Sanford Auerbach

Genome-wide Analysis of Genetic Loci Associated With Alzheimer Disease

CONTEXT Genome-wide association studies (GWAS) have recently identified CLU, PICALM, and CR1 as novel genes for late-onset Alzheimer disease (AD). OBJECTIVES To identify and strengthen additional loci associated with AD and confirm these in an independent sample and to examine the contribution of recently identified genes to AD risk prediction in a 3-stage analysis of new and previously published GWAS on more than 35,000 persons (8371 AD cases). DESIGN, SETTING, AND PARTICIPANTS In stage 1, we identified strong genetic associations (P < 10(-3)) in a sample of 3006 AD cases and 14,642 controls by combining new data from the population-based Cohorts for Heart and Aging Research in Genomic Epidemiology consortium (1367 AD cases [973 incident]) with previously reported results from the Translational Genomics Research Institute and the Mayo AD GWAS. We identified 2708 single-nucleotide polymorphisms (SNPs) with P < 10(-3). In stage 2, we pooled results for these SNPs with the European AD Initiative (2032 cases and 5328 controls) to identify 38 SNPs (10 loci) with P < 10(-5). In stage 3, we combined data for these 10 loci with data from the Genetic and Environmental Risk in AD consortium (3333 cases and 6995 controls) to identify 4 SNPs with P < 1.7x10(-8). These 4 SNPs were replicated in an independent Spanish sample (1140 AD cases and 1209 controls). Genome-wide association analyses were completed in 2007-2008 and the meta-analyses and replication in 2009. MAIN OUTCOME MEASURE Presence of Alzheimer disease. RESULTS Two loci were identified to have genome-wide significance for the first time: rs744373 near BIN1 (odds ratio [OR],1.13; 95% confidence interval [CI],1.06-1.21 per copy of the minor allele; P = 1.59x10(-11)) and rs597668 near EXOC3L2/BLOC1S3/MARK4 (OR, 1.18; 95% CI, 1.07-1.29; P = 6.45x10(-9)). Associations of these 2 loci plus the previously identified loci CLU and PICALM with AD were confirmed in the Spanish sample (P < .05). However, although CLU and PICALM were confirmed to be associated with AD in this independent sample, they did not improve the ability of a model that included age, sex, and APOE to predict incident AD (improvement in area under the receiver operating characteristic curve from 0.847 to 0.849 in the Rotterdam Study and 0.702 to 0.705 in the Cardiovascular Health Study). CONCLUSIONS Two genetic loci for AD were found for the first time to reach genome-wide statistical significance. These findings were replicated in an independent population. Two recently reported associations were also confirmed. These loci did not improve AD risk prediction. While not clinically useful, they may implicate biological pathways useful for future research.

Head injury and the risk of AD in the MIRAGE study

Objectives: It has been suggested in some studies that head injury is a risk factor for AD, and that this risk is heightened among carriers of the APOE-ε4 allele. We examined the effects of head injury and APOE genotype on AD risk in a large family study. Subjects: A total of 2,233 probands who met criteria for probable or definite AD and their 14,668 first-degree family members (4,465 parents, 7,694 siblings, and 2,509 spouses) were ascertained at 13 centers in the United States, Canada, and Germany participating in the MIRAGE (Multi-Institutional Research in Alzheimer Genetic Epidemiology) project. Information on head injury was collected by interview of multiple informants and review of medical records. Nondemented relatives and spouses served as control subjects for this study. Methods: Odds of AD for head trauma with or without loss of consciousness were computed by comparing probands with unaffected spouses using conditional logistic regression analysis. To account for the unique biologic relationship between probands and their parents and siblings, odds of AD were computed using a generalized estimating equation (GEE) Poisson regression approach. GEE logistic regression was used to examine the joint effects of APOE genotype and head injury on the odds of AD in probands and a control group comprised of unaffected siblings and spouses. Results: Comparison of probands with their unaffected spouses yielded odds ratios for AD of 9.9 (95% CI, 6.5 to 15.1) for head injury with loss of consciousness and 3.1 (2.3 to 4.0) for head injury without loss of consciousness. The corresponding odds derived from the comparison of probands with their parents and sibs were 4.0 (2.9 to 5.5) for head injury with loss of consciousness and 2.0 (1.5 to 2.7) for head injury without loss of consciousness. Head injury without loss of consciousness did not significantly increase the risk of AD in spouses (OR = 1.3; 95% CI, 0.4 to 4.1). The joint effects of head injury and APOE genotype were evaluated in a subsample of 942 probands and 327 controls (spouses and siblings). Head injury increased the odds of AD to a greater extent among those lacking ε4 (OR = 3.3) than among ε4 heterozygotes (OR = 1.8) or homozygotes (OR = 1.3). Conclusion: Head injury is a risk factor for AD. The magnitude of the risk is proportional to severity and heightened among first-degree relatives of AD patients. The influence of head injury on the risk of AD appears to be greater among persons lacking APOE-ε4 compared with those having one or two ε4 alleles, suggesting that these risk factors may have a common biologic underpinning.

Association of Plasma Leptin Levels With Incident Alzheimer Disease and MRI Measures of Brain Aging

CONTEXT The adipokine leptin facilitates long-term potentiation and synaptic plasticity in the hippocampus, promotes beta-amyloid clearance, and improves memory function in animal models of aging and Alzheimer disease (AD). OBJECTIVE To relate baseline circulating leptin concentrations in a community-based sample of individuals without dementia to incident dementia and AD during follow-up and magnetic resonance imaging (MRI) measures of brain aging in survivors. DESIGN, SETTING, AND PARTICIPANTS Prospective study of plasma leptin concentrations measured in 785 persons without dementia (mean [SD] age, 79 [5] years; 62% female), who were in the Framingham original cohort at the 22nd examination cycle (1990-1994). A subsample of 198 dementia-free survivors underwent volumetric brain MRI between 1999 and 2005, approximately 7.7 years after leptin was assayed. Two measures of brain aging, total cerebral brain volume and temporal horn volume (which is inversely related to hippocampal volume) were assessed. MAIN OUTCOME MEASURE Incidence of dementia and AD during follow-up until December 31, 2007. RESULTS During a median follow-up of 8.3 years (range, 0-15.5 years), 111 participants developed incident dementia; 89 had AD. Higher leptin levels were associated with a lower risk of incident dementia and AD in multivariable models (hazard ratio per 1-SD increment in log leptin was 0.68 [95% confidence interval, 0.54-0.87] for all-cause dementia and 0.60 [95% confidence interval, 0.46-0.79] for AD). This corresponds to an absolute AD risk over a 12-year follow-up of 25% for persons in the lowest quartile (first quartile) vs 6% for persons in the fourth quartile of sex-specific leptin levels. In addition, a 1-SD elevation in plasma leptin level was associated with higher total cerebral brain volume and lower temporal horn volume, although the association of leptin level with temporal horn volume did not reach statistical significance. CONCLUSION Circulating leptin was associated with a reduced incidence of dementia and AD and with cerebral brain volume in asymptomatic older adults.

Thyroid Function and the Risk of Alzheimer Disease : The Framingham Study

BACKGROUND Clinical hypothyroidism and hyperthyroidism are recognized causes of reversible dementia, but previous studies relating thyrotropin levels to cognitive performance in clinically euthyroid persons have yielded inconsistent results. METHODS We related serum thyrotropin concentrations measured at baseline (March 1977-November 1979) to the risk of Alzheimer disease (AD) in 1864 cognitively intact, clinically euthyroid Framingham original cohort participants (mean age, 71 years; 59% women). Sex-specific Cox proportional hazards models were constructed using tertiles of thyrotropin concentration (tertile 2 as the referent) and adjusting for age, apolipoprotein E epsilon4 allele status, educational level, plasma homocysteine level, current smoking, body mass index, prevalent stroke, and atrial fibrillation. RESULTS During a mean follow-up of 12.7 years (range, 1-25 years), 209 participants (142 women) developed AD. Women in the lowest (<1.0 mIU/L) and highest (>2.1 mIU/L) tertiles of serum thyrotropin concentration were at increased risk for AD (multivariate-adjusted hazard ratio, 2.39 [95% confidence interval, 1.47-3.87] [P < .001] and 2.15 [95% confidence interval, 1.31-3.52] [P = .003], respectively) compared with those in the middle tertile. Thyrotropin levels were not related to AD risk in men. Analyses excluding individuals receiving thyroid supplementation did not significantly alter these relationships. In analyses limited to participants with serum thyrotropin levels of 0.1 to 10.0 mIU/L, the U-shaped relationship between thyrotropin level and AD risk was maintained in women but not when analyses were limited to those with thyrotropin levels of 0.5 to 5.0 mIU/L. CONCLUSION Low and high thyrotropin levels were associated with an increased risk of incident AD in women but not in men.

Activation of phasic pontine‐wave generator in the rat: a mechanism for expression of plasticity‐related genes and proteins in the dorsal hippocampus and amygdala

A number of behavioral studies have emphasized the importance of interactions between the pontine‐wave (P‐wave) generator and the dorsal hippocampus (DH) in two‐way active avoidance (TWAA) memory processing; however, the direct involvement of the P‐wave generator in the TWAA training trial‐induced molecular events in the DH and amygdala has not been systematically evaluated. Here we demonstrate that the TWAA learning training trials activate P‐wave generator, and increase phosphorylation of CREB (pCREB) and expression of activity‐regulated cytoskeletal‐associated (Arc) protein, as well as messenger ribonucleic acid (mRNAs) of Arc, brain‐derived nerve growth factor (BDNF) and early growth response‐1 (Egr‐1) in the DH and amygdala. Selective elimination of P‐wave‐generating cells abolished P‐wave activity and suppressed TWAA learning training trial‐induced expression of pCREB and Arc proteins and Arc, BDNF and Egr‐1 mRNAs in the DH and amygdala. Following a session of TWAA training, all rats were equal in terms of time spent in wakefulness, slow‐wave sleep and rapid eye movement (REM) sleep irrespective of P‐wave lesions. The second set of experiments demonstrated that localized cholinergic stimulation of the P‐wave generator increased expression of Arc, BDNF and Egr‐1 mRNAs in the DH. Together, these findings provide the first direct evidence that activation of P‐wave‐generating cells is critically involved in the TWAA training trial‐induced expression of plasticity‐related genes in the DH and amygdala. These findings are discussed in relation to the role of P‐wave generator activation for the REM sleep‐dependent development and cognitive functions of the brain.

Effect of continuous positive airway pressure treatment on seizure control in patients with obstructive sleep apnea and epilepsy

In patients with epilepsy, improvement in seizure control with treatment of coexisting obstructive sleep apnea (OSA) has been reported, but there is lack of data on the effect of continuous positive airway pressure (CPAP) compliance on seizure control in these patients. We examined the variability in seizure frequency in patients who were CPAP compliant and those who were not CPAP compliant. We undertook a retrospective review of clinical and polysomnographic data of adult patients with OSA and epilepsy seen at the Boston University Medical Center Epilepsy and Sleep Clinics between 2000 and 2010. Data were reviewed for CPAP compliance and seizure frequency after at least 6 months of CPAP use. Only patients with no changes in antiepileptic drug regimens during CPAP trial were included. Of the 660 patients identified, 41 fulfilled inclusion criteria, of whom 28 were CPAP compliant and 13 were not CPAP compliant. In the compliant group, CPAP use led to decreased seizure frequency from 1.8 per month to 1 per month (p = 0.01). In the noncompliant group, no significant difference in seizure frequency was noted between baseline (2.1 per month) and at follow‐up (1.8 per month, p = 0.36). Sixteen of 28 CPAP‐compliant subjects were seizure free, whereas only 3 of 13 non‐CPAP compliant subjects were seizure free [relative risk (RR) 1.54, p = 0.05]. Patients with epilepsy and OSA not compliant with CPAP treatment are at higher risk of seizures than are CPAP‐compliant patients. To validate this observation, further prospective studies are warranted.

The underdiagnosis of sleep disorders in patients with multiple sclerosis.

STUDY OBJECTIVES To report at a population level the prevalence of restless legs syndrome, insomnia, and the risk of obstructive sleep apnea in multiple sclerosis patients. Sleep patterns and associations with fatigue and daytime sleepiness were identified. METHODS A cross-sectional study was performed using a written survey that was mailed to 11,400 individuals from the Northern California Chapter of the National Multiple Sclerosis (MS) Society Database who self-identified as having MS. The survey included individual questions relating to demographics as well as several standard validated questionnaires related to primary sleep disorders, sleepiness, fatigue severity, and sleep patterns. RESULTS Among the 11,400 surveys mailed out, 2,810 (24.6%) were returned. Of these, 2,375 (84.5%) met the inclusion criteria. Among the completed surveys, 898 (37.8%) screened positive for obstructive sleep apnea, 746 (31.6%) for moderate to severe insomnia, and 866 (36.8%) for restless legs syndrome. In contrast, only 4%, 11%, and 12% of the cohort reported being diagnosed by a health care provider with obstructive sleep apnea, insomnia, and restless legs syndrome, respectively. Excessive daytime sleepiness was noted in 30% of respondents based on the Epworth Sleepiness Scale. More than 60% of the respondents reported an abnormal level of fatigue based on the Fatigue Severity Scale. Both abnormal fatigue and sleepiness scores were associated with screening positive for obstructive sleep apnea, insomnia, and restless legs syndrome. CONCLUSION A significant percentage of MS subjects in our sample screened positive for one or more sleep disorders. The vast majority of these sleep disorders were undiagnosed. Greater attention to sleep problems in this population is warranted, especially in view of fatigue being the most common and disabling symptom of MS.

REM and NREM sleep mentation.

We review the literature on the neurobiology of rapid eye movement (REM) and non-rapid eye movement (NREM) sleep states and associated dreams. REM is associated with enhanced activation of limbic and amygdalar networks and decreased activation in dorsal prefrontal regions while stage II NREM is associated with greater cortical activation than REM. Not surprisingly, these disparate brain activation patterns tend to be associated with dramatically different dream phenomenologies and dream content. We present two recent studies which content-analyzed hundreds of dream reports from REM and NREM sleep states. These studies demonstrated that dreamer-initiated aggressive social interactions were more characteristic of REM than NREM, and dreamer-initiated friendliness was more characteristic of NREM than REM reports. Both REM and NREM dreams therefore may function to simulate opposing types of social interactions, with the REM state specializing in simulation of aggressive interactions and the NREM state specializing in simulation of friendly interactions. We close our review with a summary of evidence that dream content variables significantly predict daytime mood and social interactions.

Hallucinations, Dreaming, and Frequent Dozing in Parkinson Disease: Impact of Right-hemisphere Neural Networks

ObjectiveTo relate sleep disturbances in Parkinson disease (PD) to hemispheric asymmetry of initial presentation. BackgroundSleep disturbances are common in PD arising from the neurodegenerative process underlying the disease, which is usually lateralized at onset. Patients with left-side Parkinson disease onset (LPD: right hemisphere dysfunction) exhibit reduced vigilance relative to those with right-side Parkinson disease onset (RPD: left hemisphere dysfunction), leading us to hypothesize that sleep-related disturbances, particularly excessive daytime sleepiness, would be more severe for LPD than for RPD. MethodsThirty-one nondemented participants with PD (17 RPD and 14 LPD) and 17 age-matched control (CO) participants with chronic health conditions were administered the Parkinson Disease Sleep Scale and polysomnography was performed on a subset of the PD participants. ResultsBoth PD subgroups exhibited more nighttime motor symptoms than the CO group, but only LPD endorsed more nocturnal hallucinations and daytime dozing. Controlling for mood additionally revealed more vivid dreaming in LPD than RPD. There were no significant differences between LPD and RPD on measures of sleep architecture. ConclusionsIncreased dreaming, hallucinations, and daytime somnolescence in LPD may be related to changes in right-hemisphere neural networks implicated in the generation and control of visual images, arousal, and vigilance. Our results underscore the need to consider side of onset in regard to sleep disturbances in PD.

Clock Drawing Test Ratings by Dementia Specialists: Interrater Reliability and Diagnostic Accuracy

The authors conducted a study of clock drawing test scoring by dementia specialists to determine interrater reliability and diagnostic accuracy. The authors randomly assigned 25 clocks from each of six predetermined groups based on consensus diagnosis (cognitive comparison subjects, subjects with a memory complaint but with normal neuropsychological testing, subjects with probable and possible mild cognitive impairment, and subjects with possible and probable Alzheimers disease) to dementia specialists for blinded scoring using a binary yes/no impairment system and a 0-10 scale as subjectively determined by each individual clinician rater. The authors collapsed the six groups into three (comparison subjects, mild cognitive impairment patients, and Alzheimers disease patients) and analyzed interrater reliability, sensitivity, and specificity for consensus diagnosis of mild cognitive impairment and Alzheimers disease. The authors found excellent interrater reliability, sensitivity, and specificity for predicting consensus diagnosis. The 0-10 clock drawing test rating scale was more predictive of consensus diagnosis than the binary impairment scale. Based on rating systems, clock drawing test scoring by dementia clinicians had excellent interrater reliability and sensitivity for differentiating the mild Alzheimers disease subjects from comparison subjects.