Abstract

Abstract
Background: Sleep disturbances are increasingly recognized as modifiable risk factors for dementia and cognitive decline. However, limited evidence exists on how self-reported sleep duration and quality relate to cognitive performance in middle-aged individuals with subjective cognitive complaints but without objective cognitive impairment. This study aimed to investigate these associations across multiple cognitive domains.
Methods: This cross-sectional study included 70 adults aged 40–60 presenting with forgetfulness at a tertiary neurology clinic. Participants completed a comprehensive neuropsychological battery and the Pittsburgh Sleep Quality Index (PSQI). The Beck Depression Inventory (BDI) was used to assess depressive symptoms. Cognitive domains assessed included attention, verbal memory, language, executive and visuospatial functions. Group comparisons were conducted using appropriate parametric and non-parametric tests. Correlations were examined with Spearman’s rank coefficient, and multiple linear regression analyses were performed to control for depressive symptoms. Bonferroni correction was applied for multiple testing.
Results: Poor sleep quality (PSQI >5) was associated with significantly lower performance in attention (forward digit span) and immediate verbal memory tasks. Longer sleep duration was positively correlated with global cognition (MMSE), language (Boston Naming Test), and executive function (phonemic verbal fluency), and negatively correlated with recognition memory. After controlling for depressive symptoms, the association between poor sleep quality and immediate memory remained significant, while other associations persisted at a trend level after Bonferroni correction.
Conclusion: Sleep duration and quality were associated with specific cognitive domains in middle-aged adults, independently of depressive symptoms. These findings highlight sleep as a potentially modifiable factor influencing cognitive health in midlife. To elucidate causality and investigate sleep-based therapies for dementia prevention, more longitudinal studies employing objective sleep metrics are necessary.

Key words: sleep duration, cognition, middle age, sleep quality