Slow-wave sleep and waking cognitive performance among older adults with and without insomnia complaints

Previous research has shown that healthy young adults with relatively fast reaction times on daytime testing have significantly more nocturnal slow-wa ve sleep than do age-matched subjects with relatively slow reaction times o n such testing. The current study was conducted to examine the relationship between slow-wave sleep and cognitive performance among older adults with and without insomnia complaints. A sample of 32 noncomplaining older (age g reater than or equal to 60 years) normal sleepers and a like aged sample of 32 insomniacs, recruited to participate in a larger study, served as subje cts. All subjects underwent nocturnal sleep monitoring immediately prior to undergoing a battery of daytime tests that measured simple reaction time, vigilance/signal detection, and complex reaction time. Results from the nor mal sleepers showed no relationship between daytime cognitive performance m easures and a variety of computer-derived nocturnal slow-wave sleep measure s. In contrast, insomniac subjects with relatively slow reaction times show ed relative deficits in a spectral analytically derived measure of slow-wav e power in the 2 to 4 Hz bandwidth. These results suggest that relative per formance deficits among some older insomniacs may be related to specific sl ow-wave sleep deficiencies. However, among older normal sleepers, intersubj ect differences in performance appear unrelated to slow-wave sleep measures . Additional research is needed to further explore the possible restorative role slow-wave sleep may serve for cognitive functions other than those ex amined herein. (C) 1999 Elsevier Science Inc.