Running Head: Frequency of insomnia in OSAHS
Frequency of insomnia report in patients with obstructive sleep apnoea hypopnea
Smith, Simon PhD1., Sullivan, Karen PhD2., Hopkins, Wendy, BPsych(Hons)2, & Douglas,
1 = The Prince Charles Hospital, Brisbane
2 = Queensland University of Technology, Brisbane
Financial assistance for the conduct of this project was provided by the School of
Psychology and Counselling at Queensland University of Technology and is gratefully
acknowledged. The writing up of this work was partly funded by a manuscript completion
grant awarded to Karen Sullivan by the School of Psychology and Counselling,
Queensland University of Technology.
Ethical clearance for this project was granted by The Prince Charles Hospital Human
Research Ethics Committee and the Queensland University of Technology Human
Research Ethics Committee.
Correspondence concerning this article should be addressed to Simon Smith at the School
of Psychology, University of Queensland, St Lucia Q 4070 AUSTRALIA, Fax +617 3365
4466 Tel +617 3365 6408. Electronic mail should be sent to email@example.com
Frequency of Insomnia in OSAHS 2
Insomnia and Obstructive Sleep Apnoea Hypopnea Syndrome (OSAHS) are the
two most common sleep disorders, and both have significant associated health costs.
Despite this, relatively little is known about the prevalence or impact of Insomnia in those
with OSAHS, although a recent suggested there may be substantial comorbidity between
these disorders . The primary aim of this study was to further explore the prevalence of
Insomnia in OSAHS. A secondary aim was to assess the effect of factors that may impact
on both conditions, including mood and sleep-beliefs. Consecutive patients referred to an
accredited Sleep Investigations Unit (n = 105) completed a brief standardized battery of
validated questionnaires assessing sleep-related variables and mood. Results showed a
high rate of prevalence of clinical Insomnia in this OSAHS population, and a strong
positive correlation between OSAHS and insomnia symptom severity. Further, OSAHS
patients with comorbid Insomnia had increased levels of depression, anxiety and stress
compared to patients with OSAHS-only, and both patient groups reported similar and
significant levels of dysfunctional beliefs about sleep. Findings in relation to habitual
sleep, assessed using subjective (diary) and objective criteria (PSG), were mixed but
generally showed greater sleep disturbance among those with OSAHS-plus compared to
those with OSAHS-only. Overall these findings suggest that comorbidity of Insomnia in
OSAHS patients may lead to increased OSAHS severity and that patients with both
conditions may experience more symptoms relating to depression, anxiety and stress.
These findings underscore the need for insomnia assessment and management services,
even in clinics that primarily service patients with OSAHS.
Keywords: Insomnia, Obstructive Sleep Apnea-Hypopnea Syndrome, Sleep disorders.
Prevalence of Insomnia in OSAHS 1
Obstructive Sleep Apnoea Hypopnea Syndrome (OSAHS) and Insomnia are the
two most common sleep disorders [2,3], yet the co-occurrence and potential for interaction
between OSAHS and Insomnia has rarely been examined. Findings from preliminary
studies suggest there may be a comorbid relationship between these two disorders .
Indeed, a relationship between insomnia and OSAHS has been demonstrated previously in
a range of samples including the elderly , patients with Post-Traumatic Stress Disorder
, and those seeking treatment for sleep problems in primary care  and sleep clinic
Estimates of percentage of OSAHS patients who also have insomnia range from
8% (primary care sample ) to between 29 and 43% (older adults ). Of particular
relevance to this study however, is the finding that between 25 and 50% of sleep clinic
clients referred for investigation of OSAHS have been found to have comorbid insomnia [1,
7]. The finding that as many as one in two OSAHS patients seen at sleep clinics may have
concurrent insomnia suggests there may be a significant relationship between OSAHS and
Insomnia, however specific limitations of past research need to be addressed before the
nature of this relationship can be more clearly understood.
A limitation of the two OSAHS-insomnia studies conducted previously in sleep
clinic settings relates to the assessment and diagnosis of insomnia. For example, although
Krakow et al. found that 50% of patients presenting for investigation of sleep-disordered
breathing exhibited significant Insomnia symptoms, a three-item scale only was used to
diagnose Insomnia . This scale is not a well-established tool for the assessment of
insomnia. In the study by Sahai, Staats and Olsen , 24 out of 99 patients diagnosed with
OSAHS via PSG were found to have clinically significant Insomnia on the basis of case
note review. However, the Sahai et al. study  was retrospective and may have been
Prevalence of Insomnia in OSAHS 2
limited by the quality or variability of data recorded in patient files, particularly in relation
to the assessment of insomnia. In both studies, the use of unpublished or unvalidated
Insomnia assessment tools may have resulted in over- or under-inflation of Insomnia
prevalence estimates. Finally, it should be noted that although both previous studies used
conventional criteria (ie. PSG data) to assess OSAHS, the assessment of OSAHS in these
studies could have have been improved by the inclusion of other standardised measures of
OSAHS symptoms to assess the subjective severity of the apnea complaint.
Diagnoses of insomnia and OSAHS rely to varying extents on subjective reports of
sleep disturbance. However, variables that have been shown to impact on subjective sleep
complaints have not typically been assessed in previous insomnia-OSAHS studies. That is,
measures of depression, anxiety and dysfunctional sleep-related cognitions have been
shown to be more predictive of subjective sleep complaints than are objective measures of
disturbance . The inclusion of measures to assess variables such as depression may shed
further light on the nature of the relationship between these two disorders, and would
expand previous research in this area. In general, it would seem reasonable to expect
patients with OSAHS and insomnia may report more impairment than those with OSAHS-
only, given that previous research has shown that Insomnia and OSAHS share some
characteristics such as sleep disruption and decreased mood [9-11], and that factors thought
to perpetuate and maintain insomnia include poor sleep habits and dysfunctional sleep
The primary aim of the current study was to investigate the prevalence of
significant Insomnia in a consecutive series of patients presenting to a tertiary care setting
for investigation of suspected OSAHS, and to do so in a manner that addressed a specific
weakness identified in previous OSAHS-insomnia research (specifically, the failure to use
standardized Insomnia assessment tools; the failure to include comprehensive assessment
Prevalence of Insomnia in OSAHS 3
of OSAHS symptoms). Thus, the first hypothesis for this study was that a high proportion
of patients with diagnosed OSAHS would report significant Insomnia. The second aim of
this study was to explore the implications of OSAHS-insomnia comorbidity on factors
known to affect subjective reports of sleep quality (ie. mood and sleep cognition) and sleep
behaviour. Specifically, it was expected that having insomnia plus OSAHS would result in
more adverse health effects than having OSAHS alone.
Participants were consecutive adult patients referred by their general practitioner
for investigation of OSAHS at a Sleep Investigations Unit. One hundred and five patients
were included in the sample (73 males, mean age = 53.91 +/- 13.67 years [range: 18 to
87]). The mean length of sleep disturbance in this sample was 11.97 +/- 10.99 years.
Participants did not receive compensation for their participation.
Measures used in this study were primarily selected to assess signs and symptoms
of Insomnia and OSAHS. Participants completed a battery of four questionnaires
(presented in a latin squares design to reduce order effects) and a sleep diary (the
Pittsburgh Sleep Diary (PghSD)) which was completed over two-weeks. The
questionnaires included in the battery were: the Survey Screen for the Prediction of Apnea
(SSPA), the Insomnia Severity Index (ISI), Depression Anxiety and Stress Scales (DASS)
and the Dysfunctional Beliefs and Attitudes Scale (DBAS-10). All participants went on to
PSG diagnostic study and data on objective sleep parameters were extracted from
consenting patient’s hospital charts. Several of the measures used in this study yield total
and subscale scores (e.g. SSPA, DASS, DBAS) and in most instances both score types
Prevalence of Insomnia in OSAHS 4
were used in statistical analysis unless otherwise stated. A brief description of each
measure including subscale scores follows.
Survey Screen for the Prediction of Apnea (SSPA). The Survey Screen for the Prediction
of Apnea (SSPA ) is a 13-item questionnaire examining the symptoms of OSAHS.
Items are rated on a six-point Likert scale as frequency of occurrence ranging from never
(score of zero) to five to seven times per week (score of four), with a don’t know response
scored as five. The SSPA contains four subscales labelled apnea symptom frequency
(three items), difficulty sleeping (five items), excessive daytime sleepiness (three items),
and narcolepsy symptoms (two items). The reliability of the SSPA has been investigated
previously  and found to be adequate.
Dysfunctional Beliefs and Attitudes About Sleep Scale-10 (DBAS –10). The short version
of Morin’s Dysfunctional Beliefs and Attitudes about Sleep Scale (DBAS) , the DBAS-
10 , was used in this study. The DBAS-10 is a 10-item analog scaled questionnaire that
focuses on respondent’s personal rating of statements of beliefs and attitudes about sleep.
It measures five subscales: misconceptions of the causes of insomnia; misattributions or
amplifications of the consequences of insomnia; unrealistic sleep expectations; diminished
perceptions of control and faulty beliefs about sleep-promoting practices . The DBAS-
10 comprises of three factors ; beliefs about the immediate negative consequences of
insomnia (five items); beliefs about the long-term negative consequences of insomnia
(three items) and beliefs about the need for control over insomnia (two items). Response
options range from strongly disagree to strongly agree with respondents asked to place a
mark along the ten centimeter line to indicate the extent of agreement with given
statements. For the three factors, higher scores indicate increased dysfunctional beliefs and
attitudes about sleep. Adequate reliability has been reported for the three DBAS-10 factors
, and the validity of factors has been demonstrated previously (i.e., DBAS-10 factor
Prevalence of Insomnia in OSAHS 5
scores are sensitive to treatment effects and are highly correlated with the DBAS total
Insomnia Severity Index (ISI). The Insomnia Severity Index (ISI1; ) is a self-report
questionnaire measuring a time interval of two weeks. Consisting of seven items
measuring patients’ perceptions of their Insomnia, participants’ rate ISI items on a scale of
not at all (score of zero) to very much (score of four). ISI items correspond generally to
diagnostic criteria of significant Insomnia according to the DSM-IV. These include the
severity of sleep onset, sleep maintenance and early morning awakenings, satisfaction with
the current sleep patterns, interference with daily functioning, noticability of sleep
impairment and the degree of worry or distress . Scores range from 0 to 28, with higher
scores indicating more severe insomnia. Morin  recommends that scores ranging from
zero to seven be classified as no clinically significant Insomnia, eight to 14 as subthreshold
Insomnia, 15 to 21 as moderate clinical Insomnia and 22 to 28 as severe clinical Insomnia.
The psychometric properties of the ISI (reliability and validity) have been investigated
previously and found to be adequate .
Five additional items originating from an earlier version of the ISI were added to
the index for this study. Four of the items ask respondents to indicate, on a scale of not at
all (zero) to very much (four), the extent to which participants believe racing thoughts,
muscle tension / pain, bad sleep habits and natural aging processes affect their sleep.
These questions were included to assess factors that patients may identify as the cause of
their sleep problem.
The last additional ISI item asks the respondent to circle statements that best apply
to the problems experienced after a poor night’s sleep. Four categories including
statements concerning fatigue and sleepiness, cognitive functioning, mood problems and
1 The ISI was originally known as the Sleep Impairment Index (SII ).
Prevalence of Insomnia in OSAHS 6
physical problems are presented for the patient to circle. This item ascertains the daytime
consequences of the patients sleep problem. The five additional items were not included in
the ISI total score.
Depression Anxiety Stress Scale-21 (DASS - 21). The Depression Anxiety Stress Scales
(DASS ) consists of 21-items measuring the three negative emotional states of
depression (seven items), anxiety (seven items) and stress (seven items). The DASS-21
was included in this study to provide a screening assessment of the level of
psychopathology among participants, as an indicator of the mental health of participants.
Using a four-point Likert scale respondents are required to rate the frequency of DASS-21
symptoms over a time frame of the last week. The DASS yields a total score as well as
separate indices of depression, anxiety, and depression and has been normed on an
Australian sample. The psychometric properties (reliability and validity) of the DASS-21
total scores and subscales have been investigated previously and are considered adequate
The Pittsburgh Sleep Diary (PghSD). The Pittsburgh Sleep Diary (PghSD ) is a 24-item
diary measuring the subjective patterns of sleep. The PghSD comprises two components
relating to waketime and bedtime behaviours. The format of the diary contains items
measured on five-point Likert scale, visual analogue scale or fill-in-the-blanks format.
Respondents are required to fill out the sleep diary for 14 consecutive days each morning
and night. The bedtime component of the diary assesses four areas including the timing of
breakfast, lunch and dinner; the consumption of caffeine, alcohol and tobacco; the use of
medications and the timing and duration of exercise and naps. The waketime component
of the diary assesses four areas including the timing of bed, turning out of lights, sleep
onset latency and awakening; the method of final waking; the incidence, duration and
reasons for wake after sleep onset and sleep quality, mood on final awakening and
Prevalence of Insomnia in OSAHS 7
alertness on awakening. The PghSD has adequate test-retest reliability, is sensitive to
differences in sleep patterns due to age, gender, weekends, personality and circadian type,
and yields moderate stable correlations with PSG measures of sleep .
Patients were invited to participate in the study by their Sleep Physician during
routine clinical appointments. The questionnaire battery included a patient information
sheet detailing the study and their involvement along with a consent form requiring the
patient signature confirming voluntary involvement in the study. The questionnaire battery
was given to the patients who agreed to take part in the study and was completed on site.
The sleep diary was taken home to complete and returned to the hospital via return-paid
mail. With the participants’ consent, information regarding respiratory disturbance index
(RDI; a measure of OSAHS severity), sleep efficacy (%), and age was then obtained from
their hospital charts.
Prevalence of Insomnia in OSAHS 8
Data Analysis Review
The data analysis for this project was conducted using SPSS for windows (version
11) statistical software. A small amount of missing data on age and RDI variables (n = 1
and n = 5 respectively) was replaced with the series mean in accordance with procedures
described in Tabachnick and Fidell . All tests of statistical significance were calculated
at the alpha level of 0.05. Effect sizes between groups were calculated with eta squared
(?²) or Cram?r’s V.
Prevalence of Insomnia in OSAHS patients
To examine the prevalence of significant Insomnia in patients with OSAHS, data
was sorted by selecting those patients that met the research criteria for significant
Insomnia. The criteria for Insomnia included 1) an ISI score of 15 or more (corresponding
to moderate Insomnia) 2) length of sleep complaint longer than 6 months 3) SOL or
WASO longer than 30 minutes on PSG and 4) at least one negative daytime consequence
of sleep disturbance. The criterion for the diagnosis of OSAHS was derived from PSG data
and review by a sleep physician, reflecting routine clinical practice at the study site. There
were three patients who did not subsequently receive a diagnosis of OSAHS and data from
these participants was therefore excluded from subsequent between group analyses. A
frequency table was produced to assess the number of patients who had significant
Insomnia out of the OSAHS patient group. As expected there was a high prevalence of
Insomnia in OSAHS patients, with 41 (39%) of the OSAHS patients having significant
Insomnia according to the research criteria.
Impact of comorbid OSAHS and Insomnia
Preliminary analyses were calculated to explore the general relationship between
sleep symptom measures, prior to exploring comorbidity or testing for group differences.