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

Published online by Cambridge University Press:  17 February 2020

Sonya Kaur
Affiliation:
Department of Neurology, University of Miami Miller School of Medicine, Miami, FL, USA Evelyn F. McKnight Brain Institute, University of Miami Miller School of Medicine, Miami, FL, USA
Nikhil Banerjee
Affiliation:
Evelyn F. McKnight Brain Institute, University of Miami Miller School of Medicine, Miami, FL, USA Department of Psychology, University of Miami, Miami, FL, USA
Michelle Miranda
Affiliation:
Department of Neurology, University of Miami Miller School of Medicine, Miami, FL, USA Evelyn F. McKnight Brain Institute, University of Miami Miller School of Medicine, Miami, FL, USA
Mitchell Slugh
Affiliation:
Department of Neurology, University of Miami Miller School of Medicine, Miami, FL, USA Evelyn F. McKnight Brain Institute, University of Miami Miller School of Medicine, Miami, FL, USA
Ni Sun Suslow
Affiliation:
Department of Neurology, University of Miami Miller School of Medicine, Miami, FL, USA
Katalina F. McInerney
Affiliation:
Department of Neurology, University of Miami Miller School of Medicine, Miami, FL, USA Evelyn F. McKnight Brain Institute, University of Miami Miller School of Medicine, Miami, FL, USA
Xiaoyan Sun
Affiliation:
Department of Neurology, University of Miami Miller School of Medicine, Miami, FL, USA Evelyn F. McKnight Brain Institute, University of Miami Miller School of Medicine, Miami, FL, USA
Alberto Ramos
Affiliation:
Department of Neurology, University of Miami Miller School of Medicine, Miami, FL, USA Evelyn F. McKnight Brain Institute, University of Miami Miller School of Medicine, Miami, FL, USA
Tatjana Rundek
Affiliation:
Department of Neurology, University of Miami Miller School of Medicine, Miami, FL, USA
Ralph L. Sacco
Affiliation:
Department of Neurology, University of Miami Miller School of Medicine, Miami, FL, USA Evelyn F. McKnight Brain Institute, University of Miami Miller School of Medicine, Miami, FL, USA
Bonnie E. Levin*
Affiliation:
Department of Neurology, University of Miami Miller School of Medicine, Miami, FL, USA Evelyn F. McKnight Brain Institute, University of Miami Miller School of Medicine, Miami, FL, USA
*
Correspondence should be addressed to: Bonnie E. Levin, Division of Neuropsychology, University of Miami Miller School of Medicine, 1120 NW 14th Street, Suite 1336, Miami, FL33136, USA. Phone +1 305 243 7529. Email: Blevin@med.miami.edu
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Abstract

Type
Letter to the Editor
Copyright
© International Psychogeriatric Association 2020

We thank Dr. Kawada for his interest in our study “Sleep Quality mediates the relationship between Frailty and Cognitive Dysfunction in non-demented middle aged to older adults.” Using a nonparametric bootstrapping procedure, we found an indirect effect of frailty on measures of executive function, memory, and processing speed through poor self-reported sleep. This effect was apparent despite control for demographically relevant covariates (i.e. age, education, ethnicity).

Dr. 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., Reference Kaur2019) 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.

An additional concern included the need to specify type of sleep disorder. While examination of the differential effects of sleep disorders on frailty and cognition would have been interesting, this was not the focus of the current study. Furthermore, we attempted to control for disordered sleep by evaluating the use of medication and score on the Epworth Sleepiness Scale, a measure of daytime somnolence known to significantly distinguish between patients with diagnosed sleep disorders such as obstructive sleep apnea, narcolepsy, and idiopathic hypersomnia from control participants (Johns, Reference Johns1991) as potential covariates in all analyses.

Finally, Dr. Kawada’s suggestion that individuals under 60 years of age may have psycho-social factors associated with poor sleep is well taken but a sub-analysis stratifying by age was not possible due to a limited sample size (n = 154). Instead, we attempted to control for this possibility by including age as a covariate in all analyses.

References

Johns, M.W. (1991). A new method for measuring daytime sleepiness: the Epworth sleepiness scale. Sleep, 14(6), 540545. doi: 10.1093/sleep/14.6.540.CrossRefGoogle ScholarPubMed
Kaur, S.et al. (2019). Sleep quality mediates the relationship between frailty and cognitive dysfunction in non-demented middle aged to older adults. International Psychogeriatrics, 31(6), 779788. doi: 10.1017/S1041610219000292.CrossRefGoogle ScholarPubMed