Yang An

National Institute on Aging, Baltimore, Maryland, United States

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Publications (49)344.14 Total impact

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    ABSTRACT: Excessively elevated resting metabolic rate (RMR) for persons of a certain age, sex, and body composition is a mortality risk factor. Whether elevated RMR constitutes an early marker of health deterioration in older adult has not been fully investigated. Using data from the Baltimore Longitudinal Study of Aging, we hypothesized that higher RMR (i) was cross-sectionally associated with higher multimorbidity and (ii) predicted higher multimorbidity in subsequent follow-ups. The analysis included 695 Baltimore Longitudinal Study of Aging participants, aged 60 or older at baseline, of whom 248 had follow-up data available 2 years later and 109 four years later. Multimorbidity was assessed as number of chronic diseases. RMR was measured by indirect calorimetry and was tested in regression analyses adjusted for covariates age, sex, and dual-energy x-ray absorptiometry-measured total body fat mass and lean mass. Baseline RMR and multimorbidity were positively associated, independent of covariates (p = .002). Moreover, in a three-wave bivariate autoregressive cross-lagged model adjusted for covariates, higher prior RMR predicted greater future multimorbidity above and beyond the cross-sectional and autoregressive associations (p = .034). RMR higher than expected, given age, sex, and body composition, predicts future higher multimorbidity in older adults and may be used as early biomarker of impending health deterioration. Replication and the development of normative data are required for clinical translation. Published by Oxford University Press on behalf of the Gerontological Society of America 2014.
    The Journals of Gerontology Series A Biological Sciences and Medical Sciences 11/2014; · 4.31 Impact Factor
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    ABSTRACT: Background The delineation of the relative temporal trajectories of specific cognitive measures associated with Alzheimer's disease (AD) is important for evaluating preclinical markers and monitoring disease progression. Methods We characterized the temporal trajectories of measures of verbal episodic memory, short-term visual memory, and mental status using data from 895 participants in the Baltimore Longitudinal Study of Aging. Results The California Verbal Learning Test (CVLT) immediate recall was the first measure to decline, followed by CVLT delayed recall. However, further along the disease progression scale, CVLT delayed recall and visual memory changed more rapidly than CVLT immediate recall. Conclusions Our findings reconcile reports of early changes in immediate recall with greater reliance on delayed recall performance in clinical settings. Moreover, the utility of cognitive markers in evaluating AD progression depends on the stage of cognitive decline, suggesting that optimal endpoints in therapeutic trials may vary across different stages of the disease process.
    Alzheimer's and Dementia 11/2014; · 17.47 Impact Factor
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    ABSTRACT: Sphingomyelin metabolism has been linked to several diseases and to longevity. However, few epidemiological studies have quantified individual plasma sphingomyelin species (identified by acyl-chain length and saturation) or their relationship between demographic factors and disease processes. In this study, we determined plasma concentrations of distinct sphingomyelin species in 992 individuals, aged 55 and older, enrolled in the Baltimore Longitudinal Study of Aging. Participants were followed, with serial measures, up to 6 visits and 38 years (3972 total samples). Quantitative analyses were performed on a high-performance liquid chromatography-coupled electrospray ionization tandem mass spectrometer. Linear mixed models were used to assess variation in specific sphingomyelin species and associations with demographics, diseases, medications or lifestyle factors, and plasma cholesterol and triglyceride levels. We found that most sphingomyelin species increased with age. Women had higher plasma levels of all sphingomyelin species and showed steeper trajectories of age-related increases compared to men. African Americans also showed higher circulating sphingomyelin concentrations compared to Caucasians. Diabetes, smoking, and plasma triglycerides were associated with lower levels of many sphingomyelins and dihydrosphingomyelins. Notably, these associations showed specificity to sphingomyelin acyl-chain length and saturation. These results demonstrate that longitudinal changes in circulating sphingomyelin levels are influenced by age, sex, race, lifestyle factors, and diseases. It will be important to further establish the intra-individual age- and sex-specific changes in each sphingomyelin species in relation to disease onset and progression.
    Aging cell 10/2014; · 7.55 Impact Factor
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    ABSTRACT: Multimorbidity increases with aging, but risk factors beyond age are unknown.
    The Journals of Gerontology Series A Biological Sciences and Medical Sciences 08/2014; · 4.31 Impact Factor
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    ABSTRACT: Although overweight and obesity are associated with poor health outcomes in the elderly, the biological bases of obesity-related behaviors during aging are poorly understood. Common variants in the FTO gene are associated with adiposity in children and younger adults as well as with adverse mental health in older individuals. However, it is unclear whether FTO influences longitudinal trajectories of adiposity and other intermediate phenotypes relevant to mental health during aging. We examined whether a commonly carried obesity-risk variant in the FTO gene (rs1421085 single-nucleotide polymorphism) influences adiposity and is associated with changes in brain function in participants within the Baltimore Longitudinal Study of Aging, one of the longest-running longitudinal aging studies in the United States. Our results show that obesity-related risk allele carriers of FTO gene show dose-dependent increments in body mass index during aging. Moreover, the obesity-related risk allele is associated with reduced medial prefrontal cortical function during aging. Consistent with reduced brain function in regions intrinsic to impulse control and taste responsiveness, risk allele carriers of FTO exhibit dose-dependent increments in both impulsivity and intake of fatty foods. We propose that a common neural mechanism may underlie obesity-associated impulsivity and increased consumption of high-calorie foods during aging.Molecular Psychiatry advance online publication, 27 May 2014; doi:10.1038/mp.2014.49.
    Molecular Psychiatry 05/2014; 20(1). · 15.15 Impact Factor
  • JAMA neurology. 05/2014; 71(5):651-2.
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    ABSTRACT: Older adults with intact cognition before death and substantial Alzheimer disease (AD) lesions at autopsy have been termed "asymptomatic AD subjects" (ASYMAD). We previously reported hypertrophy of neuronal cell bodies, nuclei, and nucleoli in the CA1 of the hippocampus (CA1), anterior cingulate gyrus, posterior cingulate gyrus, and primary visual cortex of ASYMAD versus age-matched Control and mild cognitive impairment (MCI) subjects. However, it was unclear whether the neuronal hypertrophy could be attributed to differences in the severity of AD pathology. Here, we performed quantitative analyses of the severity of β-amyloid (Aβ) and phosphorylated tau (tau) loads in the brains of ASYMAD, Control, MCI, and AD subjects (n = 15 per group) from the Baltimore Longitudinal Study of Aging. Tissue sections from CA1, anterior cingulate gyrus, posterior cingulate gyrus, and primary visual cortex were immunostained for Aβ and tau; the respective loads were assessed using unbiased stereology by measuring the fractional areas of immunoreactivity for each protein in each region. The ASYMAD and MCI groups did not differ in Aβ and tau loads. These data confirm that ASYMAD and MCI subjects have comparable loads of insoluble Aβ and tau in regions vulnerable to AD pathology despite divergent cognitive outcomes. These findings imply that cognitive impairment in AD may be caused or modulated by factors other than insoluble forms of Aβ and tau.
    Journal of neuropathology and experimental neurology. 03/2014;
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    ABSTRACT: Interleukin-6 (IL-6) is a pro-inflammatory cytokine produced by immune cells and other cell types such as microglia throughout the brain. Higher levels of IL-6 in older adults have been cross-sectionally and longitudinally associated with physical and cognitive impairment, as well as increased dementia risk. The association between IL-6 levels and structural and functional brain changes is less clear. In the present study, we investigated the relationship between IL-6 concentrations and cortical thinning with aging. Magnetic Resonance Imaging (MRI) scans from the Baltimore Longitudinal Study of Aging were analyzed for 121 older subjects (M = 69.3; SD = 7.3; range = 56.1–85.9 yrs) who were repeatedly tested over an average period of 7.5 yrs, and who remained non-demented for the entire follow-up period. The Freesurfer longitudinal processing stream was utilized for image processing, and IL-6 measures were based on serum ELISA assays averaged across time points. Results showed that higher mean IL-6 concentrations were associated with accelerated annual rates of cortical thinning in the inferior temporal poles bilaterally. Additional pronounced regions of IL-6 -accelerated thinning included the transverse frontopolar gyri within the left hemisphere, and subcentral gyrus and sulcus within the right hemisphere. Our results indicate that sustained high levels of the inflammatory biomarker IL-6 are associated with regionally increased rates of age-related cortical thinning. These data build on previous findings that link IL-6 to chronic disease and demonstrate one mechanism through which high levels of inflammation may have adverse effects on physical and cognitive function.
    Translational Neuroscience. 03/2014; 5(1):1-7.
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    ABSTRACT: Hearing impairment in older adults is independently associated in longitudinal studies with accelerated cognitive decline and incident dementia, and in cross-sectional studies, with reduced volumes in the auditory cortex. Whether peripheral hearing impairment is associated with accelerated rates of brain atrophy is unclear. We analyzed brain volume measurements from magnetic resonance brain scans of individuals with normal hearing versus hearing impairment (speech-frequency pure tone average>25dB) followed in the neuroimaging substudy of the Baltimore Longitudinal Study of Aging for a mean of 6.4years after the baseline scan (n=126, age 56-86years). Brain volume measurements were performed with semi-automated region-of-interest (ROI) algorithms, and brain volume trajectories were analyzed with mixed-effects regression models adjusted for demographic and cardiovascular factors. We found that individuals with hearing impairment (n=51) compared to those with normal hearing (n=75) had accelerated volume declines in whole brain and regional volumes in the right temporal lobe (superior, middle, and inferior temporal gyri, parahippocampus, p<.05). These results were robust to adjustment for multiple confounders and were consistent with voxel-based analyses, which also implicated right greater than left temporal regions. These findings demonstrate that peripheral hearing impairment is independently associated with accelerated brain atrophy in whole brain and regional volumes concentrated in the right temporal lobe. Further studies investigating the mechanistic basis of the observed associations are needed.
    NeuroImage 01/2014; · 6.13 Impact Factor
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    ABSTRACT: To develop targeted intervention strategies for the treatment of Alzheimer's disease, we first need to identify early markers of brain changes that occur before the onset of cognitive impairment. Here, we examine changes in resting-state brain function in humans from the Baltimore Longitudinal Study of Aging. We compared longitudinal changes in regional cerebral blood flow (rCBF), assessed by (15)O-water PET, over a mean 7 year period between participants who eventually developed cognitive impairment (n = 22) and those who remained cognitively normal (n = 99). Annual PET assessments began an average of 11 years before the onset of cognitive impairment in the subsequently impaired group, so all participants were cognitively normal during the scanning interval. A voxel-based mixed model analysis was used to compare groups with and without subsequent impairment. Participants with subsequent impairment showed significantly greater longitudinal rCBF increases in orbitofrontal, medial frontal, and anterior cingulate regions, and greater longitudinal decreases in parietal, temporal, and thalamic regions compared with those who maintained cognitive health. These changes were linear in nature and were not influenced by longitudinal changes in regional tissue volume. Although all participants were cognitively normal during the scanning interval, most of the accelerated rCBF changes seen in the subsequently impaired group occurred within regions thought to be critical for the maintenance of cognitive function. These changes also occurred within regions that show early accumulation of pathology in Alzheimer's disease, suggesting that there may be a connection between early pathologic change and early changes in brain function.
    Journal of Neuroscience 11/2013; 33(46):18008-14. · 6.75 Impact Factor
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    ABSTRACT: IMPORTANCE Older adults commonly report disturbed sleep, and recent studies in humans and animals suggest links between sleep and Alzheimer disease biomarkers. Studies are needed that evaluate whether sleep variables are associated with neuroimaging evidence of β-amyloid (Aβ) deposition. OBJECTIVE To determine the association between self-reported sleep variables and Aβ deposition in community-dwelling older adults. DESIGN, SETTING, AND PARTICIPANTS Cross-sectional study of 70 adults (mean age, 76 [range, 53-91] years) from the neuroimaging substudy of the Baltimore Longitudinal Study of Aging, a normative aging study. EXPOSURE Self-reported sleep variables. MAIN OUTCOMES AND MEASURES β-Amyloid burden, measured by carbon 11-labeled Pittsburgh compound B positron emission tomography distribution volume ratios (DVRs). RESULTS After adjustment for potential confounders, reports of shorter sleep duration were associated with greater Aβ burden, measured by mean cortical DVR (B = 0.08 [95% CI, 0.03-0.14]; P = .005) and precuneus DVR (B = 0.11 [0.03-0.18]; P = .007). Reports of lower sleep quality were associated with greater Aβ burden measured by precuneus DVR (B = 0.08 [0.01-0.15]; P = .03). CONCLUSIONS AND RELEVANCE Among community-dwelling older adults, reports of shorter sleep duration and poorer sleep quality are associated with greater Aβ burden. Additional studies with objective sleep measures are needed to determine whether sleep disturbance causes or accelerates Alzheimer disease.
    JAMA neurology. 10/2013;
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    ABSTRACT: Despite the recent identification of several novel risk genes for Alzheimer's disease (AD), little is known about their influence on the age at onset (AAO) of AD. The AAO is a phenotype with a heritable component distinct from disease risk and may be a useful trait to study in the context of developing interventions for delaying the onset of AD. We studied the influence of 10 recently identified AD risk genes and APOE in relation to AAO in a large cohort of AD patients (N = 2569). We find that the novel AD risk gene, PICALM, exerts a small effect on the AAO of AD with earlier disease onset in risk allele carriers. In addition, we confirmed the previously reported association between the APOE ε4 allele and earlier disease onset. None of the other AD risk genes influenced AAO of AD. Our results suggest that besides APOE, other genes associated with AD risk do not exert large effects on the AAO phenotype of AD.
    Neurobiology of aging 07/2013; · 5.94 Impact Factor
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    ABSTRACT: IMPORTANCE Long-term longitudinal studies are needed to delineate the trajectory of depressive symptoms across adulthood and to individuate factors that may contribute to increases in depressive symptoms in older adulthood. OBJECTIVES To estimate the trajectory of depressive symptoms across the adult life span; to test whether this trajectory varies by demographic factors (sex, ethnicity, and educational level) and antidepressant medication use; and to test whether disease burden, functional limitations, and proximity to death explain the increase in depressive symptoms in old age. DESIGN Longitudinal study. SETTING Community. PARTICIPANTS The study included 2320 participants (47.0% female; mean [SD] age at baseline, 58.1 [17.0] years; range, 19-95 years) from the Baltimore Longitudinal Study of Aging. MAIN OUTCOMES AND MEASURES Estimated trajectory of depressive symptoms modeled from 10 982 assessments (mean [SD] assessments per participant, 4.7 [3.6]; range, 1-21) based on the Center for Epidemiologic Studies Depression scale and 3 subscales (depressed affect, somatic complaints, and interpersonal problems). RESULTS The linear (γ10 = 0.52; P < .01) and quadratic (γ20 = 0.43; P < .01) terms were significant, which indicated that depressive symptoms were highest in young adulthood, decreased across middle adulthood, and increased again in older adulthood. The subscales followed a similar pattern. Women reported more depressed affect at younger ages, but an interaction with age suggested that this gap disappeared in old age. Accounting for comorbidity, functional limitations, and impending death slightly reduced but did not eliminate the uptick in depressive symptoms in old age. CONCLUSIONS AND RELEVANCE Symptoms of depression follow a U-shaped pattern across adulthood. Older adults experience an increase in distress that is not due solely to declines in physical health or approaching death.
    JAMA Psychiatry 06/2013; · 12.01 Impact Factor
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    ABSTRACT: BACKGROUND: We examine whether broad factors and specific facets of personality are associated with increased risk of incident Alzheimer's disease (AD) in a long-run longitudinal study and a meta-analysis of published studies. METHODS: Participants (n = 1671) were monitored for up to 22 years from a baseline personality assessment. The meta-analysis pooled results from up to five prospective studies (n = 5054). RESULTS: Individuals with scores in the top quartile of neuroticism (hazard ratio = 3.1; 95% confidence interval = 1.6-6.0) or the lowest quartile of conscientiousness (hazard ratio = 3.3; 95% confidence interval = 1.4-7.4) had a threefold increased risk of incident AD. Among the components of these traits, self-discipline and depression had the strongest associations with incident AD. The meta-analysis confirmed the associations of neuroticism (P = 2 × 10(-9)) and conscientiousness (P = 2 × 10(-6)), along with weaker effects for openness and agreeableness (P < .05). CONCLUSIONS: The current study and meta-analysis indicate that personality traits are associated with increased risk of AD, with effect sizes similar to those of well-established clinical and lifestyle risk factors.
    Alzheimer's & dementia: the journal of the Alzheimer's Association 05/2013; · 14.48 Impact Factor
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    ABSTRACT: We investigated whether individuals with impaired glucose tolerance (IGT) in midlife subsequently show regionally specific longitudinal changes in regional cerebral blood flow (rCBF) relative to those with normal glucose tolerance (NGT). Sixty-four cognitively normal participants in the neuroimaging substudy of the Baltimore Longitudinal Study of Aging underwent serial (15)O-water positron emission tomography scans (age at first scan, 69.6 ± 7.5 years) and oral glucose tolerance tests 12 years earlier (age at first oral glucose tolerance test, 57.2 ± 11.1 years). Using voxel-based analysis, we compared changes in rCBF over an 8-year period between 15 participants with IGT in midlife and 49 with NGT. Significant differences were observed in longitudinal change in rCBF between the IGT and NGT groups. The predominant pattern was greater rCBF decline in the IGT group in the frontal, parietal, and temporal cortices. Some brain regions in the frontal and temporal cortices also showed greater longitudinal increments in rCBF in the IGT group. Our findings suggest that IGT in midlife is associated with subsequent longitudinal changes in brain function during aging even in cognitively normal older individuals.
    Neurobiology of aging 04/2013; · 5.94 Impact Factor
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    ABSTRACT: To confirm associations of apolipoprotein E (ApoE) ε4 carrier status, sex, and time-dependent cognitive status with mortality risk and to investigate these joint effects of these associations in a cohort of community-dwelling U.S. adults. Prospective cohort study. The Baltimore Longitudinal Study of Aging (BLSA). Of 3,047 BLSA participants aged 17 to 98 at first visit (60.1% male), 1,704 with complete ApoE genotype data were included, of whom 1,461 aged 50 and older with one or more visits were eligible. Time to death from all, cardiovascular, and noncardiovascular causes. Probability of survival was lower for ApoE ε4 carriers, particularly those who were older. A Cox proportional hazards model for all-cause mortality yielded a hazard ratio (HR) for ApoE ε4 carrier versus noncarriers of 1.31 (95% confidence interval (CI) = 1.02-1.68). This association was also found for cardiovascular mortality. Time-dependent all-cause dementia (HR = 1.73, 95% CI = 1.33-2.26) and mild cognitive impairment (HR = 1.95, 95% CI = 1.42-2.67) increased all-cause mortality risk, associations that were also detected for noncardiovascular mortality. When individuals were free of cognitive impairment, a dose-response relationship with ε4 alleles was found for all-cause mortality (HR = 1.40, 95% CI = 0.94-2.07 for 1 ε4; HR = 2.61, 95% CI = 1.12-6.07 for 2 ε4). After onset of Alzheimer's disease (AD), carrying only one ε4 allele resulted in an approximately 77% greater all-cause mortality risk than in noncarriers. ApoE ε4 carrier status increased all-cause mortality risk in men and interacted with time-dependent AD to increase the risk of this outcome (relative excess risk due to interaction = 2.15, 95% CI = 1.22-3.07). ApoE ε4 carrier status was found to increase all-cause and cardiovascular mortality risks and interacted with sex and time-dependent AD status to affect all-cause mortality.
    Journal of the American Geriatrics Society 04/2013; 61(4):525-34. · 4.22 Impact Factor
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    ABSTRACT: In the present research, we examined the effects of age, cohort, and time of measurement on well-being across adulthood. Cross-sectional and longitudinal analyses of two independent samples-one with more than 10,000 repeated assessments across 30 years (mean assessments per participant = 4.44, SD = 3.47) and one with nationally representative data-suggested that well-being declines with age. This decline, however, reversed when we controlled for birth cohort. That is, once we accounted for the fact that older cohorts had lower levels of well-being, all cohorts increased in well-being with age relative to their own baseline. Participants tested more recently had higher well-being, but time of measurement, unlike cohort, did not change the shape of the trajectory. Although well-being increased with age for everyone, cohorts that lived through the economic challenges of the early 20th century had lower well-being than those born during more prosperous times.
    Psychological Science 01/2013; · 4.43 Impact Factor
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    ABSTRACT: Longitudinal studies on aging brain function have shown declines in frontal activity as opposed to the over-recruitment shown in cross-sectional studies. Such mixed findings suggest that age-related changes in frontal activity may be process- and region-specific, having varied associations across different frontal regions involved in distinct cognitive processes, rather than generalized across the frontal cortex. Using data from the Baltimore Longitudinal Study of Aging (BLSA), we examined individual differences through cross-sectional associations at baseline evaluation and longitudinal changes in regional cerebral blood flow (rCBF) in relation to different executive abilities in cognitively normal older adults. We found that, at baseline, greater rCBF in middle frontal regions correlated with better performance in abstraction and chunking, but greater rCBF in the insula and a distinct middle frontal region correlated with poorer inhibition and discrimination, respectively. In addition, increases in frontal rCBF over time were associated with longitudinal declines in abstraction, chunking, inhibition, discrimination, switching, and manipulation. These findings indicate process- and region-specific, rather than uniform, age-related changes in frontal brain-behavior associations, and also suggest that longitudinally high-levels of frontal engagement reflect declining rather than stable cognition.
    NeuroImage 12/2012; · 6.13 Impact Factor
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    ABSTRACT: Alzheimer's disease (AD) neuropathology is found at autopsy in approximately 30% of cognitively normal older individuals. We examined whether personality traits are associated with such resilience to clinical dementia in individuals with AD neuropathology. Broad factors and specific facets of personality were assessed up to 28 years (mean 11 ± 7 years) before onset of dementia and up to 30 years (mean 15 ± 7 years) before death in a cohort (n = 111) evaluated for AD neuropathology at autopsy. Individuals with higher baseline scores on vulnerability to stress, anxiety, and depression (neuroticism: odds ratio, 2.0; 95% confidence interval, 1.2-3.5), or lower scores on order and competence (conscientiousness: odds ratio, 0.4; 95% confidence interval, 0.2-0.9) were less likely to remain asymptomatic in the presence of AD neuropathology. Neuroticism (r = 0.26), low agreeableness (r = -0.34), and some facets were also significantly associated with advanced stages of neurofibrillary tangles, but the associations between personality traits and risk of clinical dementia were mostly unchanged by controlling for the extent of neurofibrillary tangles and Aβ neuritic plaques. In sum, a resilient personality profile is associated with lower risk or delay of clinical dementia even in persons with AD neuropathology.
    Neurobiology of aging 10/2012; · 5.94 Impact Factor
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    ABSTRACT: BACKGROUND: The rs3818361 single nucleotide polymorphism in complement component (3b/4b) receptor-1 (CR1) is associated with increased risk of Alzheimer's disease (AD). Although this novel variant is associated with a small effect size and is unlikely to be useful as a predictor of AD risk, it might provide insights into AD pathogenesis. We examined the association between rs3818361 and brain amyloid deposition in nondemented older individuals. METHODS: We used (11)C-Pittsburgh Compound-B positron emission tomography to quantify brain amyloid burden in 57 nondemented older individuals (mean age 78.5 years) in the neuroimaging substudy of the Baltimore Longitudinal Study of Aging. In a replication study, we analyzed (11)C-Pittsburgh Compound-B positron emission tomography data from 22 cognitively normal older individuals (mean age 77.1 years) in the Alzheimer's Disease Neuroimaging Initiative dataset. RESULTS: Risk allele carriers of rs3818361 have lower brain amyloid burden relative to noncarriers. There is a strikingly greater variability in brain amyloid deposition in the noncarrier group relative to risk carriers, an effect explained partly by APOE genotype. In noncarriers of the CR1 risk allele, APOE ε4 individuals showed significantly higher brain amyloid burden relative to APOE ε4 noncarriers. We also independently replicate our observation of lower brain amyloid burden in risk allele carriers of rs3818361 in the Alzheimer's Disease Neuroimaging Initiative sample. CONCLUSIONS: Our findings suggest complex mechanisms underlying the interaction of CR1, APOE, and brain amyloid pathways in AD. Our results are relevant to treatments targeting brain Aβ in nondemented individuals at risk for AD and suggest that clinical outcomes of such treatments might be influenced by complex gene-gene interactions.
    Biological psychiatry 09/2012; · 8.93 Impact Factor

Publication Stats

937 Citations
344.14 Total Impact Points


  • 2007–2014
    • National Institute on Aging
      • • Laboratory of Behavioral Neuroscience
      • • Laboratory of Personality and Cognition (LPC)
      Baltimore, Maryland, United States
  • 2013
    • Johns Hopkins Bloomberg School of Public Health
      • Department of Mental Health
      Baltimore, Maryland, United States
  • 2012–2013
    • Florida State University
      Tallahassee, Florida, United States
  • 2010–2012
    • MedStar Health Research Institute
      Maryland, United States
    • Johns Hopkins University
      • Department of Neurology
      Baltimore, MD, United States
  • 2011
    • Johns Hopkins Medicine
      • Department of Otolaryngology - Head and Neck Surgery
      Baltimore, MD, United States
  • 2009
    • University of Pennsylvania
      • Section of Biomedical Image Analysis - SBIA
      Filadelfia, Pennsylvania, United States