Lack of reproducibility of resting-state functional MRI findings in migraine with aura

BACKGROUND

Several studies have applied resting-state functional MRI to examine whether functional brain connectivity is altered in migraine with aura patients. These studies had multiple limitations, including small sample sizes, and reported conflicting results. Here, we performed a large, cross-sectional brain imaging study to reproduce previous findings.

METHODS

We recruited women aged 30-60 years from the nationwide Danish Twin Registry. Resting-state functional MRI of women with migraine with aura, their co-twins, and unrelated migraine-free twins was performed at a single centre. We carried out an extensive series of brain connectivity data analyses. Patients were compared to migraine-free controls and to co-twins.

RESULTS

Comparisons were based on data from 160 patients, 30 co-twins, and 136 controls. Patients were similar to controls with regard to age, and several lifestyle characteristics. We replicated clear effects of age on resting-state networks. In contrast, we failed to detect any differences, and to replicate previously reported differences, in functional connectivity between migraine patients with aura and non-migraine controls or their co-twins in any of the analyses.

CONCLUSION

Given the large sample size and the unbiased population-based design of our study, we conclude that women with migraine with aura have normal resting-state brain connectivity outside of migraine attacks.

Universal DNA methylation age across mammalian tissues

Aging, often considered a result of random cellular damage, can be accurately estimated using DNA methylation profiles, the foundation of pan-tissue epigenetic clocks. Here, we demonstrate the development of universal pan-mammalian clocks, using 11,754 methylation arrays from our Mammalian Methylation Consortium, which encompass 59 tissue types across 185 mammalian species. These predictive models estimate mammalian tissue age with high accuracy (r > 0.96). Age deviations correlate with human mortality risk, mouse somatotropic axis mutations and caloric restriction. We identified specific cytosines with methylation levels that change with age across numerous species. These sites, highly enriched in polycomb repressive complex 2-binding locations, are near genes implicated in mammalian development, cancer, obesity and longevity. Our findings offer new evidence suggesting that aging is evolutionarily conserved and intertwined with developmental processes across all mammals.

Is it all in the baseline? Trajectories of chair stand performance over 4 years and their association with grey matter structure in older adults

Understanding individual variability in response to physical activity is key to developing more effective and personalised interventions for healthy ageing. Here, we aimed to unpack individual differences by using longitudinal data from a randomised-controlled trial of a 12-month muscle strengthening intervention in older adults. Physical function of the lower extremities was collected from 247 participants (66.3 ± 2.5 years) at four time-points. At baseline and at year 4, participants underwent 3 T MRI brain scans. K-means longitudinal clustering was used to identify patterns of change in chair stand performance over 4 years, and voxel-based morphometry was applied to map structural grey matter volume at baseline and year 4. Results identified three groups showing trajectories of poor (33.6%), mid (40.1%), and high (26.3%) performance. Baseline physical function, sex, and depressive symptoms significantly differed between trajectory groups. High performers showed greater grey matter volume in the motor cerebellum compared to the poor performers. After accounting for baseline chair stand performance, participants were re-assigned to one of four trajectory-based groups: moderate improvers (38.9%), maintainers (38.5%), improvers (13%), and decliners (9.7%). Clusters of significant grey matter differences were observed between improvers and decliners in the right supplementary motor area. Trajectory-based group assignments were unrelated to the intervention arms of the study. In conclusion, patterns of change in chair stand performance were associated with greater grey matter volumes in cerebellar and cortical motor regions. Our findings emphasise that how you start matters, as baseline chair stand performance was associated with cerebellar volume 4 years later.

Midlife perceived stress is associated with cognitive decline across three decades

BACKGROUND

Research indicates detrimental effects of stress on brain health and cognitive functioning, but population-based studies using comprehensive measures of cognitive decline is lacking. The present study examined the association of midlife perceived stress with cognitive decline from young adulthood to late midlife, controlling for early life circumstances, education and trait stress (neuroticism).

METHODS

The sample consisted of 292 members of the Copenhagen Perinatal Cohort (1959-1961) with continued participation in two subsequent follow-up studies. Cognitive ability was assessed in young adulthood (mean age 27 years) and midlife (mean age 56 years) using the full Wechsler Adult Intelligence Scale (WAIS), and perceived stress was measured at midlife using the Perceived Stress Scale. The association of midlife perceived stress with decline in Verbal, Performance and Full-Scale IQ was assessed in multiple regression models based on Full Information Maximum Likelihood estimation.

RESULTS

Over a mean retest interval of 29 years, average decline in IQ score was 2.42 (SD 7.98) in Verbal IQ and 8.87 (SD 9.37) in Performance IQ. Mean decline in Full-scale IQ was 5.63 (SD 7.48), with a retest correlation of 0.83. Controlling for parental socio-economic position, education and young adult IQ, higher perceived stress at midlife was significantly associated with greater decline in Verbal (β = - 0.012), Performance (β = - 0.025), and Full-scale IQ (β = - 0.021), all p < .05. Across IQ scales, additionally controlling for neuroticism in young adulthood and change in neuroticism had only minor effects on the association of midlife perceived stress with decline.

CONCLUSIONS

Despite very high retest correlations, decline was observed on all WAIS IQ scales. In fully adjusted models, higher midlife perceived stress was associated with greater decline on all scales, indicating a negative association of stress with cognitive ability. The association was strongest for Performance and Full-scale IQ, perhaps reflecting the greater decline on these IQ scales compared to Verbal IQ.

Stress diagnoses in midlife and risk of dementia: a register-based follow-up study

OBJECTIVES

Previous studies indicated that stress diagnoses increase the risk of dementia. However, previous results may be biased by confounding, reverse causation and misclassification. Therefore, the main aim of this study was to investigate the association between clinically diagnosed stress in midlife and later dementia risk, while addressing limitations of previous studies.

METHODS

The study population was selected from all individuals in Denmark born 1935-1956. Individuals diagnosed with stress in midlife (aged 37-58 years) were matched (1:5) with individuals without stress diagnoses based on sex and birthdate (N = 103,484). Data were retrieved from national registers. Cox regression models were adjusted for socio-demographic factors and different morbidities.

RESULTS

We found a 2.20 (95% CI: 1.93-2.50) times higher rate of dementia among individuals with any stress diagnosis registered in midlife compared with no stress diagnosis. Hazard rate ratios of dementia were 1.73 (95% CI: 1.13-2.65) among individuals with acute stress reactions, 2.37 (95% CI: 2.05-2.74) among individuals with adjustment disorders, and 2.20 (95% CI: 1.73-2.80) among individuals with unspecified stress reactions. Individuals with PTSD and other stress reactions had non-significantly elevated rates of dementia. Adjustment for confounding only slightly attenuated the association, and reverse causation did not appear to bias the results substantially.

CONCLUSION

Our results support the hypothesis that severe stress in midlife is an important risk factor for dementia. This finding emphasizes the importance of identifying and treating severe stress in midlife to reduce potential detrimental consequences for brain health in later life.

The impact of rising sea temperatures on an Arctic top predator, the narwhal

Arctic top predators are expected to be impacted by increasing temperatures associated with climate change, but the relationship between increasing sea temperatures and population dynamics of Arctic cetaceans remains largely unexplored. Narwhals (Monodon monoceros) are considered to be among the most sensitive of Arctic endemic marine mammals to climate change due to their limited prey selection, strict migratory patterns and high site fidelity. In the context of climate change, we assume that the population dynamics of narwhals are partly influenced by changes in environmental conditions, with warm areas of increasing sea temperatures having lower abundance of narwhals. Using a unique large dataset of 144 satellite tracked narwhals, sea surface temperature (SST) data spanning 25 years (1993–2018) and narwhal abundance estimates from 17 localities, we (1) assessed the thermal exposure of this species, (2) investigated the SST trends at the summer foraging grounds, and (3) assessed the relationship between SST and abundance of narwhals. We showed a sharp SST increase in Northwest, Mideast and Southeast Greenland, whereas no change could be detected in the Canadian Arctic Archipelago (CAA) and in the Greenland Sea. The rising sea temperatures were correlated with the smallest narwhal abundance observed in the Mideast and Southeast Greenland (< 2000 individuals), where the mean summer sea temperatures were the highest (6.3 °C) compared to the cold waters of the CAA (0.7 °C) that were associated with the largest narwhal populations (> 40,000 individuals). These results support the hypothesis that warming ocean waters will restrict the habitat range of the narwhal, further suggesting that narwhals from Mideast and Southeast Greenland may be under pressure to abandon their traditional habitats due to ocean warming, and consequently either migrate further North or locally go extinct.

Mid- to late-life migraine diagnoses and risk of dementia: a national register-based follow-up study

BACKGROUND

Previous studies found an association between migraine and dementia, which are two leading causes of disability. However, these studies did not differentiate between migraine types and did not investigate all prevalent dementia subtypes. The main objective of this national register-based study was to investigate whether migraine was a risk factor for dementia. Additionally, we explored potential differences in dementia risk for migraine with and without aura.

METHODS

We obtained data on birth cohorts born between 1935 and 1956 (n = 1,657,890) from Danish national registers. Individuals registered with migraine before age 59 (n = 18,135) were matched (1:5) on sex and birthdate with individuals without migraine (n = 1,378,346). Migraine was defined by International Classification of Diseases (ICD) diagnoses and dementia was defined by ICD diagnoses and anti-dementia medication. After matching, 62,578 individuals were eligible for analysis. For the statistical analyses, we used Cox regression models and adjusted for socio-demographic factors and several psychiatric and somatic morbidities.

RESULTS

During a median follow-up time of 6.9 (IQR: 3.6-11.2) years, 207 individuals with migraine developed dementia. Compared with individuals without migraine, we found a 50% higher rate of dementia among individuals with migraine (HR = 1.50; 95% CI: 1.28-1.76). Individuals without aura had a 19% higher rate of dementia (HR = 1.19; 95% CI: 0.84-1.70), and individuals with aura had a two times higher rate of dementia (HR = 2.11; 95% CI: 1.48-3.00).

CONCLUSIONS

Our findings support the hypothesis that migraine is a midlife risk factor for dementia in later life. The higher rate of dementia in individuals with a hospital-based diagnosis of migraine with aura emphasizes the need for studies on pathological mechanisms and potential preventative measures. Furthermore, given that only hospital-based migraine diagnoses were included in this study, future research should also investigate migraine cases derived from the primary healthcare system to include less severe migraine cases.

Migraine with aura in women is not associated with structural thalamic abnormalities

Migraine with aura is a highly prevalent disorder involving transient neurological disturbances associated with migraine headache. While the pathophysiology is incompletely understood, findings from clinical and basic science studies indicate a potential key role of the thalamus in the mechanisms underlying migraine with and without aura. Two recent, clinic-based MRI studies investigated the volumes of individual thalamic nuclei in migraine patients with and without aura using two different data analysis methods. Both studies found differences of thalamic nuclei volumes between patients and healthy controls, but the results of the studies were not consistent. Here, we investigated whether migraine with aura is associated with changes in thalamic volume by analysing MRI data obtained from a large, cross-sectional population-based study which specifically included women with migraine with aura (N = 156), unrelated migraine-free matched controls (N = 126), and migraine aura-free co-twins (N = 29) identified from the Danish Twin Registry. We used two advanced, validated analysis methods to assess the volume of the thalamus and its nuclei; the MAGeT Brain Algorithm and a recently developed FreeSurfer-based method based on a probabilistic atlas of the thalamic nuclei combining ex vivo MRI and histology. These approaches were very similar to the methods used in each of the two previous studies. Between-group comparisons were corrected for potential effects of age, educational level, BMI, smoking, alcohol, and hypertension using a linear mixed model. Further, we used linear mixed models and visual inspection of data to assess relations between migraine aura frequency and thalamic nuclei volumes in patients. In addition, we performed paired t-tests to compare volumes of twin pairs (N = 29) discordant for migraine with aura. None of our analyses showed any between-group differences in volume of the thalamus or of individual thalamic nuclei. Our results indicate that the pathophysiology of migraine with aura does not involve alteration of thalamic volume.

The influence of prolonged strength training upon muscle and fat in healthy and chronically diseased older adults

BACKGROUND

Physical muscle function and brain hippocampus size declines with age, accelerating after the age of 60. Strength training over a few months improves physical function, but less is known about how long-term strength training affects physical function and hippocampus volume. Therefore, we aimed to investigate the effect of 1-year strength training of two different intensities upon muscle mass, function, and hippocampus volume in retirement-age individuals.

METHODS

In this multidisciplinary randomized controlled trial (clinicaltrials.gov: NCT02123641), participants were allocated to either a) supervised, heavy resistance training (HRT, n = 149, 3/wk), b) moderate intensity resistance training (MIT, n = 154, 3/wk) or c) non-exercise activities (CON, n = 148). 451 participants were randomized (62-70 yrs., women 61%, ≈80% with a chronic medical disease) and 419 were included in the intention-to-treat analysis (n = 143, 144 and 132; HRT, MIT and CON). Changes in muscle power (primary outcome), strength and size, physical function, body composition, hippocampus volume and physical/mental well-being were analyzed.

FINDINGS

Of the participants (HRT + MIT), 83% completed training at least 2/week. Leg extensor power was unchanged in all groups, but strength training had a positive effect on isometric knee extensor strength in both groups, whereas an increased muscle mass, cross-sectional area of vastus lateralis muscle, a decreased whole-body fat percentage, visceral fat content and an improved mental health (SF-36) occurred in HRT only. Further, chair-stand performance improved in all groups, whereas hippocampus volume decreased in all groups over time with no influence of strength training.

INTERPRETATION

Together, the results indicate that leg extensor power did not respond to long-term supervised strength training, but this type of training in a mixed group of healthy and chronically diseased elderly individuals can be implemented with good compliance and induces consistent changes in physiological parameters of muscle strength, muscle mass and abdominal fat.

Objective and subjective stress, personality, and allostatic load

INTRODUCTION

Despite the understanding of allostatic load (AL) as a consequence of ongoing adaptation to stress, studies of the stress-AL association generally focus on a narrow conceptualization of stress and have thus far overlooked potential confounding by personality. The present study examined the cross-sectional association of objective and subjective stress with AL, controlling for Big Five personality traits.

METHODS

Participants comprised 5,512 members of the Copenhagen Aging and Midlife Biobank aged 49-63 years (69% men). AL was measured as a summary index of 14 biomarkers of the inflammatory, cardiovascular, and metabolic system. Objective stress was assessed as self-reported major life events in adult life. Subjective stress was assessed as perceived stress within the past four weeks.

RESULTS

Both stress measures were positively associated with AL, with a slightly stronger association for objective stress. Adjusting for personality traits did not significantly change these associations.

CONCLUSIONS

The results suggest measures of objective and subjective stress to have independent predictive validity in the context of personality. Further, it is discussed how different operationalizations of stress and AL may account for some of the differences in observed stress-AL associations.

Moderate- to high-intensity exercise does not modify cortical β-amyloid in Alzheimer's disease

Introduction

Animal models of Alzheimer's disease show that exercise may modify β-amyloid (Aβ) deposition. We examined the effect of a 16-week exercise intervention on cortical Aβ in patients with mild-to-moderate Alzheimer's disease.

Methods

Thirty-six patients with Alzheimer's disease were randomized to either one hour of aerobic exercise three times weekly for 16 weeks or usual care. Pre and post intervention, 11Carbon-Pittsburgh compound B positron emission tomography was carried out to assess cortical Aβ, and quantified using standardized uptake value rations (SUVRs).

Results

The intervention showed no effect on follow-up SUVRs in a covariance analysis with group allocation, baseline intervention SUVR, age, sex, and baseline Mini–Mental State Examination as predictors. Change in SUVRs did not correlate with changes in measures of physical or aerobic fitness.

Discussion

The present findings do not support an effect of exercise on Aβ. However, the relatively short intervention period may account for a lack of efficacy. Further studies should test earlier and longer interventions.

Big Five personality traits and allostatic load in midlife

Objective: To examine the cross-sectional associations of Big Five personality traits with midlife allostatic load, including the role of sex, socio-demographic factors and health-related behaviours. Design: Cross-sectional analyses of 5512 members of the Copenhagen Aging and Midlife Biobank, aged 49-63 years, 69% men. Main outcome measure: Allostatic load (AL) based on 14 biomarkers representing the inflammatory, cardiovascular and metabolic system. Results: Due to significant sex × trait interactions, analyses were stratified by sex. Openness and Conscientiousness were inversely associated with AL in both sexes, and Extraversion was positively associated with AL in men. Adjusting for socio-demographic factors significantly attenuated the association of Openness in both sexes and of Extraversion in men, for whom the inverse association of Agreeableness with AL was strengthened. Further adjusting for health-related behaviours, the Conscientiousness-AL association was attenuated but remained significant, and Agreeableness remained significantly associated with AL in men. Conclusion: Results imply that higher levels of Agreeableness (in men) and Conscientiousness are associated with lower levels of AL above and beyond socio-demographic factors and health-related behaviours. The study further contributes by demonstrating the relevance of sex × trait and trait × trait interactions in the personality-health literature.

A 16-Week Aerobic Exercise Intervention Does Not Affect Hippocampal Volume and Cortical Thickness in Mild to Moderate Alzheimer's Disease

Introduction: Brain imaging studies in healthy elderly subjects suggest a positive effect of aerobic exercise on both brain structure and function, while the effects of aerobic exercise in Alzheimer’s Disease (AD) has been scarcely investigated.

Methods: In a single-blinded randomized MRI study, we assessed the effects of an aerobic exercise intervention on brain volume as measured by magnetic resonance imaging (MRI) and its correlation to cognitive functioning in patients with AD. The study was a sub-study of a larger randomized controlled trial (ADEX study). Forty-one patients were assigned to a control or exercise group. The exercise group performed 60-min of aerobic exercise three times per week for 16 weeks. All participants underwent whole-brain MRI at 3 Tesla and cognitive assessment at baseline and after 16 weeks. Attendance and intensity were monitored providing a total exercise load. Changes in regional brain volumes and cortical thickness were analyzed using Freesurfer software.

Results: There was no effect of the type of intervention on MRI-derived brain volumes. In the entire group with and without training, Exercise load showed a positive correlation with changes in volume in the hippocampus, as well as frontal cortical thickness. Volume changes in frontal cortical thickness correlated with changes in measures of mental speed and attention and exercise load in the exercise group.

Conclusion: We did not find evidence to support an effect of 16 weeks of aerobic exercise on brain volume changes in patients with AD. Longer intervention periods may be needed to affect brain structure as measured with volumetric MRI.

Clinical Trial registration:ClinicalTrials.gov Identifier: NCT01681602, registered September 10th, 2012 (Retrospectively registered).

Parental socioeconomic position and midlife allostatic load: a study of potential mediators

BACKGROUND

The mechanisms underlying the association of parental socioeconomic position with later life allostatic load remain unclear. The present study aims to examine potential pathways underlying this association: personality, social relations, intelligence and education.

METHODS

The study comprised 361 members of the Copenhagen Perinatal Cohort who participated in two subsequent follow-ups: the Prenatal Development Project (mean age 27 years) and the Copenhagen Aging and Midlife Biobank study (mean age 50 years). Allostatic load was based on 14 biomarkers representing the inflammatory, metabolic and cardiovascular system measured at midlife. Information on potential mediators was collected in young adulthood, and their role in the association of parental socioeconomic position with midlife allostatic load were examined in linear regression path analyses.

RESULTS

Parental socioeconomic position at one year was inversely associated with midlife allostatic load (β = - 0.238, p < .001). No mediation effects were found for personality or social relations. In a model including intelligence and education, a significant indirect effect was found for education (β = - 0.151, p < .001). A significant direct effect remained (β = - 0.111, p = .040).

CONCLUSIONS

Parental socioeconomic position was inversely associated with allostatic load in midlife. Results suggest that part of this association was mediated by education. A better understanding of the non-cognitive pathways related to education is an important prerequisite for the development of effective intervention strategies.

Early life predictors of midlife allostatic load: A prospective cohort study

BACKGROUND

Allostatic load has been suggested as a pathway through which experiences become biologically embedded to influence health. Research on childhood predictors of allostatic load has focused on socioeconomic and psychosocial exposures, while few studies include prospective measures of biomedical exposures. Further, findings on sex differences in the association of childhood predictors with various health outcomes related to allostatic load are ambiguous.

AIMS

To examine the influence of early life biomedical and social factors in the first year of life on midlife allostatic load, assessing potential sex differences.

METHODS

This prospective cohort study includes early life information collected at birth and a one year examination for 1,648 members of the Copenhagen Perinatal Cohort who also participated in the Copenhagen Aging and Midlife Biobank study (aged 49-52 years, 56% women). Allostatic load based on 14 biomarkers was selected as a measure of midlife health status. Early life factors were categorized as predominantly biomedical or social, and their associations with midlife allostatic load were examined in domain-specific and combined sex-stratified multiple regression models.

RESULTS

The biomedical factors model explained 6.6% of the variance in midlife allostatic load in men and 6.7% in women, while the social model explained 4.1% of the variance in men and 7.3% in women. For both sexes, parental socioeconomic position at one year and maternal BMI significantly predicted midlife allostatic load in a model containing all early life factors. For women, additional significant predictors were complications at birth, birth weight and not living with parents at one year.

CONCLUSION

The results confirm an association of lower childhood socioeconomic position with higher adult allostatic load while demonstrating the importance of other prenatal and early life exposures and highlighting potential sex differences.

Disability in progressive MS is associated with T2 lesion changes

BACKGROUND

Progressive multiple sclerosis (MS) is characterised by diffuse changes on brain magnetic resonance imaging (MRI), which complicates the use of MRI as a diagnostic and prognostic marker. The relationship between MRI measures (conventional and non-conventional) and clinical disability in progressive MS therefore warrants further investigation.

OBJECTIVE

To investigate the relationship between clinical disability and MRI measures in patients with progressive MS.

METHODS

Data from 93 primary and secondary progressive MS patients who had participated in 3 phase 2 clinical trials were included in this cross-sectional study. From 3T MRI baseline scans we calculated total T2 lesion volume and analysed magnetisation transfer ratio (MTR) and the diffusion tensor imaging indices fractional anisotropy (FA) and mean diffusivity (MD) in T2 lesions, normal-appearing white matter (NAWM) and cortical grey matter. Disability was assessed by the Expanded Disability Status Scale (EDSS) and the MS functional composite.

RESULTS

T2 lesion volume was associated with impairment by all clinical measures. MD and MTR in T2 lesions were significantly related to disability, and lower FA values correlated with worse hand function in NAWM. In multivariable analyses, increasing clinical disability was independently correlated with increasing T2 lesion volumes and MTR in T2 lesions.

CONCLUSION

In progressive MS, clinical disability is related to lesion volume and microstructure.

Spinal cord atrophy in anterior-posterior direction reflects impairment in multiple sclerosis

OBJECTIVE

To investigate how atrophy is distributed over the cross section of the upper cervical spinal cord and how this relates to functional impairment in multiple sclerosis (MS).

METHODS

We analysed the structural brain MRI scans of 54 patients with relapsing-remitting MS (n=22), primary progressive MS (n=9), secondary progressive MS (n=23) and 23 age- and sex-matched healthy controls. We measured the cross-sectional area (CSA), left-right width (LRW) and anterior-posterior width (APW) of the spinal cord at the segmental level C2. We tested for a nonparametric linear relationship between these atrophy measures and clinical impairments as reflected by the Expanded Disability Status Scale (EDSS) and Multiple Sclerosis Impairment Scale (MSIS).

RESULTS

In patients with MS, CSA and APW but not LRW were reduced compared to healthy controls (P<.02) and showed significant correlations with EDSS, MSIS and specific MSIS subscores.

CONCLUSION

In patients with MS, atrophy of the upper cervical cord is most evident in the antero-posterior direction. As APW of the cervical cord can be readily derived from standard structural MRI of the brain, APW constitutes a clinically useful neuroimaging marker of disease-related neurodegeneration in MS.

Cognitive ability in young adulthood and risk of dementia in a cohort of Danish men, brothers, and twins

INTRODUCTION

We examined the association between cognitive ability in young adulthood and dementia in Danish men, brothers, and male twins.

METHODS

In total, 666,986 men born between 1939 and 1959 were identified for dementia diagnosis in national registries from 1969 to 2016. The association between cognitive ability from draft board examination and dementia was examined using Cox regression.

RESULTS

During a 44-year follow-up, 6416 (0.96%) men developed dementia, 1760 (0.26%) and 970 (0.15%) of which were classified as Alzheimer's and vascular dementia, respectively. Low cognitive ability was associated with increased risk of dementia (hazard ratio [HR]_{per SD decrease} 1.33 [95% confidence interval {CI} = 1.30-1.35]) with the strongest associations for vascular dementia (HR_{per SD decrease} 1.47 [95% CI = 1.31-1.56]) and a weaker for Alzheimer's disease (HR_{per SD decrease} 1.07 [95% CI = 1.03-1.13]). The intrabrother and twin analyses (taking shared family factors into account) showed attenuated risk estimates but with wide CIs.

DISCUSSION

Low early-life cognitive ability increases the risk of dementia before the age of 78 years. The association is partly explained by shared family factors.

Physical activity as intervention for age-related loss of muscle mass and function: protocol for a randomised controlled trial (the LISA study)

INTRODUCTION

Physical and cognitive function decline with age, accelerating during the 6th decade. Loss of muscle power (force×velocity product) is a dominant physical determinant for loss of functional ability, especially if the lower extremities are affected. Muscle strength training is known to maintain or even improve muscle power as well as physical function in older adults, but the optimal type of training for beneficial long-term training effects over several years is unknown. Moreover, the impact of muscle strength training on cognitive function and brain structure remains speculative. The primary aim of this randomised controlled trial is to compare the efficacy of two different 1 year strength training regimens on immediate and long-lasting improvements in muscle power in retirement-age individuals. Secondary aims are to evaluate the effect on muscle strength, muscle mass, physical and cognitive function, mental well-being, health-related quality of life and brain morphology.

METHODS AND ANALYSIS

The study includes 450 home-dwelling men and women (62-70 years). Participants are randomly allocated to (1) 1 year of supervised, centre-based heavy resistance training, (2) home-based moderate intensity resistance training or (3) habitual physical activity (control). Changes in primary (leg extensor power) and secondary outcomes are analysed according to the intention to treat principle and per protocol at 1, 2, 4, 7 and 10 years.

ETHICS AND DISSEMINATION

The study is expected to generate new insights into training-induced promotion of functional ability and independency after retirement and will help to formulate national recommendations regarding physical activity schemes for the growing population of older individuals in western societies. Results will be published in scientific peer-reviewed journals, in PhD theses and at public meetings. The study is approved by the Regional Ethical Committee (Capital Region, Copenhagen, Denmark, number H-3-2014-017).

TRIAL REGISTRATION NUMBER

NCT02123641.

High-dose erythropoietin in patients with progressive multiple sclerosis: A randomized, placebo-controlled, phase 2 trial

Background:

Erythropoietin (EPO) is a part of an endogenous neuroprotective system in the brain and may address pathophysiological mechanisms in progressive multiple sclerosis (MS).

Objective:

To evaluate a treatment effect of EPO on progressive MS.

Methods:

This was a single-center, randomized, double-blind, placebo-controlled phase 2 trial, in which 52 patients with secondary or primary progressive MS were allocated to treatment with recombinant EPO (48,000 IU) or placebo, administered intravenously 17 times during 24 weeks. Patients had an Expanded Disability Status Score (EDSS) from 4 to 6.5 and clinical progression without relapses in the 2 preceding years. The primary outcome was the change in a composite measure of maximum gait distance, hand dexterity, and cognition from baseline to 24 weeks.

Results:

A total of 50 patients completed the study. Venesection was performed often but no thromboembolic events occurred. We found no difference in the primary outcome between the EPO and the placebo group using the intention-to-treat principle ( p = 0.22). None of the secondary outcomes, neither clinical nor magnetic resonance imaging (MRI) measures showed any significant differences.

Conclusion:

This study provides class II evidence that treatment with high-dose EPO is not an effective treatment in patients with moderately advanced progressive MS.

Migraine with aura and risk of silent brain infarcts and white matter hyperintensities: an MRI study

A small number of population-based studies reported an association between migraine with aura and risk of silent brain infarcts and white matter hyperintensities in females. We investigated these relations in a population-based sample of female twins. We contacted female twins ages 30–60 years identified through the population-based Danish Twin Registry. Based on questionnaire responses, twins were invited to participate in a telephone-based interview conducted by physicians. Headache diagnoses were established according to the International Headache Society criteria. Cases with migraine with aura, their co-twins, and unrelated migraine-free twins (controls) were invited to a brain magnetic resonance imaging scan performed at a single centre. Brain scans were assessed for the presence of infarcts, and white matter hyperintensities (visual rating scales and volumetric analyses) blinded to headache diagnoses. Comparisons were based on 172 cases, 34 co-twins, and 139 control subjects. Compared with control subjects, cases did not differ with regard to frequency of silent brain infarcts (four cases versus one control), periventricular white matter hyperintensity scores [adjusted mean difference (95% confidence interval): −0.1 (−0.5 to 0.2)] or deep white matter hyperintensity scores [adjusted mean difference (95% confidence interval): 0.1 (−0.8 to 1.1)] assessed by Scheltens’ scale. Cases had a slightly higher total white matter hyperintensity volume compared with controls [adjusted mean difference (95% confidence interval): 0.17 (−0.08 to 0.41) cm ³ ] and a similar difference was present in analyses restricted to twin pairs discordant for migraine with aura [adjusted mean difference 0.21 (−0.20 to 0.63)], but these differences did not reach statistical significance. We found no evidence of an association between silent brain infarcts, white matter hyperintensities, and migraine with aura.

White Matter Lesions, Carotid and Coronary Atherosclerosis in Late-Onset Depression and Healthy Controls

BACKGROUND

Cerebral white matter lesions (WMLs) are more common in individuals with late-onset or late-life depression. It has been proposed that carotid atherosclerosis may predispose to WMLs by inducing cerebral hypoperfusion. This hemodynamic effect of carotid atherosclerosis could be important for the formation of WMLs in depression.

METHODS

The case-control study included 29 patients with late-onset major depressive disorder and 27 controls matched for sex, age, and tobacco use. WML volume, carotid intima-media thickness, and coronary plaque volume were assessed using magnetic resonance imaging, ultrasound scan, and coronary computed tomography (CT) angiography, respectively.

RESULTS

The mean age for the total sample was 59.7 ± 4.7 years. There was no difference in carotid intima-media thickness between patients and controls (p = 0.164), whereas a higher WML volume in the patients was found (p = 0.051). In both patients and controls, WML volume was associated with carotid but not with coronary atherosclerosis. In adjusted multiple linear regression, a 0.1mm increase in averaged carotid intima-media thickness was associated with a 52% (95% CI: 8.4-112, p = 0.032) increase in WML volume. The association between carotid intima-media thickness and WML volume was, however, similar in patients and controls.

CONCLUSIONS

In older persons aged between 50 and 70 years, WMLs do not seem to be a part of generalized atherosclerotic disease, but seem to be dependent on atherosclerosis in the carotid arteries. Carotid atherosclerosis, however, could not explain the higher WML load observed in the depressed patients, and thus, studies are needed to establish the mechanisms linking depression and WMLs.

Training shortest-path tractography: Automatic learning of spatial priors

Tractography is the standard tool for automatic delineation of white matter tracts from diffusion weighted images. However, the output of tractography often requires post-processing to remove false positives and ensure a robust delineation of the studied tract, and this demands expert prior knowledge. Here we demonstrate how such prior knowledge, or indeed any prior spatial information, can be automatically incorporated into a shortest-path tractography approach to produce more robust results. We describe how such a prior can be automatically generated (learned) from a population, and we demonstrate that our framework also retains support for conventional interactive constraints such as waypoint regions. We apply our approach to the open access, high quality Human Connectome Project data, as well as a dataset acquired on a typical clinical scanner. Our results show that the use of a learned prior substantially increases the overlap of tractography output with a reference atlas on both populations, and this is confirmed by visual inspection. Furthermore, we demonstrate how a prior learned on the high quality dataset significantly increases the overlap with the reference for the more typical yet lower quality data acquired on a clinical scanner. We hope that such automatic incorporation of prior knowledge and the obviation of expert interactive tract delineation on every subject, will improve the feasibility of large clinical tractography studies.

Monthly oral methylprednisolone pulse treatment in progressive multiple sclerosis

BACKGROUND

There is a large unmet need for treatments for patients with progressive multiple sclerosis (MS). Phase 2 studies with cerebrospinal fluid (CSF) biomarker outcomes may be well suited for the initial evaluation of efficacious treatments.

OBJECTIVE

To evaluate the effect of monthly oral methylprednisolone pulse treatment on intrathecal inflammation in progressive MS.

METHODS

In this open-label phase 2A study, 15 primary progressive and 15 secondary progressive MS patients received oral methylprednisolone pulse treatment for 60 weeks. Primary outcome was changes in CSF concentrations of osteopontin. Secondary outcomes were other CSF biomarkers of inflammation, axonal damage and demyelination; clinical scores; magnetic resonance imaging measures of disease activity, magnetization transfer ratio (MTR) and diffusion tensor imaging (DTI); motor evoked potentials; and bone density scans.

RESULTS

We found no change in the CSF concentration of osteopontin, but we observed significant improvement in clinical scores, MTR, DTI and some secondary CSF outcome measures. Adverse events were well-known side effects to methylprednisolone.

CONCLUSION

Monthly methylprednisolone pulse treatment was safe, but had no effect on the primary outcome. However, improvements in secondary clinical and MRI outcome measures suggest that this treatment regimen may have a beneficial effect in progressive MS.

Trichuris suis ova therapy in relapsing multiple sclerosis is safe but without signals of beneficial effect

Background:

An observational study has suggested that relapsing–remitting multiple sclerosis patients with helminth infections have lower disease activity and progression than uninfected multiple sclerosis patients.

Objective:

To evaluate the safety and efficacy on MRI activity of treatment with TSO in relapsing MS.

Methods:

The study was an open-label, magnetic resonance imaging assessor-blinded, baseline-to-treatment study including ten patients with relapsing forms of multiple sclerosis. Median (range) age was 41 (24–55) years, disease duration 9 (4–34) years, Expanded Disability Status Scale score 2.5 (1–5.0), and number of relapses within the last two years 3 (2–5). Four patients received no disease modifying therapy, while six patients received IFN-β. After an observational period of 8 weeks, patients received 2500 ova from the helminth Trichuris suis orally every second week for 12 weeks. Patients were followed with serial magnetic resonance imaging, neurological examinations, laboratory safety tests and expression of immunological biomarker genes.

Results:

Treatment with Trichuris suis orally was well-tolerated apart from some gastrointestinal symptoms. Magnetic resonance imaging revealed 6 new or enlarged T2 lesions in the run-in period, 7 lesions in the early period and 21 lesions in the late treatment period. Two patients suffered a relapse before treatment and two during treatment. Eight patients developed eosinophilia. The expression of cytokines and transcription factors did not change.

Conclusions:

In a small group of relapsing multiple sclerosis patients, Trichuris suis oral therapy was well tolerated but without beneficial effect.

Application of the PredictAD decision support tool to a Danish cohort of patients with Alzheimer's disease and other dementias

BACKGROUND

The diagnosis of Alzheimer's disease (AD) is based on an ever-increasing body of data and knowledge making it a complex task. The PredictAD tool integrates heterogeneous patient data using an interactive user interface to provide decision support. The aim of this project was to investigate the performance of the tool in distinguishing AD from non-AD dementia using a realistic clinical dataset.

METHODS

We retrieved clinical data from a group of patients diagnosed with AD (n = 72), vascular dementia (VaD, n = 30), frontotemporal dementia (FTD, n = 25) or dementia with Lewy bodies (DLB, n = 14) at the Copenhagen Memory Clinic at Rigshospitalet. Three classification methods were applied to the data in order to differentiate between AD and a group of non-AD dementias. The methods were the PredictAD tool's Disease State Index (DSI), the naïve Bayesian classifier and the random forest.

RESULTS

The DSI performed best for this realistic dataset with an accuracy of 76.6% compared to the accuracies for the naïve Bayesian classifier and random forest of 67.4 and 66.7%, respectively. Furthermore, the DSI differentiated between the four diagnostic groups with a p value of <0.0001.

CONCLUSION

In this dataset, the DSI method used by the PredictAD tool showed a superior performance for the differentiation between patients with AD and those with other dementias. However, the methods need to be refined further in order to optimize the differential diagnosis between AD, FTD, VaD and DLB.

Changes in blood testosterone concentrations after surgical and chemical sterilization of male free-roaming dogs in southern Chile

There is a growing interest in chemical sterilization as an alternative to surgical castration in large-scale sterilization campaigns to control canine populations. An important step toward understanding the short-term and long-term effects of chemical sterilants is to determine their impact on blood testosterone concentrations, particularly as these could influence dog behavior after treatment. A field trial was conducted with 118 free-roaming male dogs in the Chilean Patagonia, where 36 dogs were chemically sterilized using EsterilSol, 39 dogs were surgically castrated, and 43 dogs remained intact as controls. Blood testosterone levels were determined at four time periods: on enrollment 6 months before treatment (t-6m), at the time of treatment (t0, within one hour after surgical castration or chemical sterilization and during a concurrent 2-week period for the control group), four (t+4m), and six (t+6m) months after treatment. Intrinsic and temporal factors were evaluated; age was significantly associated with testosterone, where dogs 2- to 4-year-old had the highest testosterone concentrations (P = 0.036), whereas body weight and body condition scores were not associated with testosterone; testosterone concentration was not influenced by time of day, month, or season. After treatment (t+4m and t+6m), all of the surgically castrated dogs had testosterone concentrations below 1.0 ng/mL. On the basis of this cut point (<1 ng/mL), testosterone remained unchanged in 66% of the chemically sterilized dogs at both t+4m and t+6m; it remained low for 22% of dogs at both t+4m and t+6m; it was unchanged at t+4m but low at t+6m in 9% of dogs; and, it was low at t+4m but reverted back to unchanged at t+6m in one dog (3%). Incidentally, testosterone in chemically sterilized dogs increased dramatically within 1 hour of treatment (t0), more than doubling (131%) the concentration of control dogs at the time of treatment (t0), likely because of severe necrosis of interstitial cells. The use of EsterilSol as a method of sterilizing dogs had a variable effect on blood testosterone concentrations. Approximately, 30% of chemically sterilized dogs had a reduced testosterone concentration (actual maximum, 1 ng/mL) after 6 months, similar to that of surgically castrated dogs. Most chemically sterilized dogs, however, showed no long-term changes in blood testosterone concentrations.

[MRI of the pineal gland]

The pineal gland (CP) is located centrally in the brain and produces melatonin. Cysts and concrements are frequent findings on MRI but their significance is still unclear. The visualization of CP is difficult due to its location and surrounding structures and so far, no standardized method exists. New studies suggest a correlation between CP-morphology and melatonin secretion as well as a connection between melatonin, disturbed circadian rhythm, and the development of cancer and cardiovascular diseases, underlining the need for a standardized approach to CP on MRI.

Hearts and minds: linking vascular rigidity and aerobic fitness with cognitive aging

Human aging is accompanied by both vascular and cognitive changes. Although arteries throughout the body are known to become stiffer with age, this vessel hardening is believed to start at the level of the aorta and progress to other organs, including the brain. Progression of this vascular impairment may contribute to cognitive changes that arise with a similar time course during aging. Conversely, it has been proposed that regular exercise plays a protective role, attenuating the impact of age on vascular and metabolic physiology. Here, the impact of vascular degradation in the absence of disease was investigated within 2 groups of healthy younger and older adults. Age-related changes in executive function, elasticity of the aortic arch, cardiorespiratory fitness, and cerebrovascular reactivity were quantified, as well as the association between these parameters within the older group. In the cohort studied, older adults exhibited a decline in executive functions, measured as a slower performance in a modified Stroop task (1247.90 ± 204.50 vs. 898.20 ± 211.10 ms on the inhibition and/or switching component, respectively) than younger adults. Older participants also showed higher aortic pulse wave velocity (8.98 ± 3.56 vs. 3.95 ± 0.82 m/s, respectively) and lower VO₂ max (29.04 ± 6.92 vs. 42.32 ± 7.31 mL O2/kg/min, respectively) than younger adults. Within the older group, faster performance of the modified Stroop task was associated with preserved aortic elasticity (lower aortic pulse wave velocity; p = 0.046) and higher cardiorespiratory fitness (VO₂ max; p = 0.036). Furthermore, VO₂ max was found to be negatively associated with blood oxygenation level dependent cerebrovascular reactivity to CO₂ in frontal regions involved in the task (p = 0.038) but positively associated with cerebrovascular reactivity in periventricular watershed regions and within the postcentral gyrus. Overall, the results of this study support the hypothesis that cognitive status in aging is linked to vascular health, and that preservation of vessel elasticity may be one of the key mechanisms by which physical exercise helps to alleviate cognitive aging.

Secondary progressive and relapsing remitting multiple sclerosis leads to motor-related decreased anatomical connectivity

Multiple sclerosis (MS) damages central white matter pathways which has considerable impact on disease-related disability. To identify disease-related alterations in anatomical connectivity, 34 patients (19 with relapsing remitting MS (RR-MS), 15 with secondary progressive MS (SP-MS) and 20 healthy subjects underwent diffusion magnetic resonance imaging (dMRI) of the brain. Based on the dMRI, anatomical connectivity mapping (ACM) yielded a voxel-based metric reflecting the connectivity shared between each individual voxel and all other brain voxels. To avoid biases caused by inter-individual brain-shape differences, they were estimated in a spatially normalized space. Voxel-based statistical analyses using ACM were compared with analyses based on the localized microstructural indices of fractional anisotropy (FA). In both RR-MS and SP-MS patients, considerable portions of the motor-related white matter revealed decreases in ACM and FA when compared with healthy subjects. Patients with SP-MS exhibited reduced ACM values relative to RR-MS in the motor-related tracts, whereas there were no consistent decreases in FA between SP-MS and RR-MS patients. Regional ACM statistics exhibited moderate correlation with clinical disability as reflected by the expanded disability status scale (EDSS). The correlation between these statistics and EDSS was either similar to or stronger than the correlation between FA statistics and the EDSS. Together, the results reveal an improved relationship between ACM, the clinical phenotype, and impairment. This highlights the potential of the ACM connectivity indices to be used as a marker which can identify disease related-alterations due to MS which may not be seen using localized microstructural indices.

Natalizumab in progressive MS: results of an open-label, phase 2A, proof-of-concept trial

OBJECTIVE

Natalizumab inhibits the migration of systemic immune cells to the CNS and may be beneficial in progressive multiple sclerosis (MS). The objective of the study was to examine the effects of natalizumab in progressive MS.

METHODS

In an open-label phase 2A study, 24 patients with progressive MS were included to receive natalizumab treatment for 60 weeks. Response to natalizumab was assessed in CSF and MRI studies. The primary endpoint was change in CSF osteopontin, a biomarker of intrathecal inflammation, from baseline to week 60.

RESULTS

Seventeen patients completed the study. No new safety issues were encountered. CSF osteopontin decreased by 65 ng/mL (95% confidence interval 34-96 ng/mL; p = 0.0004) from baseline to week 60 in conjunction with decreases in other CSF biomarkers of inflammation, axonal damage, and demyelination. Magnetization transfer ratio increased in both cortical gray and normal-appearing white matter and correlated with decreases in CSF neurofilament light chain.

CONCLUSIONS

Natalizumab treatment of progressive MS reduces intrathecal inflammation and tissue damage, supporting a beneficial effect of natalizumab treatment in progressive MS and suggesting that systemic inflammation contributes to the pathogenesis. Moreover, the study establishes the feasibility of using CSF biomarkers in proof-of-concept trials, allowing a low number of participants and short study duration.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that in patients with progressive MS, natalizumab reduces biomarkers of intrathecal inflammation.

Necrosuppurative orchitis and scrotal necrotizing dermatitis following intratesticular administration of zinc gluconate neutralized with arginine (EsterilSol) in 2 mixed-breed dogs

Intratesticular injection of EsterilSol (zinc gluconate neutralized with arginine) is a chemical sterilant for male dogs sometimes used in population control campaigns. Adverse reactions have been reported in 1% to 4% of treated dogs, but detailed histomorphologic descriptions are lacking. During a behavioral study conducted in the Chilean Patagonia in 2012, severe necrosuppurative orchitis and ulcerative dermatitis were observed in 2 of 36 (6%) dogs sterilized with EsterilSol according to the manufacturer's instructions. Reactions were noted on days 8 and 7 postinjection and required scrotal ablation on days 8 and 13, respectively; neither reaction was associated with the injection site. Although self-trauma following administration may have contributed, the cause of the adverse reactions is uncertain. EsterilSol is a relatively uncomplicated method to sterilize male dogs, but the occurrence of severe adverse reactions several days after administration emphasizes the need for the provision of long-term monitoring and veterinary care during sterilization campaigns using this product.

Blood-brain barrier permeability of normal appearing white matter in relapsing-remitting multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) affects the integrity of the blood-brain barrier (BBB). Contrast-enhanced T1 weighted magnetic resonance imaging (MRI) is widely used to characterize location and extent of BBB disruptions in focal MS lesions. We employed quantitative T1 measurements before and after the intravenous injection of a paramagnetic contrast agent to assess BBB permeability in the normal appearing white matter (NAWM) in patients with relapsing-remitting MS (RR-MS).

METHODOLOGY/PRINCIPAL FINDINGS

Fifty-nine patients (38 females) with RR-MS undergoing immunomodulatory treatment and nine healthy controls (4 females) underwent quantitative T1 measurements at 3 tesla before and after injection of a paramagnetic contrast agent (0.2 mmol/kg Gd-DTPA). Mean T1 values were calculated for NAWM in patients and total cerebral white matter in healthy subjects for the T1 measurements before and after injection of Gd-DTPA. The pre-injection baseline T1 of NAWM (945±55 [SD] ms) was prolonged in RR-MS relative to healthy controls (903±23 ms, p = 0.028). Gd-DTPA injection shortened T1 to a similar extent in both groups. Mean T1 of NAWM was 866±47 ms in the NAWM of RR-MS patients and 824±13 ms in the white matter of healthy controls. The regional variability of T1 values expressed as the coefficient of variation (CV) was comparable between the two groups at baseline, but not after injection of the contrast agent. After intravenous Gd-DTPA injection, T1 values in NAWM were more variable in RR-MS patients (CV = 0.198±0.046) compared to cerebral white matter of healthy controls (CV = 0.166±0.018, p = 0.046).

CONCLUSIONS/SIGNIFICANCE

We found no evidence of a global BBB disruption within the NAWM of RR-MS patients undergoing immunomodulatory treatment. However, the increased variation of T1 values in NAWM after intravenous Gd-DTPA injection points to an increased regional inhomogeneity of BBB function in NAWM in relapsing-remitting MS.

Visual processing speed in old age

Mental speed is a common concept in theories of cognitive aging, but it is difficult to get measures of the speed of a particular psychological process that are not confounded by the speed of other processes. We used Bundesen's (1990) Theory of Visual Attention (TVA) to obtain specific estimates of processing speed in the visual system controlled for the influence of response latency and individual variations of the perception threshold. A total of 33 non-demented old people (69-87 years) were tested for the ability to recognize briefly presented letters. Performance was analyzed by the TVA model. Visual processing speed decreased approximately linearly with age and was on average halved from 70 to 85 years. Less dramatic aging effects were found for the perception threshold and the visual apprehension span. In the visual domain, cognitive aging seems to be most clearly related to reductions in processing speed.

Plasma NT-proBNP and white matter hyperintensities in type 2 diabetic patients

Abstract

Elevated plasma N-terminal (NT)-proBNP from the heart as well as white matter hyperintensities (WMH) in the brain predict cardiovascular (CV) mortality in the general population. The cause of poor prognosis associated with elevated P-NT-proBNP is not known but WMH precede strokes in high risk populations. We assessed the association between P-NT-proBNP and WMH or brain atrophy measured with magnetic resonance imaging (MRI) in type 2 diabetic patients, and age-matched controls.

Methods and results

We measured P-NT-proBNP(ng/l) in 20 diabetic patients without prior stroke but with(n = 10) or without(n = 10) asymptomatic coronary artery disease(CAD) in order to include patients with a wide-ranging CV risk profile. All patients and 26 controls had a 3D MRI and brain volumes(ml) with WMH and brain parenchymal fraction(BPF), an indicator of brain atrophy, were determined.

P-NT-proBNP was associated with WMH in linear regression analysis adjusted for CV risk factors(r = 0.94, p = 0.001) and with BPF in univariate analysis(r = 0.57, p = 0.009). Patients divided into groups of increased P-NT-proBNP levels were paralleled with increased WMH volumes(geometric mean[SD];(2.86[5.11] ml and 0.76[2.49] ml compared to patients with low P-NT-proBNP 0.20[2.28] ml, p = 0.003)) and also when adjusted for age, sex and presence of CAD(p = 0.017). The association was strengthened by CV risk factors and we did not find a common heart or brain specific driver of both P-NT-proBNP and WMH. Patients and particular patients with CAD had higher WMH, however no longer after adjustment for age and sex.

Conclusion

P-NT-proBNP was associated with WMH in type 2 diabetic patients, suggesting a linkage between heart and brain disease.

Corpus callosum tissue loss and development of motor and global cognitive impairment: the LADIS study

OBJECTIVE

To examine the impact of corpus callosum (CC) tissue loss on the development of global cognitive and motor impairment in the elderly.

METHODS

This study was based on the Leukoaraiosis and Disability (LADIS) study. Assessment of cognitive and motor functions and magnetic resonance imaging (MRI) were done at baseline and at a 3-year follow-up in nondemented elderly subjects.

RESULTS

328 of 639 LADIS subjects had MRIs at baseline and at the 3-year follow-up, which allowed for assessment of CC. Logistic regression revealed differential tissue loss rates in posterior CC in subjects converting to dementia, compared to nonconverters (p < 0.05). Anterior and posterior CC tissue loss was significantly correlated with self-perceived memory impairment in nonconverters (p < 0.05). CC tissue loss was also significantly associated with impaired single leg stance time (p < 0.01).

CONCLUSION

The present longitudinal study on CC supports the role of callosal tissue loss in the development of global cognitive as well as motor impairment.

Callosal tissue loss parallels subtle decline in psychomotor speed. a longitudinal quantitative MRI study. The LADIS Study

Cross-sectional studies have suggested that corpus callosum (CC) atrophy is related to impairment in global cognitive function, mental speed, and executive functions in the elderly. Longitudinal studies confirming these findings have been lacking. We investigated whether CC tissue loss is associated with change in cognitive performance over time in subjects with age-related white matter lesions (WML). Two-hundred-fifty-three subjects, aged 65-84 years, were evaluated by using repeated MRI and neuropsychological evaluation at baseline and after 3 years. The effect of overall and regional CC tissue loss on cognitive decline was analyzed with hierarchical linear regression models. After controlling for age, sex, education, and baseline cognitive performance, the rates of tissue loss in the total CC area, and in rostrum/genu and midbody subregions were significantly associated with decline in a compound measure of cognitive speed and motor control, but not in those of executive functions, memory, or global cognitive function. Total CC area and midbody remained significant predictors of speed also after adjusting for baseline WML volume, WML progression, and global brain atrophy. However, the relationship between anterior CC and speed performance was mediated by WML volume. In conclusion, the overall and regional rate of CC tissue loss parallels longitudinal slowing of psychomotor performance. The adverse effect of CC tissue loss on psychomotor function may be driven by altered interhemispheric information transfer between homologous cortical areas.

An ex vivo imaging pipeline for producing high-quality and high-resolution diffusion-weighted imaging datasets

Diffusion tensor (DT) imaging and related multifiber reconstruction algorithms allow the study of in vivo microstructure and, by means of tractography, structural connectivity. Although reconstruction algorithms are promising imaging tools, high-quality diffusion-weighted imaging (DWI) datasets for verification and validation of postprocessing and analysis methods are lacking. Clinical in vivo DWI is limited by, for example, physiological noise and low signal-to-noise ratio. Here, we performed a series of DWI measurements on postmortem pig brains, which resemble the human brain in neuroanatomical complexity, to establish an ex vivo imaging pipeline for generating high-quality DWI datasets. Perfusion fixation ensured that tissue characteristics were comparable to in vivo conditions. There were three main results: (i) heat conduction and unstable tissue mechanics accounted for time-varying artefacts in the DWI dataset, which were present for up to 15 h after positioning brain tissue in the scanner; (ii) using fitted DT, q-ball, and persistent angular structure magnetic resonance imaging algorithms, any b-value between ∼2,000 and ∼8,000 s/mm(2) , with an optimal value around 4,000 s/mm(2) , allowed for consistent reconstruction of fiber directions; (iii) diffusivity measures in the postmortem brain tissue were stable over a 3-year period. On the basis of these results, we established an optimized ex vivo pipeline for high-quality and high-resolution DWI. The pipeline produces DWI data sets with a high level of tissue structure detail showing for example two parallel horizontal rims in the cerebral cortex and multiple rims in the hippocampus. We conclude that high-quality ex vivo DWI can be used to validate fiber reconstruction algorithms and to complement histological studies.

White matter hyperintensities and prepulse inhibition in a mixed elderly population

Prepulse inhibition (PPI) of the startle response, a measure for sensorimotor gating, exhibits a relatively high inter-individual variability in elderly subjects. The aim of this study was to investigate whether white matter hyperintensities (WMH), frequently identified on cranial magnetic resonance imaging (MRI) in elderly subjects with and without cognitive impairment, may contribute to variations in PPI. A passive acoustic PPI paradigm was applied in 92 human subjects (53 healthy and 39 patients with Alzheimer's disease or mild cognitive impairment) between 60 and 85years of age. WMH were rated visually on craniel MRI FLAIR images using the Fazekas scale. WMH were identified in 70% of all subjects. The latency to peak of the startle response increased significantly with increasing WMH load, whereas the inhibition of the startle response (PPI) was neither significantly related to the degree of WMH nor to cognitive performance. We conclude that the presence of WMH in the fronto-striatal brain circuit may affect the latency of the startle response, but not information processing in elderly subjects.