ABSTRACTObjectives: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.
Keywords: Frailty; cognitive function; older adults; sleep quality.