No effect of thyroid hormones on 5-year mortality in patients with subjective cognitive decline, mild cognitive disorder, and Alzheimer's disease

Depressive symptoms-Not a predictor for five-year mortality in patients with subjective cognitive decline, non-amnestic and amnestic mild cognitive impairment

The main aim of the present study is to evaluate the influence of depressive symptoms on mortality in patients with SCD (subjective cognitive decline), naMCI (non-amnestic mild cognitive impairment), and aMCI (amnestic mild cognitive impairment). Additional factors (age, sex, years of school attendance, and neuropsychological performance) were considered to determine the impact on survival probability. A monocentric retrospective data analysis based on adjusted patient protocols (n = 1221) from the observation period 1998-2021, using the Cox Proportional Hazards model, assessed whether depressivity had an explanatory value for survival, considering SCD as the reference level in relation to naMCI and aMCI. Covariates were included blockwise. Cox regression revealed that depressiveness (Beck Depression Inventory, Geriatric Depression Scale) did not make a significant contribution as a risk factor for mortality in all five model blocks, BDI-II with HR 0.997 [0.978; 1.02] and GDS-15 with HR 1.03 [0.98; 1.08]. Increasing age with HR 1.09 [1.07; 1.11] and male sex with HR (inverted) 1.53 [1.17; 2.00] appeared as risk factors for increased mortality across all five model blocks. aMCI (vs. SCD) with HR 1.91 [1.33; 2.76] showed a significant explanatory value only up to the fourth model block. By adding the six dimensions of the Neuropsychological Test Battery Vienna in the fifth model block, the domains attention and perceptual speed with HR 1.34 [1.18; 1.53], and executive functions with HR 1.24 [1.11; 1.39], showed substantial explanatory values for survival. Accordingly, no tendency can be attributed to depressiveness as a risk factor on the probability of survival, whereas the influence of certain cognitive dimensions, especially attention and perceptual speed, and executive functions, can be seen as protective for survival.

Hemoglobin A1c Serum Level Predicts 5-year Mortality in Patients with Cognitive Impairment

Background

Subjective cognitive decline (SCD) and mild cognitive impairment (MCI) may occur as preclinical stages of Alzheimer's disease (AD), ultimately leading to dementia. Glycated hemoglobin A1c (HbA1c) is a diagnostic marker for diabetes mellitus and indicates mortality risk.

Objectives

This university-based, exploratory retrospective study examined the impact of HbA1c serum level on 5-year mortality among individuals with cognitive impairment.

Methods

Included were 1076 subjects aged at least 50 years who visited the Memory Outpatient Clinic of the Medical University of Vienna due to memory problems. Participants were diagnosed with SCD, MCI, or AD subsequent to neurological examination, standard laboratory blood tests, and neuropsychological testing. Survival was compared between diagnostic subgroups and with respect to HbA1c categories using log-rank tests based on Kaplan-Meier functions. The Neuropsychological Test Battery Vienna (NTBV) was dimensionally reduced, and a principal component analysis (PCA) was performed to further analyze results. Corresponding factor scores, HbA1c values, and baseline characteristics were included in Cox proportional hazards models to assess 5-year mortality risk.

Results

During the observation period, 323 patients (30%) died at a mean age comparable between diagnostic subgroups (SCD 84.2 ± 10.1, MCI 81.2 ± 8.3, AD 82.2 ± 7.4 years). Individuals with normal serum HbA1c levels had significant advantages in survival within the MCI (12.9 ± .3 vs. 10.0 ± .8 years) and the AD subgroups (8.2 ± .4 vs. 5.5 ± .6 years), and metric HbA1c predicted 5-year mortality (HR 1.24).

Conclusion

This study demonstrates an association between abnormal HbA1c serum levels and increased mortality.

Thyroid hormone levels in Alzheimer disease: a systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

Thyroid hormone (TH) disturbances are perceived to contribute to cognitive impairment and dementia. However, there is no consensus on the association between TH levels and Alzheimer Disease (AD). In this study, we aimed to compare serum and cerebrospinal fluid (CSF) TH levels in AD patients to controls by performing a meta-analysis.

METHODS

We systematically searched online databases for papers comparing CSF or serum TH levels in AD patients to controls, and performed a meta-analysis on the extracted data.

RESULTS

Out of 1604 records identified, 32 studies were included. No significant difference in serum TSH (standardized mean difference (SMD): -0.03; 95% confidence interval (CI): -0.22-0.16), total T4 (SMD: 0.10; 95% CI: -0.29-0.49), and free T4 (SMD: 0.25; 95% CI: -0.16-0.69) levels were observed. However, there was significantly lower serum total T3 (SMD: -0.56; 95%CI: -0.97 to -0.15) and free T3 (SMD: -0.47; 95%CI: -0.89 to -0.05) levels in AD group compared to controls. Subgroup analyses on studies including only euthyroid patients did not show any significant difference in either of the thyroid hormone levels. Also, no significant difference in CSF total T4 and total T3/total T4 ratios but significantly lower CSF total T3 (SMD: -2.45; 95% CI: -4.89 to -0.02) in AD group were detected.

CONCLUSION

Serum total and free T3 and CSF total T3 levels are significantly lower in AD patients compared to controls. The temporality of changes in thyroid hormone levels and AD development should be illustrated by further longitudinal studies.

Homocysteine - A predictor for five year-mortality in patients with subjective cognitive decline, mild cognitive impairment and Alzheimer's dementia

BACKGROUND

Subjective Cognitive Decline (SCD) and Mild Cognitive Impairment (MCI) are preclinical stages of Alzheimer's Disease (AD), which is the most common entity of dementia. Homocysteine is an amino acid in the methionine cycle, and many studies revealed a significant association between elevated homocysteine serum levels and the progression of dementia. The primary objective of this retrospective study was to investigate whether elevated homocysteine serum levels could be associated with mortality and neuropsychological test results in individuals suffering from SCD, MCI or AD.

METHODS

This study is a single-center explorative retrospective data analysis with 976 data protocols from the Memory Outpatient's Clinic of the Medical University of Vienna included. All patients underwent a neurological examination, a laboratory blood test, and neuropsychological testing to establish a diagnosis of either SCD, MCI, or AD. Data was evaluated by Kaplan-Meier functions, factor analysis, and binary logistic regression models.

RESULTS

Patients with AD showed significantly higher mean homocysteine levels (SCD 12.15 ± 4.71, MCI 12.80 ± 4.81, AD 15.0 ± 6.44 μmol/L) compared to those with SCD and MCI (p ≤ .001). The mean age of patients with AD (75.2 ± 7.8) was significantly older at the time of testing than of patients with MCI (69.1 ± 9.6) or SCD (66.8 ± 9.3). Since homocysteine levels increase with age, this could be a possible explanation for the higher levels of AD patients. The age at death did not differ significantly between all diagnostic subgroups, resulting in the shortest survival times for AD patients. Homocysteine levels were negatively associated with in Mini-Mental State Examination (MMSE) and Neuropsyhcological Test Battery Vienna (NTBV) factors F1-F4 (F1 = attention, F2 = memory, F3 = executive functions, F4 = naming/verbal comprehension). Moreover, higher homocysteine levels significantly predicted shorter five-year survival in the logistic regression models, even after adjusting for age, diagnostic subgroups, sex, years of education and results of neuropsychological testing.

CONCLUSION

The results of this study suggest that homocysteine levels are independently associated with impaired cognitive function and increased five-year mortality.