in predicting cognitive decline are unknown., Objectives: To evaluate whether p217+tau can predict the rate of cognitive decline observed over two-year average follow-up and compare this to prediction based on Aβ (18F-NAV4694) and tau (18F-MK6240) PET. We also explored the sample size required to detect a 30% slowing in cognitive decline in a 2-year trial and selection test cost using p217+tau (pT+) as compared to PET Aβ (A+) and tau (T+) with and without p217+tau pre-screening., Design: A prospective observational cohort study., Setting: Participants of the Australian Imaging, Biomarker and Lifestyle Flagship Study of Ageing (AIBL) and Australian Dementia Network (ADNeT)., Participants: 153 cognitively unimpaired (CU) and 50 cognitively impaired (CI) individuals., Measurements: Baseline p217+tau Simoa® assay, 18F-MK6240 tau-PET and 18F-NAV4694 Aβ-PET with neuropsychological follow-up (MMSE, CDR-SB, AIBL-PACC) over 2.4 ± 0.8 years., Results: In CI, p217+tau was a significant predictor of change in MMSE (β = -0.55, p < 0.001) and CDR-SB (β =0.61, p < 0.001) with an effect size similar to Aβ Centiloid (MMSE β = -0.48, p = 0.002; CDR-SB β = 0.43, p = 0.004) and meta-temporal (MetaT) tau SUVR (MMSE: β = -0.62, p < 0.001; CDR-SB: β = 0.65, p < 0.001). In CU, only MetaT tau SUVR was significantly associated with change in AIBL-PACC (β = -0.22, p = 0.008). Screening pT+ CI participants into a trial could lead to 24% reduction in sample size compared to screening with PET for A+ and 6-13% compared to screening with PET for T+ (different regions). This would translate to an 81-83% biomarker test cost-saving assuming the p217+tau test cost one-fifth of a PET scan. In a trial requiring PET A+ or T+, p217+tau pre-screening followed by PET in those who were pT+ would cost more in the CI group, compared to 26-38% biomarker test cost-saving in the CU., Conclusions: Substantial cost reduction can be achieved using p217+tau alone to select participants with MCI or mild dementia for a clinical trial designed to slow cognitive decline over two years, compared to participant selection by PET. In pre-clinical AD trials, p217+tau provides significant cost-saving if used as a pre-screening measure for PET A+ or T+ but in MCI/mild dementia trials this may add to cost both in testing and in the increased number of participants needed for testing., Competing Interests: Christopher C. Rowe has received research grants from NHMRC, Enigma Australia, Biogen, Eisai and Abbvie. He is on the scientific advisory board for Cerveau Technologies and has consulted for Prothena, Eisai, Roche, and Biogen Australia. Victor L. Villemagne is and has been a consultant or paid speaker at sponsored conference sessions for Eli Lilly, Life Molecular Imaging, GE Healthcare, IXICO, Abbvie, Lundbeck, Shanghai Green Valley Pharmaceutical Co Ltd, and Hoffmann La Roche. Ashley I. Bush is a shareholder in Alterity Ltd, Cogstate Ltd and Mesoblast Ltd. He is a paid consultant for, and has a profit share interest in Collaborative Medicinal Development Pty Ltd. He has received lecture fees from Biogen P/L. Paul Maruff was a full-time employee of Cogstate. Ziad S. Saad, Gallen Triana-Baltzer, Randy Slemmon and Hartmuth C. Kolb are employees of Janssen Pharmaceuticals. The other authors did not report any conflict of interest.

Background: The National Institute on Aging and Alzheimer's Association (NIA-AA) have proposed a new Research Framework: Towards a biological definition of Alzheimer's disease, which uses a three-biomarker construct: Aß-amyloid, tau and neurodegeneration AT(N), to generate a biomarker based definition of Alzheimer's disease., Objectives: To stratify AIBL participants using the new NIA-AA Research Framework using cerebrospinal fluid (CSF) biomarkers. To evaluate the clinical and cognitive profiles of the different groups resultant from the AT(N) stratification. To compare the findings to those that result from stratification using two-biomarker construct criteria (AT and/or A(N))., Design: Individuals were classified as being positive or negative for each of the A, T, and (N) categories and then assigned to the appropriate AT(N) combinatorial group: A-T-(N)-; A+T-(N)-; A+T+(N)-; A+T-(N)+; A+T+(N)+; A-T+(N)-; A-T-(N)+; A-T+(N)+. In line with the NIA-AA research framework, these eight AT(N) groups were then collapsed into four main groups of interest (normal AD biomarkers, AD pathologic change, AD and non-AD pathologic change) and the respective clinical and cognitive trajectories over 4.5 years for each group were assessed. In two sensitivity analyses the methods were replicated after assigning individuals to four groups based on being positive or negative for AT biomarkers as well as A(N) biomarkers., Setting: Two study centers in Melbourne (Victoria) and Perth (Western Australia), Australia recruited MCI individuals and individuals with AD from primary care physicians or tertiary memory disorder clinics. Cognitively healthy, elderly NCs were recruited through advertisement or via spouses of participants in the study., Participants: One-hundred and forty NC, 33 MCI participants, and 27 participants with AD from the AIBL study who had undergone CSF evaluation using Elecsys® assays. INTERVENTION (if any): Not applicable., Measurements: Three CSF biomarkers, namely amyloid β1-42, phosphorylated tau181, and total tau, were measured to provide the AT(N) classifications. Clinical and cognitive trajectories were evaluated using the AIBL Preclinical Alzheimer Cognitive Composite (AIBL-PACC), a verbal episodic memory composite, an executive function composite, California Verbal Learning Test - Second Edition; Long-Delay Free Recall, Mini-Mental State Examination, and Clinical Dementia Rating Sum of Boxes scores., Results: Thirty-eight percent of the elderly NCs had no evidence of abnormal AD biomarkers, whereas 33% had biomarker levels consistent with AD or AD pathologic change, and 29% had evidence of non-AD biomarker change. Among NC participants, those with biomarker evidence of AD pathology tended to perform worse on cognitive outcome assessments than other biomarker groups. Approximately three in four participants with MCI or AD had biomarker levels consistent with the research framework's definition of AD or AD pathologic change. For MCI participants, a decrease in AIBL-PACC scores was observed with increasing abnormal biomarkers; and increased abnormal biomarkers were also associated with increased rates of decline across some cognitive measures., Conclusions: Increasing biomarker abnormality appears to be associated with worse cognitive trajectories. The implementation of biomarker classifications could help better characterize prognosis in clinical practice and identify those at-risk individuals more likely to clinically progress, for their inclusion in future therapeutic trials., Competing Interests: Samantha C. Burnham: reports speaker honoraria from Novartis outside the scope of the submitted work and research funding paid to her employers from F. Hoffmann-La Roche Ltd. Preciosa M. Coloma: is a full-time employee of, and own shares in, F. Hoffmann-La Roche Ltd. Simon Laws: received personal fees from Alzhyme outside the scope of the submitted work. James Doecke: reports research funding paid to his employers from F. Hoffmann-La Roche Ltd. David Ames: reports receipt of financial assistance to his employer to assist with an international drug trial of an anti-Alzheimer’s agent, owned by Eli Lilly. Christopher C. Rowe: reports speaker honoraria from GE Healthcare and Avid Radiopharmaceuticals, consulting fees from Avid Radiopharmaceuticals, AstraZeneca, and Piramal Imaging, and research grants from Avid Radiopharmaceuticals, GE Healthcare, and Piramal Imaging all outside the scope of the submitted work. Colin L. Masters: reports personal fees from Prana Biotechnology, Eli Lilly, and Actinogen outside the scope of the submitted work. Victor L. Villemagne: reports speaker honoraria from GE Healthcare, Piramal Imaging, and Avid Radiopharmaceuticals, and consulting fees from Lundbeck, AbbVie, Shanghai Green Valley Pharmaceutical Co. outside the scope of the submitted work and consulting fees from F. Hoffmann-La Roche Ltd. All other authors declare no conflicts of interest

The aim of this paper was to investigate the association of three well-recognised dietary patterns with cognitive change over a 3-year period. Five hundred and twenty-seven healthy participants from the Australian Imaging, Biomarkers and Lifestyle study of ageing completed the Cancer Council of Victoria food frequency questionnaire at baseline and underwent a comprehensive neuropsychological assessment at baseline, 18 and 36 months follow-up. Individual neuropsychological test scores were used to construct composite scores for six cognitive domains and a global cognitive score. Based on self-reported consumption, scores for three dietary patterns, (1) Australian-style Mediterranean diet (AusMeDi), (2) western diet and (3) prudent diet were generated for each individual. Linear mixed model analyses were conducted to examine the relationship between diet scores and cognitive change in each cognitive domain and for the global score. Higher baseline adherence to the AusMeDi was associated with better performance in the executive function cognitive domain after 36 months in apolipoprotein E (APOE) ɛ4 allele carriers (P<0.01). Higher baseline western diet adherence was associated with greater cognitive decline after 36 months in the visuospatial cognitive domain in APOE ɛ4 allele non-carriers (P<0.01). All other results were not significant. Our findings in this well-characterised Australian cohort indicate that adherence to a healthy diet is important to reduce risk for cognitive decline, with the converse being true for the western diet. Executive function and visuospatial functioning appear to be particularly susceptible to the influence of diet.

To assess the diagnostic utility of CSF BACE1 activity for discriminating Alzheimer disease (AD) from other dementias, particularly Creutzfeldt-Jakob disease (CJD), the authors studied 26 patients with sporadic CJD, 21 patients with AD, and 21 patients with various non-AD, non-CJD dementias (DCs). CSF BACE1 activity was elevated in AD in comparison with DC (p = 0.01). Unexpectedly, CSF BACE1 activity was also increased in sporadic CJD (p = 0.02).

Objective: To define the protease-resistant prion protein (PrPres) types and associated clinical profiles in Australian patients with sporadic Creutzfeldt-Jakob disease (CJD) to allow comparison with those reported from other continents and concomitantly reaffirm absence of variant CJD (vCJD)., Methods: Reassessment of available clinical and neuropathologic data on patients referred to the Australian National Creutzfeldt-Jakob Disease Registry (ANCJDR) who died between January 1, 1992, and June 30, 2003, was conducted. Molecular classification of PrPres was determined by immunoblot analysis of available frozen brain tissue. Brain homogenate pH and codon 129 genotype on the prion protein gene (PRNP) were established., Results: PrPres patterns in 35 of 37 patients with sporadic CJD conformed to one of three common reported types. Of a range of clinical features assessed, illness duration was the only clinical feature significantly associated with PrPres type. Two patients displayed coexistence of more than one PrP type, with one displaying a novel pattern of three PrPres types in a single brain region. The absence of vCJD was reconfirmed, supported by the lack of the typical PrPres glycoform pattern., Conclusions: Given Australia's geographic isolation and environmental uniqueness, the general congruity of these results with those reported from other continents suggests that endogenous factors predominantly determine sporadic Creutzfeldt-Jakob disease (CJD) phenotypic subtypes or "strains." These results support a clinicopathologic classification system whereby both PrPres type and codon 129 genotype are utilized to most accurately depict phenotypic subtypes or strains of sporadic CJD.

Objective: To ascertain all persons who developed a transmissible spongiform encephalopathy (TSE) within Australia during the 30-year period 1970 to 1999 through a comprehensive national surveillance program and subject the group to detailed epidemiologic analysis., Methods: Cases were ascertained through reviews of morbidity separation coding data from all university-affiliated tertiary referral hospitals, as well as the centralized data bases of state and territory health departments, regular national death certificate searches, and semiannual mailout questionnaires to all neurologists and pathologists throughout Australia. Prospective monitoring commenced in September 1993., Results: A total of 387 patients were confirmed as having TSE during this epoch. The majority of cases were sporadic Creutzfeldt-Jakob disease (CJD) (90.7%), with 7.2% heredofamilial and 2.1% iatrogenic. Over this 30-year period, the national average annual sporadic CJD incidence rate per million progressively increased from 0.31 for the decade 1970 through 1979 to 0.77 for 1980 through 1989, reaching 1.03 for 1990 through 1999. Death certificates were found to have a false-positive rate of 11.5% and sensitivity of 83.0% for sporadic CJD., Conclusions: Within Australia, there has been a gradual increase in the incidence of transmissible spongiform encephalopathy over the three-decade period 1970 through 1999, peaking in 1999 at 1.4/million/year for sporadic Creutzfeldt-Jakob disease. This increase is believed secondary to improved case ascertainment. Variant Creutzfeldt-Jakob disease was not identified during this period. Age- and sex-adjusted comparisons showed a decline in incidence rates in the elderly in both sexes, usually from age 74 years. Death certificates were a useful but imperfect method of case detection.

The Australian National Creutzfeldt-Jakob Disease Registry (ANCJDR) commenced surveillance in September 1993 as part of the Commonwealth's response to 4 cases of pituitary hormone (gonadotrophin)-associated Creutzfeldt-Jakob disease (CJD). With the passage of time, the Registry has become responsible for ascertaining all human transmissible spongiform encephalopathies (TSE; also known as prion diseases) within Australia since 1970. Included in the spectrum of diseases monitored are classical (sporadic, genetic, and health care acquired) CJD, and variant CJD (vCJD), first reported in 1996 in the United Kingdom. Variant CJD has not yet been diagnosed in Australia. Final classification of persons with suspected human prion disease is based upon all available clinical, investigational and pathological information. Ascertainment methods are diverse and include prompted, half-yearly personal communications from neurologists and neuropathologists, death certificate searches, and morbidity separation coding searches of major hospital, and State and Territory databases. More recently, referral for diagnostic CSF 14-3-3 protein testing (performed by the ANCJDR) has considerably increased prospective notifications of suspect cases. As at September 2001 there were 460 cases on the register; 237 definite cases, 168 probable and 55 incomplete cases awaiting final classification.

We screened 703 Australian subjects for an intronic polymorphism in the presenilin-1 (PS-1) gene. PS-1 intronic allele 1 homozygosity was not associated with individuals with early- or late-onset sporadic Alzheimer's disease (EOAD or LOAD). Carriers for the PS-1 intronic allele 1 were also not associated with significantly increased risk for AD regardless of gender. Our results for the Australian population are consistent with those of recent reports for other populations and do not support the conclusion that the PS-1 intronic polymorphism is associated with AD.

Among 20 consecutive autopsies of amyotrophic lateral sclerosis (ALS) occurring in Caucasians in Western Australia (WA), 85% were males. The median age of onset was 58.9 years and the average duration of illness was 2.4 years. Twenty-two randomly selected ALS occurring among natives in Guam also showed a male predominance of 75%, younger age of onset (median 48.5 years) and longer survival period (median 3.4 years). 45% of the WA patients presented with bulbar involvement at the time of first examination. These patients had the lowest median survival period of 1.5 years when compared with the other forms of ALS, the classic upper and lower motor system involvement and progressive muscular atrophy. Theneuropathologic lesions of ALS in WA and Guam were similar with the exception that neurofibrillary tangles were frequently present in the Guamanian brains. In 14%, neuronal loss, gliosis and frequency of tangles in the cerebral cortex especially in Ammon's horn, substantia nigra, and locus ceruleus, were sufficiently severe to indicate the coexistence of another disorder, Parkinsonism-Dementia Complex. This condition was not clinically recognized. In the WA cases only one patient had tangles in the brain and he had concurrent Alzheimers disease. While senile plaques were present in this patient they were usually absent in the Guamanian brains.