Classification models for early identification of persons at risk for dementia in primary care: an evaluation in a sample aged 80 years and older

Subjective Cognitive Decline: Level of Risk for Future Dementia and Mild Cognitive Impairment, a Meta-Analysis of Longitudinal Studies

Subjective Cognitive Decline (SCD) in older adults has been identified as a risk factor for dementia, although the literature is inconsistent, and it is unclear which factors moderate progression from SCD to dementia. Through separate meta-analyses, we aimed to determine if SCD increased the risk of developing dementia or mild cognitive impairment (MCI). Furthermore, we examined several possible moderators. Longitudinal studies of participants with SCD at baseline, with data regarding incident dementia or MCI, were extracted from MEDLINE and PsycINFO. Articles were excluded if SCD occurred solely in the context of dementia, MCI, or as part of a specific disease. Pooled estimates were calculated using a random-effects model, with moderator analyses examining whether risk varied according to SCD definition, demographics, genetics, recruitment source, and follow-up duration. Risk of study bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS)-2 tool. 46 studies with more than 74,000 unique participants were included. SCD was associated with increased risk of developing dementia (HR = 1.90, 95% CI 1.52-2.36; OR = 2.48, 95% CI 1.97-3.14) and MCI (HR = 1.73, 95% CI 1.18-2.52; OR = 1.83, 95% CI 1.56-2.16). None of the potential moderating factors examined influenced the HR or OR of developing dementia. In contrast, including worry in the definition of SCD, younger age, and recruitment source impacted the OR of developing MCI, with clinic samples demonstrating highest risk. SCD thus represents an at-risk phase, ideal for early intervention, with further research required to identify effective interventions for risk reduction, and cognitive-behavioural interventions for cognitive management. PROSPERO, protocol number: CRD42016037993.

The role of cognitive reserve on terminal decline: a cross-cohort analysis from two European studies: OCTO-Twin, Sweden, and Newcastle 85+, UK

OBJECTIVE

Cognitive performance shows a marked deterioration in close proximity to death, as postulated by the terminal decline hypothesis. The effect of education on the rate of terminal decline in the oldest people (i.e. persons 85+ years) has been controversial and not entirely understood. In the current study, we investigated the rate of decline prior to death with a special focus on the role of education and socioeconomic position, in two European longitudinal studies of ageing: the Origins of Variance in the Old-Old: Octogenarian Twins (OCTO-Twin) and the Newcastle 85+ study.

METHODS

A process-based approach was used in which individuals' cognitive scores were aligned according to distance to death. In a coordinated analysis, multilevel models were employed to examine associations between different markers of cognitive reserve (education and socioeconomic position) and terminal decline using the mini-mental state examination (MMSE), controlling for age at baseline, sex, dementia incidence and time to death from the study entry to the time of death within each cohort.

RESULTS

The current findings suggest that education was positively associated with higher MMSE scores prior to death in the OCTO-Twin, but not in the Newcastle 85+ study, independent of socioeconomic position and other factors such as baseline age, sex and time to death from the study entry. However, education was not associated with the rate of terminal decline in both of these studies.

CONCLUSIONS

Our results offer only partial support to the cognitive reserve hypothesis and cognitive performance prior to death.

Dementia risk estimates associated with measures of depression: a systematic review and meta-analysis

OBJECTIVES

To perform a systematic review of reported HRs of all cause dementia, Alzheimer's disease (AD) and vascular dementia (VaD) for late-life depression and depressive symptomatology on specific screening instruments at specific thresholds.

DESIGN

Meta-analysis with meta-regression.

SETTING AND PARTICIPANTS

PubMed, PsycInfo, and Cochrane databases were searched through 28 February 2014. Articles reporting HRs for incident all-cause dementia, AD and VaD based on published clinical criteria using validated measures of clinical depression or symptomatology from prospective studies of general population of adults were selected by consensus among multiple reviewers. Studies that did not use clinical dementia diagnoses or validated instruments for the assessment of depression were excluded. Data were extracted by two reviewers and reviewed by two other independent reviewers. The most specific analyses possible using continuous symptomatology ratings and categorical measures of clinical depression focusing on single instruments with defined reported cut-offs were conducted.

PRIMARY OUTCOME MEASURES

HRs for all-cause dementia, AD, and VaD were computed where possible for continuous depression scores, or for major depression assessed with single or comparable validated instruments.

RESULTS

Searches yielded 121,301 articles, of which 36 (0.03%) were eligible. Included studies provided a combined sample size of 66,532 individuals including 6593 cases of dementia, 2797 cases of AD and 585 cases of VaD. The increased risk associated with depression did not significantly differ by type of dementia and ranged from 83% to 104% for diagnostic thresholds consistent with major depression. Risk associated with continuous depression symptomatology measures were consistent with those for clinical thresholds.

CONCLUSIONS

Late-life depression is consistently and similarly associated with a twofold increased risk of dementia. The precise risk estimates produced in this study for specific instruments at specified thresholds will assist evidence-based medicine and inform policy on this important population health issue.

A hierarchy of predictors for dementia-free survival in old-age: results of the AgeCoDe study

OBJECTIVE

Progression from cognitive impairment (CI) to dementia is predicted by several factors, but their relative importance and interaction are unclear.

METHOD

We investigated numerous such factors in the AgeCoDe study, a longitudinal study of general practice patients aged 75+. We used recursive partitioning analysis (RPA) to identify hierarchical patterns of baseline covariates that predicted dementia-free survival.

RESULTS

Among 784 non-demented patients with CI, 157 (20.0%) developed dementia over a follow-up interval of 4.5 years. RPA showed that more severe cognitive compromise, revealed by a Mini-Mental State Examination (MMSE) score < 27.47, was the strongest predictor of imminent dementia. Dementia-free survival time was shortest (mean 2.4 years) in such low-scoring patients who also had impaired instrumental activities of daily living (iADL) and subjective memory impairment with related worry (SMI-w). Patients with identical characteristics but without SMI-w had an estimated mean dementia-free survival time of 3.8 years, which was still shorter than in patients who had subthreshold MMSE scores but intact iADL (4.2-5.2 years).

CONCLUSION

Hierarchical patterns of readily available covariates can predict dementia-free survival in older general practice patients with CI. Although less widely appreciated than other variables, iADL impairment appears to be an especially noteworthy predictor of progression to dementia.

Prevalence and correlates of mild cognitive impairment in adults aged over 50 years with subjective cognitive complaints in primary care centers

AIM

To examine the prevalence and correlates of mild cognitive impairment in adults aged over 50 years attending primary care centers with complaints of cognitive failure.

METHODS

A sample of 689 individuals aged ≥ 50 years with no previous diagnosis of dementia was assessed by use of the Mini-Mental State Examination, the Cambridge Cognitive Examination-Revised and the California Verbal Learning Test--to evaluate the mild cognitive impairment as dependent variables--and administration of a questionnaire on cognitive complaints and other instruments--to measure correlates.

RESULTS

The prevalence of mild cognitive impairment was 31.40%, and positive associations were found for age, occupation, subjective memory complaints, reading habits and level of vocabulary. In the logistic regression, modeled mild cognitive impairment was associated with age (70 years or older), subjective cognitive complaints and level of vocabulary.

CONCLUSION

Almost one-third of the adults aged ≥ 50 years attending primary care centers with subjective cognitive complaints were affected by mild cognitive impairment. Early evaluation of cognitive functioning is essential to establish adequate preventive and intervention strategies.

Affective disorders and risk of developing dementia: systematic review

BACKGROUND

Affective disorders are associated with cognitive disturbances but their role as risk factors for dementia is still not fully investigated.

AIMS

To evaluate the risk of developing dementia in individuals with a history of affective disorder.

METHOD

We conducted a systematic review of case-control and cohort studies addressing the risk of developing dementia in people with affective disorders. To the best of our knowledge, this is the first systematic review that has included studies evaluating this risk specifically in people with bipolar disorder.

RESULTS

Fifty-one studies were included. Most of the studies found an increased risk for developing dementia in individuals with depression. Greater frequency and severity of depressive episodes seem to increase this risk. The evidence is contradictory regarding whether there is a difference in risk in people with early- or late-onset depression. The few available risk estimates for dementia in people with bipolar disorder suggest an even higher risk than for those with depression.

CONCLUSIONS

Affective disorders appear to be associated with an increased risk of developing dementia, and one that is dependent on clinical and demographic variables. Depression may be both a prodrome and a risk factor for dementia. Future research should aim to elucidate the mechanisms that mediate these links.

Clinical recognition of dementia and cognitive impairment in primary care: a meta-analysis of physician accuracy

OBJECTIVE

We aimed to examine the ability of the general practitioners (GPs) to recognize a spectrum of cognitive impairment from mild cognitive impairment (MCI) to severe dementia in routine practice using their own clinical judgment.

METHOD

Using PRISMA criteria, a meta-analysis of studies testing clinical judgment and clinical documentation was conducted against semi-structured interviews (for dementia) and cognitive tests (for cognitive impairment). We located 15 studies reporting on dementia, seven studies that examined recognition of broadly defined cognitive impairment, and eight regarding MCI.

RESULTS

By clinical judgment, clinicians were able to identify 73.4% of people with dementia and 75.5% of those without dementia but they made correct annotations in medical records in only 37.9% of cases (and 90.5% of non-cases). For cognitive impairment, detection sensitivity was 62.8% by clinician judgment but 33.1% according to medical records. Specificity was 92.6% for those without cognitive impairment by clinical judgment. Regarding MCI, GPs recognized 44.7% of people with MCI, although this was recorded in medical notes only 10.9% of the time. Their ability to identify healthy individuals without MCI was between 87.3% and 95.5% (detection specificity).

CONCLUSION

GPs have considerable difficulty identifying those with MCI and those with mild dementia and are generally poor at recording such diagnoses in medical records.

A method to combine cognitive and neurophysiological assessments of the elderly

BACKGROUND

The development of better treatments for brain diseases of the elderly will necessitate more sensitive and efficient means of repeatedly assessing an individual's neurocognitive status.

AIM

To illustrate the development of an assessment combining episodic memory and working memory tasks with simultaneous electroencephalography and evoked potential (EP) brain function measures.

METHODS

Data from matched groups of elderly subjects with mildly impaired episodic verbal memory on neuropsychological tests and those with no objective signs of impairment were used for scale development. An exploratory multivariate divergence analysis selected task performance and neurophysiological variables that best recognized impairment. Discriminant validity was then initially assessed on separate impaired and unimpaired groups.

RESULTS

Decreased response accuracy and parietal late positive component EP amplitude in the episodic memory task best characterized impaired subjects. Sensitivity in recognizing impairment in the validation analysis was 89% with 79% specificity (area under the curve = 0.94). Retest reliability was 0.89 for the unimpaired and 0.74 for the impaired validation groups.

CONCLUSION

These promising initial results suggest that with further refinement and testing, an assessment combining cognitive task performance with simultaneous neurofunctional measures could eventually provide an important benefit for clinicians and researchers.