Cognitive performance and sleep quality in the elderly suffering

from chronic insomnia

Relationship between objective and subjective measures

Celyne H. Bastien*, Emilie Fortier-Brochu, Isabelle Rioux,Melanie LeBlanc, Meagan Daley, Charles M. Morin

Ecole de Psychologie and Centre d’Etude des Troubles du Sommeil, Universite Laval, Ste-Foy, Quebec, Canada G1K 7P4

Abstract

Objective: The objective of the present study was to evaluate

the relationship between objective and subjective sleep quality

and objective and subjective evaluation of cognitive performance

in older adults suffering of chronic insomnia (using or not

benzodiazepines, BZs) or self-reported good sleepers. Methods:

Three groups of participants 55 years and older were evaluated:

20 insomnia sufferers using BZs chronically, 20 drug-free

insomnia sufferers and 20 good sleepers. Objective sleep

(PSG) and subjective sleep (sleep diaries, SD) were measured.

Objective measures of cognitive performance (attention/concen-

tration, verbal/visual memory, executive function and psycho-

motor speed) and subjective perception of daily performance

were evaluated. Results: Correlational analysis revealed that

objective and subjective measures of daytime performance are

differentially related to sleep quality for the three groups. An

objective good night of sleep is associated with better cognitive

performance in good sleepers and drug-free individuals. On the

other hand, the impression of having slept well is related to

better cognitive performance in good sleepers and chronic

insomnia sufferers using BZs. Conclusion: Daytime perform-

ance and sleep quality are related, but differently so for a good

sleeper, an insomnia sufferer without treatment, or one using

BZs to alleviate sleep difficulties. D 2003 Elsevier Science Inc.

All rights reserved.

Keywords: Insomnia; Performance; Sleep quality; Hypnotics; Benzodiazepines

Introduction

According to available epidemiological data, 12–25% of

people 65 years of age and older complain of insomnia on a

regular basis [1,2]. The elderly report greater difficulty

maintaining sleep whereas younger adults complain more

frequently of difficulties initiating sleep [3]. Pharmacother-

apy remains the most frequently used treatment for elderly

insomnia sufferers [4]. According to Mellinger et al. [2],

14% of the elderly consume hypnotics, compared to 7.4% of

adults under 65. Elsewhere, 11% of people over the age of

65 were found to have been using hypnotic medication

regularly during the previous year and 4% had been con-

suming hypnotics for more than 10 years [5].

The sedative medications most frequently prescribed to

facilitate sleep are GABAergic substances like benzodiaze-

pines (BZs). In the short-term, BZs have the effect of

reducing sleep latency and the length and frequency of

nocturnal awakenings, and of increasing the total duration

of sleep and its quality [3]. Furthermore, the occurrence of

the EEG ‘‘speeding’’ in association with BZs use is gen-

erally thought to represent the intensification of processes

associated with sensory inhibition (i.e., increase in sleep

spindle activity) [6,7]. However, these improvements in

sleep continuity are paralleled by an increase in the amount

of time spent in light sleep (Stage 2), by a moderate

reduction in the time spent in REM sleep and by substantial

reduction in the time spent in deep sleep (Stages 3 and 4).

Recently, Vignola et al. [8] found that the sleep patterns of

elderly insomnia sufferers using BZs on a chronic basis (1–

34 years of use) was as disturbed as those of elderly

suffering of chronic insomnia who had not received treat-

ment for their sleep difficulties [8].

0022-3999/03/$ – see front matter D 2003 Elsevier Science Inc. All rights reserved.

PII: S0022 -3999 (02 )00544 -5

* Corresponding author. Ecole de Psychologie, Universite Laval, Ste-

Foy, Quebec, Canada G1K 7P4. Tel.: +1-418-656-2131x8344; fax: +1-418-

656-5152.

E-mail address: celyne.bastien@psy.ulaval.ca (C.H. Bastien).

Journal of Psychosomatic Research 54 (2003) 39–49

Besides their effects on sleep, BZs are associated with

certain undesirable secondary effects, most notably depend-

ence, daytime sleepiness, sedation and anterograde amnesia

[9–12]. A number of studies investigating the cognitive

effects of chronic BZs use in adults with anxiety strongly

suggest an alteration in verbal learning, memory, visuo-

spatial ability and psychomotor capacity [13,14]. On the

other hand, research looking at the effects of BZs on

cognitive function in patients with insomnia has produced

different results. As such, no performance deficit was

detected in elderly insomnia sufferers using BZs chronically

relative to a sample of good sleepers [8].

After a poor night of sleep, individuals suffering of

insomnia usually report disruption of mood, alteration of

motor abilities, social discomfort and a certain cognitive

inefficiency that is accompanied by sleepiness [15]. These

daytime consequences represent an important concern for

individuals with insomnia [16]. Objectively, an alteration of

neuropsychological function has been found in adult insom-

nia sufferers relative to good sleepers. More specifically,

people with insomnia exhibit alterations in tasks measuring

balance, attention and reaction time [16], and access to

information stored in semantic memory [17]. However, no

difference has been detected for psychomotor function

[17,18], episodic memory [16] divided attention [16], verbal

learning and recognition of figures and words [18]. Contrary

to Hauri [16], Broman et al. [18] found no alteration in

reaction time in insomnia sufferers. In elderly with insom-

nia, some studies suggest a deterioration in attention and

concentration [8].

Investigation into other characteristics of insomnia points

to a more negative subjective evaluation of performance by

individuals with insomnia than by good sleepers. As such,

adults with insomnia have weaker expectations of their

performance, evaluate their performance more negatively

and report having performed less well than individuals of

similar age and actual capability level [18]. Available data

suggest that, even in the absence of objective deficits, such a

negative evaluation of performance also exists in drug-free

elderly suffering of insomnia as compared to good sleepers

and elderly insomnia sufferers using BZs [8].

A relationship also appears between objective sleep

quality and performance in insomnia sufferers. As such,

longer nocturnal awakening periods are associated with

reduced objective performance at tasks measuring psycho-

motor ability [17,18]. Furthermore, the duration of sleep is

positively correlated with the subjective evaluation of per-

formance [18]. However, these results were obtained using

small samples (e.g., 10 per group) [17] in which a large

proportion of individuals were experiencing psychological

distress (e.g., 16/26 participants).

In insomnia sufferers 55 years and older, subjectively

evaluated poor sleep quality is associated with reduced

performance in tasks measuring vigilance, psychomotor

speed, recall, problem resolution and speed and accuracy

in complex decision-making [19]. On the other hand,

objectively evaluated poor sleep quality appears to be

more closely linked short-term memory functions. A

formal comparison between the performance observed in

elderly with insomnia and that of elderly good sleepers

was not undertaken.

Considering the widespread use of BZs in the elderly

population suffering of insomnia, it is important to deepen

our understanding of the impact of chronic use of BZs on

cognitive function. Furthermore, understanding the relation-

ship between sleep quality and cognitive performance has

important clinical implications both in terms of better

understanding insomnia sufferers’ complaints of daytime

consequences, as well as in terms of treatment planning and

implementation. In regards to the cognitive performance,

analysis will be based on the same sample data obtained by

Vignola et al. [8]. Their results did not investigate any

relationships between the subjective and objective perform-

ance of sleep and cognitive functions. In the Vignola et al.’s

[8] study, objective sleep was measured with two nights

following the neuropsychological testing and subjective

sleep was measured from the completion of 2 weeks of

sleep diary (SD). As such, the purpose of the present study

is to expend previous findings and, with the use of a

correlational approach, to examine the relationship between

the objective and subjective evaluation of sleep and cog-

nitive performance in elderly insomnia sufferers who do or

not use BZs on a chronic basis, as well as in good sleepers.

By targeting the night just before the evaluation of cognit-

ive performance, one should better understand the relation-

ship between cognitive functioning and the preceding night

of sleep.

Methods

Participants

The 60 participants in this study were divided into

three groups of 20, including a group of 20 insomnia

sufferers utilizing BZs chronically as sleep aids (INSBZ;

10 males and 10 females), 20 insomnia sufferers not

taking medication (INS; 9 males and 11 females) and

20 good sleepers (GS; 11 males and 9 females). All

participants were 55 years of age or older, with a mean

age of 62.5 years (S.D. = 5.8). Inclusion criteria for both

groups of insomnia sufferers were: (a) presence of a

subjective complaint of insomnia defined by difficulty

initiating sleep (sleep latency > 30 min) and/or maintain-

ing sleep (nocturnal awakenings >30 min), (b) presence of

insomnia at least three nights per week, (c) problems

present for a minimum of 6 months, (d) presence of at

least one complaint of a negative consequence associated

with daytime functioning due to insomnia and (e) pres-

ence of marked psychological distress and/or disruption of

occupational and social functioning due to insomnia. The

participants in the INSBZ group had been using BZs to

C.H. Bastien et al. / Journal of Psychosomatic Research 54 (2003) 39–4940

facilitate sleep at least four nights per week for more than

3 months, while the INS group had to be drug-free for at

least 1 month before entering the study. Finally, partic-

ipants in the GS group did not meet any criteria for

insomnia and were not using any medication to aid sleep.

For each group, the presence or absence of insomnia

complaints was confirmed by information obtained from

SD [20] over a period of 2 weeks. The exclusion criteria for

all participants were: (a) presence of a major medical

condition (e.g., cancer) or of a degenerative neurological

condition (e.g., dementia), (b) presence of major psycho-

pathology (e.g., depression), (c) presence of another sleep

disorder (e.g., sleep apnea), (d) a score of 23 or higher on

the Beck Depression Inventory (BDI) [21], (e) a score

lower than 27 on the Folstein Mini-Mental State Exam

(FMMSE) [22] or (f) use of psychotropic medication or any

other medication that alters sleep. For the two insomnia

groups, inclusion and exclusion criteria were taken from the

International Classification of Sleep Disorders (ICSD-10)

[23] and the Diagnostic and Statistical Manual of Mental

Disorders (DSM-IV) [24].

Participants had a mean education level of 12.9 years

(S.D. = 4.0). In addition, the majority were married (76.7%)

and retired (70.0%). The mean duration of insomnia was

25.8 years (S.D. = 15.7). On average, participants in the

INSBZ condition had been using BZs as sleep aid for

13.5 years (S.D. = 10.0, range 1–34). The mean frequency

of BZs use was 6.6 nights per week (S.D. = 1.1).

Sleep measures

Data for objective sleep were obtained using polysom-

nographic recording (PSG). This included data obtained

from electroencephalogram (EEG), electrooculogram

(EOG) and electromyogram (EMG). Sleep latency, fre-

quency of nocturnal awakenings, sleep efficiency, total

sleep time, total wake time and the proportion of time

spent in each sleep stage were used as clinical sleep

variables. Data collected on the first night of sleep in the

laboratory, prior to neuropsychological analysis, were used

in the present analysis.

The SD [20] measures the subjective quality of sleep. It

is completed in the morning, upon wakening, and permits

collection of diverse information concerning the perception

of sleep, such as sleep latency, the frequency of nocturnal

awakenings, total wake time, total sleep time, sleep quality,

subjective sleep depth and feeling of being well-rested. The

SD obtained following the first night of sleep in the

laboratory was used in this analysis.

The Insomnia Severity Index (ISI) [20] is composed of

seven items that evaluate: (a) the severity of sleep-onset

(initial), (b) sleep maintenance (middle), (c) early morning

awakening (terminal) problems, (d) satisfaction with current

sleep pattern, (e) interference with daily functioning, (f)

noticeability of impairment attributed to the sleep problem

and (g) level of distress caused by the sleep problem. Each

of these items is rated on a five-point Likert scale (‘‘0’’= not

at all, ‘‘4’’= extremely) and the time interval is ‘‘in the last

2 weeks.’’ Total scores range from 0 to 28, with high scores

indicating greater insomnia severity. The ISI is available in

three different versions: patient (self-administered), signific-

ant other (usually a spouse) and clinician. The ISI has

adequate internal consistency and correlates adequately with

subjective and objective sleep measures [25]. In the present

study, only the patient version of the ISI was computed.

Table 1

Neuropsychological instruments used to measure each factor

Factor Neuropsychological instruments

Verbal and visual

memory (VVM)

Verbal Paired Associates I

(immediate recall)

Verbal Paired Associates II

(delayed recall)

Visual Reproduction I

(immediate recall)

Visual Reproduction II

(delayed recall)

Psychomotor speed (PS) Digit Symbol Substitution Test

Purdue Pegboard

Trail Making Tests A and B

Wilkinson’s Four-Choice

Reaction Time

Attention and concentration (AC) Digit Span Forward

Digit Span Backward

Executive functions (EF) Wisconsin Card Sorting Test

Table 2

Means and standard deviations of descriptive variables

INS, n= 20 INSBZ, n= 20 GS n= 20F ratio

Variable M (S.D.) M (S.D.) M (S.D.) (2,57)

Sociodemographic

Age (years) 61.70 (6.43) 62.30 (5.89) 63.35 (5.15) 0.41

Education (years) 13.60 (5.15) 11.65 (2.76) 13.35 (3.67) 1.42

Mental abilities

Mini-Mental

State (MMS)

29.10 (1.12) 28.75 (1.25) 28.85 (1.04) 0.50

Vocabulary

(standard score)

12.65 (3.84) 12.00 (3.09) 13.30 (2.36) 0.85

Information

(standard score)

10.15 (3.51) 10.00 (3.01) 11.50 (3.40) 1.24

Sleep

Sleep Impairment

Index (SII)

17.90 (4.85)a 16.85 (4.55)b 1.60 (1.88) 104.59*

Psychological

BDI 9.00 (4.48)a 9.40 (7.16)b 1.75 (1.68) 15.01*

BAI 9.10 (8.38)a 8.60 (5.44)b 1.20 (1.47) 11.51*

INS = Insomniacs without benzodiazepine, INSBZ = insomniacs with

benzodiazepine, GS = good sleepers.

Adapted from Vignola et al. [8].a Significant difference between INS and GS ( P < .01).b Significant difference between INSBZ and GS ( P < .01).

* P< .01.

C.H. Bastien et al. / Journal of Psychosomatic Research 54 (2003) 39–49 41

Neuropsychological measures

Factorial analysis described by Vignola et al. permits the

grouping of cognitive function measures used in the battery

of tests into four factors. A comprehensive list of the

neuropsychological instruments used in the present study

are noted in Table 1.

Memory was evaluated using the Verbal Paired Asso-

ciates Tests I and II [26] and Visual Reproduction Tests I

and II [26], which measure, respectively, verbal and visual

memory. The first administration of these two tests requires

immediate recall of the items presented, whereas the second

tests delayed recall. Attention and concentration were eval-

uated through the aid of Digit Span tests [26] in which

repetition of numbers in order (Digit Span Forward) and in

inverse order (Digit Span Backward) was required. Inverse

order recall is also a measure of the ability to perform an

operation in working memory. Psychomotor speed was

measured using four different tests. The Digit Symbol

Substitution Test [27] measures visuo-motor speed and

coordination. The Purdue Pegboard [28] was used to meas-

ure manual dexterity. The Trail Making Tests A and B [29]

require complex visual surveying and measure psychomotor

speed, agility, alternating visual attention and mental flex-

Table 4

Means and standard deviations of subjective sleep variables

INS INSBZ GS

Variable M S.D. n M S.D. n M S.D. n df F

SOL 78.00 78.19 20 66.55 59.11 20 39.00 37.19 20 2, 57 2.19

WASO 54.44 45.67 18 70.79 83.72 19 33.8 39.50 20 2, 54 1.89

TWT 172.00 126.93 20 185.89 109.31 19 97.75 102.73 20 2, 56 3.44*

TST 286.40 115.63 20 264.21a 113.84 19 372.35 107.12 20 2, 56 5.10**

Freshness upon awakening 2.58b 0.79 12 3.00a 1.13 12 3.18 1.25 11 2, 32 9.41**

Soundness 2.08 0.79 12 3.08 1.32 13 3.18 1.25 11 2, 33 3.32*

SE 63.32 25.48 20 58.60a 24.15 19 80.96 21.38 20 2, 33 4.86*

FNA 2.78 1.35 18 2.12 1.90 17 3.37 2.93 19 2, 56 1.47

INS= Insomniacs without benzodiazepine, INSBZ= insomniacs with benzodiazepine, GS = good sleepers.a Difference between INSBZ and GS.b Difference between INS and GS.

* P < .05.

** P < .01.

Table 5

Correlations between objective and subjective measures of sleep

SubjectiveObjective measures

measures SL TWT TST FEN SE % S 1 % S 2

Good sleepers (GS)

SL

WASO

TWT

TST

Fre

Sou

SQ

SE

FNA

Drug-free insomniacs (INS)

SL .66** .45*

WASO .47*

TWT .57**

TST � .61**

Fre

Sou

SQ

SE � .57**

FNA

SOL TWT TST FEN SE % S 1 % S 2

Benzodiazepine users (INSBZ)

SOL

WASO

TWT .52* � .48*

TST .46*

Fre

Sou

SQ

SE � .48* .46*

FNA

SOL=Sleep-onset latency, WASO=wake after sleep-onset, TWT= total

wake time, TST= total sleep time, FNA= frequency of night awakening,

SE = sleep efficiency, % S 1 = time spent in Stage 1, % S 2 = time spent in

Stage 2, Fre = freshness upon awakening, Sou = soundness of sleep,

SQ= sleep quality.

* P< .05.

** P< .01.

Table 3

Means and standard deviations of objective sleep variables

INS, n= 20 INSBZ, n= 20 GS, n= 20F ratio

Variable M (S.D.) M (S.D.) M (S.D.) (2,57)

SOL 29.07 (23.61) 27.06 (15.50) 27.54 (19.91) 0.06

TWT 127.91 (58.59) 126.06 (58.59) 100.79 (47.01) 1.62

FNA 3.90 (3.24) 3.25 (2.20) 2.75 (2.15) 0.99

SE 91.78 (88.26) 72.61 (11.96) 80.60 (8.55) 0.69

TST 319.66 (81.29) 329.33 (60.51) 372.52 (38.12) 4.05

% Stage 1 11.85 (5.90) 10.56 (4.91) 10.61 (6.32) 0.32

% Stage 2 62.79 (10.08) 60.98 (9.07) 66.35 (9.86) 1.57

INS = Insomniacs without benzodiazepine, INSBZ = insomniacs with

benzodiazepine, GS =Good sleepers.

C.H. Bastien et al. / Journal of Psychosomatic Research 54 (2003) 39–4942

ibility. Wilkinson’s Four-Choice Reaction Time Test [30]

was used to evaluate reaction time and vigilance. Finally,

executive function was measured with the Wisconsin Card

Sorting Test [31] that measures abstraction skills, mental

flexibility and the ability to maintain a pattern of responses.

Several instruments permitted the measurement of sub-

jective perception of daytime functioning. Participants used

a visual analogue scale (VAS) of 100 mm to indicate their

level of wakefulness, energy and mood. While the actual

state scale (ASS) permitted participants to evaluate their

level of fatigue, anxiety, motivation, concentration as well

as their performance expectations, the evaluation of per-

formance scale (EPS) asked participants to indicate the

quality of their performance and their satisfaction with their

performance, and to compare their performance with that of

other individuals of the same age who possess the same

actual capacities.

Procedures

Recruitment, informed consent and remuneration

Participants were recruited by placing advertisements in

local newspapers. After completing a telephone interview,

interested individuals were scheduled for a in-house inter-

view during which they were asked to sign a consent form

and to then complete several questionnaires and assess-

ment procedures aimed at screening them for their eligib-

ility. The in-house screening included a psychological

evaluation in order to determine the presence of psycho-

pathology, a clinical sleep evaluation and a medical exam.

Evaluations were performed by a variety of examiners,

including graduate students in psychology and a physician.

Eligible participants were enrolled into the study and were

compensated for their participation. A sum of CAN$150

was offered to GS to compensate them for their participa-

tion in the study, while a nonpharmacological treatment

for insomnia was offered to members of the other groups

at no cost.

In lab study procedures

Participants retained for the study then spent three

consecutive nights in the sleep laboratory. Subjects arrived

at the lab at 8:00 p.m. and slept according to their normal

schedule (i.e., they selected their bedtime and rise time).

Upon awakening, participants completed a SD. The battery

of neuropsychological tests was administered after the first

of the three nights in the laboratory, approximately 1 h after

Table 6

Correlations between objective measures of performance and objective sleep quality

Objective measures

Functions SOL TWT TST FNA SE % S 1 % S 2 % S 4

Good sleepers (GS)

VVM � .48a,* � .45a,* .51b,*

� .53b,* � .45b,*

PS � .48c,*

AC

EF � .79d,**

Drug-free insomniacs (INS)

VVM � .53b,* .52a,* � .59a,**

PS .69e,** � .46c,* .61d,**

.56c,*

AC � .58f,**

EF

Benzodiazepine users (INSBZ)

VVM .49b,* .60a,**

PS .48c,*

AC

EF

SL=Sleep-onset latency, TWT= total wake time (SOL+TWT1), TST= total sleep time, FNA= frequency of night awakening, SE = sleep efficiency,

% S 1 = time spent in Stage 1, % S 2 = time spent in Stage 2, % S 4 = time spent in Stage 4, VVM=visual and verbal memory, PS = psychomotor speed,

AC= attention and concentration, EF = executive functions.a Delayed recall.b Immediate recall.c Purdue Board.d Wisconsin Card Sorting Test.e Wilkinson reaction time.f Digit Span (Backward).

* P < .05.

** P < .01.

C.H. Bastien et al. / Journal of Psychosomatic Research 54 (2003) 39–49 43

rising (between 7:30 and 9:00). The EASS and the VAS

were administered prior to neuropsychological evaluation.

The EPS was administered after each test as well as at the

end of the neuropsychological evaluation. This evaluation

lasted between 1.5 and 2 h.

Results

Descriptive analysis

Demographic and clinical profile data

Descriptive statistics for each of the sociodemographic,

psychological, general ability and sleep variables for the

three groups of participants are presented in Vignola et al.

[8] and are adapted in Table 2. Univariate analysis of

variance performed for each of these variables demonstrates

equivalence of age, occupation, education and general

mental abilities. Differences between groups were identified

for measures of insomnia severity, anxiety and depression.

Tukey multiple comparison tests revealed that the two

insomnia groups, as compared to good sleepers, exhibited

greater symptom severity on the ISI (P < .01), Beck Anxiety

Inventory (BAI; P < .01) and the BDI (P < .01). The two

insomnia groups did not differ in terms of scores obtained

on the ISI, BAI or BDI.

A MANOVA was computed on the objective sleep

measures to determine whether the three groups differed

for those variables. Means and standard deviations for those

variables are presented in Table 3. There was no significant

difference among the three groups on PSG measures,

including sleep onset latency, total wake time, total sleep

time, frequency of night awakening, sleep efficiency and the

percentages of time spent in Stages 1 and 2.

One-way ANOVAs computed on the subjective sleep

measures revealed significant differences between group.

Means and standard deviations for those variables are

presented in Table 4. Post-hoc comparisons revealed that

INSBZ had a longer total wake time, a shorter total sleep

time, a lower score for freshness upon awakening and

soundness of sleep than GS. INS had a lower score than

GS for freshness upon awakening.

Group differences on the subjective and objective meas-

ures of cognitive performance have been reported in Vignola

et al. [8]. In general, their results showed that individuals

with insomnia, both medicated and unmedicated, performed

Table 7

Correlations between objective measures of performance and subjective sleep quality

Subjective sleep measures

Functions SOL TWT TST Fre Sou SQ SE FNA

Good sleepers (GS)

VVM � .52a,* � .61b,* .51a,*

.52c,*

PS � .49d,* � .58d,* .57d,** .63d,*

AC � .53e,* .76e,** .66f,* .56e,*

.67f,* .69e,*

EF

Drug-free insomniacs (INS)

VVM .45c,* � .52c,* � .60c,* � .48c,*

PS

AC

EF

Benzodiazepine users (INSBZ)

VVM � .49c,* � .57c,* .46c,*

� .55a,**

PS

AC

EF

SOL= sleep-onset latency, TWT= total wake time, TST= total sleep time, Fre = freshness upon awakening, Sou = soundness of sleep, SQ= sleep quality,

SE = sleep efficiency, FNA= frequency of night awakening, VVM=visual and verbal memory, PS = psychomotor speed, AC= attention and concentration,

EF = executive functions.a Delayed visual reproduction.b Delayed verbal memory.c Immediate visual reproduction.d Trail Making Test.e Digit Span (Backward).f Digit Span (Forward).

* P < .05.

** P < .01.

C.H. Bastien et al. / Journal of Psychosomatic Research 54 (2003) 39–4944

worse than good sleepers on the attention/concentration

factor. There were no other objective evidence of perform-

ance impairments. Subjectively, unmedicated insomniacs

had lower performance expectancies and rated their perform-

ance more negatively relative to medicated insomniacs and

good sleepers. Again, although interesting, these results did

not investigate any interrelationships between the subjective

and objective performance of sleep and cognitive functions

among the three groups.

Correlational analyses: the associations between sleep and

neuropsychological measures

These data were analyzed using a correlational approach.

The significance level used was .05 (a= .05). The Spearman

coefficient was utilized for the four nonparametric variables

(Visual Reproduction I and II, Forward Digit Span and

Backward Digit Span), while the Pearson coefficient was

used for the remaining parametric measures.

Objective and subjective quality of sleep

Significant correlation coefficients between objective and

subjective measures of sleep are presented for each group

separately in Table 5. Absolute values of significant cor-

relation coefficients vary between .45 and .66. In INSBZ,

subjective evaluation of sleep parameters is not associated

with objective measures of these same parameters. In INS,

objective difficulties in maintaining sleep are associated

with subjective difficulties initiating and maintaining sleep.

Also, objective difficulties initiating sleep are associated

with subjective difficulties initiating sleep. In INSBZ,

objective difficulties maintaining sleep are associated with

subjective difficulties maintaining sleep.

Table 8

Correlations between subjective performance and subjective quality of sleep

Daytime functioning Cognitive performance

VAS EASS EPS

Sleep Ev En Hu Fa An Mo Co AP Qu Sa Au Re

Good sleepers (GS)

SOL

TWT

TST

Fre � .61* � .78**

Sou � .64* � .66 * .61*

SQ � .65*

FNA

SE

Drug-free insomniacs (INS)

SOL

TWT .50* .46*

TST � .59** .48*

Fre .71** � .85**

Sou

SQ � .63* � .45*

FNA

SE � .50*

Al En Mo Ti An Mo Co Pe Qu Sa Ot Re

Benzodiazepine users (INSBZ)

SOL � .46* � .56*

TWT � .60*

TST

Fre

Sou

SQ

FNA � .59** � .50* � .52* .52* � .50*

SE .49* .57*

VAS= visual analogue scale, EASS= evaluation of actual state mood, EPS = evaluation of performance scale, Al = alertness, En = energy, Mo=mood,

Ti = tiredness, An = anxiety, Mo =motivation, Co = concentration, Pe = performance expectancy, Qu = quality of performance, Sa = satisfaction with

performance, Ot = compared with others, Re = compared to real capacities, SOL= sleep-onset latency, TWT= total wake time, TST= total sleep time,

Fre = freshness upon awakening, Sou = soundness of sleep, SQ= sleep quality, FNA= frequency of night awakening, SE = sleep efficiency.

* P < .05.

** P < .01.

C.H. Bastien et al. / Journal of Psychosomatic Research 54 (2003) 39–49 45

Objective performance and objective sleep quality

Significant correlation coefficients identified between

objective performance measures and quality of sleep

measures are depicted in Table 6. The correlations

observed between objective performance measures and

the percentage of time spent in Stages 3–4 sleep are

not presented due to the low proportion of time spent in

these stages in participants. Absolute values for the

significant correlation coefficients vary between .45 and

.79. For GS and INS, difficulties in initiating sleep are

associated with an alteration of verbal memory. This

difficulty is also associated with poorer performance on

executive function tests in GS and a change in psycho-

motor speed, attention and concentration in INS. Difficult-

ies maintaining sleep are associated with alterations in

psychomotor speed in GS and INS, and deterioration of

verbal memory in GS. In INSBZ, difficulties initiating

sleep appear to be associated with better performance in

verbal memory tasks.

Objective performance and subjective sleep quality

Significant correlation coefficients between subjective

sleep parameters and objective measures of cognitive per-

formance and significant relationships are illustrated in

Table 9

Correlations between objective and subjective measures of performance

Daytime functioning Cognitive performance

VAS EASS EPS

Functions Al En Mo Ti An Mo Co Pe Qu Sa Ot Re

Good sleepers (GS)

VVM .54a,* .63b,** .49b,* .45c,* .46c,*

.46c,*

PS � .54d,* � .52e,* .45f,* .48f,* .52f,* � .47d,*

� .48e,* � .60d,**

.44d,*

AC � .48g,* .46h,*

� .47h,*

EF .67i,** � .60j,** � .52j,* � .70j,** � .48j,*

� .54j,*

Drug-free inomniacs (INS)

VVM .70c,** .59c,** .52c,*

PS

AC .52j, *

EF

Benzodiazepine users (INSBZ)

VVM � .62c,** .48b,* .50k,* .46b,*

.56b,*

PS � .46l, * � .60l,**

AC .45h,*

EF

VAS= visual analogue scale, EASS= evaluation of actual state mood, EPS = evaluation of performance scale, Al = alertness, En = energy, Mo=mood,

Ti = tiredness, An = anxiety, Mo =motivation, Co = concentration, Pe = performance expectancy, Qu = quality of performance, Sa = satisfaction with

performance, Ot = compared with others, Re = compared to real capacities, VVM=visual and verbal memory, PS = psychomotor speed, AC= attention and

concentration, EF = executive functions.a Immediate visual recall.b Delayed verbal recall.c Delayed visual reproduction.d Trail Making Test B.e Trail Making Test A.f Purdue Board.g Digit Span (Forward).h Digit Span (Backward).i Wisconsin (number of categories).j Wisconsin (perseveration).k Immediate verbal recall.l Wilkinson Reaction Time Test.

* P < .05.

** P < .01.

C.H. Bastien et al. / Journal of Psychosomatic Research 54 (2003) 39–4946

Table 7. Absolute values of significant correlation coef-

ficients vary between .45 and .76. In GS, the subjective

depth, quality and efficiency of sleep are associated with

better performance on attention and concentration tests,

but poorer memory performance. Subjective difficulties

in initiating sleep are associated with alterations in

memory, attention and concentration. In GS, subjective

difficulties in initiating and maintaining sleep appear to

be associated with better psychomotor speed. Finally,

subjective difficulties maintaining sleep are associated

with memory alterations. In INS, visual memory

improves when subjective sleep depth increases, but

diminishes when subjective difficulties in maintaining

sleep increase. In INSBZ, subjective difficulties initiating

and maintaining sleep are associated with an alteration in

visual memory.

Subjective performance and subjective quality of sleep

Table 8 illustrates the significant relationships between

subjective measures of sleep quality and subjective meas-

ures of daytime function. Absolute values of significant

correlation coefficients vary between .45 and .85. In INSBZ

and INS, the impression of having experienced deep restor-

ative sleep is associated with a better evaluation of daytime

functioning. For INS, temporal indicators of sleep quality

are associated with a more negative evaluation of daytime

functioning. As well, expectations of INS towards their

performance increase when they have the impression of

having slept poorly. For INSBZ, only the number of

nocturnal awakenings is associated with a more negative

evaluation of daytime functioning. On the other hand,

subjective difficulties initiating and maintaining sleep are

associated with a more negative subjective evaluation of

performance on neuropsychological tests.

Objective performance and subjective performance

Significant relationships and correlation coefficients

between subjective measures of daytime functioning and

performance on tests, and objective measures of perform-

ance on tests are presented in Table 9. Absolute values of

significant correlation coefficients vary between .44 and .70.

In INSBZ, good performance on tests of memory, attention,

concentration and executive function is associated with a

higher subjective evaluation of daytime functioning. Per-

formance on memory, psychomotor speed and executive

function tasks was also related to a higher subjective

evaluation of performance on neuropsychological tests.

For the two insomnia groups (INS and INSBZ), however,

better subjective evaluation of daytime functioning was not

associated with better cognitive performance, and only

performance on memory tasks was associated with subject-

ive evaluation of performance on tests. In addition, for

INSBZ, a subjective negative evaluation of daytime func-

tioning was associated with better objective performance.

Discussion

The goal of the present study was to examine the

relationship between objective and subjective sleep quality

and daytime performance in elderly good sleepers, or suffer-

ing from chronic insomnia and who were either using or not

BZs as a sleep aid. The first goal was to verify the presence

of a positive relationship between cognitive performance and

objective sleep quality. It would appear that certain objective

sleep parameters are associated with different aspects of

cognitive performance. In good sleepers and drug-free

insomniacs, a good night’s sleep is associated with better

cognitive performance. These results correspond with earlier

studies that have shown an association between the quality of

sleep and performance on certain tasks [16–18]. The obser-

vation that a shorter sleep latency is associated with poorer

performance on verbal memory tasks in BZ users could be

attributable to the persistence of the drugs’ sedative effect at

the moment of test completion. However, Vignola et al. [8]

found that BZs did not affect sleep after prolonged use,

suggesting the development of a tolerance to the drugs. Other

authors, on the other hand, have suggested continued effec-

tiveness of BZs even after long-term use [9]. In addition, it

seems that only partial tolerance to some effects of BZs on

memory occurs [32].

The hypothesis that subjective sleep quality is associated

with better cognitive performance is also supported by the

results of the present study. In fact, it appears that good

sleepers and chronic insomnia sufferers using BZs perform

better on certain tasks when they have the impression of

having slept well. The relationship between performance on

attention tasks and subjective sleep quality in good sleepers

supports results obtained by Vignola et al. [8]. However, in

insomnia sufferers, better performance on visual memory

tasks following a subjective bad night could be due to the

fact that these individuals invest more effort in maintaining

good performance when they think they have slept poorly.

These results corroborate those obtained by Broman et al.

[18] and Schneider-Helmert [34], according to whom,

people suffering of insomnia have a tendency to compensate

for their cognitive deficits by increasing their efforts, par-

ticularly where visual tasks are concerned. In fact, the

results indicate that untreated insomnia sufferers base their

evaluation of their overall cognitive performance on their

judgment of performance on a single visual memory task.

The third objective of this study was to test for a

relationship between cognitive performance and subjective

evaluation of daytime performance. It seems that the three

groups of participants subjectively evaluate their daytime

functioning in a way that corresponds with certain aspects of

their actual performance, but the nature of this relationship

varies as a function of group. In good sleepers, a stronger

correspondence between their evaluation of daytime per-

formance and actual performance appears. In the two groups

of insomnia sufferers, the absence of a relationship between

daytime functioning and performance on tests indicates that,

C.H. Bastien et al. / Journal of Psychosomatic Research 54 (2003) 39–49 47

even though there is an objective alteration of performance

that appears to be related to a poorer objective sleep quality

in these individuals, subjective complaints of daytime func-

tioning, regardless of medication use, do not appear to be

associated with an objective cognitive alteration. This phe-

nomenon of discrepant subjective and objective evaluations

could be related to false beliefs concerning daytime con-

sequences of insomnia [8,20].

Finally, the hypothesis that subjective sleep quality is

associated with subjective evaluation of daytime perform-

ance was also supported by the observed correlations. Once

again, this relationship varies as a function of group

observed. In good sleepers and unmedicated insomnia

sufferers, the impression of having slept well appears more

important than subjective sleep duration in terms of its

influence on functioning upon awakening. However, the

fact that the level of alertness is associated with a shorter

sleep duration in people with insomnia could reflect the

phenomenon of cortical activation described by Bonnet and

Arand [33]. Some researchers propose that this activation

could further interfere with certain aspects of cognitive

performance as well as the ability to channel energy [8]. It

appears, in fact, that insomnia sufferers expend more energy

than good sleepers to overcome their fatigue [18]. As such,

they report investing greater effort than do good sleepers to

maintain performance levels rather than succumb to fatigue

after a poor night of sleep [18]. The phenomenon of

compensation could explain the fact that the expectations

insomnia sufferers have regarding their performance

increase when the feel they have slept poorly [18,34].

Furthermore, BZ users evaluate their performance on neuro-

psychological tests more favourably when they have the

impression of having slept well. Some authors have in fact

suggested that prolonged use of BZs leads to overestimation

of sleep time and mental capabilities [11]. This effect on the

perception of sleep and performance could be attributable to

anterograde amnesia associated with BZ use.

Results of the present study also indicate that the rela-

tionship between objective and subjective measures of sleep

quality differ from one group to another. While untreated

insomnia sufferers correctly subjectively identify their

objective difficulties initiating and maintaining sleep,

chronic BZs users only subjectively recognize their dif-

ficulties maintaining sleep. In good sleepers, no relationship

appears to exist between subjective and objective sleep

difficulties. It is thus possible that people with insomnia

perceive variations in their sleep better than good sleepers.

This could be the result of elevated cortical activity observed

in insomnia sufferers. Similarly, BZs used in the treatment of

insomnia could diminish cortical activation levels and, con-

sequently, alter the perception of sleep [33].

The generalizability of the present results may be limited

owing to several factors. First, the moderately small sample

size per group limits the power of the statistical analyses

used to detect significant relationships between the varia-

bles. In addition, the participants consisted of elderly

persons in excellent physical and psychological health

who are not likely representative of the general population

of elderly individuals. Furthermore, several authors have

demonstrated that the sleep of individuals evaluated in a

laboratory setting is different than that observed in their

home [35]. More specifically, the first night spent in the

laboratory is usually considered a period of adaptation.

Consequently, the sleep measures obtained at this time are

probably not representative of the typical sleep quality of

participants. This procedure increases reactivity to the

experimental context and could be responsible for factors

such as the increase in psychomotor speed witnessed in

good sleepers after a bad night’s sleep. The desire to

perform well on tests, despite the impression of not having

slept well, may have contributed to increased efforts put

forth by the participants on the tasks in question.

Despite these limitations, it is still possible to conclude

that daytime performance and sleep quality are related, but

in a manner that differs depending upon whether individuals

are good sleepers, insomnia sufferers without treatment, or

those using BZs to treat their insomnia. Some of the

observed relationships support the hypothesis of a height-

ened activation level in both groups of insomnia sufferers.

Furthermore, support was found for the hypothesis that

people with insomnia compensate for their daytime dif-

ficulties by investing greater effort. It is thus important to

consider the phenomena of cortical activation and com-

pensation when considering treatment. Given the secondary

effects associated with long-term utilization of BZs, it is

particularly pertinent to question their actual efficacy in

improving sleep and daytime performance. Results obtained

in this study highlight the importance of examining non-

pharmacologic alternatives to treatment. For example, beha-

vioural-cognitive treatment represents a viable alternative in

so far as it addresses the modification of sleep habits and

false beliefs surrounding sleep.

Acknowledgments

Preparation of this article was supported in part by the

National Institute of Mental Health Grant #MH55469 and

Fonds de la recherche en sante du Quebec (FRSQ).

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