Effects of Age, Sex, and Ethnicity on the Association Between Apolipoprotein E Genotype and Alzheimer Disease A Meta-analysis Lindsay A. Farrer, PhD; L. Adrienne Cupples, PhD; Jonathan L. Haines, PhD; Bradley Hyman, MD, PhD; Walter A. Kukull, PhD; Richard Mayeux, MD; Richard H. Myers, PhD; Margaret A. Pericak-Vance, PhD; Neil Risch, PhD; Cornelia M. van Duijn, PhD; for the APOE and Alzheimer Disease Meta Analysis Consortium Objective.\p=m-\To examine more closely the association between apolipoprotein E (APOE) genotype and Alzheimer disease (AD) by age and sex in populations of various ethnic and racial denominations. Data Sources.\p=m-\Forty research teams contributed data on APOEgenotype, sex, age at disease onset, and ethnic background for 5930 patients who met criteria for probable or definite AD and 8607 controls without dementia who were recruited from clinical, community, and brain bank sources. Main Outcome Measures.\p=m-\Odds ratios (ORs) and 95% confidence intervals (Cls) for AD, adjusted for age and study and stratified by major ethnic group (Cau- casian, African American, Hispanic, and Japanese) and source, were computed for APOE genotypes \m=elem\2/\m=elem\2,\m=elem\2/\m=elem\3,\m=elem\2/\m=elem\4,\m=elem\3/\m=elem\4 and \m=elem\4/\m=elem\4 relative to the \m=elem\3/\m=elem\3 group. The influence of age and sex on the OR for each genotype was assessed using logistic regression procedures. Results.\p=m-\Among Caucasian subjects from clinic- or autopsy-based studies, the risk of AD was significantly increased for people with genotypes \m=elem\2/\m=elem\4 (OR=2.6, 95% Cl=1.6-4.0), \m=elem\3/\m=elem\4 (OR=3.2, 95% Cl=2.8-3.8), and \m=elem\4/\m=elem\4 (OR=14.9, 95% CI=10.8-20.6); whereas, the ORs were decreased for people with genotypes \m=elem\2/\m=elem\2 (OR=0.6, 95% Cl=0.2-2.0) and \m=elem\2/\m=elem\3 (OR=0.6, 95% Cl=0.5-0.8). The APOE \m=elem\4\x=req-\ AD association was weaker among African Americans and Hispanics, but there was significant heterogeneity in ORs among studies of African Americans (P<.03). The APOE \m=elem\4\p=m-\AD association in Japanese subjects was stronger than in Caucasian subjects (\m=elem\3/\m=elem\4: OR=5.6, 95% Cl=3.9-8.0; \m=elem\4/\m=elem\4: OR=33.1, 95% Cl=13.6\x=req-\80.5). The \m=elem\2/\m=elem\3 genotype appears equally protective across ethnic groups. We also found that among Caucasians, APOE genotype distributions are similar in groups of pa- tients with AD whose diagnoses were determined clinically or by autopsy. In addi- tion, we found that the APOE\m=elem\4 effect is evident at all ages between 40 and 90 years but diminishes after age 70 years and that the risk of AD associated with a given genotype varies with sex. Conclusions.\p=m-\The APOE\m=elem\4 allele represents a major risk factor for AD in all ethnic groups studied, across all ages between 40 and 90 years, and in both men and women. The association between APOE\m=elem\4 and AD in African Americans re- quires clarification, and the attenuated effect of APOE\m=elem\4 in Hispanics should be investigated further. JAMA. 1997;278:1349-1356 EPIDEMIOLOGIC and molecular evi¬ dence suggests there are multiple causes for Alzheimer disease (AD). Most ofthe known genetic causes—including de¬ fects in the amyloid precursor protein (APP) gene and the presenilin 1 and pre¬ senilin 2 genes13—are rare and account for less than 2% of cases.4 These muta¬ tions behave as classic autosomal domi¬ nant traits. Simply put, with rare excep¬ tions, persons inheriting one of these de¬ fects will develop AD unless they die prematurely from other causes. Apolipoprotein E (APOE indicates the gene and APOE indicates the pro¬ tein), a plasma protein involved in cho¬ lesterol transport and encoded by a gene on chromosome 19,5 is the fourth genetic factor implicated in the risk of develop¬ ing AD. There are 3 common alíeles (e2, e3, and e4) corresponding to 6 pheno- types, each with different isoelectric points. In typical Caucasian populations, e3 is the most common alíele, occurring on more than 75% of chromosomes. The average frequencies of e2 and e4 are 8% and 15%, respectively.5 Initial reports demonstrated that the APOE e4 alíele is disproportionately represented among patients with late-onset AD (symptoms occurring after age 65 years),6"8 but this association was soon extended to pa¬ tients with early-onset AD.9"11 Subse¬ quent confirmations in numerous ethnic populations have established the APOE genotype as perhaps the most important biological marker for susceptibility for AD identified thus far, accounting for 45% to 60% of its genetic component.12·13 Individuals who are heterozygous for the e4 alíele have an odds ratio (OR) be¬ tween 2.2 and 4.4 of developing AD com¬ pared with persons who have the e3/e3 genotype, while those who are homozy¬ gous for e4 have an OR ranging from 5.1 to 34.3.4'14 In contrast, the e2 alíele may confer a protective effect because it is slightly underrepresented in patients From the Departments of Neurology (Drs Farrer and Myers) and Epidemiology and Biostatistics (Drs Farrer and Cupples), Boston University School of Medicine, Boston, Mass; Molecular Neurogenet- ics Unit (Dr Haines) and Department of Neurology (Drs Haines and Hyman), Massachusetts General Hospital, Boston; Department of Epidemiology, University of Washington, Seattle (Dr Kukull); Ger- trude H. Sergievsky Center and Department of Neurology, Columbia University, New York, NY (Dr Mayeux); Division of Neurology, Duke University Medical Center, Durham, NC (Dr Pericak-Vance); Department of Genetics, Stanford University School of Medicine, Stanford, Calif (Dr Risch); and Department of Epidemiology, Erasmus University, Rotterdam, the Netherlands (Dr van Duijn). Dr Haines is associated with Athena Neurosciences, San Francisco, Calif, for the commercial use of the apo- lipoprotein E test as a diagnostic tool and as a result may receive future income from the use of this test. A complete listing of the APOE and Alzheimer Dis- ease Meta Analysis Consortium appears at the end of this article. Reprints; Lindsay A. Farrer, PhD, Department of Neu- rology, Boston University School of Medicine, 80 E Con- cord St, Boston, MA 02118 (e-mail: [email protected]). DownloadedFrom:http://jama.jamanetwork.com/byaMcGillUniversityLibrariesUseron01/23/2014
Transcript
Effects of Age, Sex, and Ethnicity on theAssociation Between Apolipoprotein EGenotype and Alzheimer DiseaseA Meta-analysisLindsay A. Farrer, PhD; L. Adrienne Cupples, PhD; Jonathan L. Haines, PhD; Bradley Hyman, MD, PhD;Walter A. Kukull, PhD; Richard Mayeux, MD; Richard H. Myers, PhD; Margaret A. Pericak-Vance, PhD;Neil Risch, PhD; Cornelia M. van Duijn, PhD; for the APOE and Alzheimer Disease Meta Analysis Consortium
Objective.\p=m-\To examine more closely the association between apolipoprotein E(APOE) genotype and Alzheimer disease (AD) by age and sex in populations ofvarious ethnic and racial denominations.
Data Sources.\p=m-\Forty research teams contributed data on APOEgenotype, sex,age at disease onset, and ethnic background for 5930 patients who met criteria forprobable or definite AD and 8607 controls without dementia who were recruitedfrom clinical, community, and brain bank sources.
Main Outcome Measures.\p=m-\Odds ratios (ORs) and 95% confidence intervals(Cls) for AD, adjusted for age and study and stratified by major ethnic group (Cau-casian, African American, Hispanic, and Japanese) and source, were computed forAPOE genotypes \m=elem\2/\m=elem\2,\m=elem\2/\m=elem\3,\m=elem\2/\m=elem\4,\m=elem\3/\m=elem\4and\m=elem\4/\m=elem\4 relative to the \m=elem\3/\m=elem\3 group.The influence of age and sex on the OR for each genotype was assessed usinglogistic regression procedures.
Results.\p=m-\Among Caucasian subjects from clinic- or autopsy-based studies, therisk of AD was significantly increased for people with genotypes \m=elem\2/\m=elem\4 (OR=2.6,95% Cl=1.6-4.0), \m=elem\3/\m=elem\4 (OR=3.2, 95% Cl=2.8-3.8), and \m=elem\4/\m=elem\4 (OR=14.9, 95%CI=10.8-20.6); whereas, the ORs were decreased for people with genotypes \m=elem\2/\m=elem\2(OR=0.6, 95% Cl=0.2-2.0) and \m=elem\2/\m=elem\3 (OR=0.6, 95% Cl=0.5-0.8). The APOE\m=elem\4\x=req-\
AD association was weaker among African Americans and Hispanics, but there was
significant heterogeneity in ORs among studies of African Americans (P<.03). TheAPOE \m=elem\4\p=m-\AD association in Japanese subjects was stronger than in Caucasiansubjects (\m=elem\3/\m=elem\4: OR=5.6, 95% Cl=3.9-8.0; \m=elem\4/\m=elem\4: OR=33.1, 95% Cl=13.6\x=req-\80.5).The \m=elem\2/\m=elem\3 genotype appears equally protective across ethnic groups. We also foundthat among Caucasians, APOE genotype distributions are similar in groups of pa-tients with AD whose diagnoses were determined clinically or by autopsy. In addi-tion, we found that the APOE\m=elem\4 effect is evident at all ages between 40 and 90 yearsbut diminishes after age 70 years and that the risk of AD associated with a givengenotype varies with sex.
Conclusions.\p=m-\The APOE\m=elem\4 allele represents a major risk factor for AD in allethnic groups studied, across all ages between 40 and 90 years, and in both menand women. The association between APOE\m=elem\4 and AD in African Americans re-
quires clarification, and the attenuated effect of APOE\m=elem\4 in Hispanics should beinvestigated further.
JAMA. 1997;278:1349-1356
EPIDEMIOLOGIC and molecular evi¬dence suggests there are multiple causesfor Alzheimer disease (AD). Most oftheknown genetic causes—including de¬fects in the amyloid precursor protein(APP) gene and the presenilin 1 and pre¬senilin 2 genes13—are rare and accountfor less than 2% of cases.4 These muta¬tions behave as classic autosomal domi¬nant traits. Simply put, with rare excep¬tions, persons inheriting one of these de¬fects will develop AD unless they dieprematurely from other causes.
Apolipoprotein E (APOE indicatesthe gene and APOE indicates the pro¬tein), a plasma protein involved in cho¬lesterol transport and encoded by a geneon chromosome 19,5 is the fourth geneticfactor implicated in the risk of develop¬ing AD. There are 3 common alíeles (e2,e3, and e4) corresponding to 6 pheno-types, each with different isoelectricpoints. In typical Caucasian populations,e3 is the most common alíele, occurringon more than 75% of chromosomes. Theaverage frequencies of e2 and e4 are 8%and 15%, respectively.5 Initial reportsdemonstrated that the APOE e4 alíele isdisproportionately represented amongpatients with late-onset AD (symptomsoccurring after age 65 years),6"8 but thisassociation was soon extended to pa¬tients with early-onset AD.9"11 Subse¬quent confirmations in numerous ethnicpopulations have established the APOEgenotype as perhaps the most importantbiological marker for susceptibility forAD identified thus far, accounting for45% to 60% of its genetic component.12·13Individuals who are heterozygous forthe e4 alíele have an odds ratio (OR) be¬tween 2.2 and 4.4 ofdeveloping AD com¬
pared with persons who have the e3/e3genotype, while those who are homozy¬gous for e4 have an OR ranging from 5.1to 34.3.4'14 In contrast, the e2 alíele mayconfer a protective effect because it isslightly underrepresented in patients
From the Departments of Neurology (Drs Farrerand Myers) and Epidemiology and Biostatistics(Drs Farrer and Cupples), Boston University Schoolof Medicine, Boston, Mass; Molecular Neurogenet-
ics Unit (Dr Haines) and Department of Neurology(Drs Haines and Hyman), Massachusetts GeneralHospital, Boston; Department of Epidemiology,University of Washington, Seattle (Dr Kukull); Ger-trude H. Sergievsky Center and Department ofNeurology, Columbia University, New York, NY(Dr Mayeux); Division of Neurology, Duke UniversityMedical Center, Durham, NC (Dr Pericak-Vance);Department of Genetics, Stanford University
School of Medicine, Stanford, Calif (Dr Risch); andDepartment of Epidemiology, Erasmus University,Rotterdam, the Netherlands (Dr van Duijn).
Dr Haines is associated with Athena Neurosciences,San Francisco, Calif, for the commercial use of the apo-lipoprotein E test as a diagnostic tool and as a resultmay receive future income from the use of this test.
A complete listing of the APOE and Alzheimer Dis-ease Meta Analysis Consortium appears at the end ofthis article.
Reprints; Lindsay A. Farrer, PhD, Department of Neu-rology, Boston University School of Medicine, 80 E Con-cord St, Boston, MA 02118 (e-mail: [email protected]).
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with AD,15 but this is unclear in some
populations.16·17 The APOE genotype alsois associated with the age at onset of ADin a dose-dependent fashion such that themore e4 alíeles there are, the younger theage at disease onset tends to be, and ageat onset tends to be older among personswith the e2/e3 genotype.15·18,19
Several biological explanations of thisassociation have been offered,20"23 butnone adequately explain why at least onethird of patients with AD lack e44·6 andwhy as many as 50% ofpeople who have adouble dose of e4 and survive to age 80years do not develop AD.24,25 Factors suchas family history, sex, serious head injury,smoking, cholesterol level, and estrogenmay modify the APOE-re\ated risk.11·26"31The risk ofAD attributable to the APOEe4 alíele is significant at both ends of theage spectrum,9"11·32 but there is disagree¬ment regarding the strength ofthe asso¬ciation among the very elderly.32"34 It isunclear whether variability in APOEgenotype-specific risks of AD across
populations is in part the result of bias inthe recruitment or diagnostic incongru¬ities of case patients or controls or themodifying effects ofdifferent genetic andenvironmental backgrounds. For ex¬
ample, the APOE e4-AD association inAfrican Americans is controversial35·36and apparently absent in a Nigeriansample ofpatients with AD and controls.37
The detection of small effects, such asthe protective effect ofthe APOE e2 al¬íele or effects among relatively smallstrata ofthe population (eg, nonagenar¬ians or ethnic or racial minorities), re¬
quires a subject population much largerthan that obtainable for most individualresearch studies. To this end, we haveassembled a data set containing diagnos¬tic, demographic, and APOE genotypeinformation on more than 15 000 patientswith AD and controls contributed by 40research teams from many differentparts ofthe world. In this article, we re¬
port a meta-analysis using raw data thatfurther strengthens the association ofAPOE e4 with AD in Caucasian andJapanese subjects and defines more pre¬cisely than in other studies the APOEe4-AD association in African-Americanand Hispanic subjects.
METHODSSample Recruitment
A committee comprising individualswith expertise in genetics and diagnosisof AD, epidemiology, and statistics wasconstituted to set the goals of this studyand identifypertinent datato be collected.AMEDLINE search was used to assist inthe identification of data sets. Letters ofinvitation to participate in this projectwere sent to representatives of groups
who had published or made known to thecommittee the existence of data on theAPOE e4-AD association prior to July 1,1995. Ofthe 48 groups sent invitations, 44agreed to participate, 1 declined, and 3 didnot respond. Data were received from 40of the 44 positive responders. For eachsubject the following information was
sought: a unique identifier, diagnostic sta¬tus, sex, censoring age (ie, age at last ex¬amination or death), age at disease onset(ifaffected), ethnicity, family history, andAPOE genotype. The data set includedcase patients who had a provisional or fi¬nal diagnosis of AD, AD-like dementia,and other neuropsychiatrie illness andcontrols. Subjects with dementia who didnot meet criteria for definite or probableAD and subjects with other neuropsychi¬atrie illnesses were not considered. Casepatients were diagnosed as having defi¬nite or probable AD, and controls werefree ofneurodegenerative and neuropsy¬chiatrie illnesses. Case patients withknown mutations in the APP or preseni¬lin genes or coexisting neuropathologicalfindings (eg, Lewy bodies, Parkinson dis¬ease changes) were excluded. Selectedcharacteristics of the patients with ADand controls at each of the 40 participat¬ing centers are listed in Table l.39"68
Pooling CriteriaAscertainment.—Participating cen¬
ters used a variety of sampling strate¬gies such as case-control, cohort, andcross-sectional samples and mixturesthereof. Some centers enrolled subjectswith AD only. Review of the designs ateach center suggested a trichotomousclassification scheme based on one ofthefollowing recruitment settings: commu¬
nity/population, clinic/hospital, or au¬
topsy/brain bank. Several centers ascer¬tained subjects under multiple designs(Table 1). Subjects who were enrolled ina clinic-based setting and whose diagno¬sis was confirmed at autopsy were as¬
signed as clinic ascertainment.Ethnicity.—Subjects were catego¬
rized by a variety of ethnic or racial des¬ignations, as follows: Caucasian (6264),Anglo-Saxon (667), French (704), FrenchCanadian (792), Scandinavian (77), Finn¬ish (259), Italian (280), Dutch (1848), Ger¬man (270), Ashkenazi Jewish (201),Sephardic Jewish (5), African American(475), American Indian (2), Hispanic (528),Asian (10), Japanese (2313), Chinese (1),other (7), and unknown (18). Japanese,Hispanic, and African-American sub¬jects were classified into separate groupsbecause ofevidence indicating APOE al¬íele frequency differences, distinct pat¬terns ofassociation with AD, or both.10·35The 38 subjects labeled as American In¬dian, Chinese, Asian, and other or un¬known ethnicity were dropped from the
analysis. The distribution ofAPOE geno¬types was similar among the remainingCaucasian groups (data not shown), andthese groups were pooled into a singleCaucasian group.
Diagnostic Categories.—The diag¬noses ofdefinite (ie, autopsy-confirmed)and probable AD were established at allsites using standardized research crite¬ria.38·69 The enormity of the sample en¬abled detection of a statistically signifi¬cant difference in the distribution ofAPOE genotypes between Caucasiancase patients with definite and probableAD ( 2=12.76, df=5, P=.03), but thisdoes not appear to be meaningful be¬cause the difference in the e4 alíele fre¬quency was only 1.4%. It was thereforedeemed appropriate to pool case pa¬tients with probable and definite AD insubsequent analyses. Non-Caucasiancase patients with definite and probableAD were combined in each of the otherethnic groups because there were so fewdiagnosed as having definite AD.
forms using 1 of 2 basic approaches. In afewstudies, APOE phenotypeswere de¬termined from plasma very low-densitylipoproteins after ultracentrifugation.The isolated very low-density lipopro¬tein particles were lyophilized, delipi-dated, and subjected to isoelectric focus¬ing within a pH range of 4 to 6.5, usingpreviously described methods.70 Moststudies conducted APOE genotypingbya polymerase chain reaction (PCR)-based approach71 using DNA isolatedfrom blood or autopsy tissue. The APOEgene was amplified according to condi¬tions developed in the individual labora¬tories. The PCR product was digestedwith either Hhal or Cfol following astandard procedure,72 and fragmentswere separated on either an agarose or
standard, nondenaturing 6% polyacryl-amide gel. Alternatively, biotinylatedPCR products were analyzed using a re¬verse DNA hybridization test.48Statistical Methods 2 test was used to compare APOE
alíele frequencies by diagnostic categoryand ethnicgroup. Subj ects were analyzedwithin ascertainment and ethnic stratapreviously described. In each stratum, an
age- and study-adjusted OR for AD ac¬
cording to presence or absence ofat least1 e4 alíele was estimated using Mantel-Haenszel statistics.73 For the Caucasiangroups, age was adjusted by the use of 10classes (0-49 years, 50-54 years, 55-59years, 60-64 years, 65-69 years, 70-74years, 75-79 years, 80-84 years, 85-89years, and >90 years). Age classes were
collapsed into fewer categories for the
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Table 1.—Characteristics of Case Patients With Alzheimer Disese (AD) and Controls*
Case Patients With AD Controls
StudytNo.
(% Female)Mean (SD)Onset Age
No.(% Female)
Mean (SD)Examination Age Ethnicity}:
Benjamin et al3! 139(55.4 76.0 7.2)|| 42.7) 64.2(16.0)Benjamin et al4t 61 (70.5 79.7 9.7) 14 57.1) 82.4 (8.5)Betard et al" 122(69.7 71.1 80.8 (4.9)Betard et al4' 38 (65.8 81.1 10.8) 45.9) 81.0(5.7)Blacker et al42H 310(69.0 71.4 1.6) ) 95% C; 5% AA; 0.3% HChartier-Harlin et al9 45 (84.4 70.0 6.7) 45 73.3) 72.5(10.8)Chartler-Harlln et al9 115(60.9 83.2 6.1) 37 56.8) 82.5 (8.4)Corder et al15 190(58.4 67.2 9.1) 100 59.0) 69.1 (7.3) 93%C;7%AADuara et al4: 196(73.5 75.0 46 67.4) 71.8(11.1) 64%C;4%AA; 32% HDuara et al4' 23 (43.5 4.7) 150 66.0) 72.1 (7.8) 73% C; 12% AA; 15% HFallin et al4' 130(67.7 70.0 10.0) 137 72.3) 79.0 (8.0) 83%C;2%AA; 15% HFarrer et al2! 441 (50.3 68.3 9.1) 166 56.6) 70.8 (10.Í 99.7% C; 0.3% JFrisoni et al45 157(76.4 69.3 120 58.3) 69.4(11.2)Galasko et al4' 175(43.4 68.8 7.7) 91 52.8) 73.8 (8.2) 91%C;3%AA; 7% H
Gearing et al4' 41 (46.3 68.1 11.1) 64 95% C; 5% AA
Lehtovirta et al5' 204 (70.1 70.6 8.5) 55 63.6) 73.5 (6.2)Lippa et al5i 19(21.0 67.3 12.9) 44.4) 68.3(15.0) 93% C; 7% HLucotte et al56 128(69.5 75.6 5.9)Maestre et al35 305 (75.7 79.7 7.6) 485 67.0) 73.0 (6.6) 22% C; 33% AA; 45% HMahieux et al5' 112(67.9 73.4 7.5) 466 36.0) 37.2(10.6) 99.6% C; 0.4% HMartins et al5' 141 (57.4 9.8) 78 25.6) 66.2(16.0)Nalbantoglu et al" 93 (49.5; 76.3 9.2)# 73 30.1) 71.1 (14.7)Noguchi et al5! 38(81.6; 79.7 8.3)# 584 27.4) 55.8(11.5) C/POkulzumi et al'0 83(61.4; 66.8 10.3) 149 45.6) 49.1 (21.3)PIckering-Brown et al6' 61 (60.7; 65.1 11.1)Poirier et al8 90 (66.7 64.0 9.1) 74 60.8) 75.9 (9.7)Rebeck et al2' 213(62.4; 72.9 11.0) 128 59.4) 79.4(13.5)Smith et al6' 27 (48.2; 65.0 6.4) 130 56.9) 71.8(12.4)Smith et al62 74 (62.2; 73.2 1.2) 10 40.0) 77.5 (7.7)Sorbi et al" 135(61.5; 58.5 10.4) 196 57.6) 54.8 (28.5)St Clair et al63 154(69.5 68.1 13.1)# 38.3) 77.1 (7.0)Talbot et al6' 157(53.5 70.6 1.6) 112 56.2) 78.5 (9.6) 98% C; 2% AATsai et al65 115(74.8 78.2 9.0) 268 69.8) 82.5 (7.7)Ueki et al66 77 (62.3 71.0 8.3) 616 50.5) 48.4 (20.3)van Duijn et al" 348 (44.0 69.3 13.4) 1500 43.6) 67.4 (8.3)Yoshizawa et al8; 83 (77.1 65.6 11.8) 608 47.6 (7.Í C/PZubenko et al6' £>(...) 38 63.2) 56.3 (9.6)Zubenko et al6' 86 (47.8) 68.7 (7.8) 23 60.5) 67.1 (11.9) 97% C; 3% AA
Ellipses indicate not applicable.fAdditional data were used to supplement the data from many of the studies listed In this table.íFor ethnicity, C indicates Caucasian; AA, African American; H, Hispanic; and J, Japanese.§For ascertainment, C indicates clinic/hospital; P, population/community; and A, autopsy/brain bank.||N=23.IIData set comprises affected sibling pairs; 1 sibling from each pair was randomly selected.#Age at examination.
smaller African-American and Hispanicgroups (0-69 years, 70-79 years, and >80years) and the Japanese group (0-59, 60-69,70-79, and >80 years). Odds ratios ad¬justed for age and study were also com¬
puted for APOE genotypes e2/e2, e2/e3,2/e4, e3/e4, and e4/e4 relative to the e3/e3group. In addition, a 2 statistic recom¬mended by Breslow and Day74 was com-
puted to assess whether data sets in eachstratum could be pooled. The non-Cauca¬sian groups could not be evaluated by as¬certainment scheme because there were
too few observations.The influence oíAPOE genotype, age,
and sex on the odds ofdeveloping AD wasassessed using logistic regression.75 To ac¬commodate the polychotomous classiti-
cation oíAPOE genotype in the regres¬sion analysis, 4 indicator variables weremade to represent the genotype classese2/€2 or e2/e3, e2/e4, e3/e4, and e4/e4. Thesevariables took on the value of 1 if the sub¬ject had the corresponding genotype; oth¬erwise, the value was 0. The e3/e3 geno¬type was the referent. Age at onset ofADamong case patients and age at last ex-
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Table 2.—Apolipoprotein E [APOE) Genotype and Alíele Distributions in Case Patients With AlzheimerDisease (AD) and Controls by Ethnic Group
signed to the age variable. Nonlinear ef¬fects of age were considered by use ofanwith age-squared term. Interaction be¬tween APOE, age, and sex was evalu¬ated by deriving product terms for eachgenotype with age, age-squared, and sexterms. Models were evaluated using theLOGISTIC procedure in SAS.76 The rela¬tive fit values of the hierarchal modelswere determined by computing the dif¬ferences in the -2-ln likelihoods for themodels, and these differences follow a 2distribution.RESULTSEthnic Patterns
The relative increase in the frequencyof APOE e4 in case patients with ADcompared with controls is substantiallyless in African Americans (32.2%/19.0% = 1.7) than Caucasians (36.7%/13.6%=2.7) (Table 2). The frequency ofthee4/e4 genotype among case patients andcontrols is comparable across thesegroups, although the e3/e4 genotype ismore frequent in Caucasian than in Afri¬can-American case patients and less fre¬quent in Caucasian than in African-American controls. There was less of adifference between Hispanic case pa¬tients and controls in e4 frequency (19.2%/11.0%=1.7), largely because of a paucityofe4/e4 homozygotes relative to e3/e4 hét¬érozygotes. The e4 alíele is less preva¬lent in Japanese case patients and con¬
trols, but the ratio appears similar to thatin Caucasians (27.8%/8.9%=3.1). The e2 al¬íele is more than twice as frequent in con¬trols than case patients among Cauca¬sians. A similar trend was noted in theJapanese controls and case patients, al¬though €2 was equally frequent in African-American and Hispanic case patients andcontrols. Analysis ofthe alíele frequencydata revealed that all the control popula¬tions are in Hardy-Weinberg equilibrium(Caucasians: 2=2.65, rJ/=3, P=.5; Afri¬can Americans: 2=4.35, d/=3, P=.3; His¬panics: 2=2.02, df=3, P=.6; Japanese:
2=6.39, df= 3, =. 1), suggesting that eth¬nic differences in the pattern of associa¬tion are not attributable to recent admix¬ture of populations with differentdistributions oí APOE genotypes.Comparability Across Studies
The odds ofAD for subjects with at least1 e4 alíele compared with subjects with¬out e4 were calculated for each study,stratified by ethnic group (data availableon request). The variability in the OR(ranging from 2.1 to 8.1) across 22 clinic-or hospital-based studies of Caucasianswas not significant. Preliminary analysisofthe ORs computed for Caucasians in au¬
topsy-based studies revealed significantheterogeneity (Breslow-Day P=.02).However, examination ofthe subject re¬cruitment procedures in these data setsrevealed that the controls in the groupfrom Nalbantoglu et al12 were selected onthe because they had few plaques andtangles. The proportion of 73 controls inthe data set from Nalbantoglu et al12 whohad at least 1 e4 alíele (5.5%) was signifi¬cantly lower (P<.001) than the propor¬tion among 287 controls from other au¬
topsy studies (26.8%); whereas, theproportions of case patients from thesestudies who had at least 1 4 alíele werethe same (60.2% and 62.3%, respectively;P=.7). Because ofthe substantially lowere4 frequency and the unique selection cri¬teria for the Nalbantoglu et al12 controls,these 73 subjectswere excluded. Réévalu¬ation of the data from the autopsy stud¬ies suggested that the ORs were not dif¬ferent. The test of the variability amongclinic- and autopsy- studies combined wasnot significant (combined OR=4.2, Bres¬low-Day P=.2), suggesting that these datacould be pooled for subsequent analysis.By contrast, the APOE e4-AD associa¬tion in the population-based studies wassomewhat weaker and significantly vari¬able (P=.004); however, with the excep¬tion of one ofthe smaller studies yieldingan OR of 7.7, the range of ORs was rela¬tively narrow (2.0-4.2).
Table 3.—Odds Ratios for Developing AlzheimerDisease (AD) According to Apolipoprotein E(APOE) Genotype and Ethnic Group, Adjusted forAge and Study*
*Odds ratios for genotypes derived assuminga reference odds ratio of 1 for APOE e3/€3 genotype.
tThese values are a test for heterogeneity of oddsratios for genotype among data sets.
The age-adjusted odds ofAD forAPOEgenotypes that had at least 1 e2 or e4 alíelerelative to the e3/e3 genotype are shownin Table 3. People with the e3/e4 genotypehad increased odds of AD (ranging from2.2 in Hispanics to 5.6 in Japanese).African Americans were an exception(OR=1.1), but there was significant het¬erogeneity among studies in this group.Odds ofAD were also increased between1.8 and 3.2 times among e2/e4 subjects inall ethnic groups, except in the subset ofCaucasians from population-based stud¬ies who were heterogeneous with respectto risk associated with this genotype. Theodds ofAD associated with homozygosityof e4 were very high in Caucasians (12.5-14.9) and Japanese (33.1), but in Hispanicsthe odds were identical to those for thee3/e4 group (2.2). The OR for e4/e4 AfricanAmericans (5.7) was intermediate to theORs for Caucasians or Japanese and His¬panics, but that may be deceptive becauseofthe significant variability among stud¬ies ofAfrican Americans. The e2/e3 geno-
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le¬
u¬
rs-
3/ 4 4/ 4 2/ 4 2/ 2 2/ 3
60 65 70Age, y
Figure 1.—Relative odds of Alzheimer disease according to apolipoprotein E(APOE) genotype and age among Caucasian subjects ascertained in clinic- andautopsy-based studies. These odds were generated from a logistic regressionmodel for subjects with genotypes APOEe2/e2 or e2/e3, e2/e4, e3/e4, and e4/e4relative to the e3/e3 group. Curves were derived from a model that includedAPOEáummy variables, age, age-squared, and second-order Interaction termsinvolving APOE variables and age.
ß 3/ 4A Women 3/ 4 Men 4/ 4 Women 4/ 4
60 65 70Age, y
75 80 85 90
Figure 2.—Relative odds of Alzheimer disease according to apolipoprotein E(APOE) genotypes e3/e4 and e4/e4, age, and sex among Caucasian subjectsascertained in clinic- and autopsy-based studies. Curves were derived from amodel including APOE dummy variables, age, age-squared, sex, and second-order interaction terms involving APOE variables, age, and sex.
type is protective and had a similar OR inall ethnic groups, although ORs were sig¬nificant in the larger Caucasian groupsonly. There were too few e2/e2 subjects todemonstrate a significantly different riskof AD from that for e3/e3 subjects. How¬ever, among the 2 groups of studies ofCaucasians, in which more than 20 e2/e2subjects participated, the odds of AD as¬sociated with this genotype were similarto the odds for the e2/e3 genotype. Over¬all, theresults (Table 3) indicate thatpool¬ing is inappropriate among studies in theCaucasian population-based and African-American groups.
Age and Sex EffectsBecause evidence for heterogeneity
among the Caucasian population-basedand African-American studies indicatesthat pooling of data sets within thesestratais not justified, age- and sex-specificORs forADwere derived forAPOEgeno¬types e2/e2 or e2/e3, e2/e4, e3/e4, and e4/e4relative to the e3/e3 genotype among Cau¬casian (clinic- or autopsy-based), Japa¬nese, and Hispanic groups only. AmongCaucasians, the odds of AD were signifi¬cantly increased between ages 40 and 95years among e3/e4 subjects and betweenages 50 and 85 years among e4/e4 subjects.In these groups, risk increased steadily be¬tween ages 40 and 60 years but declinedwith age thereafter (Figure 1). A similarpattern was demonstrated for e2/e4 sub¬jects, but the highest odds were observedat age 70 years. The apparent protectiveeffect ofthis genotype in subjects youngerthan age 50 years was not significant ow¬
ing to the paucity of e2/e4 subjects (0.98%of case patients and 1.24% of controls) inthis age range. Age-related changes in theOR were much more dramatic among e4
homozygotes than e4 hétérozygotes. Theincreased risk associated with e4 was stillevident at age 90 years but could not beassessed reliably after age 95 years. Theprotective effect associated with the e2/e2and e2/e3 genotypes was unaffectedby age(OR=0.6 across all ages). The model allow¬ing for an interaction between APOEand sex was significant ( 2=13.43, df=4,P=.01), suggesting that the sex effect isnot uniform across all APOE genotypes.At most ages and across all genotypes,women are more likely than men to de¬velop AD (Figures 2 and 3). In comparisonwith e3/e3 individuals, the sexual dimor¬phic character in AD risk was 1.5 timesgreater in e3/e4 individuals (P=.01). Sexdifferences in odds of AD among personswith other genotypes were not signifi¬cantlydifferent from those seen among e3/e3 persons. Lack ofsignificance for the (2Je4 group that showed a relative increase infemale-male odds of1.8 is probably relatedto small sample size.
Age-related trends in the risk of ADamong Japanese e3/e4 subjects paralleledthat ofCaucasian e3/e4 subjects, althoughage did not influence risk among Hispanice3/e4 subjects (Figure 4). The effect ofageon the OR for the other genotypes couldnot be assessed reliably in these ethnicgroups because of an insufficient numberofpersons, particularly at the extremes ofthe age distribution. The effect of sex onAD risk in Japanese and Hispanics wasthe same across genotypes, although thesex-related trends among Hispanics weresimilar to those among Caucasians.
COMMENTOur meta-analysis of 40 studies rep¬
resenting nearly 30000 APOE alíelesdemonstrates a significant association
between the APOE e4 alíele and AD inCaucasians, African Americans, Hispan¬ics, and Japanese. The results of thisstudywere based on analyses ofraw dataand included investigators from theoriginal studies and the evaluation ofseveral covariates.
The goals of this study were to assessthe variability in the association betweenAPOE e4 and AD and the degree towhichdifferences in published studies were at¬tributable to demographic characteris¬tics and study design. Variability in eth¬nic or racial background, age and sex dis¬tributions, and certainty of diagnosiscould have affected the APOE e4-AD as¬sociation. Sample size variability is im¬portant as 10 ofthe 47 independent datasets had fewer than 100 total subjects;one third of these studies had fewer than50 controls.
Our results suggest that the distribu¬tion oíAPOE alíeles is the same in popu¬lations ofpatients with a clinical diagno¬sis of probable AD and those meetingautopsy criteria for AD. Therefore, it wasdeemed appropriate to pool these sub¬jects for APOE association studies. Wealso observed that within the Cauca¬sian, Hispanic, and Japanese groups, dif¬ferences in the APOE e4-AD associa¬tion were entirely attributable tosampling variance and were not statis¬tically significant. However, the appar¬ent heterogeneity among studies in theCaucasian community-based and African-American groups could not be resolved.Heterogeneity among community-based Caucasian studies may reflect bi¬ases ofprospective vs prevalent case sam¬
pling. The relative risk (RR) of AD fore4 subjects in the Rotterdam study17(OR =2.0) may be lower than that for e4
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0 Men 2/ 4A Women 2/ 41 Men 2/ 2 or 2/ 3 Women 2/ 2 or 2/ 3
Figure 3.—Relative odds of Alzheimer disease according to apolipoprotein E(APOE) genotypes e2/e2 or e2/e3 and e2/e4, age, and sex among Caucasiansubjects ascertained in clinic- and autopsy-based studies. Curves were derivedfrom a model that included APOEdummy variables, age, age-squared, sex, andsecond-order interaction terms involving APOE variables, age, and sex.
0 Clinic BasedCaucasian 3/ 4
Japanese 3/ 4A Hispanic 3/ 4
40 45 50 55 60 65 70Age, y
75 80 85 90
Figure 4.—Relative odds of Alzheimer disease according to age among Cau¬casian, Japanese, and Hispanic apolipoprotein E (APOE) e3/e4 subjects.Curves were derived from the model described in Figure 1 for each ethnic group.
subjects in the 9 other community-basedCaucasian studies (ORs between 3.0 and7.7) because it included a large numberof subjects younger than 65 years.
An elevated frequency of APOE e4among case patients was detected in ev¬
ery group, but the APOE e4-AD associa¬tion was weaker among African Ameri¬cans (ORs of 1.1 and 5.7 in e3/e4 and e4/e4subjects, respectively) than among Cau¬casians (ORs of2.7-3.2 and 12.5-14.9 in e3/e4 and e4/e4 subjects, respectively). How¬ever, the largest data set of African-American subjects was ascertained as a
community sample35 and was differentfrom the other studies of African Ameri¬cans in clinical populations.14·15·36,43 Largerand more diverse groups of AfricanAmericans need to be studied. The odds ofAD were also lower among Hispanicsthan among Caucasians, which is attrib¬uted largely to a paucity ofe4 homozygousHispanic patients. The e3/e4 genotypeconfers a significantly increased risk ofAD in Hispanics, but the e4/e4 genotypedoes not (Table 3). In contrast, the APOEe4-AD association among Japanese sub¬jects was substantially stronger (ORs of5.6 and 33.1 for e3/e4 and e4/e4 genotypes,respectively) than among Caucasians.
A protective effect ofthe e2 alíele was
observed, but it was limited to the e2/e3genotype and possibly the e2/e2 geno¬type. In comparison with the variable ef¬fect of the e3/e4 and e4/e4 genotypesacross ethnic groups, the e2/e3 geno¬type appears to be equally protective(OR=0.6) in all populations representedin our sample. The influence ofthe raree2/e2 genotype on AD risk could not bediscerned even in this very large sample.A novel finding ofour study is that, amongCaucasians and possibly other groups,genotypes e2/e4 and e3/e3 are not equiva¬lent in terms of AD risk.
Although the APOE e4-AD associa¬tion has been previously documented inpersons younger than 65 years,8'11,51·77our study is the first to demonstrate in¬creased risk in persons as young as 40years. Among Caucasians recruitedfrom clinical settings, the ORs for ADassociated with the e4 alíele increaseduntil age 60 years in e3/e4 and e4/e4 per¬sons and age 70 years in e2/e4 persons,although it diminished thereafter. Agedid not influence the benefit ofthe e2/e3genotype. Using a similar analytic strat¬egy, Corder et al15 also observed sub¬stantial decrement in risk in e3/e4 ande4/e4 persons aged 60 years and older ina smaller sample from the United States.Bickeböller et al78 also observed lowerORs for the e4 alíele in the youngest (<60years) and oldest (>80 years) age groupsand ORs below 1 for e2/e3 persons acrossall age groups.78 In a study of affectedrelative pairs, Blacker et al42 showed aweaker APOE e4-AD association afterage 70 years.
Life-table studies suggest that thehigher risk of AD in women than men isnot because ofgreater longevity in wom¬en.79 Sex effects have been attributed tosex-specific susceptibility among e3/e4hétérozygotes,27 but this is controver¬sial.78·80 Poirier et al8 observed a strongerAPOE e4-AD association in women thanmen, which is primarily attributable to a
higher proportion of e3/e4 among femalecase patients but not controls comparedwith men. After adjusting for age, our
meta-analysis confirms the presence ofasex effect on risk oí APOE e3/e4 amongCaucasians and possibly Hispanics butnot among Japanese. The present studyand genetic modeling studies81 suggestthat women may have higher suscepti¬bility to AD than men regardless ofAPOE genotype. It is likely that other
factors such as estrogen, independentlyor in concert with certain APOE geno¬types, also account for some of these sexdifferences in risk of AD.31,82
Reporting bias is unlikely to havegreatly influenced our results. Once theAPOE e4-AD association was estab¬lished15·18 and confirmed in independentdata sets,4 negative findings37·83 showingdifferent patterns of association17,32,35were equally or perhaps more likely toattract the attention of reviewers for sci¬entific and medical journals. Nearly allthese studies were included.
Our meta-analysis has shown thatodds ofAD among e4 carriers relative tothose lacking e4 initially increase buteventually decrease with age. AmongCaucasians, the APOE e4-AD associa¬tion is not uniform across sexes, and e4 isa weaker risk factor for AD among Af¬rican Americans and Hispanics thanamong Caucasians and Japanese. Eventhough a large proportion ofthe data inthis study were derived from self-se¬lected case patient and control groups,conclusions about genotype RR are ro¬bust because subjects were not selectedon the basis oí APOE status. However,these results do not address the efficacyof APOE as a diagnostic test becauseantemortem data were unavailable forcase patients who had undergone au¬
topsy. The predictive value of APOEgenotype for diagnostic purposes hasbeen estimated in relatively smallsamples of case patients with probableAD who were followed up to au¬
topsy ,62·84·85 The genotype-specific ORspresented in the figures are relativeodds, and thus are also not appropriatefor AD risk assessment in cognitivelynormal persons. Use ofAPOE genotypein predictive test situations requires ab¬solute risk information from prospective
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cohort studies. A number ofprospectivestudies are under way, but most of thesubjects in these studies have not beenfollowed up long enough or have not un¬
dergone sufficient diagnostic scrutiny toderive accurate and precise risk esti¬mates beyond age 80 years, particularlyfor the rarer genotypes like e2. BecauseORs computed in the meta-analysis ap¬proximate RRs, we anticipate that RRsestimated in prospective studies will becomparable with our findings by age,sex, and ethnic group.
This study was supported in part by contributionsfrom the Alzheimer Association, Chicago, 111,Athena Diagnostics, Ine, Worcester, Mass, and bygrant AG-09029 from the National Institutes ofHealth, Bethesda, Md.
We are indebted to numerous colleagues whocontributed to the clinical evaluation of subjects,collection of tissue specimens, APOE genotyping,and preparation of data sets. We are especiallygrateful to Michael Watson, PhD, Washington Uni¬versity, St Louis, Mo, and the American College ofMedical Genetics, Bethesda, Md, for help in initiat¬ing the study. The data setprovided by Marilyn Al¬bert, PhD, Massachusetts General Hospital, Bos¬ton, Mass, was established as part of the NationalInstitute of Mental Health's Genetics Initiative forAlzheimer Disease. The contribution of unpub¬lished data by Sandro Sorbi, MD, Universität diFirenze, Firenze, Italy, was supported by CNR PFAging and Telethon-Italia E 482.
The APOE and Alzheimer Disease Meta Analy¬sis Consortium
Steering Committee: Lindsay A. Farrer, PhD(chair), Boston University School of Medicine, Bos¬ton, Mass; L. Adrienne Cupples, PhD, Boston Uni¬versity School of Medicine; Jonathan L. Haines,PhD, Massachusetts General Hospital, Boston; Bra¬dley Hyman, MD, PhD, Massachusetts GeneralHospital; Walter A. Kukull, PhD, University ofWashington, Seattle; Richard Mayeux, MD, Colum¬bia University, New York, NY; Richard H. Myers,PhD, Boston University School of Medicine; Mar¬garet A. Pericak-Vance, PhD, Duke UniversityMedical Center, Durham, NC; Neil Risch, PhD,Stanford University Sch Medicine, Stanford, Calif;Cornelia M. van Duijn, PhD, Erasmus University,Rotterdam, the Netherlands.
Contributors: Marilyn S. Albert, PhD, Massa¬chusetts General Hospital; Luigi Amaducci, MD, Uni¬versität di Firenze, Firenze, Italy; Alex Auchus, MD,Emory University School of Medicine, Atlanta, Ga;Sanford A. Auerbach, MD, Boston University SchoolofMedicine; Warren W. Barker, MS, Mt Sinai Medi¬cal Center, Miami, Fla; Christine Bétard, PhD, Cen¬tre Hospitaller Côte-des-Neiges, Montreal, Que¬bec; Deborah Blacker, MD, ScD, MassachusettsGeneral Hospital; Angelo Bianchetti, MD, Geriat¬ric Research Group, Brescia, Italy; Marie-Christine Chartier-Harlin, PhD, Institut Pasteur deLille, Lille, France; Helena Chui, MD, Rancho LosAmigos Medical Center, Downey, Calif; Roger Clar-nette, MBBS, University ofWestern Australia, Ned-lands, Perth; Remy Couderc, PharmD, HôpitalTenon, Paris, France; Fiona Crawford, PhD, Uni¬versity ofSouth Florida, Tampa; Ranjan Duara, MD,Mt Sinai Medical Center, Miami; Jim A. Edward-son, PhD, Medical Research Council, Newcastle, En¬gland; Isabel Fortier, PhD, Centre Hospitaller Côte-des-Neiges; Bernard Frigard, MD, Institut Pasteurde Lille; Giovanni B. Frisoni, MD, Geriatric Re¬search Group; Douglas Galasko, MD, Veterans Af¬fairs Medical Center, San Diego, Calif; Samuel Gandy,MD, PhD, Cornell Medical Center, New York, NY;Serge Gautier, MD, Douglas Hospital Research Cen¬ter, Montreal, Quebec; Denis Gauvreau, PhD, Cen¬tre Hospitalier Côte-des-Neiges; Maria Gearing,PhD, Emory University School of Medicine; AlisonGoate, DPhil, Washington University; Robert C.
Green, MD, Georgia State University, Atlanta; JohnH. Growdon, MD, Massachusetts General Hospital;Kathleen S. Hall, PhD, Indiana University Schoolof Medicine, Indianapolis; John Hardy, PhD, MayoClinic, Jacksonville, Fla; Charles R. Harrington, PhD,Cambridge University, Cambridge, England; HughC. Hendrie, MB, ChB, Indiana University School ofMedicine; Albert Hofman, MD, PhD, Erasmus Uni¬versity; Henry Houlden, PhD, Mayo Clinic, Jack¬sonville; Kim A. Jobst, DM, Oxford University, Ox¬ford, England; Carole Johnstone, Oxford University;Jun Kawamata, MD, Kyoto University, Kyoto, Ja¬pan; Robert Katzman, MD, University of Califor¬nia, San Diego; Keijo Koivisto, MD, University Hos¬pital of Kuopio, Kuopio, Finland; Alexander Kurz,MD, Technical University, Munich, Germany; Jo¬hanna Kuusisto, MD, University Hospital of Kuo¬pio; Markku Laakso, MD, University Hospital ofKuo¬pio; Eric Larson, MD, University of Washington,Seattle; Nicola Lautenschlager, MD, Technical Uni¬versity; Terho Lehtimaki, MD, PhD, Tempere Uni¬versity Hospital, Tampere, Finland; Maarit Lehto-virta, MD, PhD, University Hospital ofKuopio; AllanI. Levey, MD, PhD, Emory University School ofMedicine; Carol F. Lippa, MD, Allegheny Univer¬sity Hospital, Philadelphia, Pa; Gerard Lucette, PhD,Centre Hospitalier Universitaire, Reims, France;Florence Mahieux, MD, Hôpital Tenon; David M. A.Mann, PhD, University of Manchester, Manches¬ter, England; Ralph Martins, PhD, University ofWestern Australia; Ian G. McKeith, MD, Medical Re¬search Council; Suzanne S. Mirra, MD, Emory Uni¬versity School of Medicine; Philip Montgomery,MBBS, FRACMA, University of Western Austra¬lia; Christopher M. Morris, PhD, Medical ResearchCouncil; John C. Morris, MD, Washington Univer¬sity; Ulrich Mueller, MD, PhD, Justus-Liebeg-Universität, Giessen, Germany; Michael Mullan, MD,PhD, University of South Florida; Leena Myk-kanen, MD, University Hospital of Kuopio; Bene¬detta Nacmias, PhD, Universität di Firenze; Jose¬phine Nalbantoglu, PhD, Douglas Hospital ResearchCenter; Kaoni Okuizumi, MD, Brain Research In¬stitute, Niigata University, Niigata, Japan; MiekoOtsuka, MD, PhD, Omiya Medical Center, OmiyaCity, Japan; Frank Owen, PhD, University ofManchester; Florence Pasquier, MD, Hôpital RogerSalengro, Lille, France; Robert H. Perry, MD, New¬castle General Hospital, Newcastle upon Tyne, En¬gland; Ronald C. Petersen, MD, PhD, Mayo Clinic,Rochester, Minn; Eric Pfeiffer, MD, University ofSouth Florida; Stuart M. Pickering-Brown, PhD, Uni¬versity ofManchester; Tuula Pirttila, MD, PhD, Tem¬pere University Hospital; Judes Poirier, PhD, Doug¬las Hospital Research Center; Valluri S. Rao, PhD,Brigham and Women's Hospital, Boston; Paavo Riek-kinen, Sr, MD, PhD, University Hospital ofKuopio;Yves Robitaille, MD, Centre Hospitalier Côte-des-Neiges; Allen D. Roses, MD, Duke University; Mar¬tin Rossor, MD, St Mary's Hospital Medical School,London, England; Amrik Sahota, PhD, Indiana Uni¬versity School ofMedicine; Tsunao Saitoh, PhD, Uni¬versity ofCalifornia, San Diego; David St Clair, DPhil,University of Aberdeen, Aberdeen, Scotland; Pe¬ter H. St George-Hyslop, MD, University ofToronto,Toronto, Ontario; Ann Saunders, PhD, Duke Uni¬versity; Julie Schneider, MD, Emory UniversitySchool of Medicine; Shin'ichi Shoji, MD, PhD, Uni¬versity ofTsukuba, Tsukuba City, Japan; Shun Shi-mohama, MD, PhD, Kyoto University; Arjen J.C.Slooter, MD, Erasmus University; A. David Smith,DPhil, University of Oxford; Hilkka Soininen, MD,PhD, University Hospital of Kuopio; Sandro Sorbi,MD, Universität di Firenze; Yaakov Stern, PhD, Co¬lumbiaUniversity; ChristopherTalbot, PhD, Wash¬ington University; Rudolph Tanzi, PhD, Massachu¬setts General Hospital; Marco Trabucchi, MD,Geriatric Research Group; Benjamin Tycko, MD,PhD, Columbia University; Akira Ueki, MD, PhD,Omiya Medical Center; Christine Van Broeck-hoven, PhD, University ofAntwerp, Antwerp, Bel¬gium; Patrick Vermersch, MD, Institut Pasteur deLille; Stephen Waring, DVM, PhD, Mayo Clinic,Rochester, Minn; John Wells, PhD, ENR VeteransAffairs Hospital, Bedford, Mass; Kathleen Welsh-
Böhmer, PhD, Duke University; John H. Xuereb,MD, Cambridge University; Nobuhiro Yamada, MD,PhD, University of Toyko; Kimiko Yamakawa-Kobayashi, MD, PhD, University ofTsukuba; Toshi-hiro Yoshizawa, MD, PhD, University of Tsukuba;George S. Zubenko, MD, University of PittsburghMedical Center, Pittsburgh, Pa.
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