Variability in self-reported normal sleep across the adult age span.
OBJECTIVE
Illustrate the importance of examining within- and between-person differences in sleep across the adult age span.


METHODS
Two weeks of sleep diary data were analyzed for 592 normal sleepers ranging in age from 20 to 96 years. Variability in total sleep time (TST), number of nighttime awakenings (NWAK), sleep-onset latency (SOL), and wake-time after sleep onset (WASO) were examined overall and by age, sex, and race utilizing multilevel models and multiple regression.


RESULTS
Night-to-night differences in sleep within the same individual generally exceeded differences between individuals for TST, SOL, and WASO. The amount of intraindividual variability in TST and NWAK decreased with older age. Further, the degree of reduction in variability in TST associated with age depended on sex and race, with young black females showing the greatest variability. In general, females tended to have more intraindividual variability in SOL and NWAK than males, while race differences were complicated by high variability between blacks.


CONCLUSIONS
To truly assess and understand individual differences in the sleep of older adults, future research needs to take into account night-to-night variability (including what makes sleep vary from one night to the next), in addition to average sleep.
Department of Psychology, University of Alabama, Tuscaloosa. hrdillon@crimson.ua.edu.
Haley R
HR
Dillon
Department of Psychology, University of Alabama, Tuscaloosa.
Kenneth L
KL
Lichstein
Department of Psychology, University of Alabama, Tuscaloosa.
Natalie D
ND
Dautovich
Department of Psychology, University of North Texas, Denton.
Daniel J
DJ
Taylor
Shelby County Schools, Department of Planning and Accountability, Memphis, Tennessee.
Brant W
BW
Riedel
Department of Preventive Medicine, University of Tennessee Memphis.
Andrew J
AJ
Bush
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007206:Individuality; D008297:Male; D008875:Middle Aged; D044469:Racial Groups; D057566:Self Report; D012737:Sex Factors; D012890:Sleep / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult
Age-related change; Intraindividual variability; Sleep.