© 2003 Japanese Society of Sleep Research

183

Sleep and Biological Rhythms

2003;

1

: 183–185

Blackwell Science, LtdOxford, UKSBRSleep and Biological Rhythms1446-92352003 Japanese Society of Sleep Research

12June 200340

Features of sleeping postureT Kubota

et al.10.1046/j.1446-9235.2003.00040.x

Short Communication183185BEES SGML

Correspondence: Dr T Kubota, Department of Occupational Therapy, Saitama Prefectural University, 820 Sannomiya, Kosigaya-shi, Saitama 343-8540, Japan. Email: kubota-tomio@spu.ac.jp

SHORT PAPER

Characteristic features of the nocturnal sleeping posture of healthy men

Tomio KUBOTA,

1,2,3

Nobuo OHSHIMA,

1

Naoko KUNISAWA,

4

Ryoko MURAYAMA,

4

Shukan OKANO

2

and Junko MORI-OKAMOTO

1

1

Department of Occupational Therapy, School of Health and Social Services, Saitama Prefectural University, Koshigaya, Saitama,

2

Department of Biocybernetics, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo,

3

Department of Psychophysiology, National Institute of Mental Health, National Center of Neurology and Psychiatry, Ichikawa, Chiba and

4

Department of Nursing, School of Health and Social Services, Saitama Prefectural University, Koshigaya, Saitama, Japan

Abstract

To investigate the frequency of ‘rolling over’ in bed and to clarify sleeping posture characteristicsin nocturnal sleep, the sleeping positions of 19 healthy men were videotaped over 7 h (0:00–7:00 hours) for two consecutive nights. Sleeping habits and the degree of satisfaction upon awak-ening were also surveyed by using questionnaires. A significant positive correlation (

r

=

0.60,

P

<

0.01) was observed between the most favorite hypnogenetic position of the body and the mostfrequently observed position of the head during nocturnal sleep. Furthermore, sleeping positionsvaried from individual to individual, and the same subject slept showing similar positions and rollover frequencies to those on the day before.

Key words:

questionnaire, sleeping position, video record.

INTRODUCTION

During nocturnal sleep, various body positions areobserved when the unconscious turns over in bed.Body position changes caused by turning over and thebody movements induced by myopalmus duringnatural sleep have been investigated by using variousmethodologies.

1–4

Because it was considered that sleeping positionswould show some characteristic features during naturalsleep, we videotaped and analyzed the nocturnal sleep-ing positions of healthy men for elucidating the charac-teristics of their nocturnal postures in the present study.In addition, we also investigated the relationship

between favorite hypnogenetic positions and actualsleeping positions of the body and head.

SUBJECTS AND METHODS

Subjects

The subjects studied were 19 healthy men (19–31 yearsold, mean age 21.6 years) with average sleeping habitsand who did not have any sleep disorders.

Study design

After confirming individual sleeping habits, the time tosleep was set at 0:00 hours and the time to rise was setat 07:00 hours. Individual habitual and favorite sleepingpositions were also surveyed by using ‘the questionnaireon sleeping body positions’ prepared by us.

All subjects participated in an experimental sessionfor three consecutive days. On day 1, all subjects wereassembled at 18:00 hours in the experimental room and

Accepted for publication 18 November 2002.

T Kubota

et al.

184

Sleep and Biological Rhythms

2003;

1

: 183–185

instructed to go to bed at 23:45 hours. Video-recordingof sleeping body positions was then started, and thesubjects were made to rise at 07:00 hours. The sameprocedure was repeated on day 2. On day 3, the exper-iment was completed after the subjects awoke.

Sleep environments in the experimental room usedwere 26.0

°

C room temperature, 60% relative humidityand

<

5 lux illumination. The values obtained from therecordings of the night of day 1 (night 1) and the nightof day 2 (night 2) were analyzed statistically.

Analysis methods

Video-recordings of sleeping body positions were clas-sified into 28 patterns consisting of three directions(upward, right and left) for each of the head, chest andwaist, and one direction (downward) for all. Sleepingpositions were observed at intervals of 1 s, and if posi-tions lasted for more than 10 s, it was counted as one.The results of this analysis were compared with subjects’replies to the prestudy questionnaire on sleeping bodypositions.

For the analysis of the frequent changes of sleepingpositions, the summed duration of each of the upward,rightward, leftward and downward positions of the headwas ranked in this order, and the rank orders obtainedwere statistically compared between night 1 and night2 results in individual subjects. The statistical methodsused were the Wilcoxon signed-rank test and Pearson’scorrelation coefficient in

SPSS

10.0 J for Windows (SPSSJapan Inc., Tokyo, Japan).

RESULTS

Comparison of the pattern and frequency of sleeping position changes for night 1 with those in night 2

The mean number of sleeping position patterns was7.70

±

0.54 and 7.05

±

0.42 for nights 1 and 2, respec-tively, and these values showed a correlation coefficient(r) of 0.63 (

P

<

0.01). The mean frequency of positionchanges was 32.42

±

3.22 times and 33.53

±

2.65 timesfor nights 1 and 2, respectively, with a correlation coef-ficient of 0.69 (

P

<

0.001).

Duration of individual head directions in various sleeping positions

When the direction to which the head was facing duringsleep was arranged in a descending order according to

the duration of the head in this same position, the headdirections with the longest, second longest and thirdlongest duration for night 1 were significantly correlatedwith those in night 2, with correlation coefficients of0.45 (

P

<

0.05), 0.39 (

P

<

0.05) and 0.59 (

P

<

0.01),respectively.

Results of questionnaires on habitual sleeping positions

The correlation between the favorite hypnogenic bodyposition and the actual sleeping position (head direc-tion) was investigated in the 15 subjects who indicatedthat they had favorite body sleeping positions. In indi-vidual subjects, the favorite body position was signifi-cantly correlated with the actual head direction, whichwas most frequently observed during the two nights(

r

=

0.60,

P

<

0.01).

DISCUSSION

The pattern of sleep position changes or the mean fre-quency of position changes during natural sleep wassignificantly correlated between nights 1 and 2.Shirakawa

et al

. had recorded the appearance fre-quency of coarse and fine body movements includingturnings-over for 112 nights, and also observed thatthere were no large internight variations in any onesubject, although the frequency of body movementsvaried individually.

5

It may be suggested, therefore, thatpatterns to change a sleeping position, the frequency ofposition changes, and the direction of the head posi-tion during sleep do not vary from night to night in thesame individual, although there are individualvariations.

In the questionnaires used, 15 out of 19 subjectsreplied to have favorite sleeping positions, and 39% ofthem favored the right lateral position. As subjectivefavorite body positions and actual observed head posi-tions during sleeping were positively correlated, it wasalso confirmed that night-to-night variations were small,at least in the same healthy men, although the frequencyof position changes, the number of sleeping positions,and the direction of the head varies individually. It wasalso suggested that favorite hypnogenic positions arepresent in healthy men and such positions are stronglyreflected in actual sleeping positions.

These results indicate the possibility, at clinicalscenes, that patient’s sleep may be made more com-fortable and that the depth of sleeping may beimproved when a favorite sleeping position is learned

Features of sleeping posture

Sleep and Biological Rhythms

2003;

1

: 183–185

185

beforehand from the patient who cannot turn over byhimself.

REFERENCES

1 Alihanka J. Sleep movements and associated autonomicnervous activities in young male adults.

Acta Physiol.Scand. Suppl.

1982;

511:

1–85.2 Salmi T, Leinonen L. Automatic analysis of sleep records

with static charge sensitive bed.

Electroenceph. Clin.Neurophysiol.

1986;

64:

84–7.

3 Webster JB, Kripke DF, Messin S

et al.

An activity-basedsleep monitor system for ambulatory use.

Sleep

1982;

5:

389–99.4 Aaronson ST, Rashed S, Biber MP

et al.

Brain state andbody position. A time-lapse video study of sleep.

Arch.Gen. Psychiatry

1982;

39:

330–5.5 Shirakawa S, Sumizono T, Azumi K. New findings of

body movement in human sleep by statistic analysis.

Clin. Electron. Encephalogr.

1978;

20:

386–93 (InJapanese).