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Original Article
Clinical and polysomnographic characteristics and response to continuous
positive airway pressure therapy in obstructive sleep apnea patients with
nightmares
Ahmed S. BaHammam
⇑
, Sohaila A. Al-Shimemeri, Reda I. Salama, Munir M. Sharif
University Sleep Disorders Center, College of Medicine, King Saud University, Riyadh, Saudi Arabia
article info
Article history:
Received 2 June 2012
Received in revised form 18 July 2012
Accepted 23 July 2012
Available online xxxx
Keywords:
Obstructive sleep apnea
Nightmares
Continuous positive airway pressure
Rapid eye movement sleep
Dream
Recall
abstract
Objective: To assess the characteristics of obstructive sleep apnea (OSA) patients with nightmares and the
effects of continuous positive airway pressure (CPAP) therapy on nightmares.
Methods: Consecutive patients referred with a clinical suspicion of OSA underwent attended overnight
sleep studies. OSA and nightmares were diagnosed according to the American Academy of Sleep Medicine
(AASM) criteria, and CPAP titration was performed in accordance with the AASM guidelines. A follow-up
visit was performed 3 months later, and the patients with nightmares were divided into two groups:
group 1 used CPAP with good compliance, whereas group 2 refused CPAP treatment and did not use other
alternative treatments for OSA.
Results: The study included 99 patients who had been diagnosed with OSA with nightmares. Their mean
age was 47.2 ± 11.2 years, and they had a mean apnea–hypopnea index (AHI) of 36.5 ± 34.3/h. Also
included were 124 patients with OSA without nightmares. The mean age of these patients was
45.4 ± 13.9 years, and they had a mean AHI of 40.2 ± 35/h. The patients with nightmares had a signifi-
cantly higher AHI during rapid eye movement sleep (REM) compared with the patients without night-
mares (51.7 ± 28.1 vs 39.8 ± 31.9/h). Logistic regression analysis revealed that the REM-AHI and
interrupted sleep at night were independent predictors of nightmares in the OSA patients. Nightmares
disappeared in 91% of the patients who used CPAP compared with 36% of patients who refused to use
CPAP (p< 0.001).
Conclusion: Nightmares in OSA patients are associated with a higher REM-AHI. CPAP therapy results in a
significant improvement in nightmare occurrence.
Ó2012 Elsevier B.V. All rights reserved.
1. Introduction
Fragmentation of sleep caused by recurrent episodes of upper
airway obstruction and episodic desaturations in patients with
obstructive sleep apnea (OSA) may provoke parasomnias [1,2].
Researchers have hypothesized that a shortage of oxygen during
sleep may provoke nightmares [3]. In a unique study, Boerner re-
ported that blocking the nose and mouth with a cloth induced
nightmares [4]. Because OSA is a common cause of intermittent
hypoxemia, the effect of OSA on dreaming has become a topic of
research interest. Most of the previous studies that have examined
the effect of OSA on dream recall have been retrospective in nature
and have reported contradictory results. Although some
investigators have reported less dream recall in OSA patients and
normalization of dream recall occurred following continuous posi-
tive airway pressure (CPAP) therapy, others have reported that OSA
patients have more dreams with emotional content, particularly
violent and aggressive content [5–8]. Only a limited number of
studies have assessed nightmares in OSA patients, and the results
have been contradictory [7,9–11].
The prior studies on nightmares in OSA patients have several
limitations. For example, several studies included patients with
post-traumatic stress disorder (PTSD) [7,9], whereas others were
conducted on students who snored, which does not represent typ-
ical OSA patients [10,11] and limits the generalizability of the re-
sults. Possible explanations for the discrepancies between studies
include the fact that most of the previous studies did not use a stan-
dard definition for nightmares; the use of different patient groups;
and the use of a retrospective method of dream data collection after
patient diagnosis, which may have impacted patients’ dream per-
ceptions. Carrasco et al. proposed two theories to explain the con-
tradictory results in dreams and nightmares in OSA patients [6].
They proposed that the increased arousal in OSA patients might
1389-9457/$ - see front matter Ó2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.sleep.2012.07.007
⇑
Corresponding author. Address: College of Medicine, Department of Medicine,
King Saud University, Box 225503, Riyadh 11324, Saudi Arabia. Tel.: +966 1 467
9179; fax: +966 1 467 9495.
E-mail address: ashammam@ksu.edu.sa (A.S. BaHammam).
Sleep Medicine xxx (2012) xxx–xxx
Contents lists available at SciVerse ScienceDirect
Sleep Medicine
journal homepage: www.elsevier.com/locate/sleep
Please cite this article in press as: BaHammam AS et al. Clinical and polysomnographic characteristics and response to continuous positive airway pressure
therapy in obstructive sleep apnea patients with nightmares. Sleep Med (2012), http://dx.doi.org/10.1016/j.sleep.2012.07.007
increase dream recall, whereas hypoxia might cause cognitive
impairments in OSA patients that might impair dream recall [6].
Previous studies that have addressed the effect of CPAP treat-
ment on dreaming have primarily focused on dream recall. Gross
and Lavie demonstrated that withdrawal of CPAP therapy for one
night resulted in an increased apnea–hypopnea index (AHI) and in-
creased dream recall. However, Gross and Lavie did not study
dream recall before the initiation of CPAP [12]. Another study in
a group of patients with severe OSA demonstrated that treatment
with CPAP decreased dream recall acutely and after 3 months de-
spite an increase in rapid eye movement (REM) density [6]. The ef-
fects of CPAP treatment on nightmares in OSA patients have not
been well explored. OSA patients with nightmares are frequently
seen in our practice. However, the clinical and polysomnographic
(PSG) characteristics of OSA patients with nightmares have not
been properly assessed. Although nightmares are an REM-associ-
ated parasomnia, the association between REM-related OSA and
nightmares has not been explored. Therefore, we designed this
study to assess the characteristics of PSG-diagnosed OSA patients
with nightmares, to compare the results with those of OSA patients
without nightmares and to prospectively study the effects of CPAP
therapy on nightmares.
2. Methods
2.1. Subjects
In the present prospective observational study, consecutive pa-
tients who were referred to the University Sleep Disorders Center
between January 2008 and December 2011 with a clinical suspicion
of OSA based on typical symptoms (e.g. snoring, choking attacks
during sleep, witnessed apnea or excessive daytime sleepiness)
were considered for inclusion if they were diagnosed with OSA
based on PSG, fulfilled the American Academy of Sleep Medicine
(AASM) diagnostic criteria for recurrent nightmares and agreed to
participate in this study. We also selected a group of OSA patients
who did not have nightmares who were matched with OSA patients
with nightmares for age, body mass index (BMI) and gender to com-
pare the clinical and PSG features of the two groups.
Patient histories were obtained, physical examinations were
conducted by a sleep medicine specialist upon the initial assess-
ment and psychiatric assessments were performed by a rotating
psychiatrist. Assessment for psychiatric disorders including
depression and anxiety were done according to the results of the
Mini-International Neuropsychiatric Interview (MINI) [13]. The Ep-
worth Sleepiness Scale (ESS) was used to obtain a subjective
assessment of daytime sleepiness [14]. The bed partner of each pa-
tient or another household member was also interviewed. Patients
with other sleep-related breathing disorders, non-invasive ventila-
tion or home oxygen, a daytime PaO
2
< 70 mmHg or a PaCO
2
>45-
mmHg, congestive heart failure, and psychiatric disorders (e.g.
anxiety, depression or PTSD) [15] and who used psychoactive
drugs or medications that may influence nightmares were ex-
cluded [16]. Patients with hypertension who were on beta-blockers
were also excluded. None of the patients in this study consumed
alcohol. Hypertension was defined as one or more of the following
symptoms: resting systolic blood pressure P140 mmHg, resting
diastolic blood pressure P90 mmHg, and treatment with antihy-
pertensive medication [17]. A diagnosis of diabetes mellitus was
recorded on the clinical history, and the use of diabetes medica-
tions was either revealed by the patient or determined by a review
of the patient’s medical file. This study was approved by the Insti-
tutional Review Board of the College of Medicine at King Saud Uni-
versity, and an informed consent was obtained from all of the
participants.
2.2. Study protocol
Nightmares were diagnosed according to the International Clas-
sification of Sleep Disorders (ICSD 2005), which includes recurrent
episodes of awakening from sleep with recall of intensely disturb-
ing dream mentations (with full alertness on awakening and good
recall of sleep mentation) and one of the following features: de-
layed return to sleep after the episode or occurrence of the episode
in the second half of sleep [18]. The diagnosis of nightmares was
made by a team member before the PSG was performed. In addi-
tion, the assessment of nightmares was performed before the pa-
tients knew the clinical diagnosis of their sleep disorder. The
patients were labeled as having OSA with nightmares if nightmares
occurred at least once per week, whereas patients were labeled as
OSA patients without nightmares if they had no history of
nightmares.
Per our sleep disorders center protocol, CPAP therapy is recom-
mended to all patients who are diagnosed with OSA. Patients who
refuse CPAP treatment receive conservative advice about weight
loss and are referred to otolaryngology for further assessment.
Reassessments of the patients’ nightmares were performed
3 months after the initiation of CPAP therapy, and patients with
nightmares were divided into two groups: group 1 contained the
patients who used CPAP with good compliance, and group 2 con-
tained the patients who refused CPAP treatment and did not use
other alternative treatments for OSA, such as surgery, weight
change by P5% or oral appliances during the follow-up period.
The patients who started medications that could influence night-
mares during the follow-up period were excluded [16]. The CPAP
compliance data were downloaded from built-in smartcards in
the CPAP devices, and good compliance was defined as using CPAP
for >4 h/night for >70% of the recorded period [19]. An improve-
ment in nightmares was defined as a maximum nightmare occur-
rence frequency of once per month.
2.3. Sleep studies
The nocturnal PSG recordings included electroencephalography
(taken at C3M2, C4M1, O1M2, O2M1, F3M2, and F4M1), electro-
oculography, muscle tone (electromyography of the chin and both
legs), electrocardiography, continuous finger pulse oximetry, chest
and abdominal wall movements (thoracic and abdominal belts),
airflow (thermistor and nasal prong pressure transducer), and
snoring (microphone). PSG recording was performed using Alice
5 diagnostic equipment (Respironics, Inc., Murrysville, PA, USA).
Manual scoring of the electronic raw data (i.e. sleep stages and
respiratory events) was manually performed in accordance with
the AASM criteria [20]. The scorer was blind to the clinical findings.
OSA was defined according to the International Classification of
Sleep Disorders (ICSD 2005) [18].
CPAP titration was performed during a therapeutic night in
accordance with the AASM guidelines, and CPAP was offered to
all of the patients [21]. The patients had three training sessions
on the use of CPAP during the first 2 weeks following diagnosis
(day 1, day 7 and day 14). A follow-up session in the CPAP clinic
was performed 12 weeks after the start of CPAP therapy. All of
the patients were provided with the sleep disorders center phone
number to answer their queries and help troubleshoot CPAP ther-
apy-related issues.
2.4. Statistical analysis
All of the data in the text and tables are reported as the
mean ± SD or the percentage (%). Comparisons between OSA pa-
tients with and without nightmares were performed using the
two-tailed Student’s t-test for continuous variables and the
2A.S. BaHammam et al. / Sleep Medicine xxx (2012) xxx–xxx
Please cite this article in press as: BaHammam AS et al. Clinical and polysomnographic characteristics and response to continuous positive airway pressure
therapy in obstructive sleep apnea patients with nightmares. Sleep Med (2012), http://dx.doi.org/10.1016/j.sleep.2012.07.007
chi-square test for categorical variables. If the sample was not
found to have a normal distribution, the Mann–Whitney U-test
for independent samples was used. Significance values were set
at p60.05. To explore associations between independent factors
and nightmares, a preliminary analysis used a univariate logistic
regression model where one explanatory variable was tested in
the model at a time. Variables with significant p-values were sub-
sequently evaluated using a multivariate logistic regression model.
IBM SPSS (Statistical Package for the Social Sciences) Statistics
version 19.0 and MS Excel 2010 were used for all of the data anal-
ysis and management activities.
3. Results
During the study period, 99 patients (51.5% male) were diag-
nosed with OSA with nightmares. These patients had a mean age
of 47.2 ± 11.2 years, a mean BMI of 36.6 ± 9.1 kg/m
2
and a mean
AHI of 36.5 ± 34.3/h. In addition, 124 patients (63.7% male) were
diagnosed with OSA without nightmares. These patients had a
mean age of 45.4 ± 13.9 years, a mean BMI of 35.3 ± 9.4 kg/m
2
and a mean AHI of 40.2 ± 35/h.
Table 1 presents a comparison between the demographics and
symptoms in the OSA patients with and without nightmares. Anal-
ysis of the presenting symptoms revealed that the OSA patients
with nightmares had significantly more frequent complaints of
interrupted sleep at night, choking, early morning headaches and
nocturnal palpitations compared with the OSA patients without
nightmares. The women were older and had a higher BMI than
the men in both of the groups. The distribution of comorbidities
was similar between the two groups. Table 2 presents the PSG find-
ings in the patients with and without nightmares. The patients
with nightmares had a significantly higher AHI during REM com-
pared with the patients without nightmares (51.7 ± 28.1 vs
39.8 ± 31.9/h, p= 0.006). There were no significant differences in
apnea and hypopnea duration during REM and non-REM sleep be-
tween the OSA patients with and without nightmares. There was
no relationship between the severity of OSA based on the AHI or
the time spent with O
2
saturation <90% and the presence of night-
mares (Fig. 1).
The binary logistic regression results are shown in Table 3,
revealing that REM-AHI and interrupted sleep at night were inde-
pendent predictors of nightmares in OSA patients.
3.1. Dream content
Dream content in most patients were related to suffocation. One
patient reported the following: ‘‘He dreamt that he fell in a deep
well and was gasping for breath’’ (male, 40 years, AHI 45/h). An-
other patient dreamt: ‘‘that a person was holding her neck prevent-
ing her from breathing’’ (female, 43 years, AHI 49/h). A third
patient reported: ‘‘I dreamt of drowning in dark water and was
gasping for breath’’ (female, 39 years, AHI 47/h). Most patients
woke up in intense fear and complained of palpitation and diffi-
culty in breathing. There were no reports of violent or abnormal
movements during sleep.
3.2. CPAP effect
Among the patients with OSA and nightmares, 44 patients used
CPAP regularly, whereas 55 patients refused CPAP treatment. None
of the patients underwent upper airway surgery, used oral appli-
ances, changed weight by P5% or started new medications during
the follow-up period.
Table 4 presents a comparison between the OSA patients with
nightmares who used and did not use CPAP. OSA patients who used
CPAP had more severe OSA, which was determined by higher val-
ues for the AHI, the AHI-REM, the AHI-NREM, the desaturation in-
dex and the time spent with SaO
2
<90%. The group who did not use
CPAP had a longer duration of REM sleep. Among the patients who
used CPAP, nightmares disappeared in 40 patients (91%). Among
the OSA patients who did not use CPAP, nightmares disappeared
in 20 patients (36%, p< 0.001).
4. Discussion
This study demonstrated that CPAP therapy results in a signifi-
cant improvement in nightmares in patients with OSA. We also de-
fined some PSG characteristics of OSA patients with nightmares.
Table 1
Baseline characteristics of the obstructive sleep apnea (OSA) patients with and without nightmares.
OSA with nightmare OSA without nightmare
Men Women Total Men Women Total
(n= 51) (n= 48) (n= 99) (n= 79) (n= 45) (n= 124)
Age (years) 44.7 ± 11.7
a
49.9 ± 10.2 47.2 ± 11.2 41.4 ± 13.7
a
52.4 ± 11.5 45.4 ± 13.9
Men 51 (51.5) 79 (63.7)
Body mass index (kg/m
2
) 33.3 ± 7.8
a
40.3 ± 9.1 36.6 ± 9.1 32.1 ± 6.5
a
41.1 ± 11.1 35.3 ± 9.4
Neck circumference 16.2 ± 1.5
a
14.8 ± 1.4 15.5 ± 1.6 15.7 ± 1.2
a
14.8 ± 1.2 15.3 ± 1.3
ESS 11.5 ± 6
a
8.1 ± 5.4 9.9 ± 5.9 10.7 ± 5.8 9.8 ± 5 10.4 ± 5.5
Snoring
b
42 (82.4) 39 (81.3) 81 (81.8) 58 (73.4)
b
25 (55.6) 83 (66.9)
Interrupted sleep at night
b
21 (41.2) 25 (52.1) 46 (46.5)
b
18 (22.8) 17 (37.8) 35 (28.2)
Choking
b
21 (41.2)
a
33 (68.8) 54 (54.5)
b
30 (38) 21 (46.7) 51 (41.1)
Nocturnal palpitations
b
15 (29.4) 22 (45.8) 37 (37.4)
b
12 (15.2)
a
18 (40) 30 (24.2)
Early morning headache
b
20 (39.2)
a
29 (60.4) 49 (49.5)
b
21 (26.6)
a
24 (53.3) 45 (36.3)
Nocturia (P1/night)
b
31 (60.8) 31 (64.6) 62 (62.6)
b
39 (49.4) 21 (46.7) 60 (48.4)
pH 7.4 ± 0 7.4 ± 0 7.4 ± 0 7.4 ± 0 7.4 ± 0 7.4 ± 0
PCO
2
41.7 ± 5.7 42.4 ± 10.6 42.1 ± 8.4 42 ± 4.7 44.8 ± 11.3 43 ± 7.8
PaO
2
80.9 ± 9.8 80.4 ± 17.7 80.7 ± 14.1 81.3 ± 12.2 74.2 ± 16.7 78.9 ± 14.2
HCO
3
25.7 ± 3 25.7 ± 5.3 25.7 ± 4.2 25.8 ± 2.9 27.3 ± 5.2 26.3 ± 3.9
Hypertension 10 (19.6)
a
21 (43.8) 31 (31.3) 16 (20.3)
a
20 (44.4) 36 (29.0)
Diabetes mellitus 11 (21.6)
a
20 (41.7) 31 (31.3) 12 (15.2)
a
16 (35.6) 28 (22.6)
Asthma 8 (15.7)
a
24 (50) 32 (32.3) 15 (19)
a
16 (35.6) 31 (25)
Hypothyroidism 2 (3.9)
a
11 (22.9) 13 (13.1) 3 (3.8)
a
6 (13.3) 9 (7.3)
ESS, Epworth Sleepiness Scale.
Data presented at mean ± SD or n(%).
a
Significant difference between both genders, p< 0.05 between.
b
Significant difference between OSA patients with and without nightmares, p< 0.05.
A.S. BaHammam et al. / Sleep Medicine xxx (2012) xxx–xxx 3
Please cite this article in press as: BaHammam AS et al. Clinical and polysomnographic characteristics and response to continuous positive airway pressure
therapy in obstructive sleep apnea patients with nightmares. Sleep Med (2012), http://dx.doi.org/10.1016/j.sleep.2012.07.007
Although the REM duration was not different between the OSA pa-
tients with and without nightmares, the OSA patients with night-
mares had a significantly higher AHI during REM sleep compared
with the OSA patients without nightmares. Previous studies have
shown that OSA patients with a higher AHI report a significantly
lower frequency of nightmares [5,22]. Because nightmares are an
REM-related parasomnia [18], they are likely to occur during
REM sleep, which is usually suppressed in patients with severe
OSA. Pagel and Kwiatkowski proposed that the suppression of
REM sleep in patients with severe OSA can explain the reduction
in nightmares in patients with an increased AHI [22]. Nevertheless,
no previous study has reported the details of respiratory events
during REM sleep in OSA patients with nightmares.
Although the amount of REM sleep was not different between
the OSA patients with nightmares and the OSA patients without
nightmares, the results of this study suggest that nightmares are
associated with the presence of apneas and hypopneas during
REM sleep. Apparently, respiratory events during REM sleep rather
than changes in REM sleep duration may make OSA patients more
vulnerable to nightmares. In support of this hypothesis, previous
reports have indicated that dreams and dream recall decrease after
the first night of CPAP therapy despite increases in the amount and
duration of REM sleep [6,12]. Studies have shown that air hunger
during wakefulness, which is produced by breathing air with a
higher than normal concentration of CO
2
, increases the activity of
Table 2
Polysomnographic characteristics of the obstructive sleep apnea (OSA) patients with and without nightmares.
OSA with nightmare OSA without nightmare
Men Women Total Men Women Total
(n= 51) (n= 48) (n= 99) (n= 79) (n= 45) (n= 124)
Sleep efficiency 81.6 ± 10
a
74.3 ± 15.5 78 ± 13.5 79.5 ± 14.6
a
72.4 ± 19.6 76.9 ± 16.9
Apnea/hypopnea index (AHI) 45.7 ± 37.7
a
26.8 ± 27.3 36.5 ± 34.3 40.4 ± 31.5 39.9 ± 40.7 40.2 ± 35
Non-REM-AHI 43.9 ± 39.7 22.4 ± 29.4 33.5 ± 36.6 39.5 ± 33.2 38.7 ± 42.9 39.2 ± 36.8
REM-AHI
b
53 ± 31.1 50.3 ± 25.1 51.7 ± 28.1
b
41.2 ± 30.8 36.9 ± 34.3 39.8 ± 31.9
Apnea/hypopnea duration during REM 23.7 ± 9
a
20.2 ± 4.6 22 ± 7.4 21.8 ± 4.8
a
19.3 ± 4.8 20.9 ± 4.9
Apnea/hypopnea duration during non-REM 20 ± 3.9 18.5 ± 5.3 19.3 ± 4.6 19.7 ± 4.5 19 ± 6.7 19.4 ± 5.3
Desaturation index 25.5 ± 31.8 15.4 ± 20.1 20.6 ± 27.1 18.7 ± 24.7 21.7 ± 31.9 19.8 ± 27.4
Time with O
2
<90% 9.2 ± 17.7 8.9 ± 19.4 9.1 ± 18.5 7.7 ± 17.2 13.5 ± 27 9.8 ± 21.4
Time with O
2
<95% 47.2 ± 33.3 41.8 ± 37.2 44.6 ± 35.2 38.6 ± 36.4 47 ± 34.9 41.6 ± 36
Lowest recorded SaO
2
79.9 ± 14.5 80.7 ± 11.6 80.3 ± 13.1 82.5 ± 14.9 83.5 ± 8.4 82.9 ± 12.9
Average SaO
2
92.6 ± 10.6 94.5 ± 2.8 93.5 ± 7.9 93.7 ± 9 94.2 ± 2.9 93.9 ± 7.4
Arousal index 48.1 ± 35.6
a
30.9 ± 25.7 39.8 ± 32.2 43.3 ± 29.5 47.6 ± 36.9 44.8 ± 32.3
PLMI 9.4 ± 26.1 1.3 ± 1.1 5.5 ± 19 1.2 ± 1.2 1.7 ± 1.6 1.4 ± 1.4
N1% 7.6 ± 5.7 8.4 ± 5.2 8 ± 5.5 8.2 ± 9.7 10.4 ± 11.9 9 ± 10.5
N2% 69.2 ± 16.2 70.6 ± 12.4 69.9 ± 14.4 70.4 ± 17 72.6 ± 12.8 71.2 ± 15.6
N3% 4.4 ± 10.2 4.9 ± 7.4 4.7 ± 8.7 3.9 ± 6.3 4.1 ± 8.8 4 ± 7.4
REM% 14.6 ± 8.2 14.6 ± 8.1 14.6 ± 8.1 15 ± 10.2 12.2 ± 8.5 14 ± 9.7
REM duration 36.7 ± 30.6 36.2 ± 26.4 36.5 ± 28.5 37.1 ± 35 29.9 ± 26.2 34.5 ± 32.1
REM, rapid eye movement; PLMI, periodic leg movements index; N1, stage 1; N2 stage 2; N3 stage 3.
a
p< 0.05 between both genders.
b
p< 0.05 between OSA patients with and without nightmares.
Fig. 1. Distribution of obstructive sleep apnea (OSA) severity among the OSA patients with (black bars) and without (hatched bars) nightmares.
Table 3
Independent predictors of nightmares using binary logistic regression analysis.
Unadjusted
OR
p-
Value
Adjusted
OR
p-
Value
95% CI
REM-AHI 1.013 0.006 1.014 0.005 1.004–1.024
Interrupted sleep at
night
2.207 0.005 2.024 0.026 1.089–3.759
Choking 1.718 0.046 1.305 0.395 0.707–2.411
Early morning
headaches
1.720 0.047 1.524 0.187 0.816–2.847
OR, odds ratio; CI, confidence interval; REM, rapid eye movement; AHI, apnea–
hypopnea index.
4A.S. BaHammam et al. / Sleep Medicine xxx (2012) xxx–xxx
Please cite this article in press as: BaHammam AS et al. Clinical and polysomnographic characteristics and response to continuous positive airway pressure
therapy in obstructive sleep apnea patients with nightmares. Sleep Med (2012), http://dx.doi.org/10.1016/j.sleep.2012.07.007
the limbic/paralimbic brain regions [23], which are the same brain
regions activated during REM sleep. Carrasco et al. have speculated
that respiratory events during REM sleep might result in hyperac-
tivation of the limbic system, which could lead to dreams with
high emotive contents [6].
Early morning headaches were also found to be more common
among the OSA patients with nightmares. An association between
nightmares and headaches has been previously reported [24].Ina
large study investigating the prevalence of chronic morning head-
aches in the general population, Ohayon observed that chronic
morning headaches were associated with the occurrence of more
than one nightmare per week (odds ratio: 1.76; 95% confidence
interval: 1.3–2.39; p< 0.001) [25]. Previous research has also dem-
onstrated a relationship between migraine attacks on awakening
and negatively toned dream content [26]. In the present study,
interrupted sleep at night was a predictor of nightmares in the
OSA patients. It is possible that the patients who had frequent
awakenings due to recurrent apneas/hypopneas during REM sleep
recalled more nightmares. One study showed that the patients who
are more difficult to arouse report lower nightmare frequencies
[27].
Nightmares in our study group were mostly related to suffoca-
tion. Dream contents in patients with OSA have not been well
investigated. Whereas some studies have shown that OSA patients
reported dreams related to their sleep apnea syndrome [3,12],
other studies reported no reference to respiratory events in OSA
patients [6,28]. Discrepancies between different studies could be
related to the characteristics of the group included in each study
and the adopted exclusion criteria.
CPAP therapy in OSA patients results in acute changes in sleep
physiology through an increase in slow-wave and REM sleep and
a reduction in respiratory events and respiratory-induced arousals.
These changes may impact dream recall in OSA patients. In a lon-
gitudinal study on a sample of 20 patients with severe OSA, Carr-
asco et al. demonstrated a decrease in the dream recall rate
during the first night of CPAP therapy [6]. This observation was
independent of REM sleep duration and density. The authors
hypothesized that their results were due to a reduction in sleep
fragmentation following CPAP treatment [6]. The rebound of
slow-wave sleep induced by CPAP treatment has also been pro-
posed as an explanation for the decrease in dream recall rate [6].
Another study suggested that dream recall is reduced during
REM sleep episodes that follow slow-wave sleep [29]. However,
the effect of CPAP on nightmares in OSA patients has not been well
studied. Two previous studies have shown a significant improve-
ment in nightmares in patients with PTSD and comorbid OSA after
the successful treatment of OSA [9,30]. Nevertheless, studies from
PTSD patients with comorbid OSA cannot be generalized to pa-
tients with OSA because PTSD nightmares might be triggered by
different mechanisms [3]. In the present study, the OSA patients
with nightmares who showed good adherence to CPAP experi-
enced a significant reduction in nightmare frequency. The patients
in the CPAP-compliant group used CPAP >4 h per night, whereas
the patients in the other group refused to use CPAP. Therefore,
the present findings cannot be used to determine the amount of
compliance needed to control nightmares.
A limitation of the present study is that a randomized placebo-
controlled design was not employed. Nevertheless, the findings of
prospective observational studies provide important and valuable
information about comparative effectiveness in the context of real
clinical practice settings. As proper sample size calculation was not
done, a Type II statistical error cannot be ruled out.
This study had several advantages. For example, we specifically
included wakefulness in the criteria that define nightmares to ex-
clude bad dreams that do not meet the criteria of nightmares. The
inclusion of the waking criterion is supported by the finding that
individuals are highly confident in their determination of whether
a dream has caused wakefulness [31]. We also matched patients
for gender and age because previous studies have indicated that
women tend to report nightmares more often than men and that
the nightmare frequency decreases with age [32,33]. Another
advantage of the present study was that neither the patients nor
the treating team knew the severity of OSA at the time of the
assessment for nightmares. This was important because the knowl-
edge of an illness may influence the emotive contents of a patient’s
dreams [8].
In summary, this study showed that the OSA patients with
nightmares had more sleep interruptions and a higher REM-AHI.
Importantly, CPAP therapy resulted in a significant improvement
in nightmares. Sleep-disordered breathing should be considered
as a possible cause in patients presenting with nightmares.
Conflict of interest
The ICMJE Uniform Disclosure Form for Potential Conflicts of
Interest associated with this article can be viewed by clicking on
the following link: doi:10.1016/j.sleep.2012.07.007.
Acknowledgment
This work was supported by the National Plan for Science and
Technology (King Abdulaziz City for Science and Technology and
King Saud University).
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Comparison between the obstructive sleep apnea (OSA) patients with nightmares
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therapy in obstructive sleep apnea patients with nightmares. Sleep Med (2012), http://dx.doi.org/10.1016/j.sleep.2012.07.007
