This study provides new evidence on the co-occurrence of cognitive function, sleep quality, and psychological distress in older adults with cognitive impairment (CI). In addition to confirming their co-occurrence, the present findings demonstrate that sleep quality and psychological distress are significantly associated with overall cognitive performance when analysed simultaneously within the same analytical model. This integrated approach allows for a more comprehensive understanding of how these factors interact in individuals already exhibiting cognitive impairment, rather than considering them as isolated or sequential risk factors. Importantly, the results suggest that sleep disturbances and psychological distress can not only coexist with cognitive impairment but also represent interactive dimensions linked to cognitive performance in this population. This finding expands upon previous research by highlighting the importance of analysing these variables together, providing a more ecologically valid representation of the clinical profile of older adults with cognitive impairment.

Overall, the results revealed the co-occurrence of cognitive impairment, moderate levels of psychological distress, and poor sleep quality in the sample. Significant associations were identified between global cognitive performance and sleep quality and psychological distress, suggesting that poorer cognitive functioning is related to greater sleep disturbances and higher levels of emotional distress in older adults with CI. These findings not only align with previous evidence but also extend it by demonstrating that these associations remain significant when examined simultaneously within an integrated analytical model[,14,35,36,37.

Although the relationship between sleep disturbances and cognitive decline has been widely documented, fewer studies have simultaneously examined the interaction between sleep quality, psychological distress, and cognitive functioning in older adults already presenting cognitive impairment.

In line with our findings, sleep disorders appear to play a significant role in the cognitive functioning of older adults. In the present study, poorer sleep quality was significantly associated with lower overall cognitive performance. These findings are consistent with previous evidence indicating that sleep disorders, particularly insomnia and poor sleep efficiency, are associated with cognitive decline and may be associated with an increased risk of further cognitive decline and potential progression to dementia17,19. Sleep fragmentation and alterations in sleep architecture can negatively affect neuronal retrieval processes and memory consolidation mechanisms, which are essential for maintaining cognitive function during aging37. In line with this, studies comparing older adults with and without cognitive impairment have reported poorer sleep quality and lower sleep efficiency in individuals with cognitive impairment2,22.

Beyond sleep disturbances, psychological distress also appears to play a significant role in the cognitive functioning of older adults. In this study, higher levels of perceived stress, anxiety, and depressive symptoms were associated with poorer cognitive performance. These findings are consistent with previous literature indicating that depression12 and anxiety23 are common among individuals with cognitive impairment and can negatively influence cognitive processes. Psychological distress may contribute to cognitive decline through multiple mechanisms, including heightened physiological stress responses, neuroendocrine dysregulation, and behavioral changes that affect sleep and daily functioning15. Importantly, our findings indicate that sleep quality remains significantly associated with cognitive performance even when psychological distress variables are considered simultaneously, suggesting an independent and clinically relevant role of sleep in cognitive functioning.

Insomnia symptoms and poor sleep efficiency were predictors of cognitive decline in older adults without symptoms of dementia17,21, demonstrating that sleep quality significantly influences cognitive function, especially in individuals with CI. The study by An et al. (2014) analysed sleep quality using the PSQI test, similar to the one used in the present investigation, comparing the effects of sleep on cognitive functions between older adult patients with and without CI, using instruments similar to those used here ( MoCA)2. They found that the scores for habitual sleep duration and efficiency in the MCI group were significantly lower than those of the control group. Furthermore, the total scores of the PQSI were negatively correlated with the MoCA. In that investigation by An et al. (2014), MCI scores within the group diagnosed with MCI showed significant differences, with scores being higher in patients without sleep disorders. They concluded that the incidence of sleep disorders is higher in older adults with MCI, compared to those with cognitive health. Specifically, the effects of sleep disorders on cognitive function were primarily reflected in attention and visuospatial/executive function, which was also identified in this study.

The interaction between sleep quality and psychological distress may further exacerbate cognitive vulnerability in older adults38. Poor sleep quality has been associated with greater emotional dysregulation, while chronic psychological distress can disrupt sleep patterns, creating a reciprocal relationship that may accelerate cognitive decline39. Previous studies have also suggested that sleep quality may partially mediate the relationship between depressive symptoms and cognitive performance23. In this context, the coexistence of sleep disorders and psychological distress observed in this sample highlights the importance of considering these factors together when examining cognitive health in aging populations. Taken together, these findings support a potential mechanistic framework in which sleep disturbances and psychological distress interact to influence cognitive functioning in older adults with CI. Sleep disruption may impair neuronal recovery processes and memory consolidation, while chronic psychological distress may activate neuroendocrine stress pathways and increase inflammatory responses, both of which may contribute to cognitive vulnerability during aging15,38.

Research exploring the relationship between psychological distress and cognitive impairment (CI) has yielded mixed results. Some studies suggest that distress may contribute to the onset or worsening of cognitive decline13, while others indicate that it may arise as a psychological response to the perception of cognitive decline24. Furthermore, some authors have cautioned that symptoms of emotional distress in older adults can sometimes be misinterpreted as indicators of cognitive impairment25. These findings highlight the complexity of the relationship between psychological distress and CI and underscore the need for further research to clarify the directionality of these associations.

Longitudinal research has provided further evidence of the potential role of stress in cognitive decline. For example, long-term cohort studies have found that higher levels of chronic stress are associated with an increased risk of developing cognitive impairment (CI)39. Similarly, a high level of perceived stress has been associated with a higher incidence of amnestic CI, independent of other risk factors41. Systematic reviews and meta-analyses also support the association between stress and an increased risk of cognitive decline, although the magnitude of this relationship varies depending on the specific stress indicators examined15.

Despite the growing body of evidence linking sleep disturbances, psychological distress, and cognitive decline, some studies have reported inconsistent findings. For example, research comparing individuals with insomnia with and without CI did not identify significant differences in psychological distress levels between groups19. However, even in these cases, alterations in sleep architecture were associated with poorer cognitive performance, reinforcing the importance of sleep quality as a relevant factor in cognitive health during aging41. Overall, these findings suggest that the associations between sleep, psychological distress, and cognitive functioning are multifactorial and likely influenced by interacting biological, psychological, and behavioral mechanisms.

From a clinical perspective, these findings highlight the importance of incorporating systematic screening for sleep disorders and psychological distress in older adults with cognitive impairment. Early identification of sleep problems, anxiety, depressive symptoms, and perceived stress can facilitate a more comprehensive clinical assessment and enable timely intervention. Furthermore, the results support the need for integrated management strategies that address sleep quality and emotional well-being alongside cognitive monitoring. Therefore, multidisciplinary approaches involving physicians, psychologists, and other healthcare professionals may be particularly beneficial for improving quality of life and potentially slowing cognitive decline in older populations.

Limitation

This study has several limitations that should be considered when interpreting the results. First, although participants were recruited from healthcare settings and underwent clinical and neuropsychological assessments, cognitive impairment was not established using standardized diagnostic criteria for specific clinical conditions (e.g., mild cognitive impairment), which may limit diagnostic accuracy and comparability with other studies. Second, the cross-sectional design and use of single-point measurements preclude establishing causal relationships between cognitive performance, sleep quality, and psychological distress. Third, sleep quality was assessed using a self-report questionnaire (PSQI) rather than objective measures such as polysomnography or actigraphy, which may limit the accuracy of the sleep assessment. Fourth, the exclusion of participants receiving medications that significantly affect central nervous system function may limit the generalizability of the results to the general population of older adults with cognitive impairment. Finally, although multicollinearity among cognitive variables was addressed in the statistical models, the use of a small set of predictors may not reflect the full complexity of cognitive functioning.

An additional methodological consideration concerns the high intercorrelations observed among the neuropsychological measures included in this study. Because several cognitive tests assess overlapping domains (e.g., executive function, attention, and processing speed), including them simultaneously in multivariate regression models resulted in substantial multicollinearity. To ensure model stability and interpretability, we therefore adopted a reduced regression approach including a single indicator of global cognitive functioning, the Montreal Cognitive Assessment (MoCA), together with age and sex as covariates. MoCA was selected because it is a widely used and sensitive screening instrument for cognitive impairment and provides a comprehensive measure of cognitive functioning across multiple domains. Although this strategy improves the robustness of the statistical models, it also implies that the specific contribution of individual cognitive domains could not be examined separately in the final analysis.