Does sleep disturbance mediate neuropsychological functioning in older people with depression?
BACKGROUND
Depression in older adults is associated with neuropsychological dysfunction, fronto-subcortical brain changes and sleep disturbance. Research suggests that adequate sleep is critical for many aspects of cognition including processing speed, verbal skills and memory. However, the association between sleep disturbance and neuropsychological functioning in depression has not been well evaluated. The current study therefore aimed to investigate these relationships.


METHODS
Forty-eight people (mean age=59.6, sd=8.2) meeting DSM-IV criteria for unipolar major depression were included for analysis. Neuropsychological assessment included assessment of processing speed, learning and memory, verbal fluency and executive functions. Early and late insomnia were defined by scores on the Hamilton Depression Rating Scale.


RESULTS
While early insomnia was related to depression severity and poorer global cognition, late insomnia was associated with later age of depression onset, depression severity, and poorer scores on tests of verbal fluency and memory. The associations between cognition and late insomnia were not accounted for by depression severity or age of onset of disorder.


CONCLUSIONS
This study was retrospective in nature, and did not include objective measures of sleep.


CONCLUSIONS
This is the first known study to indicate that late insomnia in older people with major depression may be independently and aetiologically linked to neuropsychological performance, particularly verbal fluency and memory. It may also indicate underlying structural and neurochemical changes. Sleep and circadian disturbance may serve as a biomarker for ongoing cognitive decline and may be a potentially modifiable risk factor.
Naismith
Sharon L
SL
Clinical Research Unit, Brain and Mind Research Institute, University of Sydney, 94 Mallet Street, Camperdown NSW 2050, Australia. snaismith@med.usyd.edu.au
Norrie
Louisa
L
Lewis
Simon J
SJ
Rogers
Naomi L
NL
Scott
Elizabeth M
EM
Hickie
Ian B
IB
D000368:Aged; D000375:Aging; D003071:Cognition; D003865:Major Depressive Disorder / Q000523:psychology*; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory; D008875:Middle Aged; D009483:Neuropsychological Tests; D011569:Psychiatric Status Rating Scales; D011930:Reaction Time; D012189:Retrospective Studies; D007319:Sleep Initiation and Maintenance Disorders / Q000523:psychology; D012893:Sleep Wake Disorders / Q000523:psychology*; D014706:Verbal Learning