Association of biological sex with clinical outcomes and biomarkers of Alzheimer's disease in adults with Down syndrome.

The study of sex differences in Alzheimer's disease is increasingly recognized as a key priority in research and clinical development. People with Down syndrome represent the largest population with a genetic link to Alzheimer's disease (>90% in the 7th decade). Yet, sex differences in Alzheimer's disease manifestations have not been fully investigated in these individuals, who are key candidates for preventive clinical trials. In this double-centre, cross-sectional study of 628 adults with Down syndrome [46% female, 44.4 (34.6; 50.7) years], we compared Alzheimer's disease prevalence, as well as cognitive outcomes and AT(N) biomarkers across age and sex. Participants were recruited from a population-based health plan in Barcelona, Spain, and from a convenience sample recruited via services for people with intellectual disabilities in England and Scotland. They underwent assessment with the Cambridge Cognitive Examination for Older Adults with Down Syndrome, modified cued recall test and determinations of brain amyloidosis (CSF amyloid-ß 42 / 40 and amyloid-PET), tau pathology (CSF and plasma phosphorylated-tau181) and neurodegeneration biomarkers (CSF and plasma neurofilament light, total-tau, fluorodeoxyglucose-PET and MRI). We used within-group locally estimated scatterplot smoothing models to compare the trajectory of biomarker changes with age in females versus males, as well as by apolipoprotein ɛ4 carriership. Our work revealed similar prevalence, age at diagnosis and Cambridge Cognitive Examination for Older Adults with Down Syndrome scores by sex, but males showed lower modified cued recall test scores from age 45 compared with females. AT(N) biomarkers were comparable in males and females. When considering apolipoprotein ɛ4, female ɛ4 carriers showed a 3-year earlier age at diagnosis compared with female non-carriers (50.5 versus 53.2 years, P = 0.01). This difference was not seen in males (52.2 versus 52.5 years, P = 0.76). Our exploratory analyses considering sex, apolipoprotein ɛ4 and biomarkers showed that female ɛ4 carriers tended to exhibit lower CSF amyloid-ß 42/amyloid-ß 40 ratios and lower hippocampal volume compared with females without this allele, in line with the clinical difference. This work showed that biological sex did not influence clinical and biomarker profiles of Alzheimer's disease in adults with Down syndrome. Consideration of apolipoprotein ɛ4 haplotype, particularly in females, may be important for clinical research and clinical trials that consider this population. Accounting for, reporting and publishing sex-stratified data, even when no sex differences are found, is central to helping advance precision medicine.

Support vector machine learning and diffusion-derived structural networks predict amyloid quantity and cognition in adults with Down's syndrome.

Down's syndrome results from trisomy of chromosome 21, a genetic change which also confers a probable 100% risk for the development of Alzheimer's disease neuropathology (amyloid plaque and neurofibrillary tangle formation) in later life. We aimed to assess the effectiveness of diffusion-weighted imaging and connectomic modelling for predicting brain amyloid plaque burden, baseline cognition and longitudinal cognitive change using support vector regression. Ninety-five participants with Down's syndrome successfully completed a full Pittsburgh Compound B (PiB) PET-MR protocol and memory assessment at two timepoints. Our findings indicate that graph theory metrics of node degree and strength based on the structural connectome are effective predictors of global amyloid deposition. We also show that connection density of the structural network at baseline is a promising predictor of current cognitive performance. Directionality of effects were mainly significant reductions in the white matter connectivity in relation to both PiB+ status and greater rate of cognitive decline. Taken together, these results demonstrate the integral role of the white matter during neuropathological progression and the utility of machine learning methodology for non-invasively evaluating Alzheimer's disease prognosis.

Disorders of hypothalamic function: Insights from Prader-Willi syndrome and the effects of craniopharyngioma.

Either physical damage or being born with a specific genetic abnormality can impact on the functioning of the hypothalamus, resulting in diverse physical manifestations and/or specific behavior disorders. The impact of physical damage due to craniopharyngioma (CP) and/or surgery to remove a craniopharyngioma is compared and contrasted with the impact resulting from the genetic abnormalities associated with Prader-Willi syndrome (PWS). Similarities between PWS and CP posttreatment include hyperphagia and weight gain, low growth hormone levels, low bone density in adults, hypogonadism, disturbed temperature regulation, disturbed sleep and daytime sleepiness, memory difficulties, and problems with behavior and with peer relationships. These disturbances are an indication of the hypothalamus's central role in homeostasis. Most of the abnormalities appear to be more severe postoperatively in people with CP. Differences include higher ghrelin levels in PWS, complete absence of pituitary hormones in many cases of CP, higher incidence of thyroid dysfunction in CP, "growth without growth hormone" in obese children with CP, different types of diabetes (diabetes insipidus in CP and diabetes mellitus in PWS), and evidence of developmental delay and low IQ in people with PWS.

Long-term cognitive outcome in adult survivors of an early childhood posterior fossa brain tumour.

PURPOSE: Posterior fossa brain tumours (PFT) and their treatment in young children are often associated with subsequent cognitive impairment. However, reported follow-up periods rarely exceed 10 years. This study reports very long-term cognitive consequences of surviving an early childhood PFT. METHODS: 62 adult survivors of a PFT, ascertained from a national register, diagnosed before 5 years of age, and a sibling control, received a single IQ assessment an average of 32 years (range 18-53) after initial diagnosis, using the Weschler Abbreviated Scale of Intelligence. Regression models were fitted to survivor-sibling pair differences on verbal and performance IQ (VIQ and PIQ) scores to investigate whether increasing time between PFT diagnosis and follow-up IQ assessment contributed to survivor-sibling IQ differences. RESULTS: At follow-up, survivors had, on average, VIQ 15 points and PIQ 19 points lower than their siblings. There was no significant effect of time since diagnosis on survivor-sibling VIQ difference. Survivors who received radiotherapy showed no significant effect of time since diagnosis on survivor-sibling PIQ difference. Survivors who did not receive radiotherapy demonstrated a trend for it to reduce. CONCLUSIONS: VIQ and PIQ deficits persist in adulthood, suggesting the effect of a fixed injury imposing on cognitive development, rather than an ongoing pathological process. IMPLICATIONS FOR CANCER SURVIVORS: The findings will help parents and others supporting survivors of an early life PFT to identify and plan for possible cognitive outcomes, and highlight the importance of early interventions to optimize cognitive function during the developmental period.

Clinical and biomarker changes of Alzheimer's disease in adults with Down syndrome: a cross-sectional study.

BACKGROUND: Alzheimer's disease and its complications are the leading cause of death in adults with Down syndrome. Studies have assessed Alzheimer's disease in individuals with Down syndrome, but the natural history of biomarker changes in Down syndrome has not been established. We characterised the order and timing of changes in biomarkers of Alzheimer's disease in a population of adults with Down syndrome. METHODS: We did a dual-centre cross-sectional study of adults with Down syndrome recruited through a population-based health plan in Barcelona (Spain) and through services for people with intellectual disabilities in Cambridge (UK). Cognitive impairment in participants with Down syndrome was classified with the Cambridge Cognitive Examination for Older Adults with Down Syndrome (CAMCOG-DS). Only participants with mild or moderate disability were included who had at least one of the following Alzheimer's disease measures: apolipoprotein E allele carrier status; plasma concentrations of amyloid ß peptides 1-42 and 1-40 and their ratio (Aß1-42/1-40), total tau protein, and neurofilament light chain (NFL); tau phosphorylated at threonine 181 (p-tau), and NFL in cerebrospinal fluid (CSF); and one or more of PET with 18F-fluorodeoxyglucose, PET with amyloid tracers, and MRI. Cognitively healthy euploid controls aged up to 75 years who had no biomarker abnormalities were recruited from the Sant Pau Initiative on Neurodegeneration. We used a first-order locally estimated scatterplot smoothing curve to determine the order and age at onset of the biomarker changes, and the lowest ages at the divergence with 95% CIs are also reported where appropriate. FINDINGS: Between Feb 1, 2013, and June 28, 2019 (Barcelona), and between June 1, 2009, and Dec 31, 2014 (Cambridge), we included 388 participants with Down syndrome (257 [66%] asymptomatic, 48 [12%] with prodromal Alzheimer's disease, and 83 [21%] with Alzheimer's disease dementia) and 242 euploid controls. CSF Aß1-42/1-40 and plasma NFL values changed in individuals with Down syndrome as early as the third decade of life, and amyloid PET uptake changed in the fourth decade. 18F-fluorodeoxyglucose PET and CSF p-tau changes occurred later in the fourth decade of life, followed by hippocampal atrophy and changes in cognition in the fifth decade of life. Prodromal Alzheimer's disease was diagnosed at a median age of 50·2 years (IQR 47·5-54·1), and Alzheimer's disease dementia at 53·7 years (49·5-57·2). Symptomatic Alzheimer's disease prevalence increased with age in individuals with Down syndrome, reaching 90-100% in the seventh decade of life. INTERPRETATION: Alzheimer's disease in individuals with Down syndrome has a long preclinical phase in which biomarkers follow a predictable order of changes over more than two decades. The similarities with sporadic and autosomal dominant Alzheimer's disease and the prevalence of Down syndrome make this population a suitable target for Alzheimer's disease preventive treatments. FUNDING: Instituto de Salud Carlos III, Fundació Bancaria La Caixa, Fundació La Marató de TV3, Medical Research Council, and National Institutes of Health.

The validity and reliability of the CAMDEX-DS for assessing dementia in adults with Down syndrome in Brazil

Objective: Alzheimer's disease occurs at a higher prevalence and an earlier age in individuals with Down syndrome (DS) than typically developing individuals. However, diagnosing dementia in individuals with intellectual disability remains a challenge due to pre-existing cognitive deficits. The aim of this study was to investigate the validity and reliability of the Brazilian version of the Cambridge Examination for Mental Disorders of Older People with Down's syndrome and Others with Intellectual Disabilities (CAMDEX-DS) for individuals with DS. Methods: Two psychiatrists, working independently, evaluated 92 adults with DS ≥ 30 years of age. The concurrent validity of the CAMDEX-DS was analyzed in relation to the gold standard of established international criteria. In a subgroup of 20 subjects, the concurrent validity of the CAMDEX-DS was analyzed in relation to an independent objective assessment of cognitive decline over three years. We analyzed the inter-rater reliability of cognitive assessment. Results: The diagnostic accuracy of the CAMDEX-DS compared to the gold standard was 96.7%. CAMDEX-DS-based diagnosis was considered consistent with cognitive decline. The probability of a participant with dementia having cognitive decline was 83%. Inter-rater reliability for the participant assessment was good, with a kappa of > 0.8 for 93% of the CAMDEX-DS items. Conclusion: The CAMDEX-DS can be considered the first valid and reliable instrument for evaluating dementia in adults with DS in Brazil. Its use in such individuals could improve clinical practice and research.

The Down syndrome brain in the presence and absence of fibrillar ß-amyloidosis.

People with Down syndrome (DS) have a neurodevelopmentally distinct brain and invariably developed amyloid neuropathology by age 50. This cross-sectional study aimed to provide a detailed account of DS brain morphology and the changes occuring with amyloid neuropathology. Forty-six adults with DS underwent structural and amyloid imaging-the latter using Pittsburgh compound B (PIB) to stratify the cohort into PIB-positive (n = 19) and PIB-negative (n = 27). Age-matched controls (n = 30) underwent structural imaging. Group differences in deep gray matter volumetry and cortical thickness were studied. PIB-negative people with DS have neurodevelopmentally atypical brain, characterized by disproportionately thicker frontal and occipitoparietal cortex and thinner motor cortex and temporal pole with larger putamina and smaller hippocampi than controls. In the presence of amyloid neuropathology, the DS brains demonstrated a strikingly similar pattern of posterior dominant cortical thinning and subcortical atrophy in the hippocampus, thalamus, and striatum, to that observed in non-DS Alzheimer's disease. Care must be taken to avoid underestimating amyloid-associated morphologic changes in DS due to disproportionate size of some subcortical structures and thickness of the cortex.

Prevalence, associations, and predictors of apathy in adult survivors of infantile (<5 years of age) posterior fossa brain tumors.

BACKGROUND: Apathy is associated with pervasive and disadvantageous effects on daily functioning. It has been observed transiently in some children after surgery for posterior fossa tumors. In this study, our objective was to examine prevalence, associations, and predictors of apathy in adult survivors of an infantile posterior fossa brain tumor (PFT). METHODS: One hundred seventeen adult survivors of a childhood PFT diagnosed before age 5 years and 60 of their siblings were assessed in a cross-sectional study a mean of 32 years (range, 18-53 years) after survivors' initial tumor diagnoses, using the Marin Apathy Evaluation Scale (AES), the Weschler Abbreviated Scale of Intelligence and the Composite International Diagnostic Interview for psychiatric disorders. RESULTS: Marin Apathy Evaluation Scale, the Weschler Abbreviated Scale of Intelligence reached or exceeded a criterion score for clinically significant apathy in 35% of survivors, compared with 18% in a sibling comparison group. In both siblings and survivors, apathy was associated with lower verbal and full-scale IQ and, among survivors, with having undergone partial rather than total tumor resection (independent of irradiation status). Apathy was not related to presence of concurrent International Classification of Diseases, 10(th) Revision, depression. Female sex was associated with late apathy after a PFT, with increased likelihood of women reaching the apathy criterion relative to men if they were survivors. CONCLUSIONS: Clinically significant and potentially treatable apathy occurs relatively commonly in adult survivors of an infantile childhood PFT, particularly women. Clinicians, including those managing posterior fossa pathology in very young children, should be aware of this association, and future research should clarify whether specific treatment-related variables are implicated in increasing this risk of apathy.

Behavioural and cognitive abnormalities in an imprinting centre deletion mouse model for Prader-Willi syndrome.

The genes in the imprinted cluster on human chromosome 15q11-q13 are known to contribute to psychiatric conditions such as schizophrenia and autism. Major disruptions of this interval leading to a lack of paternal allele expression give rise to Prader-Willi syndrome (PWS), a neurodevelopmental disorder with core symptoms of a failure to thrive in infancy and, on emergence from infancy, learning disabilities and over-eating. Individuals with PWS also display a number of behavioural problems and an increased incidence of neuropsychiatric abnormalities, which recent work indicates involve aspects of frontal dysfunction. To begin to examine the contribution of genes in this interval to relevant psychological and behavioural phenotypes, we exploited the imprinting centre (IC) deletion mouse model for PWS (PWS-IC(+/-)) and the five-choice serial reaction time task (5-CSRTT), which is primarily an assay of visuospatial attention and response control that is highly sensitive to frontal manipulations. Locomotor activity, open-field behaviour and sensorimotor gating were also assessed. PWS-IC(+/-) mice displayed reduced locomotor activity, increased acoustic startle responses and decreased prepulse inhibition of startle responses. In the 5-CSRTT, the PWS-IC(+/-) mice showed deficits in discriminative response accuracy, increased correct reaction times and increased omissions. Task manipulations confirmed that these differences were likely to be due to impaired attention. Our data recapitulate several aspects of the PWS clinical condition, including findings consistent with frontal abnormalities, and may indicate novel contributions of the imprinted genes found in 15q11-q13 to behavioural and cognitive function generally.

The transition between the phenotypes of Prader-Willi syndrome during infancy and early childhood.

AIM: Prader-Willi syndrome (PWS) is a genetic disorder historically characterized by two phenotypic stages. The early phenotype in infants is associated with hypotonia, poor suck, and failure to thrive. In later childhood, PWS is associated with intellectual disability, hyperphagia, as well as growth and sex hormone deficiency. Little is known about the transition between phenotypes. This study investigates the nature of the change in infancy and childhood PWS. METHOD: Forty-six children (22 females, 24 males; mean age 2 y 9 mo, SD 18.9 mo; range 7 mo-5 y) with genetically confirmed PWS participated. Information was obtained on childhood height and weight, and eating behaviour from case notes and by parental interview. RESULTS: Weight standard deviation scores (SDS) started to exceed height by the end of the first year. Height SDS appeared to fall from near normal at birth until stabilizing below normal around 2 years. Half of the children whose body mass index (BMI) was higher than normal at interview had food interests greater than that of their peers, and the age at which increased age-appropriate eating was first noted was later than the increase of BMI SDS. INTERPRETATION: Obesity may develop before the increased interest in food, suggesting underlying physiological factors independent of appetite control may be important.

Elevated fasting plasma ghrelin in prader-willi syndrome adults is not solely explained by their reduced visceral adiposity and insulin resistance.

Plasma ghrelin is elevated in Prader-Willi syndrome (PWS). This might contribute to obesity or GH deficiency in such patients. Visceral adiposity and insulin resistance are reduced in PWS, which might lead to hyperghrelinemia. We measured fasting plasma ghrelin in control female (n = 39), PWS female (n = 12), and PWS male (n = 6) adults. In controls and PWS, ghrelin was negatively correlated with visceral adiposity, fasting insulin, and homeostasis model insulin resistance index. There was no significant correlation with serum IGF-I in PWS. In stepwise linear regression, visceral adiposity (P < 0.02) had a stronger inverse correlation with ghrelin than sc fat depots in controls and PWS, possibly through hyperinsulinemia, as the correlations with insulin resistance were even stronger (P < 0.01). PWS females had significantly (P < 0.001) elevated ghrelin (mean +/- SD, 661 +/- 360 pg/ml), compared with both nonobese (363 +/- 163) and obese (191 +/- 66) controls. Ghrelin was increased 3.4- to 3.6-fold in PWS females adjusting for total adiposity, 3.2- to 3.4-fold adjusting for visceral adiposity, and 3.0-fold adjusting for insulin resistance. Fasting plasma glucagon-like peptide-1 was normal in PWS females. The hyperghrelinemia in PWS adults is therefore not solely explained by their reduced visceral adiposity and relative hypoinsulinemia. Its cause and consequences await further elucidation.