Memory before and after sleep in patients with moderate obstructive sleep apnea.
OBJECTIVE
The aim of this study was to investigate the effects of obstructive sleep apnea (OSA) on procedural and declarative memory encoding in the evening prior to sleep, on memory consolidation during subsequent sleep, and on retrieval in the morning after sleep.


METHODS
Memory performance (procedural mirror-tracing task, declarative visual and verbal memory task) and general neuropsychological performance were assessed before and after one night of polysomnographic monitoring in 15 patients with moderate OSA and 20 age-, sex-, and IQ-matched healthy subjects.


RESULTS
Encoding levels prior to sleep were similar across groups for all tasks. Conventional analyses of averaged mirror tracing performance suggested a significantly reduced overnight improvement in OSA patients. Single trial analyses, however, revealed that this effect was due to significantly flattened learning curves in the evening and morning session in OSA patients. OSA patients showed a significantly lower verbal retention rate and a non-significantly reduced visual retention rate after sleep compared to healthy subjects. Polysomnography revealed a significantly reduced REM density, increased frequency of micro-arousals, elevated apnea-hypopnea index, and subjectively disturbed sleep quality in OSA patients compared to healthy subjects.


CONCLUSIONS
The results suggest that moderate OSA is associated with a significant impairment of procedural and verbal declarative memory. Future work is needed to further determine the contribution of structural or functional alterations in brain circuits relevant for memory, and to test whether OSA treatment improves or normalizes the observed deficits in learning.
Kloepfer
Corinna
C
Department of Psychiatry and Psychotherapy, University Medical Center Freiburg, Germany. corinna.kloepfer@uniklinik-freiburg.de
Riemann
Dieter
D
Nofzinger
Eric A
EA
Feige
Bernd
B
Unterrainer
Josef
J
O'Hara
Ruth
R
Sorichter
Stephan
S
Nissen
Christoph
C
D000704:Analysis of Variance; D015984:Causality; D015897:Comorbidity; D005260:Female; D005858:Germany / Q000453:epidemiology; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000453:epidemiology*; D008570:Memory, Short-Term; D008875:Middle Aged; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D017286:Polysomnography / Q000379:methods / Q000706:statistics & numerical data; D012720:Severity of Illness Index; D012890:Sleep; D020181:Sleep Apnea, Obstructive / Q000453:epidemiology*; D012894:Sleep Stages; D011795:Surveys and Questionnaires; D014706:Verbal Learning
Sleep. 2006 Aug;29(8):1068-73
16944676
Neurology. 2005 Aug 23;65(4):642-4
16116137
Sleep Breath. 2008 Nov;12(4):397-9
18516635
Sleep Med Rev. 1999 Mar;3(1):59-78
15310490
Learn Mem. 2004 Nov-Dec;11(6):679-85
15576885
J Clin Exp Neuropsychol. 1987 Oct;9(5):545-62
3667899
Neuroscience. 2004;126(2):313-23
15207349
Nature. 2005 Oct 27;437(7063):1272-8
16251952
Sleep. 1999 Sep 15;22(6):749-55
10505820
J Sleep Res. 2007 Mar;16(1):128-34
17309772
Proc Natl Acad Sci U S A. 2007 May 1;104(18):7723-8
17449637
Sleep Med Rev. 2006 Feb;10(1):49-62
16376591
Biol Psychiatry. 2006 Dec 15;60(12):1324-30
16876140
Sleep. 2000 May 1;23(3):369-81
10811381
Pneumologie. 2001 Jul;55(7):339-42
11481581
Biol Psychiatry. 2004 Dec 15;56(12):951-6
15601605
Am J Respir Crit Care Med. 2002 May 1;165(9):1217-39
11991871
Neuron. 2002 Jul 3;35(1):205-11
12123620
J Appl Physiol (1985). 2002 Jul;93(1):141-6
12070197
Science. 1994 Jul 29;265(5172):676-9
8036517
Sleep. 2007 Aug;30(8):955-8
17702263
J Cogn Neurosci. 1997 Jul;9(4):534-47
23968216
Neuron. 2004 Sep 30;44(1):121-33
15450165
Sleep. 2002 Jun 15;25(4):401-11
12071541
Science. 2001 Nov 2;294(5544):1048-52
11691982
Sleep. 1992 Apr;15(2):173-84
11032543
Eur Respir J. 2001 May;17(5):838-47
11488314
Sleep. 1991 Dec;14(6):540-5
1798888
Sleep Med. 2006 Apr;7(3):229-34
16564216
Trends Cogn Sci. 1999 Sep;3(9):351-359
10461198
Psychophysiology. 1966 Jan;2(3):263-6
5903579
Crit Rev Neurobiol. 1991;6(3):149-82
1773451
Sleep. 2008 Jul;31(7):967-77
18652092