New insights into the genetic etiology of Alzheimer's disease and related dementias

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele.

Multiple cognitive deficits during the transition to Alzheimer's disease

The literature on cognitive markers in preclinical AD is reviewed. The findings demonstrate that impairment in multiple cognitive domains is typically observed several years before clinical diagnosis. Measures of executive functioning, episodic memory and perceptual speed appear to be most effective at identifying at-risk individuals. The fact that these cognitive domains are most implicated in normal cognitive aging suggests that the cognitive deficit observed preclinically is not qualitatively different from that observed in normal aging. The degree of cognitive impairment prior to the diagnosis of Alzheimer's disease (AD) appears to generalize relatively well across major study characteristics, including sample ascertainment procedures, age and cognitive status of participants, as well as time to diagnosis of dementia. In episodic memory, there is evidence that the size of the preclinical deficit increases with increasing cognitive demands. The global cognitive impairment observed is highly consistent with observations that multiple brain structures and functions are affected long before the diagnosis of AD. However, there is substantial overlap in the distribution of cognitive scores between those who will and those who will not be diagnosed with AD, hence limiting the clinical utility of cognitive markers for early identification of cases. Future research should consider combining cognitive indicators with other types of markers (i.e. social, somatic, genetic, brain-based) in order to increase prediction accuracy.

The impact of diabetes on cognitive impairment and its progression to dementia

INTRODUCTION

Diabetes is a well-established risk factor for dementia, but its impact on the prodromal phase of dementia is unclear.

METHODS

Cohorts of older adults who were cognitively healthy (n = 1840) or had cognitive impairment-no dementia (CIND; n = 682) were followed over 12 years to detect incident CIND and dementia, respectively.

RESULTS

Poorly controlled diabetes (glycated hemoglobin [HbA1c] ≥7.5%; reference = normoglycemia) was associated with double the risk of CIND (Cox regression multi-adjusted hazard ratio [HR] 2.01, 95% confidence interval [CI] 1.13-3.58) and triple the risk CIND progressing to dementia (HR 2.87, 95% CI 1.20-6.85). Co-morbid diabetes and heart disease doubled the risk of incident CIND and dementia, although neither disease conferred a significant risk of either outcome alone. Elevated systemic inflammation contributed to the diabetes-associated increased dementia risk.

CONCLUSIONS

Diabetes characterized by poor glycemic control or cardiovascular complications is related to a greater risk of the development and progression of cognitive impairment. Inflammation may play a role in these relationships.

Effects of vascular risk factors and APOE ε4 on white matter integrity and cognitive decline

OBJECTIVE

To investigate the effects of vascular risk factors and APOE status on white matter microstructure, and subsequent cognitive decline among older people.

METHODS

This study included 241 participants (age 60 years and older) from the population-based Swedish National Study on Aging and Care in Kungsholmen in central Stockholm, Sweden, who were free of dementia and stroke at baseline (2001-2004). We collected data through interviews, clinical examinations, and laboratory tests. We measured fractional anisotropy (FA) and mean diffusivity (MD) on diffusion tensor imaging, and estimated volume of white matter hyperintensities using automatic segmentation. We assessed global cognitive function with the Mini-Mental State Examination at baseline and at 3- and/or 6-year follow-up. We analyzed the data using multivariate linear regression and linear mixed models.

RESULTS

Heavy alcohol consumption, hypertension, and diabetes were significantly associated with lower FA or higher MD (p < 0.05). When aggregating heavy alcohol consumption, hypertension, and diabetes together with current smoking, having an increasing number of these 4 factors concurrently was associated with decreasing FA and increasing MD (ptrend < 0.01), independent of white matter hyperintensities. Vascular risk factors and APOE ε4 allele interacted to negatively affect white matter microstructure; having multiple (≥2) vascular factors was particularly detrimental to white matter integrity among APOE ε4 carriers. Lower tertile of FA and upper tertile of MD were significantly associated with faster Mini-Mental State Examination decline.

CONCLUSIONS

Vascular risk factors are associated with reduced white matter integrity among older adults, which subsequently predicted faster cognitive decline. The detrimental effects of vascular risk factors on white matter microstructure were exacerbated among APOE ε4 carriers.

Prevalence and Correlates of Olfactory Dysfunction in Old Age: A Population-Based Study

Background:

Olfactory dysfunction (OD) in old age is associated with poor health outcomes. Interrelationships among different correlates of OD can offer insights into the underlying mechanisms, but to date remain understudied.

Methods:

Odor identification performance and self-reported olfactory functioning were studied in 2,234 people aged 60–90 years, who were free of neurodegenerative disease and enrolled in the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K) study, Stockholm, Sweden. OD was defined as the inability to identify more than 10 out of 16 odors (free or cued identification) in a standardized odor identification task. OD prevalence was estimated, and associations with demographic, genetic, vascular, clinical, and behavioral factors, as well as their interactions were examined using multiple logistic regression analyses.

Results:

Overall prevalence of OD was 24.8% (CI: 23.1; 26.6). Self-reports were characterized by low sensitivity (35%), but high specificity (87%). Advancing age (OR = 15.50, CI = 9.40; 26.10 between the first and last age group), and history of coronary heart disease (OR = 1.35, 95% CI = 1.04; 1.75) were the principal factors associated with an increased probability of OD, whereas female gender (OR = 0.53, 95% CI = 0.43; 0.66) and more years of education (OR = 0.97, CI 0.94; 0.99) were linked to a lower probability. Exploratory interaction analyses indicated that prevalence of OD was particularly elevated among Apolipropotein E (APOE) ε4 allele carriers who were also obese, and that being physically active counteracted the negative impact of cerebrovascular disease on OD.

Conclusion:

Demographic and genetic factors, but also prior and current health insults, are linked to OD in old age. Modulatory effects of behavioral factors highlight their value as possible prevention targets.

Walking speed, processing speed, and dementia: a population-based longitudinal study

BACKGROUND

Slow walking speed has been shown to predict dementia. We investigated the relation of walking speed, processing speed, and their changes over time to dementia among older adults.

METHODS

This study included 2,938 participants (age 60+ years) in the population-based Swedish National study on Aging and Care in Kungsholmen, Sweden, who were free from dementia and severe walking impairment at baseline. Walking speed was assessed with participants walking at their usual pace and processing speed was defined by a composite measure of standard tests (digit cancellation, trail making test-A, pattern comparison). Dementia at 3- and 6-year follow-ups was diagnosed according to Diagnostic and Statistical Manual of Mental Disorders-IV criteria.

RESULTS

Of the 2,232 participants who were reassessed at least once, 226 developed dementia. Logistic regression models showed that each standard deviation slower baseline walking speed or decline in walking speed over time increased the likelihood of incident dementia (odds ratios 1.61, 95% confidence interval [CI] 1.31-1.98; and 2.58, 95% CI 2.12-3.14, respectively). Adjustment for processing speed attenuated these associations (odds ratios 1.26, 95% CI 1.01-1.58 and 1.76, 95% CI 1.33-2.34). Mixed-effects models revealed statistical interactions of time with dementia on change in walking and processing speed, such that those who developed dementia showed accelerated decline. At baseline, poorer performance in processing speed, but not in walking speed, was observed for persons who developed dementia during the study period.

CONCLUSIONS

Processing speed may play an important role for the association between walking speed and dementia. The slowing of walking speed appears to occur secondary to slowing of processing speed in the path leading to dementia.

Mild cognitive impairment among rural-dwelling older adults in China: A community-based study

BACKGROUND

Epidemiological studies of mild cognitive impairment (MCI) and subtypes of MCI have rarely focused on rural residents in China.

METHODS

This population-based study included 5068 participants (age ≥60 years) who were living in rural communities. We defined MCI, amnestic MCI (aMCI), and non-amnestic MCI (naMCI) following the Petersen's criteria that integrated neuropsychological assessments with in-person clinical evaluations.

RESULTS

The overall prevalence of MCI, aMCI, and naMCI was 26.48%, 22.30%, and 4.18%, respectively. The prevalence of MCI increased with age. The adjusted odds ratio (OR) of MCI was 0.71 (95% confidence interval [CI] 0.61 to 0.82) for primary school (vs. illiteracy), 0.30 (0.24 to 0.39) for middle school or above, 1.35 (1.09 to 1.67) for being farmers, 0.65 (0.54 to 0.78) for alcohol consumption, 1.43 (1.20 to 1.70) for stroke history, and 1.14 (0.95 to 1.36) for any apolipoprotein E (APOE) ε4 allele (vs ε3/ε3).

CONCLUSIONS

MCI affects over one-fourth of rural older adults in China. Overall MCI was associated with demographic factors, non-alcohol consumption, and stroke, but not with APOE genotype and cardiometabolic factors.

Association of Dual Decline in Memory and Gait Speed With Risk for Dementia Among Adults Older Than 60 Years: A Multicohort Individual-Level Meta-analysis

Importance

Dual decline in both memory and gait speed may characterize a group of older individuals at high risk for future dementia.

Objective

To assess the risk of dementia in older persons who experience parallel declines in memory and gait speed compared with those who experience no decline or decline in either memory or gait speed only.

Design, Setting, and Participants

A multicohort meta-analysis was performed of 6 prospective cohort studies conducted between 1997 and 2018 in the United States and Europe. Participants were 60 years or older, had an initial gait speed of more than 0.6 m/s (ie, free of overt dismobility), with repeated measures of memory and gait speed before dementia diagnosis during a mean follow-up of 6.6 to 14.5 years. Within each study, participants were divided into 4 groups: memory decline only, gait speed decline only, dual decline, or no decline (hereafter referred to as usual agers). Gait decline was defined as a loss of 0.05 m/s or more per year; memory decline was defined as being in the cohort-specific lowest tertile of annualized change.

Main Outcomes and Measures

Risk of incident dementia according to group membership was examined by Cox proportional hazards regression with usual agers as the reference, adjusted for baseline age, sex, race/ethnicity, educational level, study site, and baseline gait speed and memory.

Results

Across the 6 studies of 8699 participants, mean age ranged between 70 and 74 years and mean gait speed ranged between 1.05 and 1.26 m/s. Incident dementia ranged from 5 to 21 per 1000 person-years. Compared with usual agers, participants with only memory decline had 2.2 to 4.6 times higher risk for developing dementia (pooled hazard ratio, 3.45 [95% CI, 2.45-4.86]). Those with only gait decline had 2.1 to 3.6 times higher risk (pooled hazard ratio, 2.24 [95% CI, 1.62-3.09]). Those with dual decline had 5.2 to 11.7 times the risk (pooled hazard ratio, 6.28 [95% CI, 4.56-8.64]).

Conclusions and Relevance

In this study, dual decline of memory and gait speed was associated with increased risk of developing dementia among older individuals, which might be a potentially valuable group for preventive or therapeutic interventions. Why dual decline is associated with an elevated risk of dementia and whether these individuals progress to dementia through specific mechanisms should be investigated by future studies.

Effects of intensified metabolic control on CNS function in type 2 diabetes

The mild cognitive decline associated with type 2 diabetes (T2DM) has been suggested to be reversible with improved glycemic control. In order to characterise this cognitive decline and study the effects of improved glycemic control we have studied patients with T2DM (N=28) and healthy control subjects (N=21). One group of patients with diabetes (N=15) were given a 2-month treatment of intensified glycemic control, whereas the other group (N=13) maintained their regular treatment. Cognitive function in four different domains, auditory event-related potentials (ERPs) and resting EEG power spectrum were studied in the two groups of patients and in healthy control subjects before and after the 2-month trial period. There were significant differences at baseline (p<0.02) between patients with T2DM and controls. Patients had lower scores in two cognitive domains: verbal fluency (p<0.01) and visuospatial ability (p<0.03). T2DM also affected ERP with a decrease in N100 amplitude (p<0.04) and an increase in P300 latency (p<0.03). Furthermore, resting EEG activity in the beta band (13-30Hz) was reduced (p<0.04). The change between 1st and 2nd investigation was significantly different in the three groups of patients/subjects (p<0.03). Patients receiving intensified treatment for glycemic control had an improvement of cognitive ability in visuospatial ability (p<0.02) and semantic memory performance (p<0.04) together with increased resting EEG activity in the alpha band (8-13Hz, p<0.02) and connectivity in the theta (4-8Hz, p<0.03) and alpha bands (p<0.03) over central and lateral regions. Furthermore, there was an increase in the connectivity in the beta band (p<0.04) over the central regions of the scalp. In conclusion, subjects with T2DM had a similar type of cognitive function impairment and EEG/ERP abnormality as previously demonstrated for subjects with type 1 diabetes (T1DM). Intensified therapy showed cognitive improvement not shown for regular treatment, suggesting that the negative effect of T2DM on cognition is reversible by means of improved glycemic control. Furthermore, there was an improvement in electro-physiological measures, suggesting increased availability of compensatory mechanisms in subjects with intensified treatment.

Early Cognitive Deficits in Type 2 Diabetes: A Population-Based Study

Evidence links type 2 diabetes to dementia risk. However, our knowledge on the initial cognitive deficits in diabetic individuals and the factors that might promote such deficits is still limited. This study aimed to identify the cognitive domains initially impaired by diabetes and the factors that play a role in this first stage. Within the population-based Swedish National Study on Aging and Care–Kungsholmen, 2305 cognitively intact participants aged ≥60 y were identified. Attention/working memory, perceptual speed, category fluency, letter fluency, semantic memory, and episodic memory were assessed. Diabetes (controlled and uncontrolled) and prediabetes were ascertained by clinicians, who also collected information on vascular disorders (hypertension, heart diseases, and stroke) and vascular risk factors (VRFs, including smoking and overweight/obesity). Data were analyzed with linear regression models. Overall, 196 participants (8.5%) had diabetes, of which 144 (73.5%) had elevated glycaemia (uncontrolled diabetes); 571 (24.8%) persons had prediabetes. In addition, diabetes, mainly uncontrolled, was related to lower performance in perceptual speed (β – 1.10 [95% CI – 1.98, – 0.23]), category fluency (β – 1.27 [95% CI – 2.52, – 0.03]), and digit span forward (β – 0.35 [95% CI – 0.54, – 0.17]). Critically, these associations were present only among APOEɛ4 non–carriers. The associations of diabetes with perceptual speed and category fluency were present only among participants with VRFs or vascular disorders. Diabetes, especially uncontrolled diabetes, is associated with poorer performance in perceptual speed, category fluency, and attention/primary memory. VRFs, vascular disorders, and APOE status play a role in these associations.

EEG time signature in Alzheimer´s disease: Functional brain networks falling apart

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EEG microstate topographies differ between controls and memory clinic patients.

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Microstate parameters differ in a gradient-like manner in SCD, MCI and AD patients.

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Changes in topography of microstate class C correlate with CSF Aβ42 levels.

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Changes in topography of microstate class B correlate with CSF p-tau levels.

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EEG microstates detect early disruption of neurocognitive networks in AD.

Spontaneous mental activity is characterized by dynamic alterations of discrete and stabile brain states called functional microstates that are thought to represent distinct steps of human information processing. Electroencephalography (EEG) directly reflects functioning of brain synapses with a uniquely high temporal resolution, necessary for investigation of brain network dynamics. Since synaptic dysfunction is an early event and best correlate of cognitive status and decline in patients along Alzheimer's disease (AD) continuum, EEG microstates might serve as valuable early markers of AD. The present study investigated differences in EEG microstate topographies and parameters (duration, occurrence and contribution) between a large cohort of healthy elderly (n = 308) and memory clinic patients: subjective cognitive decline (SCD, n = 210); mild cognitive impairment (MCI, n = 230) and AD (n = 197) and how they correlate to conventional cerebrospinal fluid (CSF) markers of AD. Four most representative microstate maps assigned as classes A, B (asymmetrical), C and D (symmetrical) were computed from the resting state EEGs since it has been shown previously that this is sufficient to explain most of the resting state EEG data. Statistically different topography of microstate maps were found between the controls and the patient groups for microstate classes A, C and D. Changes in the topography of microstate class C were associated with the CSF Aβ42 levels, whereas changes in the topography of class B were linked with the CSF p-tau levels. Gradient-like increase in the contribution of asymmetrical (A and B) and gradient-like decrease in the contribution of symmetrical (C and D) maps were observed with the more severe stage of cognitive impairment. Our study demonstrated extensive relationship of resting state EEG microstates topographies and parameters with the stage of cognitive impairment and AD biomarkers. Resting state EEG microstates might therefore serve as functional markers of early disruption of neurocognitive networks in patients along AD continuum.

Cognitive and Physical Function in Relation to the Risk of Injurious Falls in Older Adults: A Population-Based Study

Background

We aimed to quantify the independent effect of cognitive and physical deficits on the risk of injurious falls, to verify whether this risk is modified by global cognitive impairment, and to explore whether risk varies by follow-up time.

Methods

Data on 2,495 participants (≥60 years) from the population-based Swedish National Study on Aging and Care in Kungsholmen (SNAC-K) study were analyzed using flexible parametric survival models. Two cognitive domains (processing speed and executive function) were assessed with standard tests. Physical function tests included balance (one-leg-stands), walking speed, chair stands, and grip strength. Global cognition was assessed using the Mini-Mental State Examination.

Results

A total of 167 people experienced an injurious fall over 3 years of follow-up, 310 over 5 years, and 571 over 10 years. Each standard deviation worse balance, slower walking speed, and longer chair stand time increased the risk of injurious falls over 3 years by 43%, 38%, and 23%, respectively (p < .05). Each standard deviation worse processing speed and executive function was significantly associated with 10% increased risk of injurious falls over 10 years (p < .05). In stratified analyses, deficits in physical functioning were associated with injurious falls only in people with cognitive impairment, whereas deficits in processing speed and executive function were associated with injurious falls only in people without cognitive impairment.

Conclusions

Deficits in specific cognitive domains, such as processing speed and executive function, appear to predict injurious falls in the long term. Deficits in physical function predict falls in the short term, especially in people with global cognitive impairment.

The benefits of staying active in old age: physical activity counteracts the negative influence of PICALM, BIN1, and CLU risk alleles on episodic memory functioning

PICALM, BIN1, CLU, and APOE are top candidate genes for Alzheimer's disease, and they influence episodic memory performance in old age. Physical activity, however, has been shown to protect against age-related decline and counteract genetic influences on cognition. The aims of this study were to assess whether (a) a genetic risk constellation of PICALM, BIN1, and CLU polymorphisms influences cognitive performance in old age; and (b) if physical activity moderates this effect. Data from the SNAC-K population-based study were used, including 2,480 individuals (age range = 60 to 100 years) free of dementia at baseline and at 3- to 6-year follow-ups. Tasks assessing episodic memory, perceptual speed, knowledge, and verbal fluency were administered. Physical activity was measured using self-reports. Individuals who had engaged in frequent health- or fitness-enhancing activities within the past year were compared with those who were inactive. Genetic risk scores were computed based on an integration of risk alleles for PICALM (rs3851179 G allele, rs541458 T allele), BIN1 (rs744373 G allele), and CLU (rs11136000 T allele). High genetic risk was associated with reduced episodic memory performance, controlling for age, education, vascular risk factors, chronic diseases, activities of daily living, and APOE gene status. Critically, physical activity attenuated the effects of genetic risk on episodic memory. Our findings suggest that participants with high genetic risk who maintain a physically active lifestyle show selective benefits in episodic memory performance.

Anosmia, mild cognitive impairment, and biomarkers of brain aging in older adults

Olfactory impairment is a potential marker for prodromal dementia, but the underlying mechanisms are poorly understood. This population-based study included 4214 dementia-free participants (age ≥65 years). Olfaction was assessed using the 16-item Sniffin' Sticks identification test. In the subsamples, we measured plasma amyloid beta (Aβ)40, Aβ42, total tau, and neurofilament light chain (NfL; n = 1054); and quantified hippocampal, entorhinal cortex, and white matter hyperintensity (WMH) volumes, and Alzheimer's disease (AD)-signature cortical thickness (n = 917). Data were analyzed with logistic and linear regression models. In the total sample, mild cognitive impairment (MCI) was diagnosed in 1102 persons (26.2%; amnestic MCI, n = 931; non-amnestic MCI, n = 171). Olfactory impairment was significantly associated with increased likelihoods of MCI, amnestic MCI, and non-amnestic MCI. In the subsamples, anosmia was significantly associated with higher plasma total tau and NfL concentrations, smaller hippocampal and entorhinal cortex volumes, and greater WMH volume, and marginally with lower AD-signature cortical thickness. These results suggest that cerebral neurodegenerative and microvascular lesions are common neuropathologies linking anosmia with MCI in older adults.

Cardiometabolic multimorbidity accelerates cognitive decline and dementia progression

INTRODUCTION

Cardiometabolic diseases (CMDs) have been individually associated with adverse cognitive outcomes, but their combined effect has not been investigated.

METHODS

A total of 2577 dementia-free participants 60 years of age or older were followed for 12 years to observe changes in cognitive function and to detect incident cognitive impairment, no dementia (CIND) and dementia. CMDs (including type 2 diabetes, heart disease, and stroke) were assessed at baseline through medical records and clinical examinations. Cardiometabolic multimorbidity was defined as the presence of two or more CMDs. Data were analyzed using multi-adjusted linear mixed-effects models, Cox regression, and Laplace regression.

RESULTS

CMD multimorbidity was associated with cognitive decline, CIND (hazard ratio [HR] 1.73; 95% confidence interval CI 1.23 to 2.44), and its progression to dementia (HR 1.86; 95% CI 1.17 to 2.97). CMD multimorbidity accelerated the onset of CIND by 2.3 years and dementia by 1.8 years.

CONCLUSIONS

CMD multimorbidity accelerates cognitive decline and increases the risk of both CIND and its conversion to dementia.

HIGHLIGHTS

We explored the combined impact of cardiometabolic diseases (CMDs) on cognition. An increasing number of CMDs dose-dependently accelerated cognitive decline. CMD multimorbidity increased the risk of both cognitive impairment and dementia. Co-morbid CMDs could be ideal targets for interventions to protect cognitive health.

Phantom Smells: Prevalence and Correlates in a Population-Based Sample of Older Adults

Loss of olfactory function is common in old age, but evidence regarding qualitative olfactory dysfunction in the general older population is scarce. The current study investigates the prevalence and correlates of phantom smell experiences (phantosmia) in a population-based study (Swedish National Study on Aging and Care in Kungsholmen [SNAC-K]) of Swedish adults (n = 2569) aged between 60 and 90 years. Phantosmia was assessed through a standardized interview and defined as reporting having experienced an odor percept in the absence of any stimuli in the surrounding environment that could emit the odor. The relationships between phantosmia and demographic, genetic, health-related, and behavioral variables were analyzed with hierarchical logistic regression analyses. The overall prevalence of phantom smells was 4.9%, and was associated with female gender, carrying the met allele of the BDNF gene, higher vascular risk burden, and reporting distorted smell sensations (parosmia). Olfactory dysfunction was, however, not related to phantosmia. The most frequently reported phantom smell was smoky/burnt. A novel finding was that some individuals reported phantom smells with an autobiographical connotation. The results from this study indicate that the prevalence of phantosmia in the general older population is not negligible and that some factors that are beneficial for preserved olfactory function, such as female gender and the BDNF met allele, are also associated with the occurrence of phantom smells.

Cognitive deficits in unipolar old-age depression: a population-based study

BACKGROUND

There is substantial variability in the degree of cognitive impairment among older depressed persons. Inconsistencies in previous findings may be due to differences in clinical and demographic characteristics across study samples. We assessed the influence of unipolar depression and severity of depression on cognitive performance in a population-based sample of elderly persons aged ⩾60 years.

METHOD

Eighty-nine persons fulfilled ICD-10 criteria for unipolar depression (mild, n = 48; moderate, n = 38; severe, n = 3) after thorough screening for dementia (DSM-IV criteria), psychiatric co-morbidities and antidepressant pharmacotherapy. Participants (n = 2486) were administered an extensive cognitive test battery.

RESULTS

Moderate/severe unipolar depression was associated with poorer performance on tasks assessing processing speed, attention, executive function, verbal fluency, episodic memory and vocabulary. Mild depression was associated with poorer performance in processing speed, and few differences between mild and moderate/severe depression were observed. No association between depression and short-term memory, general knowledge or spatial ability was observed. Increasing age did not exacerbate the depression-related cognitive deficits, and the deficits remained largely unchanged after excluding persons in a preclinical phase of dementia. Furthermore, depression-related cognitive deficits were not associated with other pharmacological treatments that may affect cognitive performance.

CONCLUSIONS

Cognitive deficits in unipolar old-age depression involve a range of domains and the cognitive deficits seem to follow the spectrum of depression severity. The finding that mild depression was also associated with poorer cognitive functioning underscores the importance of detecting mild depression in elderly persons.

Contrasting cognitive trajectories of impending death and preclinical dementia in the very old

BACKGROUND

Both impending death and preclinical dementia are associated with cognitive impairment in old age, although their effects on cognitive functioning have rarely been examined within the same study.

METHODS

Participants (n = 1,200, aged 75+ years) from a community-based study completed a measure of global cognitive performance (the Mini-Mental State Examination [MMSE]) at 3-year intervals over an 11-year period. Level and change of MMSE performance were compared for three groups: persons in close proximity to death, persons in a preclinical phase of dementia, and persons who remained alive and nondemented throughout the study.

RESULTS

There were significant group differences in MMSE performance 3 years before each outcome (death, dementia, or end of study). Those with preclinical dementia performed the poorest and declined twice as fast on the MMSE relative to the other groups. Although persons in close proximity to death declined faster in general, no accelerated decline was observed for the impending death group after persons with dementia or preclinical dementia had been excluded. Group differences were attenuated for the oldest-old (81+ years) compared to the old-old (75 to 80 years).

CONCLUSIONS

The lack of accelerated decline in proximity to death after excluding persons with dementia or preclinical dementia suggests that part of the terminal decline effect demonstrated in previous investigations may reflect preclinical dementia deficits. Further, accelerated cognitive decline might be a more reliable indicator of preclinical dementia than a low cognitive score due to confounds associated with cross-sectional cognitive performance.

The influence of APOE and TOMM40 polymorphisms on hippocampal volume and episodic memory in old age

Mitochondrial dysfunction is implicated in neurodegenerative disorders, such as Alzheimer's disease (AD). Translocase of outer mitochondrial membrane 40 (TOMM40) may be influential in this regard by influencing mitochondrial neurotoxicity. Little is known about the influence of the TOMM40 gene on hippocampal (HC) volume and episodic memory (EM), particularly in healthy older adults. Thus, we sought to discern the influence of TOMM40 single nucleotide polymorphisms (SNPs), which have previously been associated with medial temporal lobe integrity (rs11556505 and rs2075650), on HC volume and EM. The study sample consisted of individuals from the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K) who were free of dementia and known neurological disorders, and 60-87 years of age (n = 424). EM was measured by using a 16-item word list with a 2-min free recall period and delineation of the HC was performed manually. The influence of Apolipoprotein E (APOE) and TOMM40 was assessed by 2 × 2 ANOVAs and partial correlations. There was no effect of APOE and TOMM40 on EM performance and HC volume. However, partial correlations revealed that HC volume was positively associated with free recall performance (r = 0.21, p < 0.01, r (2) = 0.04). When further stratified for TOMM40, the observed association between HC volume and free recall in APOE ε4 carriers was present in combination with TOMM40 rs11556505 any T (r = 0.28, p < 0.01, R (2) = 0.08) and rs2075650 any G (r = 0.28, p < 0.01, R (2) = 0.08) "risk" alleles. This pattern might reflect higher reliance on HC volume for adequate EM performance among APOE ε4 carriers with additional TOMM40 "risk" alleles suggesting that the TOMM40 gene cannot merely be considered a marker of APOE genotype. Nevertheless, neither APOE nor TOMM40 influenced HC volume or EM in this population-based sample of cognitively intact individuals over the age of 60.

MRI load of cerebral microvascular lesions and neurodegeneration, cognitive decline, and dementia

Objective

To explore the differential associations of neurodegeneration and microvascular lesion load with cognitive decline and dementia in older people and the modifying effect of the APOE genotype on these associations.

Methods

A sample of 436 participants (age ≥ 60 years) was derived from the population-based Swedish National study on Aging and Care in Kungsholmen, Stockholm, and clinically examined at baseline (2001–2003) and 3 occasions during the 9-year follow-up. At baseline, we assessed microvascular lesion load using a summary score for MRI markers of lacunes, white matter hyperintensities (WMHs), and perivascular spaces and neurodegeneration load for markers of enlarged ventricles, smaller hippocampus, and smaller gray matter. We assessed cognitive function using the Mini-Mental State Examination (MMSE) test and diagnosed dementia following the Diagnostic and Statistical Manual of Mental Disorders, 4th edition criteria. We analyzed data using linear mixed-effects, mediation, and random-effects Cox models.

Results

During the follow-up, 46 participants were diagnosed with dementia. Per 1-point increase in microvascular lesion and neurodegeneration score (range 0–3) was associated with multiple adjusted β-coefficients of −0.35 (95% confidence interval, −0.51 to −0.20) and −0.44 (−0.56 to −0.32), respectively, for the MMSE score and multiple adjusted hazard ratios of 1.68 (1.12–2.51) and 2.35 (1.58–3.52), respectively, for dementia; carrying APOE ε4 reinforced the associations with MMSE decline. WMH volume changes during the follow-up mediated 66.9% and 12.7% of the total association of MMSE decline with the baseline microvascular score and neurodegeneration score, respectively.

Conclusions

Both cerebral microvascular lesion and neurodegeneration loads are strongly associated with cognitive decline and dementia. The cognitive decline due to microvascular lesions is exacerbated by APOE ε4 and is largely attributed to progression and development of microvascular lesions.

From Normal Cognition to Cognitive Impairment and Dementia: Impact of Orthostatic Hypotension

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The role of orthostatic hypotension (OH) in the continuum of cognitive aging remains to be clarified. We sought to investigate the associations of OH with dementia, cognitive impairment, no dementia (CIND), and CIND progression to dementia in older adults while considering orthostatic symptoms. This population-based cohort study included 2532 baseline (2001–2004) dementia-free participants (age ≥60 years; 62.6% women) in the SNAC-K (Swedish National Study on Aging and Care in Kungsholmen) who were regularly examined over 12 years. We further divided the participants into a baseline CIND-free cohort and a CIND cohort. OH was defined as a decrease by ≥20/10 mm Hg in systolic/diastolic blood pressure upon standing and further divided into asymptomatic and symptomatic OH. Dementia was diagnosed following the international criteria. CIND was defined as scoring ≥1.5 SDs below age group-specific means in ≥1 cognitive domain. Data were analyzed with flexible parametric survival models, controlling for confounding factors. Of the 2532 participants, 615 were defined with OH at baseline, and 322 were diagnosed with dementia during the entire follow-up period. OH was associated with an adjusted hazard ratio of 1.40 for dementia (95% CI, 1.10–1.76), 1.15 (0.94–1.40) for CIND, and 1.54 (1.05–2.25) for CIND progression to dementia. The associations of dementia and CIND progression to dementia with asymptomatic OH were similar to overall OH, whereas symptomatic OH was only associated with CIND progression to dementia. Our study suggests that OH, even asymptomatic OH, is associated with increased risk of dementia and accelerated progression from CIND to dementia in older adults.

Air pollution as a risk factor for Cognitive Impairment no Dementia (CIND) and its progression to dementia: A longitudinal study

BACKGROUND AND AIM

Accumulation of evidence has raised concern regarding the harmful effect of air pollution on cognitive function, but results are diverging. We aimed to investigate the longitudinal association of long-term exposure to air pollutants and cognitive impairment and its further progression to dementia in older adults residing in an urban area.

METHODS

Data were obtained from the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K). Cognitive impairment, no dementia (CIND) was assessed by a comprehensive neuropsychological battery (scoring ≥1.5 standard deviations below age-specific means in ≥1 cognitive domain). We assessed long-term residential exposure to particulate matters (PM_2.5 and PM₁₀) and nitrogen oxides (NO_x) with dispersion modeling. The association with CIND was estimated using Cox proportional hazards models with 3-year moving average air pollution exposure. We further estimated the effect of long-term air pollution exposure on the progression of CIND to dementia using Cox proportional hazards models.

RESULTS

Among 1987 cognitively intact participants, 301 individuals developed CIND during the 12-year follow-up. A 1-μg/m³ increment in PM_2.5 exposure was associated with a 75% increased risk of incident CIND (HR = 1.75, 95 %CI: 1.54, 1.99). Weaker associations were found for PM₁₀ (HR for 1-μg/m³ = 1.08, 95 %CI: 1.03-1.14) and NO_x (HR for 10 μg/m³ = 1.18, 95 %CI: 1.04-1.33). Among those with CIND at baseline (n = 607), 118 participants developed dementia during follow-up. Results also show that exposure to air pollution was a risk factor for the conversion from CIND to dementia (PM_2.5: HR for 1-μg/m³ = 1.90, 95 %CI: 1.48-2.43; PM₁₀: HR for 1-μg/m³ = 1.14, 95 %CI: 1.03-1.26; and NO_x: HR for 10 μg/m³ = 1.34, 95 %CI: 1.07-1.69).

CONCLUSION

We found evidence of an association between long-term exposure to ambient air pollutants and incidence of CIND. Of special interest is that air pollution also was a risk factor for the progression from CIND to dementia.