Sleep quality mediates the relationship between frailty and cognitive dysfunction in non-demented middle aged to older adults

Abstract

Objectives:Frailty is associated with cognitive decline in older adults. However, the mechanisms explaining this relationship are poorly understood. We hypothesized that sleep quality may mediate the relationship between frailty and cognition.Participants:154 participants aged between 50-90 years (mean = 69.1 years, SD = 9.2 years) from the McKnight Brain Registry were included.Measurements:Participants underwent a full neuropsychological evaluation, frailty and subjective sleep quality assessments. Direct relationships between frailty and cognitive function were assessed using linear regression models. Statistical mediation of these relationships by sleep quality was assessed using nonparametric bootstrapping procedures.Results:Frailty severity predicted weaker executive function (B = −2.77, β = −0.30, 95% CI = −4.05 – −1.29) and processing speed (B = −1.57, β = −0.17, 95% CI = −3.10 – −0.16). Poor sleep quality predicted poorer executive function (B = −0.47, β = −0.21, 95% CI = −0.79 – −0.08), processing speed (B = −0.64, β = −0.28, 95% CI = −0.98 – −0.31), learning (B = −0.42, β = −0.19, 95% CI = −0.76 – −0.05) and delayed recall (B = −0.41, β = −0.16, 95% CI = −0.80 – −0.31). Poor sleep quality mediated the relationships between frailty severity and executive function (B = −0.66, β = −0.07, 95% CI = −1.48 – −0.39), learning (B = −0.85, β = −0.07, 95% CI = −1.85 – −0.12), delayed recall (B = −0.47, β = −0.08, 95% CI = −2.12 – −0.39) and processing speed (B = −0.90, β = −0.09, 95% CI = −1.85 – −0.20).Conclusions:Relationships between frailty severity and several cognitive outcomes were significantly mediated by poor sleep quality. Interventions to improve sleep quality may be promising avenues to prevent cognitive decline in frail older adults.

Self-reported sleep disturbances are associated with poorer cognitive performance in older adults with hypertension: a multi-parameter risk factor investigation

“…Physical mobility for our sample, which we assessed using the TUG task, was generally within agematched, normative reference values (Bohannon, 2006). Recent work has suggested that physical frailty as a composite of slow gait, muscle weakness, unintended weight loss, low physical activity, and fatigue may serve as a mediator of sleep-cognition relationships in aging (Kaur et al, 2019). By comparison, our functional assessment, being unidimensional, may have required additional measurement domains in order to detect covariate-adjusted associations with the cognitive screen used in our analysis.…”

Interconnectedness among frailty, sleep, and cognition: recent findings and clinical implications

“…They sought to clarify whether sleep quality mediated associations between frailty and cognitive performance. Kaur et al (2019) found that frailty was directly associated with poorer executive function, but no other cognitive domains, and poorer sleep quality, after adjusting for covariates and accounting for multiple comparisons. Additionally, poorer sleep quality was associated with poorer executive function and processing speed.…”

“…There appears to be bidirectional relationships between each of the three factors Kaur et al (2019) examined, which further complicates the task of understanding these relationships, but also provides more opportunities for interventions. Although the study by Kaur et al (2019) appears to be the first published study to examine sleep as a mediator between frailty and cognition, past studies have examined pieces of this relationship and have found mixed results.…”

“…There appears to be bidirectional relationships between each of the three factors Kaur et al (2019) examined, which further complicates the task of understanding these relationships, but also provides more opportunities for interventions. Although the study by Kaur et al (2019) appears to be the first published study to examine sleep as a mediator between frailty and cognition, past studies have examined pieces of this relationship and have found mixed results. Evidence from large cohort studies has shown that frailty was associated with global cognition and perceptual speed but not with episodic memory, semantic memory, working memory, or visuospatial ability; however, it was associated with faster decline in all cognitive domains (Boyle et al, 2010).…”

Sleep quality mediates the relationship between frailty and cognitive dysfunction in non-demented middle aged to older adults

“…Kawada points out that while the use of nonparametric bootstrapping is an adequate statistical approach, there is no definite way to confirm causality. In fact, we highlighted this as a primary limitation in our manuscript (Kaur et al, 2019) and this critique applies to all observational studies. Nonetheless, we believe that our careful characterization of frailty and cognitive function in a diverse cohort of patients provides valuable data for future longitudinal studies.…”