No association or linkage between an intronic polymorphism of presenilin-1 and sporadic or late-onset familial Alzheimer disease

Recent reports have shown an association between an intronic polymorphism of the presenilin-1 (PSEN1) gene and late-onset (age at onset > 65) familial and sporadic (no family history) Alzheimer disease (AD). The reported association was independent of the effect of the only previously identified gene associated with late-onset AD, APOE. Blood samples were obtained from members of 122 multiplex AD families, 42 unrelated cases of AD with positive family histories of dementia, 456 sporadic cases of AD, and 317 controls of similar ages at examination to the cases. These samples were genotyped for an intronic polymorphism of the PSEN1 gene, located 3' to exon 8, and the data analyzed for evidence of association or linkage. The samples were also genotyped for APOE and the data analyzed to see if the association or linkage changed when controlling for APOE genotype. There was no statistically significant increase (at alpha = .01) in allele 1 (199 bp) or genotype 1/1 in the sporadic AD cases, or in a random sample of one affected from each multiplex family, compared to controls. When examining the effect of the PSEN1 polymorphism while controlling for APOE genotype, APOE genotype was strongly associated with AD, but the PSEN1 polymorphism genotype was not. Model-trait dependent (lod score) and independent (Sim1BD) methods detected no evidence of linkage between PSEN1 and AD. In this independent dataset, the previously reported association between the intronic PSEN1 polymorphism and AD cannot be confirmed, and the conclusion that PSEN1 is a major susceptibility gene for late-onset AD is not supported.

Fine mapping of the chromosome 12 late-onset Alzheimer disease locus: potential genetic and phenotypic heterogeneity

Apolipoprotein E (APOE) is the only confirmed susceptibility gene for late-onset Alzheimer disease (AD). In a recent genomic screen of 54 families with late-onset AD, we detected significant evidence for a second late-onset AD locus located on chromosome 12 between D12S373 and D12S390. Linkage to this region was strongest in 27 large families with at least one affected individual without an APOE-4 allele, suggesting that APOE and the chromosome 12 locus might have independent effects. We have since genotyped several additional markers across the region, to refine the linkage results. In analyzing these additional data, we have addressed the issue of heterogeneity in the data set by weighting results by clinical and neuropathologic features, sibship size, and APOE genotype. When considering all possible affected sib pairs (ASPs) per nuclear family, we obtained a peak maximum LOD score between D12S1057 and D12S1042. The magnitude and location of the maximum LOD score changed when different weighting schemes were used to control for the number of ASPs contributed by each nuclear family. Using the affected-relative-pair method implemented in GENEHUNTER-PLUS, we obtained a maximum LOD score between D12S398 and D12S1632, 25 cM from the original maximum LOD score. These results indicate that family size influences the location estimate for the chromosome 12 AD gene. The results of conditional linkage analysis by use of GENEHUNTER-PLUS indicated that evidence for linkage to chromosome 12 was stronger in families with affected individuals lacking an APOE-4 allele; much of this evidence came from families with affected individuals with neuropathologic diagnosis of dementia with Lewy bodies (DLB). Taken together, these results indicate that the chromosome 12 locus acts independently of APOE to increase the risk of late-onset familial AD and that it may be associated with the DLB variant of AD.

Complete genomic screen for disease susceptibility loci in nuclear families

We performed genome-wide model dependent and independent analyses on a simulated data set of 400 families segregating for a rare disorder. Regions on chromosomes 1, 3, and 5 were consistently indicated across the various analyses performed. Follow-up analyses included stratification for locus heterogeneity and clinical phenotype and studies of gene x gene and gene x environment interaction. The region around D1G024 was most notable, showing strong association and linkage with the trait. We also identified regions D3G043-46 and D5G037-39 by strong linkage and association findings and region D1G001-09 by linkage analysis. A complex statistical interaction was suggested between D1G024, D3G046 and environmental factor 1. This report suggests that traditional methods of analysis can be implemented to analyze and describe the mechanisms that may underlie the more complex genetic disorders.

No association between the HLA-A2 allele and Alzheimer disease

The apolipoprotein E (APOE)-4 allele is a major risk factor for late-onset Alzheimer disease (AD), but it does not account for all the genetic variation in late-onset AD; thus, other genetic markers must be examined. Previous studies suggest an HLA-A2 allele association with risk and earlier onset age of AD. Because these effects may be additive to those of APOE-4, we studied HLA-A2 and APOE-4 frequencies in AD patients and cognitively intact controls. A total of 712 unrelated Caucasian subjects included 479 patients with AD (435 sporadic, 44 familial) and 233 controls. Patients (mean+/-SD age 73.9+/-7.9 years, range 42-93 years) had probable AD, according to standard diagnostic criteria; controls (mean+/-SD age 70.4+/-8.5 years, range 37-92 years) were cognitively intact. APOE and HLA-A2 typing used polymerase chain reaction to indicate the number of APOE-4 alleles present as well as the presence (A1/A2, A2/A2 genotypes) or absence (A1/A1 genotype) of HLA-A2. A two-way analysis of variance was used to assess the effect of the HLA-A2 allele on age at onset of dementia. No association between HLA-A2 and APOE-4 was found, and the presence of HLA-A2 allele did not increase AD risk. There was also no evidence for an association between HLA-A2 and earlier onset age of AD. Examination age, sex, family history of AD, and recruitment site had no influence on these results. In conclusion, the HLA-A2 allele did not influence AD risk or onset age in this study population. A2 heterozygosity, and population differences, including stratification sub-structures, and other undetermined factors could contribute to discrepant findings among studies.

Analysis of association between Alzheimer disease and the K variant of butyrylcholinesterase (BCHE-K)

Butyrylcholinesterase (BCHE) is an enzyme expressed in most human tissues. Recently, an increased odds of carrying the K variant of BCHE (BCHE-K) was reported among Alzheimer disease (AD) cases as compared with controls. We tested our data set of 245 sporadic AD cases and 241 controls for an association between BCHE-K, APOE4, and AD using logistic regression and chi-square analyses. The sib transmission disequilibrium test (S-TDT) was also used to test for differences in BCHE-K allele frequencies between 163 discordant sib-pairs selected from multiplex AD families. No statistically significant differences were noted between BCHE-K case and control allele frequencies even after stratifying by APOE4 status. S-TDT analysis between the BCHE-K variant and AD was also not significant (P = 0.52). We conclude that BCHE-K is not a major genetic risk factor for AD in our study population.

Memory self-appraisal in middle-aged and older adults with the apolipoprotein E-4 allele

OBJECTIVE

Because subjective memory complaints may indicate subtle functional brain abnormalities, the authors studied the influence of the major genetic risk for Alzheimer's disease, the apolipoprotein E-4 (APOE-4) allele, on self-reports of memory performance in middle-aged and older adults.

METHOD

Subjective and objective assessments of memory performance were compared in relation to the presence or absence of the APOE-4 allele in 39 cognitively intact persons with mild memory complaints.

RESULTS

Subjects with the APOE-4 allele had lower scores on objective verbal memory and on the subjective memory measure for retrospective functioning. Among the subjects in the age range where APOE-4 has its greatest influence on the risk of Alzheimer's disease (55-74 years), the APOE-4 group had lower scores on the subjective memory measure for frequency of forgetting. Moreover, the standardized difference in retrospective functioning scores between the two genetic risk groups increased when the mid-age-range group was examined rather than the whole study group.

CONCLUSIONS

The APOE-4 allele is associated with increased subjective memory impairment in middle-aged and older adults. Longitudinal studies of age-related memory loss should include genetic risk and subjective memory measures as potential predictors of decline.

Association between bleomycin hydrolase and Alzheimer's disease in caucasians

A recent study showed modest evidence for an increased frequency of the bleomycin hydrolase (BH) V/V genotype in Alzheimer's disease (AD) patients compared with non-demented controls. To test this hypothesis, we examined this polymorphism in 621 rigorously evaluated patients and 502 control subjects (all caucasian) but were unable to detect an association between BH and AD even after controlling for age, gender, and apolipoprotein E (ApoE) genotype. We conclude that this polymorphism does not account for inherited susceptibility to AD in the populations represented in this sample.

No association of alpha1-antichymotrypsin flanking region polymorphism and Alzheimer disease risk in early- and late-onset Alzheimer disease patients

The alpha1-antichymotrypsin (AACT)-155 allele was found elsewhere to have a significant effect on Alzheimer disease (AD) risk in individuals with at least one APOE-4 allele. We compared AACT genotypes of 284 cases of sporadic AD and 172 controls. The frequency of the AACT-155 allele did not differ significantly between cases and controls, either overall or when restricted to subjects with at least one APOE-4 allele. Logistic regression controlling for age and sex failed to show an effect due to AACT either alone or acting with APOE. There was no evidence of an interaction between APOE-4 and the AACT-155 allele to reduce age at onset. Thus, our data do not support an association of AACT-155 with risk or age at onset in AD.

Evidence for anticipation in autosomal dominant limb-girdle muscular dystrophy

Anticipation, an increase in severity or decrease in age of onset (AO) inherent in the transmission of the disease gene from affected parent to affected child, has been increasingly described in human disease. To assess anticipation in a large kindred in which autosomal dominant limb-girdle muscular dystrophy (LGMD1A) is segregating, age of disease onset was collected from patient interviews of affected family members. A total of 25 parent-offspring pairs, in which the parents are three (3R), four (4R), or five (5R) generations removed from a common founding ancestor, were available for analysis. Life table analyses showed significant decreases in age at first reported symptoms in the offspring of the 3R (chi2=5.55, p=0.02) and 4R (chi2=7.81, p=0.005) parents. Pairwise analyses confirmed this decrease with a median decrease of 13 years in transmission to offspring from 3R parents and 18 years in transmission to offspring from 4R parents. The finding of anticipation in this pedigree suggests that the mutation in LGMD1A may be the result of the expansion of an unstable trinucleotide repeat.

Lack of association between apolipoprotein E genotype and sporadic amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neuro-degenerative disorder with both sporadic and familial forms. Approximately 20% of autosomal dominant ALS is caused by mutations in the Cu/Zn superoxide dismutase (SOD1) gene. The causes of the remaining forms of ALS are unknown. The apolipoprotein E (APOE) gene is a known genetic risk factor for Alzheimer disease (AD), another neuro-degenerative disease. The APOE-4 allele increases risk and decreases age at onset in AD. Studies examining ALS and APOE have failed to show a significant effect of APOE on overall risk in ALS. Studies examining the effect of APOE-4 on site of onset in ALS (bulbar or limb) have been contradictory, with some studies showing an APOE association with bulbar onset and others showing no effect. Sample size was limited in these previous reports, particularly with respect to the number of bulbar onset cases (n = 33, 34 and 53). The present study examines a large collaborative data set of ALS patients (n = 363; 95 with bulbar onset) and age-matched neurologically normal controls. The results for these data showed no significant differences in the percentage of subjects with the APOE-4/4 and APOE-4/X genotypes (X = APOE-2 or APOE-3) when comparing cases and controls in both the overall data set or in the data set stratified by site of onset. Similarly, logistic regression analysis in the overall and stratified data set while controlling for sex showed no increase or decrease in risk of ALS associated with the APOE-4 allele. In addition, there were no significant differences in age at onset between patients with APOE-X/X, and APOE-4/4 or APOE-4/X genotypes, overall or stratified by site of onset. We conclude based on these data that the APOE gene is not a major genetic risk factor for site of onset in ALS.

No genetic association between the LRP receptor and sporadic or late-onset familial Alzheimer disease

The low-density lipoprotein receptor-related protein gene (LRP1) is often mentioned as a candidate gene for Alzheimer disease (AD) because of its role as a receptor for apolipoprotein E (apoE), a major genetic risk factor for late-onset familial and sporadic AD. A recent association study of a tetranucleotide repeat polymorphism located 5' to the LRP1 gene detected an increase in the 87 base pair allele in AD cases compared to unaffected controls. Additionally, an independent study involving a genomic screen for genes associated with late-onset AD identified a region as a possible location of a late-onset AD gene on chromosome 12p between D12S373 and D12S390, about 10 cM proximal to LRP1. We examined 144 late-onset multiplex AD families, 436 sporadic AD cases, and 240 controls and found no evidence of linkage or association of LRP1 and AD. Our data indicate that genetic variation of the LRP1 gene is not a major risk factor in the etiology of AD.

Complete genomic screen in late-onset familial Alzheimer's disease

Alzheimer's disease (AD) is a complex genetic disorder. Linkage analysis has helped unravel a portion of the genetic component of AD by identifying four loci that play a role in the genetics of AD (amyloid precursor protein, presenilin 1, presenilin 2, and apolipoprotein E). These loci account for approximately 50% of the genetic etiology of AD. A total genomic screen is an efficient way to identify additional genetic effects in AD. A series of multiplex late-onset (>60 years) AD families were ascertained (NINDS-ADRDA diagnostic criteria) and sampled. A subset (n = 16) of the largest families (52 affecteds with DNA, 83 unaffecteds with DNA) were used to rapidly screen the genome (n = 280 markers) for additional major genetic effects. Critical values for regional follow-up were p < or =0.05 for SimIBD or sibpair analysis and/or a LOD score > or = 1.00. Fifteen regions warranted initial follow-up based on these criteria. An additional screening set was used (n = 38 families, 89 affecteds with DNA, 216 unaffecteds with DNA) for the follow-up analysis. These analyses revealed four regions of continued interest on chromosomes 4, 6, 12, and 20. Chromosome 12 presented the strongest results. Peak two point "affecteds only" LOD scores were 1.3, 1.6, 2.7, and 2.2 and (affected relative pair SimIBD) p values were 0.04, 0.03, 0.14, and 0.04 for D12S373, D12S1057, D12S1042, and D12S390, respectively. These markers span approximately 30 cm near the centromeric region of chromosome 12. Sibpair analysis resulted in two point Maximum Lod Score (MLS) results of 0.4, 1.2, 3.2, and 1.0 for the above markers. Multipoint MLS analysis supported these findings. Saturation mapping of all available markers in the chromosome 12 region as well as further investigation of the regions on 4, 6, and 20 is ongoing with candidate gene analysis to follow.

Complete genomic screen in late-onset familial Alzheimer disease. Evidence for a new locus on chromosome 12

CONTEXT

Four genetic loci have been identified as contributing to Alzheimer disease (AD), including the amyloid precursor protein gene, the presenilin 1 gene, the presenilin 2 gene, and the apolipoprotein E gene, but do not account for all the genetic risk for AD.

OBJECTIVE

To identify additional genetic risk factors for late-onset AD.

DESIGN

A complete genomic screen was performed (N=280 markers). Critical values for chromosomal regional follow-up were a P value of .05 or less for affected relative pair analysis or sibpair analysis, a parametric lod score of 1.0 or greater, or both. Regional follow-up included analysis of additional markers and a second data set.

SETTING

Clinic populations in the continental United States.

PATIENTS

From a series of multiplex families affected with late-onset (> or =60 years) AD ascertained during the last 14 years (National Insititute of Neurological Disorders and Stroke-Alzheimer's Disease and Related Disorders Association diagnostic criteria) and for which DNA has been obtained, a subset of 16 families (135 total family members, 52 of whom were patients with AD) was used for the genomic screen. A second subset of 38 families (216 total family members, 89 of whom were patients with AD) was used for the follow-up analysis.

MAIN OUTCOME MEASURES

Linkage analysis results generated using both genetic model-dependent (lod score) and model-independent methods.

RESULTS

Fifteen chromosomal regions warranted initial follow-up. Follow-up analyses revealed 4 regions of continued interest on chromosomes 4, 6, 12, and 20, with the strongest results observed forchromosome 12. Peak 2-point affecteds-only lod scores (n=54) were 1.3, 1.6, 2.7, and 2.2 and affected relative pairs P values (n=54) were .04, .03, .14, and .04 for D12S373, D12S1057, D12S1042, and D12S390, respectively. Sibpair analysis (n=54) resulted in maximum lod scores (MLSs) of 1.5, 2.6, 3.2, and 2.3 for these markers, with a peak multipoint MLS of 3.5. A priori stratification by APOE genotype identified 27 families that had at least 1 member with AD whose genotype did not contain an APOE*4 allele. Analysis of these 27 families resulted in MLSs of 1.0, 2.4, 3.7, and 3.3 and a peak multipoint MLS of 3.9.

CONCLUSIONS

A complete genomic screen in families affected with late-onset AD identified 4 regions of interest after follow-up. Chromosome 12 gave the strongest and most consistent results with a peak multipoint MLS of 3.5, suggesting that this region contains a new susceptibility gene for AD. Additional analyses are necessary to identify the chromosome 12 susceptibility gene for AD and to follow up the regions of interest on chromosomes 4, 6, and 20.

Apolipoprotein E epsilon2 does not increase risk of early-onset sporadic Alzheimer's disease

We examined the association of apolipoprotein E (ApoE) genotype and the risk of early-onset Alzheimer's disease (AD) in 209 white early-onset sporadic cases (43% male) and 303 white controls (48% male) of similar age distribution. The risk of AD was significantly increased, relative to the 3/3 genotype, in people with the 4/4, 3/4, and 2/4 genotypes, controlling for age at time of examination and sex. The 2/3 genotype reduced slightly the risk of AD, although the effect was not statistically significant. We conclude, contrary to some previous reports, that the ApoE epsilon2 allele does not increase the risk of early-onset sporadic AD.

Locus heterogeneity, anticipation and reduction of the chromosome 2p minimal candidate region in autosomal dominant familial spastic paraplegia

We examined 11 Caucasian pedigrees with autosomal dominant 'uncomplicated' familial spastic paraplegia (SPG) for linkage to the previously identified loci on chromosomes 2p, 14q and 15q. Chromosome 15q was excluded for all families. Five families showed evidence for linkage to chromosome 2p, one to chromosome 14q, and five families remained indeterminate. Homogeneity analysis of combined chromosome 2p and 14q data gave no evidence for a fourth as yet unidentified SPG locus. Recombination events reduced the chromosome 2p minimum candidate region (MCR) to a 3 cM interval between D2S352 and D2S367 and supported the previously reported 7 cM MCR for chromosome 14q. Age of onset (AO) was highly variable, indicating that subtypes of SPG are more appropriately defined on a genetic basis than by AO. Comparison of AO in parent-child pairs was suggestive of anticipation, with a median difference of 9.0 years (p<0.0001).

Major depression and all-cause mortality among white adults in the United States

PURPOSE

Depression is the most common psychiatric illness affecting adults. Despite the importance of a potential link between major depression and mortality, research has been surprisingly sparse.

METHODS

Information on 57,897 white adults aged 25 years and older who were included in the mental health supplement of the 1989 National Health Interview Survey was linked with the National Death Index to examine the relationship of major depression to mortality. Death status was obtained through December 1991. Sex-specific hazard rate ratios for mortality were calculated by Cox proportional hazards regression and Poisson regression to adjust for potential confounders (age, education, marital status, body mass index, and whether the target subject or a family member completed the survey about the subject).

RESULTS

Major depression was reported for 223 (0.8%) of 27,345 men and 392 (1.3%) of 30,552 women. During the 2.5-year follow-up, death certificate data were obtained for 848 (3.1%) men and 651 (2.1%) women. The adjusted hazard rate ratios for all-cause mortality associated with major depression were 3.1 (95% confidence interval; 2.0-4.9) for men and 1.7 (95% confidence interval; 0.9-3.1) for women.

CONCLUSIONS

These results suggest that major depression increases risk of all-cause mortality, particularly among men. Further research is needed to explain the mechanism.

Functional health status as a predictor of mortality in men and women over 65

This study evaluated the effect of functional health status on mortality in a sample of community-dwelling older people. White and African-American self-respondents to the 1986 National Health Interview Survey Functional Health Supplement (n = 5, 320) were included in the study. Functional health status was measured by a ten-item unidimensional activities of daily living-instrumental activities of daily living (ADL-IADL) scale and a three-item cognitive ADL scale. Proportional hazards regression was used to evaluate the effect of increasing score on the ten-item ADL-IADL scale on risk of mortality over a 5-year period while controlling for demographic, social, and health status covariates. In both men and women, increasing score on the ADL-IADL scale was predictive of mortality, adjusting for increasing age, poor self-rated health, low body mass index in women, and being an unmarried man. These findings indicate that a unidimensional scale consisting of both ADL and IADL items is useful in predicting mortality, controlling for the effect of covariates in sex-specific models.

Risk of institutionalization among community long-term care clients with dementia

South Carolina Community Long-Term Care (CLTC) data were used to identify factors increasing the risk of institutionalization in people with dementia. Clients diagnosed with dementia and observed at least twice between June 1993 and December 1994 (N = 786) were studied. Logistic regression determined that clients with a decline in ADL function who were white, had a nonrelative or child as a caregiver, and were diagnosed with Alzheimer's disease were at increased risk of institutionalization. Identifying CLTC clients at increased risk of institutionalization could be useful in designing additional interventions to prevent institutionalization or in planning the transition to institutional care.

False positive rates in a genomic screen for complex quantitative traits

We conducted a genomic screen for genes associated with Q1, Q2, and Q3 in 239 nuclear pedigrees from replicate 115, Problem Set 2A. We compared false positive (FP) and true positive (TP) rates for three significance levels and two map densities. Using the 2 cM genetic map and alpha = 0.05 produced the most FP but detected the greatest number of major genes. Following up only 31 plateaus (two or more adjacent markers with significant results) from the 2 cM screen eliminated some FP, but failed to detect MG3 for Q3. Multipoint analysis reduced the number of priority regions from 31 to seven; only two of these regions were TP. Replication of the two-point analysis of plateau markers in replicate 80 detected all of the genes associated with Q1 and Q2, but not Q3. Multipoint analysis in replicate 80 failed to replicate any genes associated with Q1, Q2, or Q3, but "replicated" two FP regions. While FP may be reduced by decreasing map density, considering only plateaus for follow up and decreasing significance levels, such adjustments may also fail to detect weak TP. Multipoint analysis and replication in independent data sets may not be reliable methods of distinguishing FP from TP.

Survival after AIDS diagnosis in South Carolina, 1982-1992

The results of this study demonstrate that age, ethnicity, and AIDS-defining diagnosis are important predictors of survival time after AIDS diagnosis, and should be considered when planning treatment and services for people with AIDS. Future studies in states with large rural populations will be helpful in further understanding the natural history of the disease in areas outside the nation's major population centers. These could improve on the results of the present study by actively following up all cases to determine mortality status, collecting detailed clinical information on AIDS-defining diagnoses (with dates), collecting information on treatment of HIV infection and associated opportunistic infections, and evaluating service utilization. Monitoring survival trends over time remains an effective tool in evaluating the success of current efforts to provide treatment and services to people with AIDS.

Naming in dementia secondary to Parkinson's, Huntington's, and Alzheimer's diseases

Confrontation naming problems have been found in patients with dementia secondary to Alzheimer's (AD), Huntington's (HD), and in a subset of Parkinson's disease (PD) patients with dementia. The source of the naming deficit has not been established. The "Perception" and the "Semantic Feature" theories have been proposed to explain this naming dysfunction. Subjects with dementia secondary to AD, HD, and PD were given three tasks to determine which theory best explained the source of confrontation naming problems. The three tasks including picture matching, visual recognition, and confrontation naming were given to 42 subjects with dementia secondary to AD, HD, and PD controlled for severity of dementia, and to age-matched controls. Subjects with dementia did not have significantly more difficulty matching pictures but did have more difficulty associating pictures through semantic features. Subjects with mild dementia secondary to AD and HD had significantly more confrontation naming errors than subjects with mild dementia secondary to PD and normal controls. All subjects with moderate dementia had significantly more confrontation naming errors than normal controls. Statistical power may have been limited due to the small number of subjects in each group. The source of the reduction in confrontation naming performance in subjects with dementia secondary to AD, HD, and PD originated in the deterioration of semantic fields. The perception theory was rejected as findings were consistent with the semantic feature theory.

Epidemiology of Alzheimer's disease

In summary, while only a few risk factors for Alzheimer's disease have been identified, several large collaborative studies of elderly populations are currently underway. As measurement techniques improve, the ability to diagnose this disease in its early stages will make the search for risk factors more feasible.

Survival of Alzheimer's disease patients with regard to pattern of care in South Carolina, 1988-1993

The length of time from diagnosis of AD to death was compared among three groups of AD patients in South Carolina. Each group received a different pattern of care. The survival time from diagnosis to death was longest among those who lived in institutions (mean three years for men, 4.6 years for women), and shortest among those who lived alone in the community (1.7 years for men, two years for women). The longer survival time of those who receive care (either in the community or in facilities) suggests that persons with AD benefit from personal attention to health needs. Providing additional support to family members of those with AD could help patients remain in the community longer, thus maintaining quality of life. For those who have no support in the community, efforts should be made to increase access to facilities.