Clinical Manifestations

Subjective cognitive decline (SCD) is defined as self-perceived cognitive impairment in individuals who remain cognitively unimpaired (CU). SCD is considered an early manifestation within the continuum of neurodegenerative diseases, its etiology is heterogeneous and not fully elucidated. Emerging evidence suggests that sleep disturbances may contribute to cognitive complaints and objective cognitive decline. This study aims to investigate sleep-related complaints in individuals with SCD evaluated from a South-Brazilian BRASCODE cohort.

We included CU individuals aged ≥65 years-old from the BRASCODE cohort who reported subjective cognitive complaints. The exclusion criteria were: presence of uncontrolled psychiatric or medical conditions, diagnosis of cerebrovascular disease, and use of psychotropic medications. Participants underwent neurocognitive and neuropsychiatric evaluation, consisting of Memory Complaint Scale (MCS), Subjective Cognitive Decline Scale (SCD-S), Mini-Mental State Examination (MMSE), Geriatric Anxiety Inventory (GAI), and Geriatric Depression Scale (GDS). Sleep quality and behavioral symptoms were assessed using the Pittsburgh Sleep Quality Index (PSQI), Mild Behavioral Impairment (MBI) checklist, and Neuropsychiatric Inventory (NPI). This analysis includes participants who completed the 12-month follow-up. Correlations between continuous variables were assessed, with p <0.05 considered significant.

A total of 100 participants enrolled between March, 2022 and November, 2023 completed the 12-month evaluation. Among these, 75% were women (n = 75), with a median age of 71 years (68-74,25) and a median of 15 years of formal education (11-18). Median scores and interquartile ranges (IQR) for the assessed scales were as follows: SCD-patient scale = 7 (6-9); SCD-informant scale = 5 (3-7); PSQI = 6 (4-9); GAI = 5 (2-8,75); GDS = 2 (1-4); MMSE = 29 (27-30); NPI = 1 (0-4); MBI-patient = 3 (0-7,25); and MBI-informant = 3 (1-7,75). A significant positive correlation was observed between PSQI and GAI scores (p = 0.01, rho = 0.25). No significant associations were found between PSQI and the SCD-patient or SCD-informant scales, MMSE scores, age, education level, or behavioral scales (MBI and NPI).

The correlation between PSQI and GAI scores suggests that poor sleep quality in CU individuals with SCD from a South-Brazilian cohort is linked to anxiety. Further studies may clarify the relationship between cognition, anxiety, and sleep disturbances.