Primary Prevention and Delay of Onset of AD/Dementia

Effects of a 3-Year Multi-Domain Intervention with or without Omega-3 Supplementation on Cognitive Functions in Older Subjects with Increased CAIDE Dementia Scores

Findings from recent Alzheimer's disease prevention trials have shown subjects with increased dementia score based upon mid-life cardiovascular risk factors, to benefit from multi-domain intervention strategies to some extent. The effects of such interventions on cognitive functions remains yet to be well-established. This study is a secondary analysis of the MAPT study, 1,293 older subjects (mean age 75 years) with high CAIDE score (i.e., ≥6) were classified according to the four intervention groups: 1) multi-domain intervention plus placebo, 2) isolated supplementation with Omega-3 polyunsaturated fatty acid (n-3 PUFA), 3) combination of the two interventions, and 4) placebo alone. Linear mixed-model repeated-measures analyses were used to assess the cognitive changes according to various neuropsychological test scores between intervention groups compared to the placebo at 36 months from baseline. Compared to the placebo, group with multi-domain intervention in combination withn-3PUFA was found to show significant improvement in the delayed total recall test of the free and cued selective reminding test (FCSRT) (mean±standard error(SE) = 0.20±0.10) and MMSE orientation test (mean±SE = 0.15±0.06) at 36 months. Isolated multi-domain intervention group showed significant less decline in the MMSE orientation test (mean±SE = 0.12±0.06) compared to the placebo. There was significant less improvement (mean±SE = - 1.01±0.46) in the FCSRT free recall test in the n-3 PUFA intervention group compared to the placebo at 36 months. Our findings show high-risk subjects for dementia screened with CAIDE dementia score might benefit from multi-domain intervention strategies as in the MAPT study, particularly in the orientation and delayed recall domain.

A Novel Therapeutic Approach to Treat Alzheimer's Disease by Neurotrophic Support During the Period of Synaptic Compensation

Alzheimer’s disease (AD), at present, is considered an incurable disease and a major dilemma with no drug to stop or slow down its progression. Drugs that are currently available in the market are able to only transiently improve the clinical symptoms. The repeated failures in developing an effective drug has led to the suggestion that the medical intervention was probably too late to be effective since the pathology starts many years before the appearance of the clinical symptoms. Probably, at the time of the appearance of clinical symptoms the brain has undergone major neuronal and synaptic loss. Because of the uncertainty on when to use a prevention therapy, especially targeting amyloid-β (Aβ) and tau pathologies, interventions that rely on the regenerative capacity of the brain such as the modulation of the inherent neurogenesis and neuronal plasticity represent a promising therapeutic strategy. Such an approach can act both at early as well as late stages of the disease and remove the barrier of the time of intervention. In this article, we review studies mainly from our laboratory that show the merit of early intervention during the synaptic and neuronal compensation period where the brain still has the capacity to self-repair by offering neurotrophic support in reversing cognitive impairment, neuronal and synaptic deficits, Aβ, and tau pathologies and decreasing mortality in a transgenic mouse model of AD.

Prevention of sporadic Alzheimer's disease: lessons learned from clinical trials and future directions

Interventions that have even quite modest effects at the individual level could drastically reduce the future burden of dementia associated with Alzheimer's disease at the population level. In the past three decades, both pharmacological and lifestyle interventions have been studied for the prevention of cognitive decline or dementia in randomised controlled trials of individuals mostly aged older than 50-55 years with or without risk factors for Alzheimer's disease. Several trials testing the effects of physical activity, cognitive training, or antihypertensive interventions showed some evidence of efficacy on a primary cognitive endpoint. However, most of these trials had short follow-up periods, and further evidence is needed to confirm effectiveness and establish the optimum design or dose of interventions and ideal target populations. Important innovations in ongoing trials include the development of multidomain interventions, and the use of biomarker or genetic inclusion criteria. Challenges include the use of adaptive trial designs, the development of standardised, sensitive outcome measures, and the need for interventions that can be implemented in resource-poor settings.

Practice effects and amyloid deposition: preliminary data on a method for enriching samples in clinical trials

Clinical trials in Alzheimer disease are moving toward prevention studies in prodromal individuals with amyloid burden. However, methods are needed to identify individuals expected to be amyloid positive for these studies to be feasible and cost-effective. The current study sought to determine whether short-term practice effects on cognitive tests can identify those with notable uptake on amyloid imaging. Twenty-five, nondemented older adults (15 cognitively intact, 10 with mild cognitive impairment) underwent amyloid imaging through F-flutemetamol and 2 cognitive testing sessions across 1 week to determine practice effects on a visual memory test. Results indicated that, whereas F-flutemetamol uptake showed little association with baseline performance on a visual memory test (r=-0.04, P=0.85), it was significantly correlated with practice effects across 1 week on that same memory measure (r=-0.45, P=0.02), with greater uptake being associated with lower practice effects. The odds ratio of notable F-flutemetamol uptake was 5 times higher in individuals with low practice effects compared with high practice effects. Although these preliminary results need to be replicated in larger samples, short-term practice effects on cognitive tests may provide an affordable screening method to identify individuals who are amyloid positive, which could enrich samples for preventative clinical trials in Alzheimer disease.

Improved design of prodromal Alzheimer's disease trials through cohort enrichment and surrogate endpoints

Alzheimer's disease (AD) trials initiated during or before the prodrome are costly and lengthy because patients are enrolled long before clinical symptoms are apparent, when disease progression is slow. We hypothesized that design of such trials could be improved by: 1) selecting individuals at moderate near-term risk of progression to AD dementia (the current clinical standard) and 2) by using short-term surrogate endpoints that predict progression to AD dementia. We used a longitudinal cohort of older, initially non-demented, community-dwelling participants (n = 358) to derive selection criteria and surrogate endpoints and tested them in an independent national data set (n = 6,243). To identify a "mid-risk" subgroup, we applied conditional tree-based survival models to Clinical Dementia Rating (CDR) scale scores and common neuropsychological tests. In the validation cohort, a time-to-AD dementia trial applying these mid-risk selection criteria to a pool of all non-demented individuals could achieve equivalent power with 47% fewer participants than enrolling at random from that pool. We evaluated surrogate endpoints measureable over two years of follow-up based on cross-validated concordance between predictions from Cox models and observed time to AD dementia. The best performing surrogate, rate of change in CDR sum-of-boxes, did not reduce the trial duration required for equivalent power using estimates from the validation cohort, but alternative surrogates with better ability to predict time to AD dementia should be able to do so. The approach tested here might improve efficiency of prodromal AD trials using other potential measures and could be generalized to other diseases with long prodromal phases.

Mortality and morbidity hazards associated with cognitive status in seniors: a Canadian population prospective cohort study

INTRODUCTION

Although cognitive impairment is widely accepted as a leading indicator of dementia, influences of cognitive status on incident dementia and mortality remain unclear. The present study investigated the morbidity hazard associated with cognitive impairment and the mortality hazard associated with dementia in comparison to cognitively intact seniors.

METHODS

A population-based sample of 2914 seniors with clinically diagnosed cognitive status at Wave I (1991-1992) of the Canadian Study of Health and Aging (CSHA) were followed-up 5 years later (1996-1997). At Wave I, there were 921 cognitively intact, 861 cognitively impaired but not demented (CIND), and 1132 seniors with dementia, respectively. The primary outcome measures 5 years later were being cognitively intact, CIND, dementia and death. Kaplan-Meier estimates, log-rank tests, and Cox's proportional models were used in the analyses.

RESULTS

Respondents with CIND at Wave I were 2.191 times (95%CI 1.706-2.814) more likely to have dementia 5 years later than cognitively intact seniors. After adjusting for confounding socio-demographic and health status factors, the odds ratio was reduced to 2.147 times (95%CI 1.662-2.774), but remained significant. Respondents with CIND had a mortality rate 1.869 times (95%CI 1.602-2.179) and seniors with dementia 3.362 times greater (95%CI 2.929-3.860) than that of seniors who were cognitively intact. After controlling the confounders, the odds remained significant at 1.576 (95%CI 1.348-1.843) for CIND respondents and 2.415 (95%CI 2.083-2.800) for seniors with dementia.

DISCUSSION

CIND increases both the risk of dementia and mortality. Early intervention with CIND is warranted to reduce both dementia incidence and mortality.

Prevention strategies for Alzheimer's disease

Symptomatic treatment during the dementia stage of Alzheimer's disease(AD) cannot delay or halt the progression of this disease. Therefore, prevention in the preclinical stage is likely the most effective way to decrease the incidence of this age-associated neurodegenerative condition, and its associated burden for individuals and society. Age, gender, family history, ApoE4, systolic blood pressure, body mass index, total cholesterol level and physical activity are all used as component of dementia risk score. There have been numerous challenges in conducting primary prevention trials in AD. Enrichment strategies for prevention studies include studying those subjects with more risk factors for AD, such as older age, those with a positive family history of late onset AD, and those who are ApoE4 positive. Each of these strategies is designed to increase the probability of developing AD thereby decreasing the sample size or the duration of follow up. Another strategy would be to target directly the pathophysiology of AD in its preclinical stages and use the biomarkers in prevention trial as surrogate markers. This will be done first in carriers of dominantly inherited early onset AD. As this research takes place networks of memory clinics must prepare to transfer new knowledge to persons interested in a preventive approach to AD.