The unbearable lightness of MCI

Recent Advancements in Pathogenesis, Diagnostics and Treatment of Alzheimer's Disease

BACKGROUND

The only conclusive way to diagnose Alzheimer's is to carry out brain autopsy of the patient's brain tissue and ascertain whether the subject had Alzheimer's or any other form of dementia. However, due to the non-feasibility of such methods, to diagnose and conclude the conditions, medical practitioners use tests that examine a patient's mental ability.

OBJECTIVE

Accurate diagnosis at an early stage is the need of the hour for initiation of therapy. The cause for most Alzheimer's cases still remains unknown except where genetic distinctions have been observed. Thus, a standard drug regimen ensues in every Alzheimer's patient, irrespective of the cause, which may not always be beneficial in halting or reversing the disease progression. To provide a better life to such patients by suppressing existing symptoms, early diagnosis, curative therapy, site-specific delivery of drugs, and application of hyphenated methods like artificial intelligence need to be brought into the main field of Alzheimer's therapeutics.

METHODS

In this review, we have compiled existing hypotheses to explain the cause of the disease, and highlighted gene therapy, immunotherapy, peptidomimetics, metal chelators, probiotics and quantum dots as advancements in the existing strategies to manage Alzheimer's.

CONCLUSION

Biomarkers, brain-imaging, and theranostics, along with artificial intelligence, are understood to be the future of the management of Alzheimer's.

Mild Cognitive Impairment that Does Not Progress to Dementia: A Population-Based Study

BACKGROUND/OBJECTIVE

In population studies, most individuals with mild cognitive impairment (MCI) do not progress to dementia in the near term, but rather remain stable MCI or revert to normal cognition. Here, we characterized MCI subgroups with different outcomes over 5 years.

SETTING/PARTICIPANTS

A population-based cohort (N=1603).

MEASUREMENTS

Clinical Dementia Rating (CDR); self-reported medical conditions, subjective cognitive concerns, self-rated health, depressive symptoms, blood pressure, medications, blood pressure, APOE genotype, cognitive domain composite scores.

DESIGN

We compared 3 MCI subgroups who progressed to dementia (n=86), stabilized at MCI (n=384), or reverted to normal (n=252), to those who remained consistently normal (n=881), defining MCI as CDR = 0.5 and dementia as CDR≥1. Using multinomial logistic regression models adjusted for demographics, we examined the associations of each group with selected baseline characteristics.

RESULTS

With the normal group for reference, worse subjective cognitive concerns, functional impairments, self-rated health, and depressive symptoms were associated with being in any MCI group. Taking more prescription medications was associated with being in the stable MCI and reverter groups; diabetes and low diastolic blood pressure were associated with stable MCI. The APOE4 genotype was associated with stable and progressive MCI; stroke was associated with progressive MCI. All MCI subgroups were likely to have lower mean composite scores in all cognitive domains and more operationally defined impairments in attention, language, and executive function; reverters were more likely to lack memory and visuospatial impairments.

CONCLUSIONS

MCI subgroups with different 5-year outcomes had some distinct characteristics suggesting different underlying causes. The progressors, unlike the reverters, had a profile broadly typical of Alzheimer's disease; the stable MCIs had other, including vascular, morbidity. These data shed light on the heterogeneity of MCI in the population. J Am Geriatr Soc 67:232-238, 2019.

Prevalence of anxiety in patients with mild cognitive impairment: A systematic review and meta-analysis

BACKGROUND

Prevalence rates of anxiety in patients with mild cognitive impairment (MCI) varied widely across studies and may confer a higher likelihood of progression to dementia. Our aim was to estimate the prevalence of anxiety in MCI and identify reasons for heterogeneity in the reported results.

METHODS

A computerized search in PubMed, EMBASE, and Psyc INFO for studies on anxiety in MCI was performed up to March 2017. The overall prevalence of anxiety in patients with MCI was pooled using a random-effects model. Heterogeneity was explored using stratification (recruitment resource; method of anxiety diagnosis; method of MCI diagnosis; and region) and random-effects meta-regression.

RESULTS

Of 2494 unique abstracts, 290 were selected for full-text review, and 39 studies, representing 10,587 patients, met all inclusion criteria. The overall pooled prevalence of depression in patients with MCI was 21.0% (95% CI, 16.2-26.7) with significant heterogeneity present (I² = 97.2%, p < 0.001). When stratified by source, the prevalence of anxiety in patients with MCI in community-based samples was 14.3% (95% CI, 9.7-20.5) and was 31.2% (95% CI, 23.6-40.0) in clinic-based samples, which was significantly different (p < 0.01). The prevalence of anxiety estimates also differed significantly, when stratification by the method of anxiety diagnosis (p < 0.01). However, the criteria used for MCI diagnosis and geographical region did not significantly influence the prevalence estimate.

LIMITATIONS

We did not consider the usage of anti-anxiety drugs and language bias.

CONCLUSIONS

The prevalence of anxiety in patients with MCI was common and variability in prevalence of anxiety across studies can be attributed partly to the source of the sample and method of anxiety diagnosis. Further research is needed to identify sources of heterogeneity.

Age-correction of test scores reduces the validity of mild cognitive impairment in predicting progression to dementia

Objectives

A phase of mild cognitive impairment (MCI) precedes most forms of neurodegenerative dementia. Many definitions of MCI recommend the use of test norms to diagnose cognitive impairment. It is, however, unclear whether the use of norms actually improves the detection of individuals at risk of dementia. Therefore, the effects of age- and education-norms on the validity of test scores in predicting progression to dementia were investigated.

Methods

Baseline cognitive test scores (Syndrome Short Test) of dementia-free participants aged ≥65 were used to predict progression to dementia within three years. Participants were comprehensively examined one, two, and three years after baseline. Test scores were calculated with correction for (1) age and education, (2) education only, (3) age only and (4) without correction. Predictive validity was estimated with Cox proportional hazard regressions. Areas under the curve (AUCs) were calculated for the one-, two-, and three-year intervals.

Results

82 (15.3%) of initially 537 participants, developed dementia. Model coefficients, hazard ratios, and AUCs of all scores were significant (p<0.001). Predictive validity was the lowest with age-corrected scores (−2 log likelihood  = 840.90, model fit χ² (1)  = 144.27, HR  = 1.33, AUCs between 0.73 and 0.87) and the highest with education-corrected scores (−2 log likelihood  = 815.80, model fit χ² (1)  = 171.16, HR  = 1.34, AUCs between 0.85 and 0.88).

Conclusion

The predictive validity of test scores is markedly reduced by age-correction. Therefore, definitions of MCI should not recommend the use of age-norms in order to improve the detection of individuals at risk of dementia.