A distinctive interaction between memory and chronic daytime somnolence in asymptomatic APOE e4 homozygotes.
OBJECTIVE
To correlate memory measures with a trait measure of chronic daytime somnolence in cognitively normal individuals with different gene doses of the apolipoprotein E (APOE) e4 allele, a common Alzheimer's disease susceptibility gene.


METHODS
Cross-sectional, exploratory study of cognitive abilities in APOE e4 homozygotes (HMZ) (n=42), heterozygotes (HTZ), (n=42) and noncarriers (NC) (n=42) who are matched for age, gender, educational level, and family history of dementia.


METHODS
Tertiary care academic medical center.


METHODS
Cognitively normal residents of Maricopa County, Arizona who are 30-70 years of age, genotyped for APOE, and have no history of a sleep disorder


METHODS
N/A.


METHODS
Epworth Sleepiness Scale (ESS) and a battery of neuropsychological tests


RESULTS
Age, education, gender, and insomnia complaints did not significantly differ among groups. Despite normal baseline memory scores, memory declined with increasing ESS on all eight memory measures in the HMZ, two of eight in the HTZ, and one of eight in the NC. Differences between HMZ and NC on the slope of memory decline with increasing ESS reached statistical significance on two verbal memory measures, AVLT Long-Term Memory (p=0.048) and Percent Delayed Recall (p=0.035).


CONCLUSIONS
Chronic daytime somnolence is associated with a distinctive decline in verbal memory in cognitively normal APOE e4 HMZ, a group at particularly high risk of Alzheimer's disease. Additional studies are needed to confirm these exploratory findings and to determine the effects of acute somnolence on cognition in these genetic subgroups.
Caselli
Richard J
RJ
Department of Neurology, Mayo Clinic Scottsdale, University of Arizona, 85259, USA. Caselli.Richard@Mayo.edu
Reiman
Eric M
EM
Hentz
Joseph G
JG
Osborne
David
D
Alexander
Gene E
GE
Boeve
Bradley F
BF
D000328:Adult; D000368:Aged; D000483:Alleles; D000544:Alzheimer Disease / Q000235:genetics* / Q000378:metabolism; D001057:Apolipoproteins E / Q000235:genetics* / Q000378:metabolism; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D006970:Disorders of Excessive Somnolence / Q000150:complications*; D005838:Genotype; D006720:Homozygote; D006801:Humans; D008569:Memory Disorders / Q000175:diagnosis / Q000209:etiology*; D008875:Middle Aged; D009483:Neuropsychological Tests
D001057:Apolipoproteins E