Apolipoprotein E genotype and major depression in a community of older adults. The Cache County Study

Association of the APOE gene variants with depression in type 2 diabetes

Background

The risk of depression among patients with diabetes is higher than the general population. The exact mechanisms linking these two diseases are mostly unknown. Energy metabolism disorders seem to be a shared pathway. One of the key genes playing important roles in energy metabolism-related pathways is the APOE gene. We aimed to investigate the association of the APOE gene variants with depression among Iranian patients with type 2 diabetes (T2DM).

Methods

Three APOE gene alleles and genotypes frequencies (E2, E3, E4) were determined in 244 patients with T2DM (114 with depression and 130 without depression) using the high-resolution melting (HRM) method on the genomic DNA extracted from the patient's peripheral blood.

Results

Apoe4 allele frequency was significantly higher in T2DM patients without depression compared with those with depression (11.9 vs. 2.2%, p-value < 0.0001 and p-value = 0.001, respectively). Conversely, the wild allele apoe3 frequency was significantly higher in T2DM patients with depression (86% vs., 69%, p-value < 0.0001). Apoe4 carrier status was associated with decreased risk of depression in patients with T2DM [OR: 0.19 (0.07-0.53)].

Conclusion

Our results showed that the apoe4 allele and apoe4 carrier status significantly reduced the risk of depression among patients with T2DM. Further studies are needed to unravel the complex role of the APOE gene in depression among patients with diabetes.

Biological factors influencing depression in later life: role of aging processes and treatment implications

Late-life depression occurring in older adults is common, recurrent, and malignant. It is characterized by affective symptoms, but also cognitive decline, medical comorbidity, and physical disability. This behavioral and cognitive presentation results from altered function of discrete functional brain networks and circuits. A wide range of factors across the lifespan contributes to fragility and vulnerability of those networks to dysfunction. In many cases, these factors occur earlier in life and contribute to adolescent or earlier adulthood depressive episodes, where the onset was related to adverse childhood events, maladaptive personality traits, reproductive events, or other factors. Other individuals exhibit a later-life onset characterized by medical comorbidity, pro-inflammatory processes, cerebrovascular disease, or developing neurodegenerative processes. These later-life processes may not only lead to vulnerability to the affective symptoms, but also contribute to the comorbid cognitive and physical symptoms. Importantly, repeated depressive episodes themselves may accelerate the aging process by shifting allostatic processes to dysfunctional states and increasing allostatic load through the hypothalamic-pituitary-adrenal axis and inflammatory processes. Over time, this may accelerate the path of biological aging, leading to greater brain atrophy, cognitive decline, and the development of physical decline and frailty. It is unclear whether successful treatment of depression and avoidance of recurrent episodes would shift biological aging processes back towards a more normative trajectory. However, current antidepressant treatments exhibit good efficacy for older adults, including pharmacotherapy, neuromodulation, and psychotherapy, with recent work in these areas providing new guidance on optimal treatment approaches. Moreover, there is a host of nonpharmacological treatment approaches being examined that take advantage of resiliency factors and decrease vulnerability to depression. Thus, while late-life depression is a recurrent yet highly heterogeneous disorder, better phenotypic characterization provides opportunities to better utilize a range of nonspecific and targeted interventions that can promote recovery, resilience, and maintenance of remission.

Role of apolipoprotein E epsilon 4 (APOE*ε4) as an independent risk factor for incident depression over a 12-year period in cognitively intact adults across the lifespan

BACKGROUND

The apolipoprotein E ε4 allele (APOE*ε4) is indicated as a risk for Alzheimer's disease and other age-related diseases. The risk attributable to APOE*ε4 for depression is less clear and may be because of confounding of the relationship between dementia and depression.

AIMS

We examined the risk of APOE* ε4 for incident depression and depressive symptomology over a 12-year period across the adult lifespan.

METHOD

Participants were from the Personality and Total Health Through Life study, aged 20 to 24 (n = 1420), 40 to 44 (n = 1592) or 60-64 (n = 1768) at baseline, and interviewed every 4 years since 1999. Ethnicities other than White, those without genotyping and those with depression at baseline, or who reported strokes and scores on the Mini-Mental State Examination <27 at any observation, were excluded.

RESULTS

Over the study period, there was no evidence that APOE*ε4+ was a risk factor for depression, including any depression (odds ratio (OR) = 0.94, 95% CI 0.77-1.16, P = 0.573), major depression (OR = 0.96, 95% CI 0.60-1.53, P = 0.860), minor depression (OR = 0.94, 95% CI 0.67-1.30, P = 0.695) or depressive symptomology (incidence rate ratio (IRR) = 1.02, 95% CI 0.97-1.08, P = 0.451). APOE*ε4 was unrelated to incident depression. Findings were consistent for all age cohorts.

CONCLUSIONS

Among cognitively intact Australian adults who were free of depression at baseline, there was little evidence that APOE*ε4+ carriers are at increased risk for depression over a 12-year period among those who are cognitively intact.

APOE ε4 associated with preserved executive function performance and maintenance of temporal and cingulate brain volumes in younger adults

The APOE ε4 allele is associated with cognitive deficits and brain atrophy in older adults, but studies in younger adults are mixed. We examined APOE genotype effects on cognition and brain structure in younger adults and whether genotype effects differed by age and with presence of depression. 157 adults (32 % ε4 carriers, 46 % depressed) between 20 and 50 years of age completed neuropsychological testing, 131 of which also completed 3 T cranial MRI. We did not observe a direct effect of APOE genotype on cognitive performance or structural MRI measures. A significant genotype by age interaction was observed for executive function, where age had less of an effect on executive function in ε4 carriers. Similar interactions were observed for the entorhinal cortex, rostral and caudal anterior cingulate cortex and parahippocampal gyrus, where the effect of age on regional volumes was reduced in ε4 carriers. There were no significant interactions between APOE genotype and depression diagnosis. The ε4 allele benefits younger adults by allowing them to maintain executive function performance and volumes of cingulate and temporal cortex regions with aging, at least through age fifty years.

Systematic review and meta-analysis of genetic studies of late-life depression

Late-life depression (LLD) is thought to be multifactorial in etiology, including a significant genetic component. While a number of candidate gene studies have been carried out, results remain inconclusive. We undertook a systematic review of all genetic association studies of depression or depressive symptoms in late life published before February 2016, and performed meta-analyses on polymorphisms investigated in three or more independent studies. A total of 46 candidate gene studies examining 56 polymorphisms in 23 genes as well as a genome-wide association study (GWAS) were included. Meta-analyses were conducted for four polymorphisms using random effects models, of which three (APOE, BDNF, SLC6A4) were associated with LLD. These genes are implicated in hippocampal plasticity and stress reactivity, suggesting that dysregulation of these pathways may contribute to LLD. Despite using a large sample, the only GWAS published to date identified only one genome-wide significant locus in the 5q21 region. In the future, larger genetic studies specifically examining LLD, including non-hypothesis-driven GWAS, are required to further identify genetic determinants of LLD.

A 9-year prospective population-based study on the association between the APOE*E4 allele and late-life depression in Sweden

BACKGROUND

It is well established that there is an association between the apolipoprotein E (APOE) ε4 allele (APOE*E4) and Alzheimer's disease. It is less clear whether there is also an association with geriatric depression. We examined the relationship between APOE*E4 and 5-year incidence of depression in a Swedish population-based sample of older adults without dementia and excluding older adults who developed dementia within 4 years after the diagnosis of depression.

METHODS

In 2000-2001, 839 women and men (age range, 70-92 years; mean age, 73.8 years) free from dementia and depression underwent neuropsychiatric and neuropsychological examinations and genotyping of the APOE*E4 allele. Follow-up evaluations were conducted in 2005 and 2009.The association between APOE*E4 allele and 5-year incidence of depression was examined, while avoiding possible confounding effects of clinical or preclinical dementia by excluding participants who had dementia at study entry, subsequently developed dementia during the 9-year follow-up period, or had a decline in Mini-Mental State Examination score of ≥5 points.

RESULTS

Among subjects without depression at study entry and without dementia or significant cognitive decline during the subsequent 9 years, APOE*E4 was prospectively associated with more severe depressive symptoms (b = 1.56, p = .007), incident minor depression (odds ratio = 1.99 [confidence interval = 1.11-3.55], p = .020), and any depression (odds ratio = 1.75 [confidence interval = 1.01-3.03], p = .048).

CONCLUSIONS

The presence of the APOE*E4 allele predicted future depression in this Swedish population study, even after excluding depressed individuals who later developed dementia, suggesting that the APOE*E4 allele could potentially identify people at high risk for clinically significant depression.

Imbalanced hippocampal functional networks associated with remitted geriatric depression and apolipoprotein E ε4 allele in nondemented elderly: a preliminary study

BACKGROUND

Apolipoprotein E (APOE) ε4 allele and a history of geriatric depression are confirmed risk factors of Alzheimer׳s disease (AD). Coexistence of both factors could notably enhance the risk of cognitive impairment in nondemented elderly. However, neural basis of the association remains unclear.

METHODS

Thirty-one remitted geriatric depression (RGD) patients and 29 cognitively normal subjects were recruited and underwent resting-state functional MRI scans. They were further divided into four groups according to their APOE genotypes. Hippocampal seed-based network analysis and two-way factorial analysis of covariance were employed to detect the main effects and interactive effects of RGD and APOE ε4 allele on the hippocampal functional connectivity (HFC) networks. Partial correlation analysis was applied to examine the cognitive significance of these altered HFC networks.

RESULTS

The HFC networks of RGD patients were decreased in the dorsal frontal and increased in the right temporal-occipital regions. For APOE ε4 carriers, the HFC networks were reduced primarily in medial prefrontal regions and enhanced in the bilateral insula. Additionally, when both factors coexisted, the left HFC network was significantly disrupted in the dorsal anterior cingulate cortex and increased in somatomotor and occipital regions. Importantly, the extent of network alterations was linked to inferior cognitive performances in RGD patients and APOE ε4 carriers.

LIMITATIONS

The small sample size may limit the generalizability of our findings.

CONCLUSIONS

RGD and APOE ε4 allele, and their interaction, are associated with the imbalanced HFC network, which may contribute to cognitive deterioration for subjects with a high risk of AD.

Baseline neuropsychiatric symptoms and the risk of incident mild cognitive impairment: a population-based study

OBJECTIVE

The authors conducted a prospective cohort study to estimate the risk of incident mild cognitive impairment in cognitively normal elderly (aged ≥70 years) individuals with or without neuropsychiatric symptoms at baseline. The research was conducted in the setting of the population-based Mayo Clinic Study of Aging.

METHOD

A classification of normal cognitive aging, mild cognitive impairment, and dementia was adjudicated by an expert consensus panel based on published criteria. Hazard ratios and 95% confidence intervals were computed using Cox proportional hazards model, with age as a time scale. Baseline Neuropsychiatric Inventory Questionnaire data were available for 1,587 cognitively normal persons who underwent at least one follow-up visit.

RESULTS

The cohort was followed to incident mild cognitive impairment (N=365) or censoring variables (N=179) for a median of 5 years. Agitation (hazard ratio=3.06, 95% CI=1.89-4.93), apathy (hazard ratio=2.26, 95% CI=1.49-3.41), anxiety (hazard ratio=1.87, 95% CI=1.28-2.73), irritability (hazard ratio=1.84, 95% CI=1.31-2.58), and depression (hazard ratio=1.63, 95% CI=1.23-2.16), observed initially, increased risk for later mild cognitive impairment. Delusion and hallucination did not. A secondary analysis, limited in significance by the small number of study participants, showed that euphoria, disinhibition, and nighttime behaviors were significant predictors of nonamnestic mild cognitive impairment but not amnestic mild cognitive impairment. By contrast, depression predicted amnestic mild cognitive impairment (hazard ratio=1.74, 95% CI=1.22-2.47) but not nonamnestic mild cognitive impairment.

CONCLUSIONS

An increased incidence of mild cognitive impairment was observed in community-dwelling elderly adults who had nonpsychotic psychiatric symptoms at baseline. These baseline psychiatric symptoms were of similar or greater magnitude as biomarkers (genetic and structural MRI) in increasing the risk of incident mild cognitive impairment.

APOE ϵ4, rated life experiences, and affect among centenarians

OBJECTIVES

The purpose of this study was to assess the relationship between apolipoprotein E (APOE), life events and engagement, and subjective well-being (as measured by positive and negative affect) among centenarians. Based on the life stress paradigm, we predicted that higher levels of stress would allow APOE to influence positive and negative affect.

METHOD

196 centenarians and near-centenarians (98 years and older) of the Georgia Centenarian Study participated in this research. The APOE, positive and negative affect, the number of recent (last 2 years) and lifelong (more than 20 years prior to testing) events, as well as a number of life engagement tasks were assessed.

RESULTS

Results suggested that centenarians carrying the APOE ϵ4 allele rated lower in positive affect, the number of lifelong events, and in engaged lifestyle, when compared to centenarians without the APOE ϵ4 allele (t = 3.43, p < .01; t = 3.19, p < .01; and t = 2.33, p < .05, respectively). Blockwise multiple regressions indicated that the APOE ϵ4 predicted positive but not negative affect after controlling for demographics. Gene-environment interactions were obtained for the APOE ϵ4 and lifelong events, suggesting that carriers of the APOE ϵ4 allele had higher scores of negative affect after having experienced more events, whereas noncarriers had reduced negative affect levels after having experienced more events.

CONCLUSION

APOE ϵ4 is directly related to positive affect and is related to negative affect in interaction with life events.

The effect of subsyndromal symptoms of depression and white matter lesions on disability for individuals with mild cognitive impairment

OBJECTIVE

To assess the effect of subsyndromal symptoms of depression (SSD) on ratings of disability for individuals with mild cognitive impairment (MCI).

METHODS

Data from 405 MCI participants from the Alzheimer's Disease Neuroimaging Initiative (ADNI) study were analyzed. Participants were evaluated at baseline and at 6-month intervals over 2 years. Severity of depressive symptoms was rated utilizing the Geriatric Depression Scale. Disability was assessed utilizing the Functional Assessment Questionnaire (FAQ). Other clinical variables included white matter lesion (WML) and intracranial brain (ICV) volumes derived from magnetic resonance imaging, ratings of overall cognitive function (Alzheimer's Disease Assessment Scale, ADAS), and apolipoprotein E (ApoE) status. Demographic variables included age, education, and gender.

RESULTS

SSD individuals had a lower volume of WML and higher frequency of ApoE ε4 alleles than nondepressed participants but the two groups did not differ with respect to other clinical or demographic variables. At baseline, SSD individuals were 1.77 times more likely to have poorer FAQ scores than individuals with no symptoms of depression after controlling for the effect of cognitive functioning, ICV, WML, and ApoE status. The presence of SSD at baseline was not associated with a poorer course of disability outcomes, cognitive functioning, or conversion to dementia over 24 months.

CONCLUSIONS

SSD demonstrated a significant impact on disability for MCI individuals, who are also at high risk for functional limitations related to neurodegenerative disease. Therefore, the treatment of SSD may represent a significant avenue to reduce the burden of disability in this vulnerable patient population.

Temporal relationships between depressive symptoms and white matter hyperintensities in older men and women

OBJECTIVE

Associations between vascular disease and depression in late life, including increased white matter hyperintensities (WMHs), have been reported. Whether depression is an etiology or a consequence of vascular disease is still unknown. We investigated the temporal relationship between depressive symptoms and WMHs in older men and women.

METHODS

We utilized data from 90 dementia-free older adults (39 women, 51 men), 57 years of age and older at baseline, from the neuroimaging substudy of the Baltimore Longitudinal Study of Aging. Participants were followed for up to 8 years. Ratings of white matter disease burden were available for the first, last, and at least one interim visit, and participants completed the Center for Epidemiologic Studies Depression Scale (CES-D) annually. Statistical models, performed separately in men and women, examined whether depressive symptoms predicted subsequent WMH ratings or WMHs predicted subsequent depressive symptoms.

RESULTS

The total CES-D score was not associated with WMHs in men or women. In men, the CES-D depressed mood subscale predicted accelerating longitudinal increases in WMHs at older ages, but WMHs did not predict subsequent depressive symptoms. In women, there were no significant associations between the CES-D depressed mood subscale and WMHs.

CONCLUSIONS

White matter disease may be a consequence of depressed mood in men but not in women. Intervention strategies for depression may slow the progression of white matter disease in older men. These results add to previous findings documenting sex differences in the correlates of depressive disorders in late life.

Depressive symptoms and APOE polymorphisms in an elderly population-based sample

AIM

Apolipoprotein E (APOE) has been regarded as the principal susceptibility gene linked with Alzheimer's disease, also suggesting a relationship with depression in the elderly population. Thus, the purpose was to investigate the association of APOE polymorphisms with depression in elderly adults.

METHODS

APOE polymorphisms were determined in a Mexican population-based sample older than 60 years (n=1566) using 5' exonuclease TaqMan genotyping assays.

RESULTS

The distribution of the APOE allele and genotype frequencies was similar in patients with and without depression. There was no significant association between the presence of alleles or genotypes and depression and anxiety (Short Anxiety Screening Test) considering several combinations of other features. However, patients with the APOE*4 allele presented more thinking and concentration impairment than those patients with the APOE*3 allele.

CONCLUSION

Genetic variation at the APOE gene may contribute to some depressive symptoms in late-onset depression, rather than being a specific risk factor.

No association between APOE and major depressive disorder in a community sample of 17,507 adults

Mood-related phenotypes are commonly comorbid with, and have been implicated in the development of, neurological disorders. APOE is a major susceptibility gene for neurodegeneration. Recent evidence from case-control studies has suggested that the apoE 2 allele is associated with major depressive disorder (MDD). However, evidence from large-scale community-based studies is limited. APOE was genotyped for 17,507 men and women, aged 41-80 years, participating in the European Prospective Investigation into Cancer-Norfolk study, who had also completed a psychosocial assessment that included measures of emotional health status defined by MDD, psychological distress (as represented by the Mental Health Inventory, MHI-5), and by an assessment of neuroticism. No associations were found between APOE genotypes and measures either of past-year or lifetime MDD, or of emotional health defined according to the MHI-5 or by neuroticism. Data from this large-scale, community-based, study are not supportive of an association between either MDD or associated measures of emotional state and APOE genotype. These findings suggest that the association between APOE and MDD risk is more modest than has been previously reported.

Resolving the relationship between ApolipoproteinE and depression

Several studies have reported an association between the ApolipoproteinE-epsilon4 (APOE4) allele and depression among elders. However others have failed to find an association. Since APOE4 is a well recognized risk factor for Alzheimer dementia, cognitive status may represent an important confounder between APOE4 and depression. In this investigation, we examined the relationship between the ApolipoproteinE-epsilon4 allele and depression among elders accounting for cognitive status. Using a case-control design (n=1052), we investigated the association between ApolipoproteinE-epsilon4 and depression in Alzheimer disease patients (n=528) and in cognitively intact controls (n=524). We demonstrated an apparent association between the APOE4 allele and depression in the combined dataset (p=0.001) when not controlling for cognitive status. However, once stratified by the presence of Alzheimer disease, there was no association in either the Alzheimer group (p=0.290) or the cognitively intact controls (p=0.494). In this dataset there is no association between the ApolipoproteinE-epsilon4 allele and depression among those with Alzheimer disease or among cognitively intact elders. However there is a significant association between female gender and depression in the cognitively intact (p=0.003) but not among those with Alzheimer disease. Additionally, individuals with Alzheimer disease and depression had a significantly younger age of onset for their Alzheimer disease than those without depression (p=0.017).

Pharmacogenomic Biomarkers in Neuropsychiatry: The Path to Personalized Medicine in Mental Disorders

Neuropsychiatric disorders and dementia represent a major cause of disability and high cost in developed societies. Most disorders of the central nervous system (CNS) share some common features, such as a genomic background in which hundreds of genes might be involved, genome-environment interactions, complex pathogenic pathways, poor therapeutic outcomes, and chronic disability.

Recent advances in genomic medicine can contribute to accelerate our understanding on the pathogenesis of CNS disorders, improve diagnostic accuracy with the introduction of novel biomarkers, and personalize therapeutics with the incorporation of pharmacogenetic and pharmacogenomic procedures to drug development and clinical practice.

The pharmacological treatment of CNS disorders, in general, accounts for 10–20% of direct costs, and less than 30–40% of the patients are moderate responders to conventional drugs, some of which may cause important adverse drugs reactions (ADRs). Pharmacogenetic and pharmacogenomic factors may account for 60–90% of drug variability in drug disposition and pharmacodynamics. Approximately 60–80% of CNS drugs are metabolized via enzymes of the CYP gene superfamily; 18% of neuroleptics are major substrates of CYP1A2 enzymes, 40% of CYP2D6, and 23% of CYP3A4; 24% of antidepressants are major substrates of CYP1A2 enzymes, 5% of CYP2B6, 38% of CYP2C19, 85% of CYP2D6, and 38% of CYP3A4; 7% of benzodiazepines are major substrates of CYP2C19 enzymes, 20% of CYP2D6, and 95% of

CYP3A4. About 10–20% of Caucasians are carriers of defective CYP2D6 polymorphic variants that alter the metabolism of many psychotropic agents. Other 100 genes participate in the efficacy and safety of psychotropic drugs. The incorporation of pharmacogenetic/ pharmacogenomic protocols to CNS research and clinical practice can foster therapeutics optimization by helping to develop cost-effective pharmaceuticals and improving drug efficacy and safety. To achieve this goal several measures have to be taken, including: (a) educate physicians and the public on the use of genetic/ genomic screening in the daily clinical practice; (b) standardize genetic testing for major categories of drugs; (c) validate pharmacogenetic and pharmacogenomic procedures according to drug category and pathology; (d) regulate ethical, social, and economic issues; and (e) incorporate pharmacogenetic and pharmacogenomic procedures to both drugs in development and drugs in the market to optimize therapeutics.

Pharmacogenetic basis for therapeutic optimization in Alzheimer's disease

Alzheimer's disease is a major health problem in developed countries. Approximately 10-15% of direct costs in dementia are attributed to pharmacological treatment, and only 10-20% of the patients are moderate responders to conventional antidementia drugs, with questionable cost effectiveness. The phenotypic expression of Alzheimer's disease is characterized by amyloid deposition in brain tissue and vessels (amyloid angiopathy), intracellular neurofibrillary tangle formation, synaptic and dendritic loss, and premature neuronal death. Primary pathogenic events underlying this neurodegenerative process include genetic factors involving more than 200 different genes distributed across the human genome, accompanied by progressive cerebrovascular dysfunction, and diverse environmental factors. Mutations in genes directly associated with the amyloid cascade (APP, PSEN1, PSEN2) are present in less than 5% of the Alzheimer's disease population; however, the presence of the epsilon4 allele of the apolipoprotein E gene (APOE) represents a major risk factor for more than 40% of patients with dementia. Genotype-phenotype correlation studies and functional genomics studies have revealed the association of specific mutations in primary loci and/or APOE-related polymorphic variants with the phenotypic expression of biological traits. It is estimated that genetics accounts for between 20% and 95% of the variability in drug disposition and pharmacodynamics. Recent studies indicate that the therapeutic response in Alzheimer's disease is genotype specific, depending on genes associated with Alzheimer's disease pathogenesis and/or genes responsible for drug metabolism (e.g. cytochrome P450 [CYP] genes). In monogenic studies, APOEepsilon4/epsilon4 genotype carriers are the worst responders to conventional treatments. Some cholinesterase inhibitors currently being use in the treatment of Alzheimer's disease are metabolized via CYP-related enzymes. These drugs can interact with many other drugs that are substrates, inhibitors or inducers of the CYP system, this interaction eliciting liver toxicity and other adverse drug reactions. CYP2D6 enzyme isoforms are involved in the metabolism of more than 20% of drugs used in CNS disorders. The distribution of the CYP2D6 genotypes in the European population of the Iberian peninsula differentiates four major categories of CYP2D6-related metabolizer types: (i) extensive metabolizers (EM) [51.61%]; (ii) intermediate metabolizers (IM) [32.26%]; (iii) poor metabolizers (PM) [9.03%]; and (iv) ultra-rapid metabolizers (UM) [7.10%]. PMs and UMs tend to show higher transaminase activity than EMs and IMs. EMs and IMs are the best responders, and PMs and UMs are the worst responders to pharmacologic treatments in Alzheimer's disease. At this early stage of the development of pharmacogenomic/pharmacogenetic procedures in Alzheimer's disease therapeutics, it seems very plausible that the pharmacogenetic response in Alzheimer's disease depends on the interaction of genes involved in drug metabolism and genes associated with Alzheimer's disease pathogenesis.

Pharmacogenomics and therapeutic prospects in dementia

Dementia is a major problem of health in developed countries. Alzheimer's disease (AD) is the main cause of dementia, accounting for 50-70% of the cases, followed by vascular dementia (30-40%) and mixed dementia (15-20%). Approximately 10-15% of direct costs in dementia are attributed to pharmacological treatment, and only 10-20% of the patients are moderate responders to conventional anti-dementia drugs, with questionable cost-effectiveness. Primary pathogenic events underlying the dementia process include genetic factors in which more than 200 different genes distributed across the human genome are involved, accompanied by progressive cerebrovascular dysfunction and diverse environmental factors. Mutations in genes directly associated with the amyloid cascade (APP, PS1, PS2) are only present in less than 5% of the AD population; however, the presence of the APOE-4 allele in the apolipoprotein E (APOE) gene represents a major risk factor for more than 40% of patients with dementia. Genotype-phenotype correlation studies and functional genomics studies have revealed the association of specific mutations in primary loci (APP, PS1, PS2) and/or APOE-related polymorphic variants with the phenotypic expression of biological traits. It is estimated that genetics accounts for 20-95% of variability in drug disposition and pharmacodynamics. Recent studies indicate that the therapeutic response in AD is genotype-specific depending upon genes associated with AD pathogenesis and/or genes responsible for drug metabolism (CYPs). In monogenic-related studies, APOE-4/4 carriers are the worst responders. In trigenic (APOE-PS1-PS2 clusters)-related studies the best responders are those patients carrying the 331222-, 341122-, 341222-, and 441112- genomic profiles. The worst responders in all genomic clusters are patients with the 441122+ genotype, indicating the powerful, deleterious effect of the APOE-4/4 genotype on therapeutics in networking activity with other AD-related genes. Cholinesterase inhibitors of current use in AD are metabolized via CYP-related enzymes. These drugs can interact with many other drugs which are substrates, inhibitors or inducers of the cytochrome P-450 system; this interaction elicits liver toxicity and other adverse drug reactions. CYP2D6-related enzymes are involved in the metabolism of more than 20% of CNS drugs. The distribution of the CYP2D6 genotypes differentiates four major categories of CYP2D6-related metabolyzer types: (a) Extensive Metabolizers (EM)(*1/*1, *1/*10)(51.61%); (b) Intermediate Metabolizers (IM) (*1/*3, *1/*4, *1/*5, *1/*6, *1/*7, *10/*10, *4/*10, *6/*10, *7/*10) (32.26%); (c) Poor Metabolizers (PM) (*4/*4, *5/*5) (9.03%); and (d) Ultra-rapid Metabolizers (UM) (*1xN/*1, *1xN/*4, Dupl) (7.10%). PMs and UMs tend to show higher transaminase activity than EMs and IMs. EMs and IMs are the best responders, and PMs and UMs are the worst responders to pharmacological treatments in AD. It seems very plausible that the pharmacogenetic response in AD depends upon the interaction of genes involved in drug metabolism and genes associated with AD pathogenesis. The establishment of clinical protocols for the practical application of pharmacogenetic strategies in AD will foster important advances in drug development, pharmacological optimization and cost-effectiveness of drugs, and personalized treatments in dementia.

Risk factors for anxiety and depression in the elderly: a review

BACKGROUND

Although a number of studies have examined risk factors for anxiety and depression at a later age, there have been no systematic comparisons of risk profiles across studies. Knowledge on such risk profiles may further our understanding of both the etiology and early recognition of these highly prevalent disorders. This paper gives a comprehensive overview and compares risk factors associated with anxiety and depression in the elderly.

METHODS

The databases MEDLINE, PsycINFO and Sociological Abstracts were systematically searched, and relevant English-language articles from January 1995 to December 2005 were reviewed. Cross-sectional and longitudinal studies on risk factors in elderly from a community or primary care setting were included. The associations between risk factors and pure anxiety or depressive symptoms or disorders were summarized and compared.

RESULTS

The abstracted risk factors from studies on anxiety (N=17) and depression (N=71) were clustered into the categories biological, psychological and social. Although risk factors for anxiety and depression showed many similarities, some differences were found. Biological factors may be more important in predicting depression, and a differential effect of social factors on depression and anxiety was found.

LIMITATION

Due to a high heterogeneity between studies, no meta-analysis could be conducted.

CONCLUSIONS

There is considerable overlap between the risk profiles for anxiety and depression in the elderly, which suggests a dimensional approach on the interrelationship between anxiety and depression is more appropriate. To improve the recognition and preventive mental health programs, a clearer understanding of differentiating etiological factors will be needed.

Apolipoprotein E ε4 allele frequency in elderly depressed patients with and without cerebrovascular disease

Late-onset depression (LOD) could be a very early manifestation of Alzheimer's disease (AD), although contradictory results have been reported. Cerebrovascular disease (CVD) may favor the development of LOD, and that the particular forms of vascular depression should be individualized. The Apolipoprotein E (ApoE) epsilon4 allele was shown to be a risk factor for AD. Its role in LOD is controversial, while it is still unknown in vascular depression. Our objective was to clarify the relationship between ApoE epsilon4 allele and LOD in patients with and without CVD. We examined the ApoE phenotypes in a sample of 311 subjects: 50 with vascular LOD, 24 with LOD without CVD, 115 with AD and 122 normal controls (NC). The study of the ApoE epsilon4 allele frequency showed significant differences between: AD group and the vascular LOD and NC groups; LOD group without CVD compared with NC group (p<0.05 to 0.001). The frequency of the epsilon4 allele in the LOD group without CVD did not differ significantly from the AD group, similarly the frequency of the epsilon4 allele in the vascular LOD group was not different from that in NC. The study suggests an association between the ApoE epsilon4 allele and the LOD without CVD. These patients could be at risk of developing AD by an epsilon4-dependent pathway. In contrast, the results show no association between the presence of ApoE epsilon4 allele and vascular depression and provide further evidence in support of the concept that ApoE epsilon4 allele is not associated with clinical CVD.

Association of APOE genetic polymorphism with cognitive function and suicide history in geriatric depression

Apolipoprotein E (APOE) has been associated with a variety of late-life neuropsychiatric disorders, including geriatric depression. This study determined whether APOE genotypes affect vulnerability to geriatric depression. We also tested the effect of the presence of the APOE epsilon4 (APOE4) allele on age of onset, suicide attempt history and cognitive function in geriatric depressed patients. We genotyped APOE in 111 elderly inpatients diagnosed as having major depression and 144 normal controls. The depressed patients were evaluated at baseline using the Hamilton Rating Scale for Depression and the Mini-Mental State Examination (MMSE) after admission. Age of onset of depression and suicide attempt history in the depressed group were evaluated by interview and medical record. We found no association between APOE genotypes and geriatric depression (p = 0.342) or APOE4 status and age of onset of depression (p = 0.281). However, compared with depressed subjects lacking the APOE epsilon4 allele, depressed subjects who were also APOE4 carriers showed significantly lower MMSE scores (p = 0.021) and an increased suicide attempt history (p = 0.012). The APOE genotype may contribute to cognitive performance and suicidality in geriatric depression, rather than being a specific risk factor for the disorder.

Protective effect of the apo epsilon2 allele in major depressive disorder in Taiwanese

OBJECTIVE

Major depression is an important comorbidity in Alzheimer's disease, which is definitely associated with the apolipoprotein E (apo E) polymorphism. The aim of this study was to explore the role of the different apo E polymorphisms in major depressive disorder (MDD) in a Taiwanese population.

METHOD

We examined apo E genotypes in 273 Taiwanese patients with MDD and 429 healthy community controls, and compared their polymorphism distribution.

RESULTS

The allelic frequency of apo epsilon2 was significantly lower in patients with MDD than in the controls, whereas no significant difference in apo epsilon4 allelic frequency between these two groups was found.

CONCLUSION

The apo epsilon4 allele was not associated with MDD in this study. However, the finding of a lower frequency of the apo epsilon2 allele in MDD could lead to the conclusion that the apo epsilon2 allele likely provides a protective effect against MDD in the Taiwanese population.

Cerebrovascular disease and late-life depression

Depression may occur as a result of vascular disease in a significant subpopulation of elderly persons. Indirect support for vascular disease as an underlying etiology of late-life depression includes the high rate of depression in patients with vascular disease, the frequency of "silent stroke" and white-matter hyperintensities in late-life depression, and the lower frequency of positive family histories of depression in such patients. The authors evaluate the associations of late-life depression with cerebrovascular disease by reviewing the existing pathophysiological, prognosis, and treatment-outcomes studies. Findings are based on review of the current literature systematically searched in electronic databases. Review of such studies indicates a high frequency of depression in older patients with cardiovascular and cerebrovascular diseases, and the possibility of a bidirectional relationship between depression and vascular disease. Studies examining patients with vascular depression have found that such patients have different symptom profiles, greater disability, and higher risk for poorer outcomes than those with nonvascular depression. Since the vascular depression hypothesis was proposed as a conceptual framework, evidence has accumulated that patients with vascular depression may have poorer outcomes that may be related in part to executive dysfunction and consequent disability. However, the association of vascular risk factors with geriatric depression has not been consistent in the studies to-date. Although an association between a subset of late-life depression and vascular disease is clear, significant gaps remain in our understanding. Further research is needed to establish the precise linkages and interactions between vascular disease and geriatric depression.