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Andrew McGhie and S. M. RussellThe Subjective Assessment of Normal Sleep Patterns

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THE SUBJECTIVE ASSESSMENT OFNORMAL SLEEP PATTERNS

By

ANDREW McGHIEand

S. M. RUSSELL

INTRODUCTIONWhENwe consider the immense human significance of sleep, the absolutenecessity for us to spend a considerable part of our lives in abject mentalannihilation, it is remarkable how little we know about it. . . .In thesewords, Sir John Eccles introduced the recently published Ciba FoundationSymposium on TheNature of Sleep(3), in which are described many of theadvances which have been made in recent years in our attempts to understandthe phenomena which are involved in the state of sleep. In one of the papersincluded in this Symposium, Bremer (2) reviews the work which has beenreported since 1954 on the neurophysiological mechanisms involved in sleep.The relationship of dreaming to the depth of sleep has been investigated bysuch workers as Kleitman (5), Dement (4) and Wolpert (11). These studieshave been made possible by the application of modern techniques of measuringmental activity. The use of electroencephalographic methods has allowed anapproximate classification of the different levels of sleep which enables differentworkers to adopt a standard frame of reference. Measurements of rapid eyemovements and of changes in muscle potential during sleep have provided moreobjective methods of assessing dream activity. Other recent studies haveattempted to make an objective assessment of the physical and mental effectsof sleep deprivation (Morris et a!., 7, Bliss eta!., 1, Murray eta!., 8, Wilkinson, 9,Williams et a!., 10).

Many of the findings arising from this recent interest in the state of sleepare of interest to psychiatrists who have long recognized the correspondencebetween disturbance of the normal sleep pattern and mental illness. Sleep disturbance has been noted in such varied psychiatric conditions as depression,anxiety states, delirium and catatonia. In depressive illness the disturbance ofthe sleep pattern may be regarded as one of the most important and characteristic of the clinical features. The prevalence of early morning wakening indepressive psychosis has caused this aspect of sleep disturbance to be regardedas a symptom of particular importance in establishing the diagnosis and inassessing the patient's response to treatment.

In view of the number of studies which have been made on different aspectsof sleep in recent years, it is perhaps somewhat surprising to find that verylittle appears to be known about the normal pattern of sleep and the way inwhich this varies with such factors as age, sex and social class. Although severalstudies have been made of the variations in the sleep rhythm in infancy, littleattention has been paid to the sleep cycle of the adult population. It tends to beassumed that the average healthy adult sleeps around 8 hours a night and afew reported studies of small groups who were at liberty to sleep as long as they

642

THE SUBJECTIVEASSESSMENTOF NORMAL SLEEP PA1TERNS 643

wished (e.g., Lewis, 6), substantiate our impression that this period representsthe normal human requirement. Although we may recognize that the length ofthe sleep period decreases with age, there have been no critical studies of thevariation of sleep with age. The present study attempts to study the sleeppatterns of a group of normal subjects and to assess the variations in the sleeprhythm with age.

METHODIn spite of the obvious deficiencies of subjective evaluation, the question

naire method seemed the only feasible method of surveying a population largeenough to allow a statistical comparison of the various age groups. In order tolimit this subjective influence as much as possible, our questionnaire was constructed so that all possible responses were already noted after each question,the subjects being required to underline the response appropriate to them. Thefirst section of the questionnaire included items relating directly to the quantitative aspects of the sleep pattern. It thus contained questions on the habitualtime of retiring to bed, the time at which the subject normally falls asleep,normal wakening time, rising time, etc. The second part of the questionnaireenquired into the more qualitative aspects of sleepe.g. did the subject describehimself as a light, moderate, or deep sleeper? was his sleep frequently brokenby night wakening? did he tend to feel tired in the morning or during the day?The last section contained items related only indirectly to sleep. The subjects wereasked if they were in the habit of taking hypnotics, if they would describe themselves as being of a nervous disposition, and finally they were asked a numberof questions on the state of their physical health. The subjects were not asked tonote their names on the questionnaire, but they were asked to give details of theirage, sex and occupation, the latter being used to obtain a rough grading of thesubject's social class according to the Registrar General's Classification ofOccupations.

SELECTIONOF SUBJECTSThe subjects who took part in the enquiry were made available through the

kind co-operation of a variety of agencies in the Dundee and Glasgow areasincluding Further Education authorities, community centres, Territorial Armyunits and old people's clubs. Each of the bodies involved supported the enquiryby distributing the questionnaires among its members and collecting thecompleted forms for subsequent dispatch to us. It will be readily seen that ourmethod of selection was unlikely to provide us with a random sample of thegeneral population, most of our subjects belonging as they did to some educational or social organization. The enquiry was designed to include subjectsfrom both the Dundee and Glasgow areas, to allow not only an extension in thenumber of subjects taking part, but also a comparison between the two communities. It proved impossible to obtain a wholly accurate assessment of thenumber of subjects who refused to co-operate in this enquiry, but it appearedthat approximately 80 per cent. of the subjects who were approached completeda questionnaire. In this manner a total of 2,446 completed questionnaires weremade available for subsequent analysis.

The age distribution of the survey population is shown in Table I. Fourteenper cent. of the subjects in the total sample omitted to note their age on thequestionnaire and consequently could not be considered in the analysis. Forpurposes of comparison the comparative figures for the Scottish populationbased on the 1961 census figures are also noted. We have shown all subjects

644 THE SUBJECTIVEASSESSMENTOF NORMALSLEEPPATTERNS [Sept.over the age of 65 years as constituting a single age group to allow ready comparison with the census figures. In analysing our data, however,we examinedthese subjects in two separate age groups of 6574years and over 75 years inorder to observe any further noticeable changes occurring some time after themale retiral age. It may be seen that the survey sample deviates most markedlyfrom the national sample at the age groups 1524,4554and 5564years. Ourpopulation over-represents the younger group and under-represents the middleaged sector of the community. This is particularly marked in the case of the malesubjects, the deviation being much less in the case of the females. It may alsobe seen that our male sample under-represents the 65 year and above group(7 per cent. as compared with 12 per cent. in the national population). In thecase of the female subjects of 65 years and over, the reverse is true (18 per cent.as compared with 14 per cent. in the national population). The sample as a wholecarries an over-weighted sex ratio (160 @2F: 100 M) as compared with the sexratio in the total population of Scotland in 1961 (108 @5F: 100 M).

TABLE IAge Distribution

Not1524 2534 35-44 4554 55-64 65+ Known

Survey Sample .. 23% 15% 17% 12% 7% 12% 14%National Population 19% 19% 19% 17% 13% 13% 0%Survey Sample

(Male) .. .. 31% 23% 18% 11% 5% 7% 5%National Population

(Male) .. .. 19% 19% 20% 18% 12% 12% 0%Survey Sample

(Female) .. .. 21% 13% 19% 14% 10% 18% 5%National Population

(Female) .. .. 19% 18% 19% 17% 13% 14% 0%

On the basis of the Registrar General's Classffication of Occupations, eachsubject was placed in a social class category. The percentage distribution of thesocial class categories is shown in Table II for our male subjects, together withthe comparative figures of the male social class distribution for Scotland as awhole. It was not possible to make a similar comparison for our female subjects,as the national figures are calculated separately for single women and workingwives. It can be seen that the social class distribution of the males in our surveysample is almost identical to that of the national population.

TABLE IISocial Class Distribution (Male)

I II ifi iv VSurvey Sample .. .. 3% 14% 50% 19% 14%National Population .. 3% 13% 51 % 18% 15%

METHOD OF ANALYSISThe information on the completed questionnaire was coded, transferred to

punch-cards and subsequently collated by a Powers-Samas machine. The resultant data were analysedby applyingthe@ techniqueor, where multiplecorn..parisons were involved, Ryan's Significance Test of Proportions. The mainvariables considered in the analysis were age, sex, area and social class and the

1962] BY ANDREWMCGHIEAND S. M. RUSSELLrelation between each of these factors and the various items of informationgiven by the questionnaire responses was examined. Age groups were consideredin decades beginning at 1524years and ending with the group 75 years and over.Although we were mainly concerned with the effect of age on the normal sleeppattern, we also considered any variations related to sex and social class differences. The preponderance of females in our sample was particularly evidentin the upper age levels. In order to ensure that apparent age differences werenot due to the unequal sex ratio, we have analysed the male and female responsesseparately for each item which showed a significant sex difference. Throughoutthe analysis of the data we have accepted as significant only these items whichare beyond the 1 per cent. level. (In most cases the differences involved were infact beyond the O@lper cent. level.)

Our treatment of the data has been selective in that we were mainly interested in finding the answers to a number of specific questions which appearedto be of relevance to the clinical field. We have been less interested in the averagepatterns of response than in the responses which deviate appreciably from theaverage. In analysing the data we have accordingly chosen an arbitrary cut-offpoint in the distribution of the responses given to each item of the questionnaire,and in presenting our results, it is the responses beyond this point which will beconsidered. The analysis of the main variable, that of age, is most easily repre-.sented in the form of histograms.

RESULTSBefore considering the responses which deviate from the average we might

first consider the distribution of the number of hours slept as reported by thesurvey population as a whole (Fig. 1). It may be seen that this approaches closelyto a normal distribution curve, 62 per cent. of the subjects reporting an averagesleep of between 7 and 8 hours per night.

We next examine the variation with age, sex, and social class of the responsesgiven to each item of the questionnaire. Any differences between the two urbanareas covered by the survey are also indicated, but there were very few caseswhere such differences reached a significant level.

1. Average Hours Sleep (5 hours)We have restricted our analysis of this item to those subjects who reported

that they habitually slept for a maximum of 5 hours per night. A comparison

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1962] 647BY ANDREW MCGHIE AND S. M. RUSSELLlittle variation with age in males. Pre-sleep difficulty is particularly evident inwomen after the age of 55 years, reaching a peak between the ages of 65 to 74years when 30 per cent. of the women gave a positive response. It would appearthat the increased difficulty in getting off to sleep with advancing age is more orless specific to women.

3. Time of Wakening (before 5 a.m.)In dealing with this item we have concentrated on subjects who reported

that they usually waken before 5 a.m. In this case no significant relationshipwas found between early morning wakening and the three variables, social class,sex and area. Indeed, early morning wakening, as here defined, constituted theonly variable in the sleep pattern which did not show a clear sex difference. Thevariation in early morning wakening with age is indicated in Figure 4. Although

55.

FIG. 4

thefrequencyof earlymorning wakening increasesslightlywithage,theincreases are insignificant until the age group 6574years. Of the subjects in thisage group, 18 per cent. report early morning wakening although this figure fallsto 12 per cent. after the age of 75 years. Although early morning wakening asrepresented in this study appears to have a very low incidence in the normalpopulation, the significant increase (from 5 per cent. to 18 per cent.) at the ageof 65 years suggests that, in assessing early morning wakening as a clinicalsymptom, the age of the patient should be taken into consideration.

4. Depth of Sleep (Light)Subjects were asked to describe their usual sleep level as being deep,

moderate or light. In our analysis we have considered only those subjects whodescribe themselves as being light sleepers. Once again there was no significantdifference between the two areas. With social class the differences were significant, the tendency towards light sleep increasing as the social class grading movesdownwards from Class I to Class V (x@=i5 85;p

648 THE SUBJECTIVEASSESSMENTOF NORMALSLEEPPATTERNS [Sept.item is presented in Figure 5 for the next two sexes separately. In the case ofthe men, it can be seen that light sleeping occurs most frequently in the age range3544years (22 per cent.) and after the age of 65 (25 per cent.). There is aninteresting drop off in the incidence of light sleeping in men between the ages of5564years at which time the reported incidence is at its lowest. In women theincrease in light sleep with age is much more marked. By the age of 35 years,25 per cent. of the women described themselves as being light sleepers and theincidence accelerates significantly after the age of 45 years to reach a peak of40 per cent. Apart from a small but insignificant decrease between the ages of5564years, the level remains constant at 40 per cent. thereafter. It would appearthat light sleeping is more pronounced in women, particularly from middle ageonwards.

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5. DisturbedSleep(FrequentNightWakening)In this item we asked subjects to describe to what extent their sleep was

usually disturbed by night wakening and we have examined only those subjectswho reported that this occurred with great frequency. Although there was noappreciable social class or area difference, there was again on this item a markedsex difference (x2=4l @07; p

1962] BY ANDREWMCGHIEAND S. M. RUSSELL 649women. At the age of 45 years, 21 per cent. of the women reported disturbedsleep, 30 per cent. at the age of 55 years and, between the ages of 6574years,43 per cent. of the women described themselves as wakening frequently duringthe night. Here again we might conclude that this change in the sleep pattern isnot evident in men until after the age of 65 years, whereas in women, disturbedsleep may be apparent from middle age onwards.

6. Morning Tiredness (Frequent)The subjects were asked if they usually felt tired in the morning and here

we have considered only those subjects who described frequent morning tiredness. Examination of the data showed a relationship between morning tirednessand social class (x2==ll P65; p

650 THE SUBJECTIVEASSESSMENTOF NORMALSLEEPPATFERNS [Sept.two sexes separately in Figure 8. Both sexes show very little variation in thefrequency of day tiredness until the age of 75 years where there is a significantincrease in the incidence reported by both sexes, reaching a maximum incidenceof 20 per cent. for men and 29 per cent. for women.

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Subjects were asked if they were in the habit of taking a hypnotic and asubsequent question attempted to establish the source of the sedative which wasbeing taken. In analysing this item we have taken into consideration only thosesubjects who describe themselves as taking a regular hypnotic issued eitherdirectly by a doctor or through a chemist. No variation between social class orarea was apparent, but again the sex difference was significant (@=4l 40;p

9. Nervous DispositionThe subjects were asked ifthey would describe themselves as being by nature

a nervous person. The incidence of positive responses to this question wasapproximately the same in each social class group, but there was a significantdifference between the two areas (A@=3713; p

652 THE SUBJECTIVEASSESSMENTOF NORMALSLEEPPATFERNS [Sept.tend to waken frequently during the night (x2=4S 73 ; p

1962] BY ANDREWMCGHIEAND S. M. RUSSELL 653a reduction in the number of hours slept, an increase in the time taken ingetting off to sleep and a greater tendency for sleep to be light and easily disturbed by frequent night wakening. At the same time we have noted that as ageadvances people tend to complain less of morning tiredness. It is possible that,as age advances, people do not subjectively experience any great harm from thechange in their sleep pattern, and that, as we grow older, we require less sleep.The variation of the sleep pattern with age is much more marked in the case ofthe female subjects of our sample. Although the two sexes do not differ significantly in the average number of hours slept, there are a number of significantvariations in the form which their sleep takes. In general the sleep pattern ofthe female tends to change earlier than that of the male, usually during middleage. The change in the male sleep pattern with age is not only less marked buttends to be fully established latersome time after the retiral age of 65 years.We have also seen that the incidencein the use of hypnoticsappears to increaserapidly with age but our findings suggest that this increase is almost entirelyspecific to women, 45 per cent. of whom admitted to taking a regular hypnoticin their 70's. The incidence of reported nervousness is again much higher in thecase of women and reaches its peak between the ages of 25 and 44 years. Thesefindings might be, of course, interpreted as merely indicating that men are lessinclined to admit to taking a regular hypnotic or to being of a nervous disposition. A positive relationship has been demonstrated between the subjectiveestimation of nervousness and specific changes in the pattern of sleep asevaluated by the subjects. Those people who describe themselves as beingnervous tend to report more difficulty in getting off to sleep and a more disturbednight's sleep. They are also more likely to complain of physical symptoms suchas heart conditions, high blood pressure and severe headaches. It would thusseem that our general physical and mental state is reflected in the form and qualityof our sleep.

Investigations of this type seem worthwhile in providing some sort ofstandard upon which an individual's sleep pattern may be more objectivelyevaluated. It is our intention to follow this investigation with a similar studyapplied to the patterns of sleep typical of patients receiving psychiatric treatment.

ACKNOWLEDGMENTSWe should like to express our thanks to the many people whose co-operation and advice

made this surveypossible.We are indebted to Dr.!. C. R. Batchelor, Physician Superintendent,DundeeRoyalMentalHospital,forhisconstructivecommentsintheinterpretationofthedata. We should also like to acknowledge the help of Dr. J. A. Chapman and Miss S. Dick,of Dundee Royal Mental Hospital, and Miss Audrey Brinkler and Miss Margaret McLaggan,of the Department of PublicHealth,Queen'sCollege,in assistingin the laborious task of collatingthe results obtained in the survey. Finally, we are most indebted to the many agencies in theDundee and Glasgow areas who kindly distributed the questionnaires among their members.

REFERENCES

1. BLISS,E. L., CLARK,L. D., and WesT, C. D. (1959). Studiesof sleep deprivation: relationship to schizophrenia,A.M.A. Arch. Neurol. and Psychiat., 81, 348.

2. BREMER,F. (1954). Theneurophysiological problem of sleep.In J. F. Delafresnaye (Ed.)Brain Mechanisms and Consciousness. Oxford: Blackwell Scientific Publications.

3. CIBAFOUNDATION(1961). Symposium, The Nature of Sleep. London: J. & A. ChurchillLimited.

4. DEMENT, W., and KLErrMAN, N. (1957).CyclicvariationsinEEG duringsleepand theirrelationto eye movements, body motilityand dreaming,Electroencepha/og.and C/in.Neurophysiol., 9, 673.

5. KLEITMAN,N. (1939).Sleep and Wakefulness. Chicago: University of Chicago Press.6. LewIs, H. E. (1961).Sleeppatterns on polar expeditions.In Ciba Foundation Symposium

on The Nature of Sleep.London: J.& A. ChurchillLimited.

654 THESUBJECTWEASSESSMENTOFNORMALSLEEPPATTERNS7. Moiuus, G. 0., WLLUAMS,H. L., and LUBIN,A. (1960). Misperceptionand disorientation

during sleep deprivation,A.M.A. Arch. Gen.Psychiat., 2, 247.8. MURRAy,E. J., SCsEIN, E. H., ERJKSON,K., HILL, W. F., and C0REN, M. (1959). The

effects of sleep deprivation on social behaviour,J. Social Psycho!., 49, 229.9. Wiuw@so@,R. T. (1957). Effectsof lack of sleep,FPRC Rep. No. 961. Cambridge:

Medical Research Council.10.Wn..u@is,H. L.,LUBIN,A.,and000DNOW,J.J.(1959).Impairedperformancewith

acutesleeploss,PsychologicalMonographs,73,14.II. WOLPERT,E. A. (1960). Studiesin psychophysiology of dreams,Arch. Gen. Psychiat., 2,

231.

Andrew McGhie, M.A., Ph.D., Principal Psychologist and Lecturer in ClinicalPsychology

S. M. Russell, M.B., Ch.B., D.C.H., D.P.M., Registrar (now with Departmentof Child Psychiatry, Glasgow)

From the Dundee Royal Mental Hospital and the Department of Psychiatry,University of St. Andrews