RESUMO
BACKGROUND: Down syndrome (DS), or trisomy 21, is one of the most common autosomal mutations. People with DS have intellectual disability (ID) and are at significantly increased risk of developing Alzheimer's disease (AD). The biological associates of both ID and AD in DS are poorly understood, but glutamate has been proposed to play a key role. In non-DS populations, glutamate is essential to learning and memory and glutamate-mediated excitotoxicity has been implicated in AD. However, the concentration of hippocampal glutamate in DS individuals with and without dementia has not previously been directly investigated. Proton magnetic resonance spectroscopy ((1)H MRS) can be used to measure in vivo the concentrations of glutamate-glutamine (Glx). The objective of the current study was to examine the hippocampal Glx concentration in non-demented DS (DS-) and demented DS (DS+) individuals. METHODS: We examined 46 adults with DS (35 without dementia and 11 with dementia) and 39 healthy controls (HC) using (1)H MRS and measured their hippocampal Glx concentrations. RESULTS: There was no significant difference in the hippocampal Glx concentration between DS+ and DS-, or between either of the DS groups and the healthy controls. Also, within DS, there was no significant correlation between hippocampal Glx concentration and measures of overall cognitive ability. Last, a sample size calculation based on the effect sizes from this study showed that it would have required 6,257 participants to provide 80% power to detect a significant difference between the groups which would indicate that there is a very low likelihood of a type 2 error accounting for the findings in this study. CONCLUSIONS: Individuals with DS do not have clinically detectable differences in hippocampal Glx concentration. Other pathophysiological processes likely account for ID and AD in people with DS.
RESUMO
People with Down syndrome (DS) develop Alzheimer's disease (AD) with an early age of onset. A tetranucleotide repeat, attt(5-8), in intron 7 of the amyloid precursor protein has been associated with the age of onset of AD in DS in a preliminary study. The authors examine the impact of this polymorphism in a larger cohort of individuals with DS. Adults with DS were genotyped for attt(5-8) and APOE. The results were analysed with respect to the age of onset of dementia. The presence of three copies of the six-repeat allele resulted in onset of dementia seven years earlier than in the presence of other genotypes. Further study is essential to elucidate the mechanism by which this polymorphism functions, with an exciting opportunity to identify novel treatment targets relevant for people with DS and AD.
RESUMO
BACKGROUND: Data from 12-week placebo-controlled trials have led to mounting concerns about increased mortality in patients with Alzheimer's disease (AD) who are prescribed antipsychotics; however, there are no mortality data from long-term placebo-controlled trials. We aimed to assess whether continued treatment with antipsychotics in people with AD is associated with an increased risk of mortality. METHODS: Between October, 2001, and December, 2004, patients with AD who resided in care facilities in the UK were enrolled into a randomised, placebo-controlled, parallel, two-group treatment discontinuation trial. Participants were randomly assigned to continue with their antipsychotic treatment (thioridazine, chlorpromazine, haloperidol, trifluoperazine, or risperidone) for 12 months or to switch their medication to an oral placebo. The primary outcome was mortality at 12 months. An additional follow-up telephone assessment was done to establish whether each participant was still alive 24 months after the enrollment of the last participant (range 24-54 months). Causes of death were obtained from death certificates. Analysis was by intention to treat (ITT) and modified intention to treat (mITT). This trial is registered with the Cochrane Central Registry of Controlled Trials/National Research Register, number ISRCTN33368770. FINDINGS: 165 patients were randomised (83 to continue antipsychotic treatment and 82 to placebo), of whom 128 (78%) started treatment (64 continued with their treatment and 64 received placebo). There was a reduction in survival in the patients who continued to receive antipsychotics compared with those who received placebo. Cumulative probability of survival during the 12 months was 70% (95% CI 58-80%) in the continue treatment group versus 77% (64-85%) in the placebo group for the mITT population. Kaplan-Meier estimates of mortality for the whole study period showed a significantly increased risk of mortality for patients who were allocated to continue antipsychotic treatment compared with those allocated to placebo (mITT log rank p=0.03; ITT p=0.02). The hazard ratio for the mITT group was 0.58 (95% CI 0.35 to 0.95) and 0.58 (0.36 to 0.92) for the ITT population. The more pronounced differences between groups during periods of follow up longer than 12 months were evident at specific timepoints (24-month survival 46%vs 71%; 36-month survival 30%vs 59%). INTERPRETATION: There is an increased long-term risk of mortality in patients with AD who are prescribed antipsychotic medication; these results further highlight the need to seek less harmful alternatives for the long-term treatment of neuropsychiatric symptoms in these patients. FUNDING: UK Alzheimer's Research Trust.
