Performance on Specific Cognitive Domains and Cause of Death: A Prospective Population-Based Study in Non-Demented Older Adults (NEDICES)

Associations of cognitive impairment and functional limitation with all-cause mortality risk in older adults: A population-based study from the National Health and Nutrition Examination Survey

Cognitive impairment and functional limitation are commonly observed in older adults. They have a complex correlation, and both are risk factors for mortality. This prospective cohort study aimed to explore the independent and joint impact of cognitive impairment and functional limitations on all-cause mortality in older adults. A total of 3,759 participants aged ≥ 60 years who had available information on mortality data, cognitive function, physical function, and covariates were enrolled. Cox proportional hazards regression models were employed to assess the independent and joint impacts of cognitive impairment and functional limitation on all-cause mortality. Smoothing curve fitting was used to show the nonlinear relationship between the Digit Symbol Coding (DSC) score and all-cause mortality. An interaction between cognitive impairment and functional limitation was identified when examining their associations with all-cause mortality. Cognitive impairment and functional limitation independently correlated with all-cause mortality risk even after adjusting for covariates and performing mutual adjustments (HR for cognitive impairment: 1.34, 95% CI 1.15-1.56; HR for functional limitation: 1.50, 95% CI 1.32-1.70). When the DSC score was > 18, as the score increased, the risk of death significantly decreased (HR 0.99, 95% CI 0.98-0.99). Participants with both cognitive impairment and functional limitation had the highest hazard ratio for all-cause mortality (HR 1.98, 95%CI 1.63-2.40). In summary, cognitive impairment and functional limitation independently correlated with increased all-cause mortality risk. A higher DSC score was a protective factor reducing the premature mortality risk. Older adults with cognitive impairment and functional limitation demonstrated the highest all-cause mortality risk.

Education and Literacy as Risk Factors of Dementia after Stroke and Transient Ischemic Attack: NEDICES Study

Background: A protective effect of education on cognitive decline after stroke has been claimed, but evidence from prospective population-based cohorts is very limited. The differential role of literacy and education on dementia after stroke remains unexplored. Objective: This research addresses the role of education and literacy in dementia incidence after stroke and transient ischemic attack (TIA). Methods: 131 participants with stroke or TIA were identified within the population-based NEDICES study (N = 5,278 persons). Participants were fully assessed at baseline (1994–1995) and incident dementia diagnosis was made by expert neurologists (DSM-IV criteria) after a mean follow-up of 3.4 years. Adjusted Cox regression analyses were applied to test the association between education, literacy, and dementia risk. Results: Within the 131 subjects with stroke or TIA, 19 (14%) developed dementia at follow-up. The Cox’s regression model (age and sex adjusted) showed that low education (HR = 3.48, 95% CI = 1.28, 9.42, p = 0.014) and literacy (HR = 3.16, 95% CI = 1.08, 9.22, p = 0.035) were significantly associated with a higher dementia risk. Low education was also associated with dementia when main confounders (i.e., cognitive/functional performance) were considered in the Cox’s model. However, after including stroke recurrence, only low/null literacy (versus education) remained as significant predictor of dementia. Finally, low/null literacy showed an effect over-and-above education on dementia risk when both factors were introduced in the adjusted Cox’s regression. Conclusion: These findings underline the importance of literacy to estimate cognitive decline after stroke in low-educated populations.

Comparison of mortality rate in older adults with and without functional awareness: the Neurological Disorders in Central Spain (NEDICES) population-based study

OBJECTIVES

The main aim of the study was to compare the rates of mortality in older adults with and without functional unawareness (FU). We also tested a possible interaction effect between levels of awareness and education, as a single cognitive reserve proxy, on mortality.

STUDY DESIGN

The study design is a longitudinal population-based cohort study.

METHODS

The Neurological Disorders in Central Spain is epidemiological study to detect main age-associated conditions in people aged 65 years and older. Participants were collected from updated population-based registers of residents in three areas of central Spain. Awareness of functional limitations was established in accordance with the discrepancy between two sources of information on functional impairments: reliable informants versus the participants themselves. Three mutually exclusive groups were formed, namely, Functional Limitation Complaints (FCs), FU, and Functional Awareness (FA). Cox's regression models, adjusted by different covariates, were used to calculate the risk of mortality for each group at 5-year follow-up (vs. reference group without limitations).

RESULTS

Of 1818 selected individuals, 229 (12.5%) showed FA, 254 (13.9%) showed FC, and 96 (5%) were classified as FU. All these groups showed an increased risk of mortality at 5-year follow-up [adjusted hazard ratio (HR) for FC < FU < FA]. However, the association of FU with mortality remained significant only for highly educated individuals.

CONCLUSIONS

Functional impairment was associated with increased mortality rates, regardless of the presence of unawareness. This study extends the role of education in modulating the symptoms and prognosis of individuals at very mild or preclinical dementia stages.