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Sleep movements and poor sleep in patients with non-specific somatic complaints — I. No first-night effect in poor and good sleepers
SLEEP MOVEMENTS AND POOR SLEEP IN PATIENTS WITH NON-SPECIFIC SOMATIC COMPLAINTS I. NO FIRST-NIGHT EFFECT IN POOR AND GOOD ERKKI KRONHOLM,
SLEEPERS
ERKKI ALANEN
and MARKKU
T. HYYPP~*
(Received 8 January 1987: accepted in revised form 26 March 1987)
Abstract-To
evaluate the possible first-night effect on the nocturnal motor activity 25 poor sleepers and 12 good sleepers slept on the Static Charge Sensitive Bed (SCSB) during two consecutive nights. The frequency of body movements in poor sleepers was almost two times higher than in good sleepers. The method itself was reproducible across two nights. There were no statistically significant and systemic level differences between the nights in the movements in bed (MIB). The difference f-test did not either reveal group differences in the magnitude or direction of changes from night to night. Results are consistent with the view that the level of motor activity is one of the determinants of sleep quality. No first-night effect exists in terms of psychomotor activity.
INTRODUCTION
FROM the very beginning the first-night effect was interpreted as an increased state of vigilance or as an arousal on the first laboratory night [l]. It has been emphasized that the phenomenon is a normal stress response to a novel and uncomfortable situation [2]. Consequently, when the physical inconvenience under the laboratory recording has been reduced to a minimum, the effect has diminished or disappeared [3-4]. But even in the subject’s own bed the electrical equipment will disturb the sleeper, and the awareness of the recording situation itself will also cause psychological distress. The subjects with whom the first-night effect most often has been investigated have been young (usually under 30 yr) and healthy (3, 5-81; older subjects have been included only in a few studies [4, 91. Psychiatric patients are usually the dominant patient group investigated [I, 2, IO]. Because the sample sizes in these studies have been small, the statistical nature of the variables has not been examined in sufficient detail [I 11. There exists a need to find a method which should be convenient, inexpensive and reliable in the screening of sleep disturbances. This method must keep physical and psychological distress at a minimum during the recording. It must register those parameters which are resistant to the subjective first-night effect but simultaneously have a high interindividual variability. Such requirements suggest a recording method which does not use direct contact with the sleeper and which can be used (if needed) without the awareness of the subject. The SCSB (Static Charge Sensitive Bed) method may satisfy these demands [12]. The aim of our investigation is to verify (or falsify) the hypothesis about the first-night effect of sleep measured by the SCSB method. We shall also consider *Correspondence should be addressed Research Centre of the Social Insurance
to Dr Markku T. Hyyppa, Psychosomatic Institution, SF-20720 Turku, Finland.
Unit. Rehabilitation
the opportunity patient dormitory
to differentiate between good and poor sleep by SCSB at the of the Rehabilitation Research Centre (RRC). Turku, Finland. METHODS
S1lhjtW.S
Twenty-five (n = 25) consecutive rehabilitation patients (aged 21-59 yr) who were admitted to the RRC because of long-lasting unspecific somatic and sleep complaints participated in the sleep study. Consultations with the psychiatrist at the RRC revealed that 16 of the poor sleepers (six women and 10 men) had depressive (or related affective) disorders, i.e. fulfilling the criteria for DIMS type 2 b in the Diagnostic Classifications of Sleep Disorders [ 131. Nine of the patients (three women and six men) had no mental disorders, thus fulfilling the criteria for DIMS type 1 [13]. The distribution of psychiatric and other medical diagnoses in the rehabilitation group is given in Table I. Twelve (n = 12) normal healthy subjects (four women and eight men, aged 25-17 yr) were recruited from the RRC personnel. They all considered themselves to be good sleepers. As for the demographic characteristics the rehabilitation group differed from the control group only in education. i.e. the latter group was more educated (Table II). To evaluate the possible first-night effect elicited by the SCSB method (Bio-Matt ‘: Finland) their sleep movements were registered during two consecutive nights. All subjects were actively willing to participate in the study. They were fully aware of the sleep study. which was approved by the Ethical Committee of the RRC.
Male 01 = 16)
Female
(r1= 0)
Non-endogeneous depression Endogeneousdepression Other affective disorders Musculo sceletal diseases Diseases of circulatory system Other diseases
TABLE
1I.-Dr-h10(;RAPHIC‘ POOR
FFATLIRE:,
bl.tEPERS
(‘ONSECUTIVE
M’HO NIGHT‘S
Normal sleepers (?I = 17) Male/female Mean age Age range Coupled Novocational education or lower vocational education Universitv education Employed
SLEPT
OF NORMAI.
ANI)
TWO
ON SCSB
Poor \kXpcr\ (II = 75)
814 35.9yr 25-l7 yr 66.7%
1h .7‘$0 83.3”/, lOO.O’%
SCSB mem~rres of sleep The SCSB is comfortable for the subject, since it does not require troublesome laboratory conditions. The SCSB has been constructed to record sleep movements and associated autonomic nervous functions without any electrodes connected to the subject [12. 14, 151. A description of the automatic analysis
Non-specific
somatic
complaints
-
I
625
of sleep records with the SCSB has recently been published [16). We have also used it in the evaluation of sleep-related apneas [ 17). In the SCSB method, two metal plates are located under the mattress and isolated from each other by a stiff insulator, and the potential difference between them is recorded. When the subject moves his hand. foot, head, fingers, etc. static charges are formed in the ‘active’ layer of the mattress. The charges induce a potential difference between the metal plates. enabling a very sensitive recording of movements, even very small ones. The frequency bandpass of the recording system was 0.3-60 cps. Respiratory movements (0.3-I Hz), ballistocardiogram (S-30 Hz) and body movements (0.3-30 Hz) can be recorded by filtering the original signal and by differing the amplification [12]. For the automatic analysis of body movements the filtered signals were fed to a PDP-I1/23 minicomputer. The program calculated the duration of each movement from the deflection5 of the SCSB recording at the fixed level somewhat above the amplitude during motionless periods 1161. (Some very low amplitude deflections would be ignored by the program, and these micro movements are excluded from the analysis.) The program classified movements in bed (MIBs) into four classes: A: duration < 5 set, B: duration > 5 set and < 10 set, C: duration > 10 set and < 1.5 sec. D: duration > 15 sec. If two MIBs were at shorter interval than 5 set from each other they were considered as one movement (121. The frequency of every movement class (movement/min), and mutual portions of movement classes, were calculated separately for the whole night and for each third of the night. Ballistocardiogram, respiratory and body movements were also displayed on paper with an ink-writing oscillograph (Mingograph R.. Siemens, Elema) using a 25 mmlsec paper speed and replay speed of the tape recorder 20 times faster than the real time. This was used for visual evaluation of the breathing patterns and of the possible apnea [17]. The apnea index was formulated as the number of apneas per hour. Subjects also fulfilled a short sleep questionnaire (sleep diary) after the registration night. Slafisrical nrtalysi.7
Statistical analyses of the results were performed 198dR, U.C.L.A.. California). The Pearson product were carried out for the analysis of the first-night variables and the X2-test for the sleep questionnaire of two consecutive nights were carried out with the
with BMDP-program (BMDP Statistical Software moment correlation, /’ test and difference t-test effect. In addition, student’s f-test for parametric and McNemar test of symmetry for the sleep diaries significance limit ofp < 0.05.
RESULTS
Analysis of two consecutive nights The frequency of movements (movement/min) of the poor sleepers was almost two times higher than that of the good sleepers during both nights (Figs 1 and 2). In order to analyze how much random variability contributes to the recordings by the SCSB method the Pearson product moment correlation coefficients between the two consecutive nights were calculated for all parameters. As seen in Table III, coefficients were high. Thus the method seems to be reproducible (or reliable). To get a more accurate picture of the relationship between intra- and inter-individual variations we compared the inter-individual variance in the whole night MIBs with the residual variance. Results from night to night showed that in normal sleepers inter-individual variance in class D was 96.9%) in class C 83.1%) in class B 44.0% and in class A 42.8%, respectively. In the patient group inter-individual variance was constantly smaller than intra-individual variance. Inter-individual variance in class D was 0%) in class C 13.9%) in class B 14.7% and in class A 45.2% respectively. In order to test whether there exists a systematic level difference between the two consecutive nights in the recorded parameters, the i(‘-test was carried out between the first and second nights. There were no statistically significant differences between the nights in either group. The difference t-test for the SCSB parameters was then carried out to delineate the possible difference in the magnitude and direction of changes from night to
Movementimin
A
n
Good sleepers
(n=lZ)
m
Poor sleepers
(17=25)
C
6 MIB
Duration
classes
D
classes
of MlBs
A c 5 set 5secc B s:lOsec 1OseccC r15sec D > 15 set
FIG;. l.-The
frequency
of movements
Normal 4eepers (n = 12)
Number of MIB/min
0.438 0.441
Class A Class I3 Cks c Class D Al. third A2. third A3. third BI. third B2. third 83. third Cl. third C2. third c‘3. third Dl. third D2. third D3. third Apnea index
O.Xwt O.c)W
0.411 0.325 0.500 0.35s 0.445 0.155 -I). 103 0.238 o.C!5* 0.726-t 0.007i 0.680* 0.701*
in bsd during
the first night
Rehabilitation plttwnt\ 01 = 25) 0.4x.5* 0.185
0.191 _-0.134
0.5 14* 0.716i O.h23+ 0.593* 0.311: O.h3li o.473” 0.30; 0, I72 0.337 0.154 _ 0.305 0.7X+
*p <
0.0.5. tp < 0.01.
Statikally
significant
differences
from zero correlation
Non-specific
somatic
complaints
-
I
627
Movementimin 0.250
@!J
Good
sleepers
m
Poor sleepers
(Z,2) (n =25)
0.200
A
B
C
D
MIB classes Duration
classes A <
of MlBs 5sec
5sec 15sec
FIG. 2. -The
frequency
of movements
in bed during
the second
night.
night between the control and patient group. The analysis revealed no distinction (with the exception of MIB-class A during the first third of the night) on the change from the first to the second night between the patient and control groups. Subjective assessment The sleep diaries of the two consecutive nights were analyzed by McNemar test of symmetry in order to reveal possible first-night effect in the subjective experience of sleep. Although the subjective experience was in general slightly better after the second night than after the first night, there were no statistically significant differences between the two nights in either group. Patients estimated the quality of their sleep statistically significantly worse than the controls did on the following criteria: the depth of sleep. sufficient length of sleep, serenity of sleep, and the amount of awakenings during night. They also estimated their affective state in the morning worse than the controls did on two items: pleasurable feelings in the morning, and energetic feelings in the morning. No gender differences were observed. Discussion The frequency of nocturnal body movements on SCSB was almost two times higher in poor sleepers than in good sleepers. However, the SCSB method did not
E.
628
KRONHOLM
et al.
reveal any significant first-night effect between the two consecutive nights either in good sleepers or in poor sleepers (rehabilitation patients with nonspecific somatic complaints). The result is consistent with the finding that telemetric motor activity does not change over four nights [8]. Absence of the first-night effect points to the lack of systematic differences between consecutive nights. It does not necessarily mean that intra-individual variance between nights should be low, however. We found that in the patient group, intra-individual variance was greater than inter-individual variance in all body movement classes. In good sleepers, this was observed only in short movement classes, while long movement classes showed extremely low intra-individual variance across two nights. This finding is concomitant with the recent report about smaller interindividual than intra-individual variance of small movements in normal sleepers [ll]. During poor sleep a sleep disturbance seems to manifest itself as a drastic increase of intra-individual variation in movements longer than 5 set from night to night. The notion of the first-night effect has also been challenged by EEG studies. There has been a failure to find any changes in stages 3 and 4 [7, 81 or in REM [S] from night to night. Some of the studies have revealed that the first night effect in healthy subjects is restricted only to the REM latency [8] or to the REM percentage and to the sleep efficiency [3]. It has also been shown that in depressed patients a significant ‘first-night effect’ was observed only in stage 2 [l], and in other psychiatric patients an effect was reported only in sleep latency [2]. In the patients with impotency but without sleep disorders no first-night effect was reported [4]. Nor was any first-night effect observed in terms of the subjective experiences of sleep. A first-night effect has previously been reported in the soundness of sleep, but it did not appear in the scores of self-rated anxiety, restlessness or rest feeling [S]. Thus it seems reasonable to assume that the first-night effect is highly determined by the experimental surroundings and the recording method itself. Consequently, a method such as the SCSB, which allows perfectly natural and non-disturbed sleep to occur, does not cause any measurable first-night effect, and the SCSB therefore gives reliable data through single-night recordings. REFERENCES
2. 3. 4. 5.
MExI)rxs J. HAWKINS D. Sleep laboratory adaptation in normal subjects and depressed patients (‘first-night effect’), ElectroencrpkL‘h ~europhysid 1967; 22: 556-558. KUPFER DJ, W~rss BL. DETKE TP. FOSIIZR FG. First-night effect revisited: a clinical note. J Rierv ,Ment Dis 1974: 159: 205-209. BR~WMAN CP. CARTWRIGHT‘ RD. The first-night effect on sleep and dreams. Eiol fsychiat 19x0; 15: 809-X12. KAI>ER GA. GRIFFIN PT. Reevaluation of the phenomena of the first-night effect. Sleep 1983: 6: 67-71. AC~NEW HW, W~RB WB. WILLIAMS RL. The first-night effect: an EEG study of sleep. Psyhoph>~siol
6. 7. 8.
Biol
9.
1966; 2: 263-226.
KALES A,J~c,ooso~ A, KALES JD, KUN T,WEISSBUCH R. All-night EEGsleepmeasurements in young adults. Psychosom Sci 1967; 7: 67-68. SCHMIDT HS, KAELBLINC; R. The differential laboratory _ adaptation of sleep. 1 parameters. Biol . P\ych;a/ 1971: 3: 33-45. COBLL P. MCPARTLAND RJ. SILVA WJ. KUPFFR DJ. Is there a first-night effect? (A revisit). Psychiut
1974: 9: 215-219.
WERR WB, CAMPBELL 1979: 3: 319-324.
SS. The first night effect revisited
with age as a variable.
Wukir~g Slre@g
Non-specific 10. 11. 12. 13. 14. 15. 16. 17.
18. 19. 20. 21. 22.
somatic
complaints
-
I
629
FOSTER FG, KUPFER DJ, COBLE P, MCPARTLAND RJ. Rapid eye movement sleep density. Archs Gen Psych& 1976; 33: 1119-1123. MERICA H, GAILLARD J-M. Statistical description and evaluation of the interrelationships of standard sleep variables for normal subjects. Sleep 1985; 8: 261-273. ALIHANKA J. Sleep movements and associated autonomic nervous activities in young male adults. Acta Physiol &and 1982; (suppl 511): 1-85. ROFFWARG HP. Chairman, Sleep Disorders Classification Committee, Diagnostic classification of sleep and arousal disorders. Sleep 1979; 1: %106. ALIHANKA J, VAAHTORANTA K. SAARIKIVI I. A new method for long-term monitoring of the ballistocardiogram, heart rate, and respiration. Am J Physiol 1981; 240: R384-392. ALIHANKA J, VAAHTORANTA K. A static charge sensttive bed. A new method for recording body movements during sleep. Electroencephalogr Clin Neurophvsiol 1979; 46: 731-734. SALMI T, LEINONEN L. Automatic analysis of sleep records with static charge sensitive bed. Electroencephalogr Clin Neurophysiol 1986; 64: 84-87. SALMI T, PARTINEN M, HYYPPA M, KRONHOL~I E. Automatic analysis of static charge sensitive bed (SCSB) recordings in the evaluation of sleep related apneas. Actu Neurol Stand 1986: 74: 36&364. HO~SON JA, SPAGNA T. MALENKA R. Ethology of sleep studied with time-lapse photography: postural immobility and sleep-cycle phase in humans. Science 1978: 201: 1251-1253 AARONSON ST, SIHAM R. BIBER MP. HOBSON JA. Brain state and body position. Archs GetI Psychiat 1982; 39: 33G335. KONINCK J, GAGNON P, LALLIER S. Sleep positions in the young adult and their relationship with the subjective quality of sleep. Sleep 1983; 6: 52-59. HINTON JM. Patterns of insomnia in depressive states. J Neural Neurosurg Psychiat lY63: 26: 184-189. FOSTER FG, KUPFER DJ. Psychomotor activity as a correlate of depression and sleep in acutely disturbed psychiatric inpatients. Am J Psychiat 1975; 132: 928-931.
SLEEPERS
ERKKI ALANEN
and MARKKU
T. HYYPP~*
(Received 8 January 1987: accepted in revised form 26 March 1987)
Abstract-To
evaluate the possible first-night effect on the nocturnal motor activity 25 poor sleepers and 12 good sleepers slept on the Static Charge Sensitive Bed (SCSB) during two consecutive nights. The frequency of body movements in poor sleepers was almost two times higher than in good sleepers. The method itself was reproducible across two nights. There were no statistically significant and systemic level differences between the nights in the movements in bed (MIB). The difference f-test did not either reveal group differences in the magnitude or direction of changes from night to night. Results are consistent with the view that the level of motor activity is one of the determinants of sleep quality. No first-night effect exists in terms of psychomotor activity.
INTRODUCTION
FROM the very beginning the first-night effect was interpreted as an increased state of vigilance or as an arousal on the first laboratory night [l]. It has been emphasized that the phenomenon is a normal stress response to a novel and uncomfortable situation [2]. Consequently, when the physical inconvenience under the laboratory recording has been reduced to a minimum, the effect has diminished or disappeared [3-4]. But even in the subject’s own bed the electrical equipment will disturb the sleeper, and the awareness of the recording situation itself will also cause psychological distress. The subjects with whom the first-night effect most often has been investigated have been young (usually under 30 yr) and healthy (3, 5-81; older subjects have been included only in a few studies [4, 91. Psychiatric patients are usually the dominant patient group investigated [I, 2, IO]. Because the sample sizes in these studies have been small, the statistical nature of the variables has not been examined in sufficient detail [I 11. There exists a need to find a method which should be convenient, inexpensive and reliable in the screening of sleep disturbances. This method must keep physical and psychological distress at a minimum during the recording. It must register those parameters which are resistant to the subjective first-night effect but simultaneously have a high interindividual variability. Such requirements suggest a recording method which does not use direct contact with the sleeper and which can be used (if needed) without the awareness of the subject. The SCSB (Static Charge Sensitive Bed) method may satisfy these demands [12]. The aim of our investigation is to verify (or falsify) the hypothesis about the first-night effect of sleep measured by the SCSB method. We shall also consider *Correspondence should be addressed Research Centre of the Social Insurance
to Dr Markku T. Hyyppa, Psychosomatic Institution, SF-20720 Turku, Finland.
Unit. Rehabilitation
the opportunity patient dormitory
to differentiate between good and poor sleep by SCSB at the of the Rehabilitation Research Centre (RRC). Turku, Finland. METHODS
S1lhjtW.S
Twenty-five (n = 25) consecutive rehabilitation patients (aged 21-59 yr) who were admitted to the RRC because of long-lasting unspecific somatic and sleep complaints participated in the sleep study. Consultations with the psychiatrist at the RRC revealed that 16 of the poor sleepers (six women and 10 men) had depressive (or related affective) disorders, i.e. fulfilling the criteria for DIMS type 2 b in the Diagnostic Classifications of Sleep Disorders [ 131. Nine of the patients (three women and six men) had no mental disorders, thus fulfilling the criteria for DIMS type 1 [13]. The distribution of psychiatric and other medical diagnoses in the rehabilitation group is given in Table I. Twelve (n = 12) normal healthy subjects (four women and eight men, aged 25-17 yr) were recruited from the RRC personnel. They all considered themselves to be good sleepers. As for the demographic characteristics the rehabilitation group differed from the control group only in education. i.e. the latter group was more educated (Table II). To evaluate the possible first-night effect elicited by the SCSB method (Bio-Matt ‘: Finland) their sleep movements were registered during two consecutive nights. All subjects were actively willing to participate in the study. They were fully aware of the sleep study. which was approved by the Ethical Committee of the RRC.
Male 01 = 16)
Female
(r1= 0)
Non-endogeneous depression Endogeneousdepression Other affective disorders Musculo sceletal diseases Diseases of circulatory system Other diseases
TABLE
1I.-Dr-h10(;RAPHIC‘ POOR
FFATLIRE:,
bl.tEPERS
(‘ONSECUTIVE
M’HO NIGHT‘S
Normal sleepers (?I = 17) Male/female Mean age Age range Coupled Novocational education or lower vocational education Universitv education Employed
SLEPT
OF NORMAI.
ANI)
TWO
ON SCSB
Poor \kXpcr\ (II = 75)
814 35.9yr 25-l7 yr 66.7%
1h .7‘$0 83.3”/, lOO.O’%
SCSB mem~rres of sleep The SCSB is comfortable for the subject, since it does not require troublesome laboratory conditions. The SCSB has been constructed to record sleep movements and associated autonomic nervous functions without any electrodes connected to the subject [12. 14, 151. A description of the automatic analysis
Non-specific
somatic
complaints
-
I
625
of sleep records with the SCSB has recently been published [16). We have also used it in the evaluation of sleep-related apneas [ 17). In the SCSB method, two metal plates are located under the mattress and isolated from each other by a stiff insulator, and the potential difference between them is recorded. When the subject moves his hand. foot, head, fingers, etc. static charges are formed in the ‘active’ layer of the mattress. The charges induce a potential difference between the metal plates. enabling a very sensitive recording of movements, even very small ones. The frequency bandpass of the recording system was 0.3-60 cps. Respiratory movements (0.3-I Hz), ballistocardiogram (S-30 Hz) and body movements (0.3-30 Hz) can be recorded by filtering the original signal and by differing the amplification [12]. For the automatic analysis of body movements the filtered signals were fed to a PDP-I1/23 minicomputer. The program calculated the duration of each movement from the deflection5 of the SCSB recording at the fixed level somewhat above the amplitude during motionless periods 1161. (Some very low amplitude deflections would be ignored by the program, and these micro movements are excluded from the analysis.) The program classified movements in bed (MIBs) into four classes: A: duration < 5 set, B: duration > 5 set and < 10 set, C: duration > 10 set and < 1.5 sec. D: duration > 15 sec. If two MIBs were at shorter interval than 5 set from each other they were considered as one movement (121. The frequency of every movement class (movement/min), and mutual portions of movement classes, were calculated separately for the whole night and for each third of the night. Ballistocardiogram, respiratory and body movements were also displayed on paper with an ink-writing oscillograph (Mingograph R.. Siemens, Elema) using a 25 mmlsec paper speed and replay speed of the tape recorder 20 times faster than the real time. This was used for visual evaluation of the breathing patterns and of the possible apnea [17]. The apnea index was formulated as the number of apneas per hour. Subjects also fulfilled a short sleep questionnaire (sleep diary) after the registration night. Slafisrical nrtalysi.7
Statistical analyses of the results were performed 198dR, U.C.L.A.. California). The Pearson product were carried out for the analysis of the first-night variables and the X2-test for the sleep questionnaire of two consecutive nights were carried out with the
with BMDP-program (BMDP Statistical Software moment correlation, /’ test and difference t-test effect. In addition, student’s f-test for parametric and McNemar test of symmetry for the sleep diaries significance limit ofp < 0.05.
RESULTS
Analysis of two consecutive nights The frequency of movements (movement/min) of the poor sleepers was almost two times higher than that of the good sleepers during both nights (Figs 1 and 2). In order to analyze how much random variability contributes to the recordings by the SCSB method the Pearson product moment correlation coefficients between the two consecutive nights were calculated for all parameters. As seen in Table III, coefficients were high. Thus the method seems to be reproducible (or reliable). To get a more accurate picture of the relationship between intra- and inter-individual variations we compared the inter-individual variance in the whole night MIBs with the residual variance. Results from night to night showed that in normal sleepers inter-individual variance in class D was 96.9%) in class C 83.1%) in class B 44.0% and in class A 42.8%, respectively. In the patient group inter-individual variance was constantly smaller than intra-individual variance. Inter-individual variance in class D was 0%) in class C 13.9%) in class B 14.7% and in class A 45.2% respectively. In order to test whether there exists a systematic level difference between the two consecutive nights in the recorded parameters, the i(‘-test was carried out between the first and second nights. There were no statistically significant differences between the nights in either group. The difference t-test for the SCSB parameters was then carried out to delineate the possible difference in the magnitude and direction of changes from night to
Movementimin
A
n
Good sleepers
(n=lZ)
m
Poor sleepers
(17=25)
C
6 MIB
Duration
classes
D
classes
of MlBs
A c 5 set 5secc B s:lOsec 1OseccC r15sec D > 15 set
FIG;. l.-The
frequency
of movements
Normal 4eepers (n = 12)
Number of MIB/min
0.438 0.441
Class A Class I3 Cks c Class D Al. third A2. third A3. third BI. third B2. third 83. third Cl. third C2. third c‘3. third Dl. third D2. third D3. third Apnea index
O.Xwt O.c)W
0.411 0.325 0.500 0.35s 0.445 0.155 -I). 103 0.238 o.C!5* 0.726-t 0.007i 0.680* 0.701*
in bsd during
the first night
Rehabilitation plttwnt\ 01 = 25) 0.4x.5* 0.185
0.191 _-0.134
0.5 14* 0.716i O.h23+ 0.593* 0.311: O.h3li o.473” 0.30; 0, I72 0.337 0.154 _ 0.305 0.7X+
*p <
0.0.5. tp < 0.01.
Statikally
significant
differences
from zero correlation
Non-specific
somatic
complaints
-
I
627
Movementimin 0.250
@!J
Good
sleepers
m
Poor sleepers
(Z,2) (n =25)
0.200
A
B
C
D
MIB classes Duration
classes A <
of MlBs 5sec
5sec
FIG. 2. -The
frequency
of movements
in bed during
the second
night.
night between the control and patient group. The analysis revealed no distinction (with the exception of MIB-class A during the first third of the night) on the change from the first to the second night between the patient and control groups. Subjective assessment The sleep diaries of the two consecutive nights were analyzed by McNemar test of symmetry in order to reveal possible first-night effect in the subjective experience of sleep. Although the subjective experience was in general slightly better after the second night than after the first night, there were no statistically significant differences between the two nights in either group. Patients estimated the quality of their sleep statistically significantly worse than the controls did on the following criteria: the depth of sleep. sufficient length of sleep, serenity of sleep, and the amount of awakenings during night. They also estimated their affective state in the morning worse than the controls did on two items: pleasurable feelings in the morning, and energetic feelings in the morning. No gender differences were observed. Discussion The frequency of nocturnal body movements on SCSB was almost two times higher in poor sleepers than in good sleepers. However, the SCSB method did not
E.
628
KRONHOLM
et al.
reveal any significant first-night effect between the two consecutive nights either in good sleepers or in poor sleepers (rehabilitation patients with nonspecific somatic complaints). The result is consistent with the finding that telemetric motor activity does not change over four nights [8]. Absence of the first-night effect points to the lack of systematic differences between consecutive nights. It does not necessarily mean that intra-individual variance between nights should be low, however. We found that in the patient group, intra-individual variance was greater than inter-individual variance in all body movement classes. In good sleepers, this was observed only in short movement classes, while long movement classes showed extremely low intra-individual variance across two nights. This finding is concomitant with the recent report about smaller interindividual than intra-individual variance of small movements in normal sleepers [ll]. During poor sleep a sleep disturbance seems to manifest itself as a drastic increase of intra-individual variation in movements longer than 5 set from night to night. The notion of the first-night effect has also been challenged by EEG studies. There has been a failure to find any changes in stages 3 and 4 [7, 81 or in REM [S] from night to night. Some of the studies have revealed that the first night effect in healthy subjects is restricted only to the REM latency [8] or to the REM percentage and to the sleep efficiency [3]. It has also been shown that in depressed patients a significant ‘first-night effect’ was observed only in stage 2 [l], and in other psychiatric patients an effect was reported only in sleep latency [2]. In the patients with impotency but without sleep disorders no first-night effect was reported [4]. Nor was any first-night effect observed in terms of the subjective experiences of sleep. A first-night effect has previously been reported in the soundness of sleep, but it did not appear in the scores of self-rated anxiety, restlessness or rest feeling [S]. Thus it seems reasonable to assume that the first-night effect is highly determined by the experimental surroundings and the recording method itself. Consequently, a method such as the SCSB, which allows perfectly natural and non-disturbed sleep to occur, does not cause any measurable first-night effect, and the SCSB therefore gives reliable data through single-night recordings. REFERENCES
2. 3. 4. 5.
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