Short-term clinical outcomes for stages of NIA-AA preclinical Alzheimer disease

OBJECTIVE

Recommendations for the diagnosis of preclinical Alzheimer disease (AD) have been formulated by a workgroup of the National Institute on Aging and Alzheimer's Association. Three stages of preclinical AD were described. Stage 1 is characterized by abnormal levels of β-amyloid. Stage 2 represents abnormal levels of β-amyloid and evidence of brain neurodegeneration. Stage 3 includes the features of stage 2 plus subtle cognitive changes. Stage 0, not explicitly defined in the criteria, represents subjects with normal biomarkers and normal cognition. The ability of the recommended criteria to predict progression to cognitive impairment is the crux of their validity.

METHODS

Using previously developed operational definitions of the 3 stages of preclinical AD, we examined the outcomes of subjects from the Mayo Clinic Study of Aging diagnosed as cognitively normal who underwent brain MRI or [(18)F]fluorodeoxyglucose and Pittsburgh compound B PET, had global cognitive test scores, and were followed for at least 1 year.

RESULTS

Of the 296 initially normal subjects, 31 (10%) progressed to a diagnosis of mild cognitive impairment (MCI) or dementia (27 amnestic MCI, 2 nonamnestic MCI, and 2 non-AD dementias) within 1 year. The proportion of subjects who progressed to MCI or dementia increased with advancing stage (stage 0, 5%; stage 1, 11%; stage 2, 21%; stage 3, 43%; test for trend, p < 0.001).

CONCLUSIONS

Despite the short follow-up period, our operationalization of the new preclinical AD recommendations confirmed that advancing preclinical stage led to higher proportions of subjects who progressed to MCI or dementia.

Voxel-based morphometry in patients with obsessive-compulsive behaviors in behavioral variant frontotemporal dementia

BACKGROUND AND PURPOSE

  Obsessions and compulsive (OC) behaviors are a frequent feature of behavioral variant frontotemporal dementia (bvFTD), but their structural correlates have not been definitively established.

METHODS

Patients with bvFTD presenting to the Mayo Clinic Alzheimer's Disease Research Center were recruited. Each patient's caregiver was given the Yale-Brown Obsessive-Compulsive scale (YBOCS) to document the type and presence of OC behaviors and to rate their severity. All subjects underwent standardized magnetic resonance imaging (MRI) that was evaluated using voxel-based morphometry (VBM). Seventeen patients with bvFTD were recruited, and 11 were included in the study and compared with 11 age- and gender-matched controls. Six were excluded for lack of MRI at the time of survey or a pre-existing neurodegenerative condition.

RESULTS

Nine of the 11 reported OC behaviors, with the most frequent compulsions being checking, hoarding, ordering/arranging, repeating rituals, and cleaning. In the VBM analysis, total YBOCS score correlated with gray matter loss in the bilateral globus pallidus, left putamen, and in the lateral temporal lobe, particularly the left middle and inferior temporal gyri (P < 0.001 uncorrected for multiple comparisons).

CONCLUSIONS

Obsessive-compulsive behaviors were frequent among these patients. The correlation with basal ganglia atrophy may point to involvement of frontal subcortical neuronal networks. Left lateral temporal lobe volume loss probably reflects the number of MAPT mutation patients included but also provides additional data implicating temporal lobe involvement in OC behaviors.

The incidence of MCI differs by subtype and is higher in men: the Mayo Clinic Study of Aging

OBJECTIVE

Although incidence rates for mild cognitive impairment (MCI) have been reported, few studies were specifically designed to measure the incidence of MCI and its subtypes using published criteria. We estimated the incidence of amnestic MCI (aMCI) and nonamnestic MCI (naMCI) in men and women separately.

METHODS

A population-based prospective cohort of Olmsted County, MN, residents ages 70-89 years on October 1, 2004, underwent baseline and 15-month interval evaluations that included the Clinical Dementia Rating scale, a neurologic evaluation, and neuropsychological testing. A panel of examiners blinded to previous diagnoses reviewed data at each serial evaluation to assess cognitive status according to published criteria.

RESULTS

Among 1,450 subjects who were cognitively normal at baseline, 296 developed MCI. The age- and sex-standardized incidence rate of MCI was 63.6 (per 1,000 person-years) overall, and was higher in men (72.4) than women (57.3) and for aMCI (37.7) than naMCI (14.7). The incidence rate of aMCI was higher for men (43.9) than women (33.3), and for subjects with ≤12 years of education (42.6) than higher education (32.5). The risk of naMCI was also higher for men (20.0) than women (10.9) and for subjects with ≤12 years of education (20.3) than higher education (10.2).

CONCLUSIONS

The incidence rates for MCI are substantial. Differences in incidence rates by clinical subtype and by sex suggest that risk factors for MCI should be investigated separately for aMCI and naMCI, and in men and women.

APOE modifies the association between Aβ load and cognition in cognitively normal older adults

OBJECTIVE

To determine the relationship between β-amyloid (Aβ) load as measured by [(11)C]-Pittsburgh compound B (PiB) PET and cognitive function in cognitively normal older adults.

METHODS

We studied 408 cognitively normal older adults who participated in the population-based Mayo Clinic Study of Aging (MCSA) from January 2009 through March 2011. The participants underwent PiB PET and neuropsychometric testing within 6 months. The association between PiB retention and cognitive function was measured by partial correlation and an interaction with APOE status was tested using linear regression after adjusting for age, sex, and education.

RESULTS

Higher PiB retention was associated with cognitive performance (Spearman partial r = -0.18; p < 0.01), specifically the memory, language, attention/executive, and visual-spatial processing domains in the whole group of participants. The association between PiB retention and cognition was modified by the APOE status on linear regression analysis even after controlling for the differences in the distribution of PiB values among APOE ε4 carriers and noncarriers (p = 0.02). Cognitive performance was associated with the Aβ deposition in the frontal, temporal, and parietal lobe association cortices in APOE ε4 carriers on SPM analysis (p < 0.001).

CONCLUSION

There is a modest association between PiB retention and cognitive function in cognitively normal older adults and this relationship between Aβ load and cognitive function is modified by APOE status. Whereas Aβ load is associated with greater cognitive impairment in APOE ε4 carriers, the cognitive function in APOE ε4 noncarriers is influenced less by the Aβ load, suggesting that APOE isoforms modulate the harmful effects of Aβ on cognitive function.

Age-related changes in the default mode network are more advanced in Alzheimer disease

OBJECTIVE

To investigate age-related default mode network (DMN) connectivity in a large cognitively normal elderly cohort and in patients with Alzheimer disease (AD) compared with age-, gender-, and education-matched controls.

METHODS

We analyzed task-free-fMRI data with both independent component analysis and seed-based analysis to identify anterior and posterior DMNs. We investigated age-related changes in connectivity in a sample of 341 cognitively normal subjects. We then compared 28 patients with AD with 56 cognitively normal noncarriers of the APOE ε4 allele matched for age, education, and gender.

RESULTS

The anterior DMN shows age-associated increases and decreases in fontal lobe connectivity, whereas the posterior DMN shows mainly age-associated declines in connectivity throughout. Relative to matched cognitively normal controls, subjects with AD display an accelerated pattern of the age-associated changes described above, except that the declines in frontal lobe connectivity did not reach statistical significance. These changes survive atrophy correction and are correlated with cognitive performance.

CONCLUSIONS

The results of this study indicate that the DMN abnormalities observed in patients with AD represent an accelerated aging pattern of connectivity compared with matched controls.

Effect of public deliberation on attitudes toward surrogate consent for dementia research

OBJECTIVE

To assess the informed, deliberative views of the older general public toward a policy of allowing surrogate consent for Alzheimer disease (AD) research.

METHODS

A total of 503 persons aged 50+ recruited by random digit dialing were randomly assigned to 1 of 3 groups: deliberation, education, or control. The deliberation group attended an all-day education/peer deliberation session; the education group received written information only. Participants were surveyed at baseline, after deliberation session (or equivalent time), and 1 month after the session, regarding their attitudes toward a policy of allowing surrogate consent for research studies of varying risks and potential benefits (a lumbar puncture study, a drug randomized controlled trial, a vaccine randomized controlled trial, and an early phase gene transfer trial).

RESULTS

At baseline, a policy of surrogate consent for AD research was supported by 55%-91%, depending on the scenario. The education group had a transient increase in support for one research scenario after receiving the information materials. In the deliberation group, support for surrogate consent was higher after deliberation for all scenarios (67% to 97%), with much of the increase sustained 1 month after the deliberation session. No changes occurred in the control group. The study's limitations include self-selection of participants due to the demanding nature of attendance at the deliberation sessions.

CONCLUSIONS

This sample of the older general public generally supported a policy of surrogate consent for AD research at baseline. Their support increased with democratic deliberation involving informed, in-depth exploration of the relevant scientific and ethical issues.

Magnetic resonance spectroscopy, β-amyloid load, and cognition in a population-based sample of cognitively normal older adults

OBJECTIVE

To determine the relationship between proton magnetic resonance spectroscopy ((1)H MRS) metabolites and β-amyloid (Aβ) load and the effects of Aβ load on the association between (1)H MRS metabolites and cognitive function in cognitively normal older adults.

METHODS

We studied 311 cognitively normal older adults who participated in the population-based Mayo Clinic Study of Aging from January 2009 through September 2010. Participants underwent (11)C-Pittsburgh compound B (PiB) PET, (1)H MRS from the posterior cingulate gyri, and neuropsychometric testing to assess memory, attention/executive, language, and visual-spatial domain functions within 6 months. Partial Spearman rank order correlations were adjusted for age, sex, and education.

RESULTS

Higher PiB retention was associated with abnormal elevations in myoinositol (mI)/creatine (Cr) (partial r(s) = 0.17; p = 0.003) and choline (Cho)/Cr (partial r(s) = 0.13; p = 0.022) ratios. Higher Cho/Cr was associated with worse performance on Auditory Verbal Learning Test Delayed Recall (partial r(s) = -0.12; p = 0.04), Trail Making Test Part B (partial r(s) = 0.12; p = 0.04), Wechsler Adult Intelligence Scale-Revised (WAIS-R) Digit Symbol (partial r(s) = -0.18; p < 0.01), and WAIS-R Block Design (partial r(s) = -0.12; p = 0.03). Associations between (1)H MRS metabolites and cognitive function were not different among participants with high vs low PiB retention.

CONCLUSION

In cognitively normal older adults, the (1)H MRS metabolite ratios mI/Cr and Cho/Cr are associated with the preclinical pathologic processes in the Alzheimer disease cascade. Higher Cho/Cr is associated with worse performance on domain-specific cognitive tests independent of Aβ load, suggesting that Cho/Cr elevation may also be dependent on other preclinical dementia pathologies characterized by Cho/Cr elevation such as Lewy body or ischemic vascular disease in addition to Aβ load.

Altered functional connectivity in asymptomatic MAPT subjects: a comparison to bvFTD

OBJECTIVE

To determine whether functional connectivity is altered in subjects with mutations in the microtubule associated protein tau (MAPT) gene who were asymptomatic but were destined to develop dementia, and to compare these findings to those in subjects with behavioral variant frontotemporal dementia (bvFTD).

METHODS

In this case-control study, we identified 8 asymptomatic subjects with mutations in MAPT and 8 controls who screened negative for mutations in MAPT. Twenty-one subjects with a clinical diagnosis of bvFTD were also identified and matched to 21 controls. All subjects had resting-state fMRI. In-phase functional connectivity was assessed between a precuneus seed in the default mode network (DMN) and a fronto-insular cortex seed in the salience network, and the rest of the brain. Atlas-based parcellation was used to assess functional connectivity and gray matter volume across specific regions of interest.

RESULTS

The asymptomatic MAPT subjects and subjects with bvFTD showed altered functional connectivity in the DMN, with reduced in-phase connectivity in lateral temporal lobes and medial prefrontal cortex, compared to controls. Increased in-phase connectivity was also observed in both groups in the medial parietal lobe. Only the bvFTD group showed altered functional connectivity in the salience network, with reduced connectivity in the fronto-insular cortex and anterior cingulate. Gray matter loss was observed across temporal, frontal, and parietal regions in bvFTD, but not in the asymptomatic MAPT subjects.

CONCLUSIONS

Functional connectivity in the DMN is altered in MAPT subjects before the occurrence of both atrophy and clinical symptoms, suggesting that changes in functional connectivity are early features of the disease.

Predicting survival in frontotemporal dementia with motor neuron disease

OBJECTIVE

To determine whether clinical and demographic features are associated with prognosis in patients with frontotemporal dementia and motor neuron disease (FTD-MND).

METHODS

This was a case series of FTD-MND categorized according to behavioral- or language-dominant symptoms at presentation and throughout the disease course. Demographic, clinical, imaging, and survival data were analyzed with respect to dominant FTD-MND type. Voxel-based morphometry was used to assess and compare regional patterns of atrophy in behavioral- and language-dominant FTD-MND types.

RESULTS

Of the 56 patients with FTD-MND who were identified, 31 had dominant behavioral symptoms and 25 had dominant language symptoms; 53 patients had died. A survival difference was present between types, with patients with behavioral-dominant symptoms surviving 506 days longer than patients with language-dominant symptoms (mean 1,397 vs 891 days; p = 0.002). There was also a difference in time from diagnosis to death (p = 0.02) between groups. Patients with language-dominant disease were more likely to have bulbar-onset than limb-onset motor neuron disease (MND) (p = 0.01). There was a similar pattern of frontal and temporal lobe atrophy in both types, although there was some evidence for the behavioral type to have more frontal atrophy and the language type to have more left temporal atrophy.

CONCLUSIONS

In our series of patients with FTD-MND, language-dominant FTD-MND was associated with bulbar-onset MND and a shorter survival. There was also evidence that the dominant FTD-MND type is related to differences in brain atrophy patterns.

Trajectories of brain and hippocampal atrophy in FTD with mutations in MAPT or GRN

OBJECTIVE

To use multiple serial MRI to assess rates and trajectories of brain and hippocampal atrophy in subjects with frontotemporal dementia (FTD) with progranulin (GRN) or microtubule-associated protein tau (MAPT) gene mutations.

METHODS

In this case-control study, we identified 8 subjects with mutations in GRN and 12 subjects with mutations in MAPT who had at least 2 serial MRIs. Serial MRIs were registered to baseline MRI for each subject using 9 df registration and rate of whole brain atrophy was calculated using the boundary-shift integral. Hippocampal volume was measured using Freesurfer. Mixed effects linear regression models were used to model volume change over time in both groups after adjusting for head size, age at baseline, and disease duration at baseline.

RESULTS

The annual rate of whole brain atrophy in the MAPT subjects was 2.4% per year (95% confidence interval [CI] 1.9-2.8). The GRN subjects showed a higher rate of whole brain atrophy at 3.5% per year (95% CI 2.8-4.2; p = 0.01). Rates of hippocampal atrophy were not different across the groups (MAPT = 7.8% [95% CI 3.9-12], GRN = 6.5% [95% CI 1.7-11], p = 0.66). Rates of whole brain atrophy in GRN, and hippocampal atrophy in MAPT, were associated with age, with older subjects showing slower rates of atrophy (p = 0.01 and p < 0.001).

CONCLUSIONS

Subjects with FTD with GRN mutations have a faster rate of whole brain atrophy than subjects with FTD with MAPT mutations, with similar rates of hippocampal atrophy. Rates of atrophy in both groups were associated with age. These findings are important for future treatment trials in FTD that use rates of atrophy as an outcome measure.

Diffusion tensor imaging and cognitive function in older adults with no dementia

OBJECTIVE

To determine the patterns of diffusivity associated with cognitive domain functions in older adults without dementia.

METHODS

We studied older adults without dementia (n = 220) who underwent neuropsychometric testing and a diffusion tensor imaging (DTI) examination at 3 T in a cross-sectional study. Memory, language, attention/executive function, and visual-spatial processing domains were assessed within 4 months of the MRI examination. A fluid-attenuated inversion recovery-based DTI sequence that enabled uncontaminated cortical diffusion measurements was performed. Associations between cortical mean diffusivity (MD) and cognitive function were tested using voxel-based regression analysis. Association between tract diffusivity and cognitive function was tested with regions of interest drawn on color-coded fractional anisotropy (FA) maps.

RESULTS

Memory function was associated with the medial temporal lobe cortical MD on voxel-based analysis (p < 0.001, corrected for multiple comparisons), and inferior longitudinal fasciculus and posterior and anterior cingulum FA on tract-based analysis (p < 0.001). Language function was associated with the left temporal lobe cortical MD (p < 0.001, corrected for multiple comparisons), inferior longitudinal fasciculus, fornix, and posterior cingulum FA (p < 0.05). Attention and executive function was associated with the posterior and anterior cingulum FA, and visual-spatial function was associated with posterior cingulum FA (p < 0.01).

CONCLUSION

Specific cognitive domain functions are associated with distinct patterns of cortical and white matter diffusivity in elderly with no dementia. Posterior cingulum tract FA was associated with all 4 cognitive domain functions, in agreement with the hypothesis that the posterior cingulate cortex is the main connectivity hub for cognitive brain networks. Microstructural changes identified on DTI may be associated with neurodegenerative pathologies underlying cognitive changes in older adults without dementia.

Vascular risk factors and longitudinal changes on brain MRI: the ARIC study

OBJECTIVE

To evaluate associations between vascular risk factors and changes in burden of infarcts, ventricular size (VS), sulcal widening (SW), and white matter hyperintensities (WMH) in an initially middle-aged, biracial cohort from the Atherosclerosis Risk in Communities (ARIC) study.

METHODS

Initial brain magnetic resonance (MR) scans and evaluations for vascular risk factors were performed in 1,812 ARIC participants in 1994-1995. In 2004-2006, 1,130 ARIC participants underwent repeat MR scans. MR scans were rated using a validated 9-point scale for VS, SW, and WMH. Infarcts were recorded. Multiple logistic regression analysis was used to assess associations between vascular risk factors and change between MR scans of one or more grades in VS, SW, WMH, or appearance of new infarcts, controlling for age, sex, and race.

RESULTS

At baseline, the 1,112 participants with usable scans (385 black women, 200 black men, 304 white women, 223 white men) had a mean age of 61.7 ± 4.3 years. In adjusted models, diabetes at baseline was associated with incident infarcts (odds ratio [OR] 1.95, 95% confidence interval [CI] 1.29-2.95) and worsening SW (OR 2.10, 95% CI 1.36-3.24). Hypertension at baseline was associated with incident infarcts (OR 1.73, 95% CI 1.23-2.42). In subjects with the highest tertile of fasting blood sugar and systolic blood pressure at baseline, the risk of incident infarcts was 3.68 times higher (95% CI 1.89-7.19) than those in the lowest tertile for both.

CONCLUSION

Both atrophic and ischemic imaging changes were driven by altered glycemic and blood pressure control beginning in midlife.

Classification of primary progressive aphasia and its variants

This article provides a classification of primary progressive aphasia (PPA) and its 3 main variants to improve the uniformity of case reporting and the reliability of research results. Criteria for the 3 variants of PPA--nonfluent/agrammatic, semantic, and logopenic--were developed by an international group of PPA investigators who convened on 3 occasions to operationalize earlier published clinical descriptions for PPA subtypes. Patients are first diagnosed with PPA and are then divided into clinical variants based on specific speech and language features characteristic of each subtype. Classification can then be further specified as "imaging-supported" if the expected pattern of atrophy is found and "with definite pathology" if pathologic or genetic data are available. The working recommendations are presented in lists of features, and suggested assessment tasks are also provided. These recommendations have been widely agreed upon by a large group of experts and should be used to ensure consistency of PPA classification in future studies. Future collaborations will collect prospective data to identify relationships between each of these syndromes and specific biomarkers for a more detailed understanding of clinicopathologic correlations.

Does TDP-43 type confer a distinct pattern of atrophy in frontotemporal lobar degeneration?

OBJECTIVE

To determine whether TDP-43 type is associated with distinct patterns of brain atrophy on MRI in subjects with pathologically confirmed frontotemporal lobar degeneration (FTLD).

METHODS

In this case-control study, we identified all subjects with a pathologic diagnosis of FTLD with TDP-43 immunoreactive inclusions (FTLD-TDP) and at least one volumetric head MRI scan (n = 42). In each case we applied published criteria for subclassification of FTLD-TDP into FTLD-TDP types 1-3. Voxel-based morphometry was used to compare subjects with each of the different FTLD-TDP types to age- and gender-matched normal controls (n = 30). We also assessed different pathologic and genetic variants within, and across, the different types.

RESULTS

Twenty-two subjects were classified as FTLD-TDP type 1, 9 as type 2, and 11 as type 3. We identified different patterns of atrophy across the types with type 1 showing frontotemporal and parietal atrophy, type 2 predominantly anterior temporal lobe atrophy, and type 3 predominantly posterior frontal atrophy. Within the FTLD-TDP type 1 group, those with a progranulin mutation had significantly more lateral temporal lobe atrophy than those without. All type 2 subjects were diagnosed with semantic dementia. Subjects with a pathologic diagnosis of FTLD with motor neuron degeneration had a similar pattern of atrophy, regardless of whether they were type 1 or type 3.

CONCLUSIONS

Although there are different patterns of atrophy across the different FTLD-TDP types, it appears that genetic and pathologic factors may also affect the patterns of atrophy.

Association of lung function with cognitive decline and dementia: the Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND

Previous studies reported a higher risk of cognitive decline and dementia amongst individuals with impaired lung function. However, many did not adjust for important confounders or did not include women and non-whites.

METHODS

We studied 10,975 men and women aged 47-70 years (23% African-Americans) enrolled in the Atherosclerosis Risk in Communities Study. Pulmonary function tests and a cognitive assessment, including the Delayed Word Recall, the Digit Symbol Substitution, and the World Fluency Tests, were carried out in 1990-1992. Repeated cognitive assessments were performed in 1996-1998 for the entire cohort, and in 1993-1995, and 2004-2006 in 904 eligible individuals. Dementia hospitalization was ascertained through 2005.

RESULTS

In analysis adjusted for lifestyles, APOE genotype, and cardiovascular risk factors, impaired lung function was associated with worse cognitive function at baseline. No association was found between lung function and cognitive decline over time. Impaired lung function at baseline was associated with higher risk of dementia hospitalization during follow-up, particularly amongst younger individuals. The hazard ratios (95% confidence intervals) of dementia hospitalization were 1.6 (0.9, 2.8) and 2.1 (1.2, 3.7) comparing the lowest with the highest quartile of forced expiratory volume in 1 s and forced vital capacity, respectively. Presence of a restrictive ventilatory pattern, but not of an obstructive pattern, was associated with reduced cognitive scores and higher dementia risk.

CONCLUSION

Reduced lung function was associated with worse performance in cognitive assessments and with an increased risk of dementia hospitalization. Future research should determine whether maintaining optimal pulmonary health might prevent cognitive impairment and dementia.

Imaging correlates of pathology in corticobasal syndrome

BACKGROUND

Corticobasal syndrome (CBS) can be associated with different underlying pathologies that are difficult to predict based on clinical presentation. The aim of this study was to determine whether patterns of atrophy on imaging could be useful to help predict underlying pathology in CBS.

METHODS

This was a case-control study of 24 patients with CBS who had undergone MRI during life and came to autopsy. Pathologic diagnoses included frontotemporal lobar degeneration (FTLD) with TDP-43 immunoreactivity in 5 (CBS-TDP), Alzheimer disease (AD) in 6 (CBS-AD), corticobasal degeneration in 7 (CBS-CBD), and progressive supranuclear palsy in 6 (CBS-PSP). Voxel-based morphometry and atlas-based parcellation were used to assess atrophy across the CBS groups and compared to 24 age- and gender-matched controls.

RESULTS

All CBS pathologic groups showed gray matter loss in premotor cortices, supplemental motor area, and insula on imaging. However, CBS-TDP and CBS-AD showed more widespread patterns of loss, with frontotemporal loss observed in CBS-TDP and temporoparietal loss observed in CBS-AD. CBS-TDP showed significantly greater loss in prefrontal cortex than the other groups, whereas CBS-AD showed significantly greater loss in parietal lobe than the other groups. The focus of loss was similar in CBS-CBD and CBS-PSP, although more severe in CBS-CBD.

CONCLUSIONS

Imaging patterns of atrophy in CBS vary according to pathologic diagnosis. Widespread atrophy points toward a pathologic diagnosis of FTLD-TDP or AD, with frontotemporal loss suggesting FTLD-TDP and temporoparietal loss suggesting AD. On the contrary, more focal atrophy predominantly involving the premotor and supplemental motor area suggests CBD or PSP pathology.

TMEM106B regulates progranulin levels and the penetrance of FTLD in GRN mutation carriers

OBJECTIVES

To determine whether TMEM106B single nucleotide polymorphisms (SNPs) are associated with frontotemporal lobar degeneration (FTLD) in patients with and without mutations in progranulin (GRN) and to determine whether TMEM106B modulates GRN expression.

METHODS

We performed a case-control study of 3 SNPs in TMEM106B in 482 patients with clinical and 80 patients with pathologic FTLD-TAR DNA-binding protein 43 without GRN mutations, 78 patients with FTLD with GRN mutations, and 822 controls. Association analysis of TMEM106B with GRN plasma levels was performed in 1,013 controls and TMEM106B and GRN mRNA expression levels were correlated in peripheral blood samples from 33 patients with FTLD and 150 controls.

RESULTS

In our complete FTLD patient cohort, nominal significance was identified for 2 TMEM106B SNPs (top SNP rs1990622, p(allelic) = 0.036). However, the most significant association with risk of FTLD was observed in the subgroup of GRN mutation carriers compared to controls (corrected p(allelic) = 0.0009), where there was a highly significant decrease in the frequency of homozygote carriers of the minor alleles of all TMEM106B SNPs (top SNP rs1990622, CC genotype frequency 2.6% vs 19.1%, corrected p(recessive) = 0.009). We further identified a significant association of TMEM106B SNPs with plasma GRN levels in controls (top SNP rs1990622, corrected p = 0.002) and in peripheral blood samples a highly significant correlation was observed between TMEM106B and GRN mRNA expression in patients with FTLD (r = -0.63, p = 7.7 × 10(-5)) and controls (r = -0.49, p = 2.2 × 10(-10)).

CONCLUSIONS

In our study, TMEM106B SNPs significantly reduced the disease penetrance in patients with GRN mutations, potentially by modulating GRN levels. These findings hold promise for the development of future protective therapies for FTLD.

Prevalence of mild cognitive impairment is higher in men. The Mayo Clinic Study of Aging

OBJECTIVE

We investigated the prevalence of mild cognitive impairment (MCI) in Olmsted County, MN, using in-person evaluations and published criteria.

METHODS

We evaluated an age- and sex-stratified random sample of Olmsted County residents who were 70-89 years old on October 1, 2004, using the Clinical Dementia Rating Scale, a neurologic evaluation, and neuropsychological testing to assess 4 cognitive domains: memory, executive function, language, and visuospatial skills. Information for each participant was reviewed by an adjudication panel and a diagnosis of normal cognition, MCI, or dementia was made using published criteria.

RESULTS

Among 1,969 subjects without dementia, 329 subjects had MCI, with a prevalence of 16.0% (95% confidence interval [CI] 14.4-17.5) for any MCI, 11.1% (95% CI 9.8-12.3) for amnestic MCI, and 4.9% (95% CI 4.0-5.8) for nonamnestic MCI. The prevalence of MCI increased with age and was higher in men. The prevalence odds ratio (OR) in men was 1.54 (95% CI 1.21-1.96; adjusted for age, education, and nonparticipation). The prevalence was also higher in subjects who never married and in subjects with an APOE epsilon3epsilon4 or epsilon4epsilon4 genotype. MCI prevalence decreased with increasing number of years of education (p for linear trend <0.0001).

CONCLUSIONS

Our study suggests that approximately 16% of elderly subjects free of dementia are affected by MCI, and amnestic MCI is the most common type. The higher prevalence of MCI in men may suggest that women transition from normal cognition directly to dementia at a later age but more abruptly.

MRS in presymptomatic MAPT mutation carriers: a potential biomarker for tau-mediated pathology

OBJECTIVE

To determine the proton magnetic resonance spectroscopy ((1)H MRS) changes in carriers of microtubule-associated protein (MAPT) mutations in a case-control study.

METHODS

Patients with MAPT mutations (N279K, V337M, R406W, IVS9-10G>T, P301L) from 5 different families (n = 24) underwent MRI and single voxel (1)H MRS from the posterior cingulate gyrus inferior precuneus at 3 T. Ten of the patients were symptomatic with median Clinical Dementia Rating sum of boxes score (CDR-SOB) of 6.5 and 14 patients were presymptomatic with CDR-SOB of 0. Age- and sex-matched controls (n = 24) were recruited.

RESULTS

Symptomatic MAPT mutation carriers were characterized by decreased N-acetylaspartate/creatine (NAA/Cr) ratio, an index of neuronal integrity, increased myoinositol (mI)/Cr ratio, a possible marker for glial activity, decreased NAA/mI, and hippocampal atrophy (p < 0.001). Whereas presymptomatic MAPT mutation carriers had elevated mI/Cr and decreased NAA/mI (p < 0.001), NAA/Cr levels and hippocampal volumes were not different from controls. Decrease in NAA/Cr (R(2) = 0. 22; p = 0.021) and hippocampal volumes (R(2) = 0.46; p < 0.001) were associated with proximity to the expected or actual age at symptom onset in MAPT mutation carriers.

CONCLUSION

(1)H MRS metabolite abnormalities characterized by an elevated mI/Cr and decreased NAA/mI are present several years before the onset of symptoms in MAPT mutation carriers. The data suggest an ordered sequencing of the (1)H MRS and MRI biomarkers. MI/Cr, a possible index of glial proliferation, precedes the decrease in neuronal integrity marker NAA/Cr and hippocampal atrophy. (1)H MRS may be a useful inclusion biomarker for preventive trials in presymptomatic carriers of MAPT mutations and possibly other proteinopathies.