changes in sleep cycle patterns with age - Science Direct

J.psyclrfat. Rev. 1974,Vol.10,pp.283306. Pergamon Press. Printed in Great Britain.

CHANGES

IN SLEEP CYCLE PATTERNS

WITH AGE

I. FEINBERG Veterans Administration Hospital, San Francisco, and Department of Psychiatry, University of California at San Francisco, California, U.S.A. (Received 17 January 1973, in revisedform 23 JuIy 1973) INTRODUCTION CYCLICAL nature of electrophysiological sleep patterns is frequently emphasized. Nevertheless, investigators have not regularly presented their data in terms of successive periods of sleep with EEG slow waves (SSW) and sleep with rapid eye movements (SREM). More commonly, studies in man have reported results for total sleep time together with percentages for SREM and SSW, with its component EEG stages 2, 3 and 4. (We employ Dement and Rleitman’sl modification of the Loomis, Harvey and Hobart2 scheme for classification of EEG sleep stages.) When data have been analyzed in smaller units, the analysis has more often been for successive hours of sleep3 or fractions (e.g., thirds or halves) of the night”” than for successive SSW periods (SSWPs) and SREM periods (SREMP’s). Analysis by hour or fraction of the night has indeed been useful in demonstrating differing rates of change in several sleep variables, notably the stage 4 component of SSW, and the ratio of SREM to SSW at different points within the night. However, these analyses are imperfectly related to the presumptive physiological unit, the sleep cycle. This unit itself merits description and we have suggested that “an appropriate analysis of electrophysiological sleep patterns of different types of subjects should include comparisons of corresponding SREM and SSW periods as well as the total durations of each kind of sleep,“’ a view which seems to be gaining some acceptance.*-lo We have found useful a computer program whose output includes analysis by cycle as well as by amounts and percentages of sleep stages for the entire night.12 Globusa has put forward a binary auto agreement method to quantify rhythmicity of SREM. The value of this technique is greatly impaired when successive cycles vary in their ratios of SSW/SREM. In this paper, we describe changes in sleep cycle patterns with age. We believeI that the changes in sleep pattern with age furnish the best available clues for the solution of two major biological problems : the function of sleep and the nature of aging in the central nervous system. For these reasons, more precise descriptions of already established trends seem worthwhile. In addition, our present analysis points to a new hypothesis regarding the relation between SSW and SREM.

THE

SUBJECTS AND METHODS

The data were derived from studies of 105 normal subjects (Ss) who ranged in age from 4 to 96 yr. Ss were studied for 4-5 consecutive nights in sleep laboratories at four 283

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institutions: St. Elizabeth’s Hospital (Washington, D.C.); the Clinical Center of the NIH (Bethesda, Md.); the Downstate Medical Center (Brooklyn, N.Y.); and the VA Hospital (San Francisco, CA.). S’s were paid volunteers. All were living at home except for an elderly group (iV = 15) who lived on a volunteer ward at the NIH for the week prior to and the five days during the study. No extensive personality investigations were carried out; normality was accepted on the basis of adequate social and occupational functioning and negative findings on brief psychiatric and medical interview. Our methods for recording and analysis of sleep records have been described elsewhere.’ Briefly, recordings were carried out with either an Offner Type T EEG or a Beckman Type R Dynagraph. The two machines have quite similar recording characteristics;they were run continuously at 15 mm/set at a gain of 8 mm/50 ,uV. Records were scored by 20 set epochs for stage of sleep, movement artifact, and eye movements (EM). Our scoring method is quite similar to that subsequently proposed in the manual edited by Rechtschaffen and Kales.14 Of special importance for the present analysis is the definition of complete SSWP’s and SREMP’s. An SREMP was accepted as complete if at least 5 min in duration (except for the first which had no minimum length). SREM episodes of duration