Olfactory identification, cognition, depressive symptoms, and 5-year mortality in patients with subjective cognitive decline, mild cognitive impairment, and Alzheimer's disease.

OBJECTIVE: An association between odor and cognitive impairment has been shown in many studies. The objective of the present hospital-based, single-center retrospective study was to assess the impact of odor impairment on the mortality of patients with Alzheimer's disease (AD), subjective cognitive decline (SCD), and mild cognitive impairment (MCI). METHODS: Odor function was measured by Sniffin Sticks (Burghart Messtechnik, Holm, Germany) and the assessment of self-reported olfactory functioning and olfaction-related quality of life (ASOF) test. Cognitive performance was assessed by an extensive neuropsychological test battery, symptoms of depression were diagnosed with the Geriatric Depressive Scale (GDS). The influence of demographic factors such as gender, age, and education were examined. RESULTS: Although the univariate analyses and pairwise post hoc comparison showed significant differences for some of the olfactory performance tests/subtests, the multivariate models showed no association between olfactory test performance and mortality among patients with cognitive impairment. "Attention," a domain of the Neuropsychological Test Battery Vienna (NTBV), as well as depressive symptoms, gender, and age, showed a significant influence on the mortality of the patient group. CONCLUSION: Lower olfactory performance showed no impact on mortality. However, decreased cognitive function of "Attention" can be considered as an influential predictor for mortality.

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

The present study aimed to investigate differences in circulating thyroid hormone levels, gender, education, depressive symptoms, and cognitive performance among patients with cognitive impairment, and also to examine their associations, as well as that of cognitive decline, with 5-year mortality. Between 1998 and 2017, a hospital-based, single-centre (Neurology Department of the General Hospital in Vienna, Austria), retrospective follow-up study enrolled 2102 patients with mild to severe cognitive impairment (grouped into subjective cognitive decline, mild cognitive impairment, and Alzheimer's disease). Cox proportional hazards models were used to calculate hazard ratios (HRs), with 95% confidence intervals (CIs), as well as to calculate stepwise adjustments for demographic variables (age, gender, and education), depressive symptoms (Geriatric Depression Scale, GDS-15), and neuropsychological abilities (four domains of a neuropsychological test battery of Vienna, NTVB). In univariate analyses, total triiodothyronine (TT3) levels differed significantly between Alzheimer's disease and mild cognitive impairment patients (pdiff  = .001). No other differences in cognitive impairment subgroups with any of the measured thyroid hormones were observed. Furthermore, in multivariate models, circulating TT3 was not associated with mortality (multivariable-adjusted HR per unit increase in TT3 = 0.56; 95% CI = 0.29-1.07). In multivariate models, we observed significantly lower 5-year mortality among women (HR = 0.56; 95% CI = 0.43-0.73) and those who scored higher on any of the four domains of the NBTV (e.g., attention and perceptual speed, HR = 0.63; 95% CI = 0.54-0.72); we also observed significantly higher 5-year mortality among patients with depressive symptoms (HR per one point score increase in GDS-15 = 1.06; 95% CI = 1.02-1.10), regardless of cognitive impairment subgroup. Among patients with various degrees of cognitive impairment, we found no associations of thyroid hormone levels with 5-year mortality. Gender, neuropsychological abilities, and depressive symptoms were each significant predictors of 5-year mortality. These results suggest that a neurocognitive test performance could serve as an important predictor of 5-year mortality among patients with cognitive impairment, although further studies with a more complete adjustment for comorbidities are needed to confirm these findings.