Lifestyle and incident dementia: A COSMIC individual participant data meta‐analysis

INTRODUCTION

The LIfestyle for BRAin Health (LIBRA) index yields a dementia risk score based on modifiable lifestyle factors and is validated in Western samples. We investigated whether the association between LIBRA scores and incident dementia is moderated by geographical location or sociodemographic characteristics.

METHODS

We combined data from 21 prospective cohorts across six continents (N = 31,680) and conducted cohort-specific Cox proportional hazard regression analyses in a two-step individual participant data meta-analysis.

RESULTS

A one-standard-deviation increase in LIBRA score was associated with a 21% higher risk for dementia. The association was stronger for Asian cohorts compared to European cohorts, and for individuals aged ≤75 years (vs older), though only within the first 5 years of follow-up. No interactions with sex, education, or socioeconomic position were observed.

DISCUSSION

Modifiable risk and protective factors appear relevant for dementia risk reduction across diverse geographical and sociodemographic groups.

HIGHLIGHTS

A two-step individual participant data meta-analysis was conducted. This was done at a global scale using data from 21 ethno-regionally diverse cohorts. The association between a modifiable dementia risk score and dementia was examined. The association was modified by geographical region and age at baseline. Yet, modifiable dementia risk and protective factors appear relevant in all investigated groups and regions.

Risk factors and cognitive correlates of white matter hyperintensities in ethnically diverse populations without dementia: The COSMIC consortium

INTRODUCTION

White matter hyperintensities (WMHs) are an important imaging marker for cerebral small vessel diseases, but their risk factors and cognitive associations have not been well documented in populations of different ethnicities and/or from different geographical regions.

METHODS

We investigated how WMHs were associated with vascular risk factors and cognition in both Whites and Asians, using data from five population-based cohorts of non-demented older individuals from Australia, Singapore, South Korea, and Sweden (N = 1946). WMH volumes (whole brain, periventricular, and deep) were quantified with UBO Detector and harmonized using the ComBat model. We also harmonized various vascular risk factors and scores for global cognition and individual cognitive domains.

RESULTS

Factors associated with larger whole brain WMH volumes included diabetes, hypertension, stroke, current smoking, body mass index, higher alcohol intake, and insufficient physical activity. Hypertension and stroke had stronger associations with WMH volumes in Whites than in Asians. No associations between WMH volumes and cognitive performance were found after correction for multiple testing.

CONCLUSION

The current study highlights ethnic differences in the contributions of vascular risk factors to WMHs.

Risk factors and cognitive correlates of white matter hyperintensities in ethnically diverse populations without dementia: the COSMIC consortium

INTRODUCTION

White matter hyperintensities (WMH) are an important imaging marker for cerebral small vessel diseases, but their risk factors and cognitive associations have not been well-documented in populations of different ethnicities and/or from different geographical regions.

METHOD

Magnetic resonance imaging data of five population-based cohorts of non-demented older individuals from Australia, Singapore, South Korea, and Sweden (N = 1,946) were examined for WMH and their associations with vascular risk factors and cognition.

RESULT

Factors associated with larger whole brain WMH volumes included diabetes, hypertension, stroke, current smoking, body mass index, higher alcohol intake and insufficient physical activity. Participants with moderate or higher physical activity had less WMH than those who never exercised, but the former two groups did not differ. Hypertension and stroke had stronger associations with WMH volumes in the White, compared to Asian subsample.

DISCUSSION

The current study highlighted the ethnic differences in the contributions of vascular risk factors to WMH.

Parental history of dementia and the risk of dementia: A cross-sectional analysis of a global collaborative study

BACKGROUND

Parental history of dementia appears to increase the risk of dementia, but there have been inconsistent results. We aimed to investigate whether the association between parental history of dementia and the risk of dementia are different by dementia subtypes and sex of parent and offspring.

METHODS

For this cross-sectional study, we harmonized and pooled data for 17,194 older adults from nine population-based cohorts of eight countries. These studies conducted face-to-face diagnostic interviews, physical and neurological examinations, and neuropsychological assessments to diagnose dementia. We investigated the associations of maternal and paternal history of dementia with the risk of dementia and its subtypes in offspring.

RESULTS

The mean age of the participants was 72.8 ± 7.9 years and 59.2% were female. Parental history of dementia was associated with higher risk of dementia (odds ratio [OR] = 1.47, 95% confidence interval [CI] = 1.15-1.86) and Alzheimer's disease (AD) (OR = 1.72, 95% CI = 1.31-2.26), but not with the risk of non-AD. This was largely driven by maternal history of dementia, which was associated with the risk of dementia (OR = 1.51, 95% CI = 1.15-1.97) and AD (OR = 1.80, 95% CI = 1.33-2.43) whereas paternal history of dementia was not. These results remained significant when males and females were analyzed separately (OR = 2.14, 95% CI = 1.28-3.55 in males; OR = 1.68, 95% CI = 1.16-2.44 for females).

CONCLUSIONS

Maternal history of dementia was associated with the risk of dementia and AD in both males and females. Maternal history of dementia may be a useful marker for identifying individuals at higher risk of AD and stratifying the risk for AD in clinical trials.

Study protocol for the BRAIN Training Trial: a randomised controlled trial of Balance, Resistance, And INterval training on cognitive function in older adults with mild cognitive impairment

INTRODUCTION

Epidemiological evidence suggests that both poor cardiovascular fitness and low muscle mass or strength markedly increase the rate of cognitive decline and incident dementia in older adults. Results from exercise trials for the improvement of cognition in older adults with mild cognitive impairment (MCI) have reported mixed results. This is possibly due to insufficient exercise intensities. The aim of the Balance, Resistance, And INterval (BRAIN) Training Trial is to determine the effects of two forms of exercise, high-intensity aerobic interval training (HIIT) and high-intensity power training (POWER) each compared with a sham exercise control group on cognition in older adults with MCI.

METHODS AND ANALYSIS

One hundred and sixty community-dwelling older (≥ 60 years) people with MCI have been randomised into the trial. Interventions are delivered supervised 2-3 days per week for 12 months. The primary outcome measured at baseline, 6 and 12 months is performance on a cognitive composite score measuring the executive domain calculated from a combination of computerised (NeuroTrax) and paper-and-pencil tests. Analyses will be performed via repeated measures linear mixed models and generalised linear mixed models of baseline, 6-month and 12-month time points, adjusted for baseline values and covariates selected a priori. Mixed models will be constructed to determine the interaction of GROUP × TIME.

ETHICS AND DISSEMINATION

Ethical approval was obtained from the University of Sydney (HREC Ref.2017/368), University of Queensland (HREC Ref. 2017/HE000853), University of British Columbia (H16-03309), and Vancouver Coastal Health Research Institute (V16-03309) Human Research Ethics. Dissemination will be via publications, conference presentations, newsletter articles, social media, talks to clinicians and consumers and meetings with health departments/managers.It is expected that communication of results will allow for the development of more effective evidence-based exercise prescription guidelines in this population while investigating the benefits of HIIT and POWER on subclinical markers of disease.

TRIAL REGISTRATION NUMBER

ACTRN12617001440314 Australian New Zealand Clinical Trials Registry.

An accelerated degeneration of white matter microstructure and networks in the nondemented old-old

The nondemented old-old over the age of 80 comprise a rapidly increasing population group; they can be regarded as exemplars of successful aging. However, our current understanding of successful aging in advanced age and its neural underpinnings is limited. In this study, we measured the microstructural and network-based topological properties of brain white matter using diffusion-weighted imaging scans of 419 community-dwelling nondemented older participants. The participants were further divided into 230 young-old (between 72 and 79, mean = 76.25 ± 2.00) and 219 old-old (between 80 and 92, mean = 83.98 ± 2.97). Results showed that white matter connectivity in microstructure and brain networks significantly declined with increased age and that the declined rates were faster in the old-old compared with young-old. Mediation models indicated that cognitive decline was in part through the age effect on the white matter connectivity in the old-old but not in the young-old. Machine learning predictive models further supported the crucial role of declines in white matter connectivity as a neural substrate of cognitive aging in the nondemented older population. Our findings shed new light on white matter connectivity in the nondemented aging brains and may contribute to uncovering the neural substrates of successful brain aging.

Difference in distribution functions: A new diffusion weighted imaging metric for estimating white matter integrity

Diffusion weighted imaging (DWI) is a widely recognized neuroimaging technique to evaluate the microstructure of brain white matter. The objective of this study is to establish an improved automated DWI marker for estimating white matter integrity and investigating ageing related cognitive decline. The concept of Wasserstein distance was introduced to help establish a new measure: difference in distribution functions (DDF), which captures the difference of reshaping one's mean diffusivity (MD) distribution to a reference MD distribution. This new DWI measure was developed using a population-based cohort (n=19,369) from the UK Biobank. Validation was conducted using the data drawn from two independent cohorts: the Sydney Memory and Ageing Study, a community-dwelling sample (n=402), and the Renji Cerebral Small Vessel Disease Cohort Study (RCCS), which consisted of cerebral small vessel disease (CSVD) patients (n=171) and cognitively normal controls (NC) (n=43). DDF was associated with age across all three samples and better explained the variance of changes than other established DWI measures, such as fractional anisotropy, mean diffusivity and peak width of skeletonized mean diffusivity (PSMD). Significant correlations between DDF and cognition were found in the UK Biobank cohort and the MAS cohort. Binary logistic analysis and receiver operator characteristic curve analysis of RCCS demonstrated that DDF had higher sensitivity in distinguishing CSVD patients from NC than the other DWI measures. To demonstrate the flexibility of DDF, we calculated regional DDF which also showed significant correlation with age and cognition. DDF can be used as a marker for monitoring the white matter microstructural changes and ageing related cognitive decline in the elderly.

Iranian Brain Imaging Database: A Neuropsychiatric Database of Healthy Brain

INTRODUCTION

The Iranian Brain Imaging Database (IBID) was initiated in 2017, with 5 major goals: provide researchers easy access to a neuroimaging database, provide normative quantitative measures of the brain for clinical research purposes, study the aging profile of the brain, examine the association of brain structure and function, and join the ENIGMA consortium. Many prestigious databases with similar goals are available. However, they were not done on an Iranian population, and the battery of their tests (e.g. cognitive tests) is selected based on their specific questions and needs.

METHODS

The IBID will include 300 participants (50% female) in the age range of 20 to 70 years old, with an equal number of participants (#60) in each age decade. It comprises a battery of cognitive, lifestyle, medical, and mental health tests, in addition to several Magnetic Resonance Imaging (MRI) protocols. Each participant completes the assessments on two referral days.

RESULTS

The study currently has a cross-sectional design, but longitudinal assessments are considered for the future phases of the study. Here, details of the methodology and the initial results of assessing the first 152 participants of the study are provided.

CONCLUSION

IBID is established to enable research into human brain function, to aid clinicians in disease diagnosis research, and also to unite the Iranian researchers with interests in the brain.

Fully-Online, Interoperable Clinical Trial Management System for Multi-Interventional RCT: Maintain Your Brain Digital Platform

Maintain Your Brain (MYB)i is a randomised controlled trial (RCT) of multiple online interventions designed to target modifiable risk factors for Alzheimer's disease and dementia. Traditional clinical trial management systems (CTMS) requirements consist of features such as management of the study, site, subject (participant), clinical outcomes, external and internal requests, education, data extraction and reporting, security, and privacy. In addition to fulfilling these traditional requirements, MYB has a specific set of features that needs to be fulfilled. These specific requirements include: (i) support for multiple interventions within a study, (ii) flexible interoperability options with third-party software providers, (iii) study participants being able to engage in online activities via web-based interfaces throughout the trial (from screening to follow-up), (iv) ability to algorithmically personalize trial activities based on the needs of the participant, and (v) the ability to handle large volumes of data over a long period. This paper outlines how the existing CTMSs fall short in meeting these specific requirements. The presented system architecture, development approach and lessons learned in the implementation of the MYB digital platform will inform researchers attempting to implement CTMSs for trials comparable to MYB in the future.

Hippocampal plasticity underpins long-term cognitive gains from resistance exercise in MCI

Dementia affects 47 million individuals worldwide, and assuming the status quo is projected to rise to 150 million by 2050. Prevention of age-related cognitive impairment in older persons with lifestyle interventions continues to garner evidence but whether this can combat underlying neurodegeneration is unknown. The Study of Mental Activity and Resistance Training (SMART) trial has previously reported within-training findings; the aim of this study was to investigate the long-term neurostructural and cognitive impact of resistance exercise in Mild Cognitive Impairment (MCI). For the first time we show that hippocampal subareas particularly susceptible to volume loss in Alzheimer's disease (AD) are protected by resistance exercise for up to one year after training. One hundred MCI participants were randomised to one of four training groups: (1) Combined high intensity progressive resistance and computerised cognitive training (PRT+CCT), (2) PRT+Sham CCT, (3) CCT+Sham PRT, (4) Sham physical+sham cognitive training (SHAM+SHAM). Physical, neuropsychological and MRI assessments were carried out at baseline, 6 months (directly after training) and 18 months from baseline (12 months after intervention cessation). Here we report neuro-structural and functional changes over the 18-month trial period and the association with global cognitive and executive function measures. PRT but not CCT or PRT+CCT led to global long-term cognitive improvements above SHAM intervention at 18-month follow-up. Furthermore, hippocampal subfields susceptible to atrophy in AD were protected by PRT revealing an elimination of long-term atrophy in the left subiculum, and attenuation of atrophy in left CA1 and dentate gyrus when compared to SHAM+SHAM (p = 0.023, p = 0.020 and p = 0.027). These neuroprotective effects mediated a significant portion of long-term cognitive benefits. By contrast, within-training posterior cingulate plasticity decayed after training cessation and was unrelated to long term cognitive benefits. Neither general physical activity levels nor fitness change over the 18-month period mediated hippocampal trajectory, demonstrating that enduring hippocampal subfield plasticity is not a simple reflection of post-training changes in fitness or physical activity participation. Notably, resting-state fMRI analysis revealed that both the hippocampus and posterior cingulate participate in a functional network that continued to be upregulated following intervention cessation. Multiple structural mechanisms may contribute to the long-term global cognitive benefit of resistance exercise, developing along different time courses but functionally linked. For the first time we show that 6 months of high intensity resistance exercise is capable of not only promoting better cognition in those with MCI, but also protecting AD-vulnerable hippocampal subfields from degeneration for at least 12 months post-intervention. These findings emphasise the therapeutic potential of resistance exercise; however, future work will need to establish just how long-lived these outcomes are and whether they are sufficient to delay dementia.

Age-Related Changes of Peak Width Skeletonized Mean Diffusivity (PSMD) Across the Adult Lifespan: A Multi-Cohort Study

Parameters of water diffusion in white matter derived from diffusion-weighted imaging (DWI), such as fractional anisotropy (FA), mean, axial, and radial diffusivity (MD, AD, and RD), and more recently, peak width of skeletonized mean diffusivity (PSMD), have been proposed as potential markers of normal and pathological brain ageing. However, their relative evolution over the entire adult lifespan in healthy individuals remains partly unknown during early and late adulthood, and particularly for the PSMD index. Here, we gathered and analyzed cross-sectional diffusion tensor imaging (DTI) data from 10 population-based cohort studies in order to establish the time course of white matter water diffusion phenotypes from post-adolescence to late adulthood. DTI data were obtained from a total of 20,005 individuals aged 18.1 to 92.6 years and analyzed with the same pipeline for computing skeletonized DTI metrics from DTI maps. For each individual, MD, AD, RD, and FA mean values were computed over their FA volume skeleton, PSMD being calculated as the 90% peak width of the MD values distribution across the FA skeleton. Mean values of each DTI metric were found to strongly vary across cohorts, most likely due to major differences in DWI acquisition protocols as well as pre-processing and DTI model fitting. However, age effects on each DTI metric were found to be highly consistent across cohorts. RD, MD, and AD variations with age exhibited the same U-shape pattern, first slowly decreasing during post-adolescence until the age of 30, 40, and 50 years, respectively, then progressively increasing until late life. FA showed a reverse profile, initially increasing then continuously decreasing, slowly until the 70s, then sharply declining thereafter. By contrast, PSMD constantly increased, first slowly until the 60s, then more sharply. These results demonstrate that, in the general population, age affects PSMD in a manner different from that of other DTI metrics. The constant increase in PSMD throughout the entire adult life, including during post-adolescence, indicates that PSMD could be an early marker of the ageing process.

57 The Use of the Physiological Profile Assessment to Improve Prediction of Fragility Fractures in Community-Dwelling Older People

Introduction

The Physiological Profile Assessment (PPA) is a validated composite measure of sensorimotor function, known to predict falls with 75% accuracy. This work aimed to investigate whether PPA is also associated with fragility fractures.

Method

Participants were 489 community-dwelling older people (age=70-90) enrolled in the longitudinal population-based Sydney Memory and Ageing Study. Participants underwent comprehensive assessments at enrolment, including the 5-item PPA (visual contrast sensitivity, lower limb proprioception, knee extension strength, simple reaction time and postural sway). Participant records were linked to emergency department, hospital and death records (2005-2014) to identify fragility fractures following baseline assessment, with median follow-up duration of 7.5 years. Negative binomial regression, with observation time as the offset, was used to assess factors associated with fractures.

Results

At baseline assessment, 281 (57.5%) participants were assessed as having low/mild fall risk [PPA<1] and 208 (42.5%) as moderate/marked/very marked fall risk [PPA score >1]. Over the study period, 72 (14.7%) individuals sustained 1 fracture, and a further 39 (8.0%) sustained 2 or more fractures.

Univariate analysis showed that increasing age (Incidence Rate Ratio (IRR) 1.1, 95%CI 1.0-1.1, p=0.0026), being female (IRR 1.8, 95%CI 1.3-2.8, p=0.0033), having osteoporosis (IRR 1.7, 95%CI 1.1-2.6, p=0.0340) and moderate/marked/very marked PPA (IRR 1.8, 95%CI 1.2-2.7, p=0.0025) were associated with fractures. In the multivariate analysis, only moderate/marked/very marked PPA (IRR 1.6, 95%CI 1.1-2.5, p=0.0159) and being female (IRR 1.8, 95%CI 1.1-2.8, p=0.0121) remained independently associated with fractures.

Conclusion

These findings show that people at increased risk of falls based on the Physiological Profile Assessment are also at increased risk of future fragility fractures regardless of the presence of osteoporosis. Early identification of this high risk population provides the opportunity to intervene with evidence based strategies to minimize falls risk as well as considering pharmacological management of bone health.

People with mild cognitive impairment are at increased risk of serious injury

IntroductionData-linkage studies using administrative hospital data have shown that people with dementia have double the rate of injury-related hospitalisations and poorer health outcomes than those without. No previous research has explored whether people with mild cognitive impairment are also at increased risk of serious injury requiring hospitalisation. Objectives and ApproachA major barrier to the use of administrative hospital data for undertaking research focusing on people with MCI is that MCI cannot be reliably identified from ICD-10 coded administrative data. To overcome this limitation, hospitalisation and death data was linked to data from participants (community-dwelling 70-90 year olds) enrolled in the population-based longitudinal Sydney Memory and Ageing Study (MAS). MAS participants underwent comprehensive neuropsychological assessments at baseline, then 2, 4 and 6 years’ follow-up to accurately determine cognitive status at each time-period. Linkage to hospital records allowed identification of injury-related hospitalisations and outcomes for the 2-year period following each assessment. ResultsThere were 335 injury-related hospitalisations for the 867 participants; 222 (25.6%) participants had at least one injury-related hospitalisation. After adjusting for age-and-sex, participants in a state of MCI had 1.7 (95%CI 1.2-2.4) times higher odds of an injury-related hospitalisation than participants in a state of normal cognition, whilst participants with dementia had 2.3 (95%CI 1.2-4.4) times higher odds. There was no difference in odds between participants with MCI and dementia. Of the 116 hospitalisations for people with MCI, the majority (79.3%) were due to falls. Non-fracture head injuries (25.9%), upper limb and trunk fractures (13.8% respectively) were the most common injury type. There were no differences in injury type, mean length of stay, or 30-day mortality between people with normal cognition, MCI and dementia. Conclusion/ImplicationsOlder people with objectively defined MCI are at higher risk of injury, predominantly as a result of falls, than their cognitively intact peers. Falls-risk screening and fall prevention initiatives may be indicated for people with MCI. Further research is required to determine which cognitive domains contribute to this increased risk.

We think you can dance! A pilot randomised controlled trial of dance for nursing home residents with moderate to severe dementia

OBJECTIVES

To evaluate the feasibility of a dance program for people with moderate to severe dementia living in nursing homeswith regards to recruitment and retention, assessment tools, intervention safety, attendance and engagement.

DESIGN

Pilot randomised controlled trial with assessments at weeks 0, 16 and 32.

SETTING

A nursing home in Sydney, Australia.

INTERVENTIONS

Experienced dance teachers conducted dance groups (intervention) or music appreciation and socialisation groups (control) for 45min, three times a week for 16 weeks.

MAIN OUTCOME MEASURES

Descriptive statistics for recruitment and retention, adverse events and attendance and engagement.

RESULTS

Recruitment was smooth, attrition was17% over 32 weeks. Engagement during the sessions was high, and no serious falls or behavioural incidents occurred. Average attendance was poorer than anticipated for dance groups (67%) in comparison to music groups (89%). A ceiling effect on the Severe Impairment Battery and the logistical challenges of the Clinical Global Impression of Change meant they may not be optimal tools.

CONCLUSIONS

It is feasible to conduct a study of group dance for people with moderate to severe dementia in residential care. Choice of attention control condition should be reconsidered.

Upregulation of glycolytic enzymes, mitochondrial dysfunction and increased cytotoxicity in glial cells treated with Alzheimer's disease plasma

Alzheimer's disease (AD) is a neurodegenerative disorder associated with increased oxidative stress and neuroinflammation. Markers of increased protein, lipid and nucleic acid oxidation and reduced activities of antioxidant enzymes have been reported in AD plasma. Amyloid plaques in the AD brain elicit a range of reactive inflammatory responses including complement activation and acute phase reactions, which may also be reflected in plasma. Previous studies have shown that human AD plasma may be cytotoxic to cultured cells. We investigated the effect of pooled plasma (n = 20 each) from healthy controls, individuals with amnestic mild cognitive impairment (aMCI) and Alzheimer's disease (AD) on cultured microglial cells. AD plasma and was found to significantly decrease cell viability and increase glycolytic flux in microglia compared to plasma from healthy controls. This effect was prevented by the heat inactivation of complement. Proteomic methods and isobaric tags (iTRAQ) found the expression level of complement and other acute phase proteins to be altered in MCI and AD plasma and an upregulation of key enzymes involved in the glycolysis pathway in cells exposed to AD plasma. Altered expression levels of acute phase reactants in AD plasma may alter the energy metabolism of glia.

Adiposity estimated using dual energy X-ray absorptiometry and body mass index and its association with cognition in elderly adults

OBJECTIVES

To determine whether obesity, estimated according to body mass index (BMI), waist circumference, and body fat and abdominal fat assessed using dual-energy X-ray absorptiometry (DEXA), was associated with cognitive performance.

DESIGN

Cross-sectional.

SETTING

Community based.

PARTICIPANTS

Individuals aged 74-94 (N = 406).

MEASUREMENTS

BMI, waist circumference, body fat, and abdominal fat were assessed using DEXA. Cognitive performance was assessed using a comprehensive neuropsychological battery.

RESULTS

When categorized using BMI, overweight individuals had higher global cognitive function and executive function scores than normal-weight individuals. This relationship did not differ according to sex. When categorized according to DEXA, there were no relationships between body fat and cognitive function in the whole group, but women in the middle and highest tertiles of DEXA body fat had better executive function than those in the lowest tertile. Men in the middle tertile of DEXA body fat had significantly better executive function and memory than those in the lowest tertile. BMI had greater power to predict executive function than DEXA body fat. No significant associations were found between cognition and estimates of abdominal adiposity.

CONCLUSION

This study found an association between being overweight and better executive function in elderly adults; this association was stronger for the simpler BMI than the more-elaborate DEXA measures.

Genetic contributions to variation in general cognitive function: a meta-analysis of genome-wide association studies in the CHARGE consortium (N=53949)

General cognitive function is substantially heritable across the human life course from adolescence to old age. We investigated the genetic contribution to variation in this important, health- and well-being-related trait in middle-aged and older adults. We conducted a meta-analysis of genome-wide association studies of 31 cohorts (N=53,949) in which the participants had undertaken multiple, diverse cognitive tests. A general cognitive function phenotype was tested for, and created in each cohort by principal component analysis. We report 13 genome-wide significant single-nucleotide polymorphism (SNP) associations in three genomic regions, 6q16.1, 14q12 and 19q13.32 (best SNP and closest gene, respectively: rs10457441, P=3.93 × 10(-9), MIR2113; rs17522122, P=2.55 × 10(-8), AKAP6; rs10119, P=5.67 × 10(-9), APOE/TOMM40). We report one gene-based significant association with the HMGN1 gene located on chromosome 21 (P=1 × 10(-6)). These genes have previously been associated with neuropsychiatric phenotypes. Meta-analysis results are consistent with a polygenic model of inheritance. To estimate SNP-based heritability, the genome-wide complex trait analysis procedure was applied to two large cohorts, the Atherosclerosis Risk in Communities Study (N=6617) and the Health and Retirement Study (N=5976). The proportion of phenotypic variation accounted for by all genotyped common SNPs was 29% (s.e.=5%) and 28% (s.e.=7%), respectively. Using polygenic prediction analysis, ~1.2% of the variance in general cognitive function was predicted in the Generation Scotland cohort (N=5487; P=1.5 × 10(-17)). In hypothesis-driven tests, there was significant association between general cognitive function and four genes previously associated with Alzheimer's disease: TOMM40, APOE, ABCG1 and MEF2C.

Cognitive lifestyle in older persons: the population-based Sydney Memory and Ageing Study

BACKGROUND

Cognitive lifestyle may be an important modifiable risk factor for dementia but has not yet been comprehensively studied in healthy elderly.

OBJECTIVE

To examine gender- and lifespan-related differences in cognitive lifestyle in a population-based cohort.

METHODS

872 individuals from the second wave of the Sydney Memory and Ageing Study (MAS) cohort were invited to complete the Lifetime of Experiences Questionnaire (LEQ), a validated measure of cognitive lifestyle. Of 555 questionnaires returned (64%), 253 were excluded due to prior diagnosis of mild cognitive impairment, leaving n = 302 cognitively-intact elders (mean age 80.1 years, ±SD 4.7, 40.1% men).

RESULTS

Total LEQ was significantly higher in men (97.9 ± 20.0) than women (90.0 ± 24.5), resulting mainly from midlife LEQ differences. Men were more likely to have worked in managerial or professional jobs (73.8% versus 39.5% women), and twice as likely to have supervised large groups of workers. In late life, women were significantly more likely to be living alone (68.1% versus 25.4% men), but otherwise significantly more engaged in specific cognitive activities, including reading novels (72.3% versus 52.0% men) and incorporating volunteer work (31.9% versus 19.7% men) and socializing (59.0% versus 37.0% men) into their typical day. Over the adult lifespan, it was more common for men and women to transition between LEQ tertiles than remain the same.

CONCLUSIONS

Cognitive lifestyle changes over the adult lifespan and exhibits a range of gender-based differences. While older women are more likely to be living alone they generally lead a more active current cognitive lifestyle.

The prevalence of "cognitive impairment no dementia" in community-dwelling elderly: a pilot study

OBJECTIVE

To determine the prevalence of "cognitive impairment no dementia" (CIND) and "amnestic mild cognitive impairment" (aMCI) in a population sample of 70-79-year-olds and the risk factors for CIND.

METHOD

Cross sectional population survey.

SETTING

Sutherland Shire, Sydney, Australia.

SUBJECTS

150 community-dwelling 70-79-year-olds were screened by telephone, 42 of whom were assessed at home.

MEASURES

Demographics, subjective ratings of physical and emotional health and memory, cardiovascular risk factors, medications, the Mini-Mental State Examination, Boston Naming Test, Trail Making Tests A and B, Block Design, Rey Auditory Verbal Learning Test (RAVLT), Visual Reproduction, Logical Memory, letter and category fluency, the National Adult Reading Test (NART), the Geriatric Depression Scale (GDS) and the "state" section of the State-Trait Anxiety Inventory (STAI-S).

RESULTS

From the 400 subjects contacted initially, 150 consented to be interviewed and 131 eligible subjects were recruited. Of a 1-in-3 random sample of 42 subjects assessed at home, 14 (33.3%) subjects met criteria for CIND, 1 (2.4%) had possible dementia and the 27 remaining (64.3%) were cognitively normal. Four (9.5%) met criteria for aMCI. Subjects with CIND were older, had lower ranking occupations and were less likely to be currently working than those classified as cognitively normal. Ten subjects with CIND did not meet criteria for aMCI because they lacked subjective memory impairment (n = 3) or had cognitive deficits other than memory (n = 7). All subjects with aMCI met criteria for CIND.

CONCLUSIONS

One-third of individuals in this population sample met criteria for CIND. CIND is a broader definition than aMCI. Further research is needed to determine the longitudinal course and clinical utility of these definitions of cognitive impairment.

Experimental investigation of stochastic pulsation and formation of light bullets with megagauss magnetic fields by an intense laser pulse propagating in a preionized plasma

The generation of extremely stable light bullets in a preformed plasma near critical density has been observed experimentally during the interaction of intense picosecond laser beam with a metallic target in air. Optical probing measurements indicate the formation of pulsating channels, typically of about 5 microm in diameter, directed towards a heating laser beam, as well as of disconnected massive plasma blocks moving also towards the laser beam. The velocities of the dense plasma blocks reach the values of 4.5x10(8) cm/s. The blocks are stable during their acceleration and propagation in air. Self-generated magnetic fields up to 4-7 MG were observed by means of the Faraday rotation of a probe laser beam.

HIV risk-taking behaviour among injecting drug users currently, previously and never enrolled in methadone treatment

This study compares the injecting and sexual risk-taking behaviour among injecting drug users (IDUs) currently, previously and never enrolled in methadone maintenance treatment (MMT). All subjects had injected during the 6 months prior to the day of interview. The current MMT group showed significantly lower injecting risk-taking behaviour subscale scores on the HIV Risk-taking Behaviour Scale (HRBS) of the Opiate Treatment Index than the previous MMT and non-MMT groups together. The current MMT group differed from the other two groups in the frequency of injecting and cleaning of injection equipment with bleach. There was no difference between the current MMT group and the other two groups combined in sexual risk-taking behaviour scores on the HRBS. There were no differences between the previous MMT and non-MMT groups in injecting and sexual risk-taking behaviour. HIV seroprevalence was low and there was no difference in seroprevalence between groups. Thus, IDUs currently enrolled in MMT are at reduced risk for HIV infection when compared with IDUs who have previously or never been enrolled in MMT. However, the absence of a difference between the current MMT and other two groups in frequency of sharing behaviours suggests the need for additional strategies among MMT clients to reduce needle-sharing. Possible strategies include the application of relapse prevention interventions and the availability of sterile injecting equipment in MMT clinics. Further research is needed to identify factors which increase attraction and retention of IDUs to MMT.

Controlled evaluation of a brief intervention for HIV prevention among injecting drug users not in treatment

This study evaluated the effectiveness of a brief intervention (BI), a one-session motivational interview, in reducing HIV risk-taking behaviour among injecting drug users (IDU) not enrolled in any form of treatment for drug dependence. IDU were randomly assigned to either BI or a non-intervention control condition (NIC). One hundred and twenty-one subjects were successfully contacted for a 3-month follow-up and 88 subjects were followed up at 6 months. There were significant reductions for the sample as a whole for injecting risk-taking subscale scores on the HIV Risk-taking Behaviour Scale between pre-treatment and follow-up. There was no significant change in sexual risk-taking behaviour. There were no significant differences between groups on any measure at 3- and 6-month follow-up. There are a number of possible reasons why the sample as a whole showed significant improvements from initial to follow-up assessments. It is possible that, having had their attention directed to their risk-taking behaviour, subjects attempted to reduce their injecting risk-taking behaviour. If this is the case and subjects in the NIC condition can be considered as having received a BI, this suggests that BIs involving a personal risk assessment are effective in reducing risk behaviours associated with injecting. However, this suggestion could only be confirmed by comparison with a non-assessment control group.

Drug use and HIV risk-taking behaviour among injecting drug users not currently in treatment in Sydney, Australia

This study investigated the drug use patterns and HIV risk-taking behaviour of 200 injecting drug users (IDU) not currently in treatment in Sydney, Australia. Although there was low HIV seroprevalence, unsafe injecting and sexual practices were common. Variables that were predictive of injecting risk-taking were higher level of heroin use, sexual relationship with an IDU and greater polydrug use. Two variables were predictive of sexual risk-taking: higher level of hallucinogen use and sexual relationship with an IDU. Female subjects were significantly more likely to have an IDU sexual partner. A higher level of cannabis use was associated with greater polydrug use and a higher level of amphetamine use was associated with greater use of opiates other than heroin. The findings are discussed in terms of the need for interventions aimed towards reducing sexual risk-taking among users of hallucinogens and towards reducing injecting and sexual risk-taking among IDU and their sexual partners. The potential difficulty in producing behaviour change among polydrug users is highlighted.