Cognitive changes in very old persons with dementia: the influence of demographic, psychometric, and biological variables

Education and Cognitive Functioning Across the Life Span

Cognitive abilities are important predictors of educational and occupational performance, socioeconomic attainment, health, and longevity. Declines in cognitive abilities are linked to impairments in older adults' everyday functions, but people differ from one another in their rates of cognitive decline over the course of adulthood and old age. Hence, identifying factors that protect against compromised late-life cognition is of great societal interest. The number of years of formal education completed by individuals is positively correlated with their cognitive function throughout adulthood and predicts lower risk of dementia late in life. These observations have led to the propositions that prolonging education might (a) affect cognitive ability and (b) attenuate aging-associated declines in cognition. We evaluate these propositions by reviewing the literature on educational attainment and cognitive aging, including recent analyses of data harmonized across multiple longitudinal cohort studies and related meta-analyses. In line with the first proposition, the evidence indicates that educational attainment has positive effects on cognitive function. We also find evidence that cognitive abilities are associated with selection into longer durations of education and that there are common factors (e.g., parental socioeconomic resources) that affect both educational attainment and cognitive development. There is likely reciprocal interplay among these factors, and among cognitive abilities, during development. Education-cognitive ability associations are apparent across the entire adult life span and across the full range of education levels, including (to some degree) tertiary education. However, contrary to the second proposition, we find that associations between education and aging-associated cognitive declines are negligible and that a threshold model of dementia can account for the association between educational attainment and late-life dementia risk. We conclude that educational attainment exerts its influences on late-life cognitive function primarily by contributing to individual differences in cognitive skills that emerge in early adulthood but persist into older age. We also note that the widespread absence of educational influences on rates of cognitive decline puts constraints on theoretical notions of cognitive aging, such as the concepts of cognitive reserve and brain maintenance. Improving the conditions that shape development during the first decades of life carries great potential for improving cognitive ability in early adulthood and for reducing public-health burdens related to cognitive aging and dementia.

Genome-wide association study of rate of cognitive decline in Alzheimer's disease patients identifies novel genes and pathways

INTRODUCTION

Variability exists in the disease trajectories of Alzheimer's disease (AD) patients. We performed a genome-wide association study to examine rate of cognitive decline (ROD) in patients with AD.

METHODS

We tested for interactions between genetic variants and time since diagnosis to predict the ROD of a composite cognitive score in 3946 AD cases and performed pathway analysis on the top genes.

RESULTS

Suggestive associations (P < 1.0 × 10-6 ) were observed on chromosome 15 in DNA polymerase-γ (rs3176205, P = 1.11 × 10-7 ), chromosome 7 (rs60465337,P = 4.06 × 10-7 ) in contactin-associated protein-2, in RP11-384F7.1 on chromosome 3 (rs28853947, P = 5.93 × 10-7 ), family with sequence similarity 214 member-A on chromosome 15 (rs2899492, P = 5.94 × 10-7 ), and intergenic regions on chromosomes 16 (rs4949142, P = 4.02 × 10-7 ) and 4 (rs1304013, P = 7.73 × 10-7 ). Significant pathways involving neuronal development and function, apoptosis, memory, and inflammation were identified.

DISCUSSION

Pathways related to AD, intelligence, and neurological function determine AD progression, while previously identified AD risk variants, including the apolipoprotein (APOE) ε4 and ε2 variants, do not have a major impact.

Normative Data for the Montreal Cognitive Assessment in Greek Older Adults With Subjective Cognitive Decline, Mild Cognitive Impairment and Dementia

OBJECTIVE

The aim of the study was to provide normative data for the MoCA in a Greek cohort of people older than 60 years who meet criteria for subjective cognitive decline (SCD), mild cognitive impairment (MCI), or dementia in order to optimize cutoff scores for each diagnostic group.

METHOD

Seven hundred forty-six community-dwelling older adults, visitors of the Day Center of Alzheimer Hellas were randomly chosen. Three hundred seventy-nine of them met the criteria for dementia, 245 for MCI and 122 for SCD.

RESULTS

Initial statistical analyses showed that the total MoCA score is not affected by gender (P = .164), or age (P = .144) but is affected by educational level (P < .001). A cutoff score of 23 for low educational level (≤6 years) can distinguish people with SCD from MCI (sensitivity 71.4%, specificity 84.2%), while 26 is the cutoff score for middle educational level (7-12 years; sensitivity 73.2%, specificity 67.0%) and high educational level (≥13 years; sensitivity 77.6%, specificity 74.7%). Montreal Cognitive Assessment can discriminate older adults with SCD from dementia, with a cutoff score of 20 for low educational level (sensitivity 100%, specificity 92.3%) and a cutoff score 23 for middle educational level (sensitivity 97.6%, specificity 92.7%) and high educational level (sensitivity 98.5%, specificity 100%).

CONCLUSION

Montreal Cognitive Assessment is not affected by age or gender but is affected by the educational level. The discriminant potential of MoCA between SCD and MCI is good, while the discrimination of SCD from dementia is excellent.

Homocysteine concentrations in the cognitive progression of Alzheimer's disease

OBJECTIVES

Hyperhomocysteinemia in Alzheimer's disease (AD) is widely reported and appears to worsen as the disease progresses. While active dietary intervention with vitamins B12 and folate decreases homocysteine blood levels, with promising clinical outcomes in Mild Cognitive Impairment (MCI), this so far has not been replicated in established AD populations. The aim of the study is to explore the relationship between hyperhomocystenemia and relevant vitamins as the disease progresses.

METHODS

In this longitudinal cohort study, 38 participants with mild to moderate AD were followed for an average period of 13months. Plasma folate, vitamin B12 and homocysteine concentrations were measured at baseline and at follow-up. Dietary intake of B vitamins was also measured. Spearman's correlations were conducted by homocysteine and B vitamin status.

RESULTS

As expected, cognitive status significantly declined over the follow-up period and this was paralleled by a significant increase in homocysteine concentrations (p=0.006). However, during this follow-up period there was no significant decline in neither dietary intake, nor the corresponding blood concentrations of vitamin B12/folate, with both remaining within normal values. Changes in blood concentrations of B vitamins were not associated with changes in homocysteine levels (p>0.05).

CONCLUSION

In this study, the increase in homocysteine observed in AD patients as the disease progresses cannot be solely explained by dietary and blood levels of folate and vitamin B12. Other dietary and non-dietary factors may contribute to hyperhomocysteinemia and its toxic effect in AD, which needs to be explored to optimise timely intervention strategies.

Do Alzheimer's disease (AD) and subcortical ischemic vascular dementia (SIVD) progress differently?

Our study aimed to compare cognitive status and declines in AD with/without small vessel disease (SVD) and SIVD at baseline and 1-year follow-up. Patients with Alzheimer's disease without small vessel disease (AD(-)SVD) (n=148), Alzheimer's disease with small vessel disease (AD(+)SVD) (n=94) and SIVD (n=60) were recruited from database of multiple centers in Korea. Basic demographics and detailed neuropsychological results were compared. AD, regardless of SVD, showed worse memory and better executive function than SIVD at baseline. Mini-Mental State Examination scores and visual memory function declined more in AD than those in SIVD whereas Barthel Activities of Daily Living (B-ADL) scores declined more in SIVD. AD showed different patterns of cognitive impairment compared with SIVD. After 1 year, AD showed more rapid cognitive decline in some domains. Further investigations with longer follow-up duration may be needed to confirm the cumulative effects of SVD in AD and different patterns of decline between AD and SIVD.

Vitamin B₁₂ status, cognitive decline and dementia: a systematic review of prospective cohort studies

Poor vitamin B₁₂ status may lead to the development of cognitive decline and dementia but there is a large variation in the quality, design of and results reported from these investigations. We have undertaken a systematic review of the evidence for the association between vitamin B₁₂ status and cognitive decline in older adults. A database search of the literature to 2011 was undertaken, using keywords related to vitamin B₁₂ and cognition. All prospective cohort studies assessing the association of serum vitamin B₁₂ or biomarkers were included. Quality assessment and extraction of the data were undertaken by two researchers. The quality assessment tool assigns a positive, neutral or negative rating. Of 3772 published articles, thirty-five cohort studies (n 14 325 subjects) were identified and evaluated. No association between serum vitamin B₁₂ concentrations and cognitive decline or dementia was found. However, four studies that used newer biomarkers of vitamin B₁₂ status (methylmalonic acid and holotranscobalamin (holoTC)) showed associations between poor vitamin B₁₂ status and the increased risk of cognitive decline or dementia diagnosis. In general, the studies were of reasonable quality (twenty-one positive, ten neutral and four negative quality) but of short duration and inadequate subject numbers to determine whether an effect exists. Future studies should be of adequate duration (at least 6 years), recruit subjects from the seventh decade, choose markers of vitamin B₁₂ status with adequate specificity such as holoTC and/or methylmalonic acid and employ standardised neurocognitive assessment tools and not screening tests in order to ascertain any relationship between vitamin B₁₂ status and cognitive decline.

The association of age with rate of cognitive decline in elderly individuals residing in supporting care facilities

OBJECTIVES

This study examines the effect of age on rate of cognitive decline in different stages of dementia, of nursing home and assisted-living residents.

METHODS

In this longitudinal study, the Mini Mental State Examination (MMSE) was used to measure rate of cognitive decline in subjects who were nondemented [Clinical Dementia Rating (CDR)=0; n=353], questionably demented (CDR=0.5; n=121), or frankly demented (CDR≥1; n=213) at baseline.

RESULTS

A generalized estimating equation was used to model the MMSE scores over time (mean follow-up 2.9±2.0 y). The generalized estimating equation model had the MMSE scores at successive follow-up time points as dependent variables and had linear and quadratic age, follow-up time from baseline, CDR at baseline, and all the interactions among them as independent variables, controlling for MMSE at baseline, sex, race, and education. The mean age of the entire sample was 85.2±7.4 years at baseline. There were no significant interactions of linear age effects with rate of cognitive decline. The analysis of interaction of quadratic age with rate of cognitive decline showed complex relationships: in the nondemented group, there was no substantial quadratic association of age with the rate of cognitive decline (P=0.13); in the questionable demented group, the oldest subjects declined relatively faster (P=0.02); and in the demented group, the youngest and oldest subjects tended to decline relatively less than subjects in the intermediate ages (P=0.07).

CONCLUSIONS

This study adds an additional aspect to the complexity of the association between age and rate of cognitive decline, showing that the direction and amplitude of this effect differs according to the stage along the course of cognitive decline.

Diabetes is associated with increased rate of cognitive decline in questionably demented elderly

BACKGROUND

This study examines whether the association of diabetes with the rate of cognitive decline varies according to dementia severity.

METHODS

Longitudinal study on subjects residing in nursing homes and assisted living (n = 342). The Mini Mental State Examination (MMSE) was used to measure the rate of cognitive decline in diabetic and nondiabetic subjects who were nondemented (Clinical Dementia Rating, CDR = 0; n = 125), questionably demented (CDR = 0.5; n = 58) or frankly demented (CDR > or =1; n = 89) at baseline. Diagnosis of diabetes was ascertained by review of medical records and history.

RESULTS

Diabetes was associated with an increased rate of decline in the MMSE score of questionably demented subjects (p < 0.0001). In frankly demented subjects, diabetes tended to be associated with less cognitive decline (p = 0.04). Diabetes was not associated with the rate of MMSE decline in nondemented subjects (p = 0.89).

CONCLUSION

In individuals with questionable dementia (CDR = 0.5), diabetes is associated with a faster rate of cognitive decline as measured by the MMSE, but not in nondemented (CDR = 0) or frankly demented (CDR > or =1) individuals.

Caregiver-recipient closeness and symptom progression in Alzheimer disease. The Cache County Dementia Progression Study

Applying Rusbult's investment model of dyadic relationships, we examined the effect of caregiver-care recipient relationship closeness (RC) on cognitive and functional decline in Alzheimer's disease. After diagnosis, 167 participants completed up to six visits, observed over an average of 20 months. Participants were 64% women, had a mean age of 86 years, and mean dementia duration of 4 years. Caregiver-rated closeness was measured using a six-item scale. In mixed models adjusted for dementia severity, dyads with higher levels of closeness (p < .05) and with spouse caregivers (p = .01) had slower cognitive decline. Effect of higher RC on functional decline was greater with spouse caregivers (p = .007). These findings of attenuated Alzheimer's dementia (AD) decline with closer relationships, particularly with spouse caregivers, are consistent with investment theory. Future interventions designed to enhance the caregiving dyadic relationship may help slow decline in AD.

Vitamin B status and cognitive performance in preclinical and clinical Alzheimer's disease: data from the Kungsholmen Project

BACKGROUND/AIMS

The impact of vitamin B status on cognitive functioning in Alzheimer's disease (AD) is disputed. Using a population-based sample, we examined the associations of vitamin B(12) and folate with cognitive functioning in clinical (n = 44) and preclinical (n = 39) AD.

METHODS

The groups were subdivided in terms of low (<200 pmol/l) versus normal levels of B(12) and low (<13 nmol/l) versus normal folate levels. Participants were administered tests of verbal and nonverbal episodic memory, visuospatial abilities and verbal fluency.

RESULTS

As expected, the preclinical AD group performed better than the AD group across most cognitive tests. More interestingly, the effects of low vitamin B(12) and folate levels were negligible across all cognitive tests in clinical and preclinical AD.

CONCLUSION

These findings suggest that the influence of vitamin B deficiency on cognitive functioning is overshadowed by the neurodegenerative processes associated with AD.

Clinical correlates of cognitive decline in vascular dementia

OBJECTIVE

To determine whether demographic data, dementia severity, functional status, whole brain volume (WBV), or subcortical hyperintensity volume (SH) predict subsequent cognitive decline in vascular dementia (VaD).

BACKGROUND

The identification of variables that accurately predict progressive cognitive decline in dementia has important clinical implications.

METHODS

A cohort of 30 patients with VaD completed neurologic and neuropsychologic examinations and magnetic resonance imaging of the brain at baseline and again after 12 months. All participants met clinical and research criteria for VaD according to standard guidelines. Change scores were computed for measures of verbal fluency, verbal learning, and visual learning. Potential correlates of cognitive change included age, education, score on the Hachinski scale, WBV, SH, and functional ability.

RESULTS

As a group, lower WBV and lower Hachinski score correlated with decline in verbal fluency and visual learning, whereas lower Hachinski score correlated with decline in verbal learning. However, when subdivided by disease type, this pattern held only for individuals with evidence of a cortical stroke at baseline. No clinical variables correlated with cognitive decline among individuals without a cortical infarction.

CONCLUSIONS

Assessment of cognitive decline in VaD should be guided by dementia subtype, with particular attention directed at severity of cerebral atrophy rather than classic symptoms of infarction.

Efficacy and tolerability of donepezil in vascular dementia: positive results of a 24-week, multicenter, international, randomized, placebo-controlled clinical trial

BACKGROUND AND PURPOSE

Clinical observations suggest that patients with vascular dementia (VaD) may benefit from treatment with cholinesterase inhibitors. This study evaluated the efficacy and safety of donepezil for relieving symptoms of dementia in VaD.

METHODS

Patients (n=603; mean age, 73.9 years; 55.2% men) with probable (70.5%) or possible (29.5%) VaD, according to criteria of the National Institute of Neurological Disorders and Stroke (NINDS) and the Association Internationale pour la Recherche et l'Enseignement en Neurosciences (AIREN), were randomized to 24 weeks of treatment with donepezil 5 mg/d (n=198), donepezil 10 mg/d (5 mg/d for first 28 days; n=206), or placebo (n=199). Analyses were based on the intent-to-treat population.

RESULTS

At week 24, both donepezil groups showed significant improvement in cognition versus placebo on the Alzheimer's Disease Assessment Scale-cognitive subscale (mean change from baseline score effect size: donepezil 5 mg/d, -1.90; P=0.001; donepezil 10 mg/d, -2.33; P<0.001). Significant improvements in patients' global function were seen versus placebo at week 24 (observed cases), on the Clinician's Interview-Based Impression of Change-Plus version only for patients on donepezil 5 mg/d (P=0.014), and on the Sum of the Boxes of the Clinical Dementia Rating only for patients on 10 mg/d (P=0.007). Donepezil-treated patients showed significant benefits in activities of daily living over placebo on the Alzheimer's Disease Functional Assessment and Change Scale (mean change from baseline score effect size at week 24: donepezil 5 mg/d, -1.31, P=0.02; donepezil 10 mg/d, -1.31, P=0.02). Donepezil was well tolerated. Withdrawal rates due to adverse events were relatively low (placebo, 11.1%; donepezil 5 mg/d, 11.1%; donepezil 10 mg/d, 21.8%; P=0.005 versus placebo).

CONCLUSIONS

These data demonstrate that donepezil is an effective and well-tolerated treatment for VaD and show it may have an important place in the management of this condition.

Cognitive impairment and mortality in older mexican americans

OBJECTIVES

To examine the extent to which cognitive status and decline in cognitive status predict mortality in older Mexican Americans.

DESIGN

Longitudinal cohort.

SETTING

Older Mexican Americans residing in five southwestern states in the United States.

PARTICIPANTS

Two thousand six hundred twenty-five persons aged 65 and older living in Texas, New Mexico, Colorado, Arizona, and California.

MEASUREMENTS

The cognitive function of participants was assessed using the Mini-Mental State Examination (MMSE) in 1993-94 and again in 1995-96. Cognitive decline was defined using two sets of criteria: a drop to 17 or less (moderate-severe cognitive impairment) on the MMSE at 2-year follow-up and a decrease of at least four points, a threshold change in scores that was used to predict mortality in this sample. Cox proportional hazards models were conducted to examine the association between the MMSE and increased risk for mortality, after controlling for sociodemographic characteristics, medical conditions, and depressive symptoms.

RESULTS

Five-year mortality risk was significantly associated with persons in the moderately-severely cognitively impaired category (hazard ratio (HR) = 2.35, P <.001). Moreover, mild cognitive impairment was also predictive of mortality in older Mexicans (HR = 1.45, P <.001). Two-year declines in cognitive functioning, particularly in persons who had declined to the moderate-severe impairment category (HR = 2.23, P <.001) and those who dropped at least four points on the MMSE (HR = 1.30, P <.001), were predictive of mortality 3 years later, after controlling for important variables.

CONCLUSIONS

Baseline moderate-severe and mild cognitive status and 2-year decline in cognitive functioning independently predict mortality in older Mexican Americans. Although age and selected medical conditions have been reported as the more salient predictors of mortality, cognitive functioning should be considered part of identifying older persons at high risk for underlying medical conditions and mortality.

Predictors of decline in MMSE scores among older Mexican Americans

BACKGROUND

The purpose of this analysis was to examine the association of sociodemographic variables and health-related conditions with 5-year declines in cognitive function among Mexican American elderly persons.

METHODS

The cognitive function of 1759 participants was assessed by using the Mini-Mental State Examination (MMSE) in 1993/1994 and again in 1998/1999. Cognitive decline was defined by two sets of criteria: (1) a drop to 17 or below on the MMSE at follow-up, and (2) a decline of at least three points, the mean change in MMSE scores among respondents who obtained scores at or above the 5th percentile distribution at baseline.

RESULTS

Cognitive decline was significantly associated with sociodemographic variables including age, education, marital status, and household composition. In addition, respondents with reported vision impairment, stroke, and diabetes were at increased risk for cognitive decline after controlling for multiple potential confounders.

CONCLUSION

Although age and education have been reported as the more salient predictors of cognitive deterioration, other sociodemographic and several medical conditions including stroke and diabetes should be considered as part of cognitive aging studies among Mexican American elders.

Memory and language in neurodegenerative diseases

This article reviews recent studies concerning memory and language disorders in Alzheimer's disease and other neurodegenerative conditions. It shows how different memory and language subcomponents may differentially be impaired in different neurodegenerative diseases and at different stages of the same disease.