Examining the bidirectional relationship between posttraumatic stress disorder symptom clusters and PAP adherence

Abstract

Study Objectives:

Obstructive sleep apnea (OSA) is a common sleep disturbance in individuals with posttraumatic stress disorder (PTSD), with an emerging literature showing that treating OSA with positive airway pressure (PAP) therapy has a moderate effect on decreasing PTSD severity. Unfortunately, PAP adherence among individuals with PTSD is low. Our study examined how baseline PTSD cluster subscores predict 6-month PAP adherence and how PAP adherence predicts change in PTSD cluster subscores over time.

Methods:

We examined PTSD and PAP adherence in 41 veterans with PTSD newly diagnosed with OSA over 6 months of PAP use (mean age = 50.27 years; 73.7% White; 13.6% female). The Posttraumatic Stress Disorder Checklist—Specific (PCL-S) was used to examine PTSD and subscales (re-experiencing, avoidance, and hyperarousal). We used longitudinal analyses to examine PTSD subscores on PAP adherence and PAP adherence predicting changes in PTSD subscores at 6-month follow-up.

Results:

Among veterans with PTSD, higher levels of re-experiencing and hyperarousal, but not avoidance, predicted lower PAP use. Overall, the high-adherent group showed a 14.36-point decrease on the PCL-S, while the low-adherent group averaged just a 3.66-point decrease. More days of PAP use were associated with greater improvement in hyperarousal and avoidance subscores but not re-experiencing.

Conclusions:

Our findings reaffirm the importance of PAP use among patients with comorbid PTSD and sleep apnea, as well as the difficulty in achieving adherent PAP use in this population. Directly addressing heightened re-experiencing and hyperarousal in PTSD may increase PAP adherence among veterans with PTSD and requires future research.

Citation:

Colvonen PJ, Goldstein LA, Sarmiento KF. Examining the bidirectional relationship between posttraumatic stress disorder symptom clusters and PAP adherence. J Clin Sleep Med. 2023;19(5):857–863.

BRIEF SUMMARY

Current Knowledge/Study Rationale: Obstructive sleep apnea (OSA) is a common sleep disturbance in individuals with posttraumatic stress disorder (PTSD), with an emerging literature showing that treating OSA with positive airway pressure (PAP) therapy has a moderate effect on decreasing PTSD severity. Unfortunately, PAP adherence among individuals with PTSD is very low.

Study Impact: Our findings found that (1) among veterans with PTSD, higher levels of re-experiencing and hyperarousal predicted lower PAP use at 6-month follow up; (2) number of days using PAP was the strongest predictor of PTSD change, with the high-adherent group showing a 14.36-point decrease on the Posttraumatic Stress Disorder Checklist—Specific (PCL-S) while the low-adherent group averaged just a 3.66-point decrease; and (3) more frequent use of PAP was associated with greater improvement in hyperarousal and avoidance subscores. This suggests addressing PTSD hyperarousal (eg, using desensitization protocols) and re-experiencing (eg, how to successfully use the Ramp function following a nightmare, which starts the PAP at a lower pressurized air setting, making it easier to fall asleep) may have the potential to maximize PAP adherence, which, in turn, will decrease PTSD symptoms.

INTRODUCTION

Obstructive sleep apnea (OSA) is a common sleep disturbance in individuals with posttraumatic stress disorder (PTSD), with prevalence rates that are considerably higher than in individuals without PTSD.^1–4 Emerging literature suggests that treating OSA with positive airway pressure (PAP) therapy (the gold standard for treating OSA) has a moderate effect on decreasing PTSD severity^1,5–7 and may be a necessary clinical intervention before starting evidence-based PTSD treatment.^8,9 Unfortunately, individuals with PTSD have lower adherence rates to PAP,^10,11 limiting positive effects of PAP treatment on PTSD symptoms. There is currently a lack of information on the relationship between the symptom clusters of PTSD (re-experiencing, avoidance, and hyperarousal) and OSA treatment adherence, and in turn, it is unknown which symptoms respond best to PAP treatment. Examining the longitudinal relationship between PTSD symptom subscores, PAP adherence, and PTSD outcomes can help identify focused treatment targets for PAP adherence and elucidate the relationship between PAP treatment and PTSD symptoms.

OSA is defined by repeated episodes of apneas (pauses in breathing) and hypopneas (shallow breathing), resulting in sleep fragmentation and decreases in blood oxygenation during sleep. The apnea-hypopnea index (AHI; number of apneas plus hypopneas per hour of sleep) is the most commonly used metric of OSA severity, with mild OSA starting at AHI ≥ 5 events/h. OSA is highly prevalent among veterans with PTSD, with an estimated 67–83% of veterans with PTSD having co-occurring OSA.^1–4 A meta-analysis on OSA in PTSD found that OSA prevalence was 75.7% when using the criterion of AHI ≥ 5 events/h and 43.6% when using AHI ≥ 10 events/h²; OSA prevalence rates were found to be significantly higher in individuals with PTSD compared with those without PTSD, which estimates suggest is approximately 10% of the general US population.¹² Although the exact mechanisms driving this high amount of comorbidity of PTSD and OSA have not yet been identified, several speculations have been made, including sleep fragmentation impeding fear extinction, fragmentation secondary to insomnia and hyperarousal predisposing to sleep-disordered breathing, sympathetic activation predisposing to upper airway collapse, and hypothalamic-pituitary-adrenal axis dysfunction.^1,5,13

The gold-standard treatment for OSA is PAP therapy, which uses forced air to keep the airway open and maintain breathing during the night. Adherent PAP use is associated with improvements in daytime sleepiness, physical health, PTSD symptoms, and quality of life.^13–15 Importantly, adherence to PAP therapy at 1 month is predictive of adherence at 1 year, suggesting that early PAP adherence is important for continued use at follow-up.^16,17 While adherence in non-PTSD samples is generally high (eg, 50–80%), individuals with PTSD have been shown to be less adherent,^2,10,11 thereby limiting its effectiveness.¹⁸ Rates of PAP adherence in individuals with PTSD range from 39% to 81% depending on the definition of adherence.^5,6,10 For example, Orr and colleagues⁵ found that, while 81% of patients were using PAP every night at 6-month follow-up, only 39% were using it more than 4 hours per night. Unfortunately, PAP nonadherence presents a significant impediment to PTSD treatment, with untreated OSA interfering with PTSD recovery.^8,9

Among those with PTSD and OSA, PAP therapy is associated with small to moderate reductions in overall PTSD symptom severity.^5–7,19,20 Ullah et al⁶ found overall PTSD symptom reduction in a veteran PTSD cohort after 6 months of PAP therapy. They found that greater PAP adherence was associated with greater improvement in PTSD symptoms overall, as well as in terms of specific symptom clusters of avoidance, intrusions, and hyperarousal. They found a larger response in terms of decreases in intrusions (eg, nightmares), which is consistent with other treatment findings.⁷

It is becoming increasingly recognized that PTSD is a multifactorial disorder^21–23 and OSA and response to OSA treatment are also not homogenous.²⁴ Understanding the relationship between PTSD subscores and OSA treatment response can help guide more targeted and effective therapy in the future.²⁵ The goal of the current study was to conduct secondary analyses of Orr and colleagues⁵ paper to re-examine baseline PTSD total and cluster subscores (re-experiencing, avoidance, and hyperarousal) on 6-month PAP adherence rates among veterans with PTSD and untreated OSA. We hypothesized that high avoidance and arousal subscores will be the most predictive of low adherence rates. We also aimed to examine how PAP adherence rates predict change in PTSD total and cluster subscores. We hypothesized that greater PAP adherence over 6 months will predict larger decreases in hyperarousal and re-experiencing subscores.

METHODS

Subjects

This study is a secondary analysis of Orr and colleagues⁵ and was approved by the VA San Diego Healthcare System Institutional Review Board (#H130095). Consecutive veterans were recruited from the sleep clinic between August 2013 and September 2014, and were eligible to participate if they had a PTSD diagnosis from a psychiatrist or psychologist in their medical file, a new diagnosis of OSA based on home sleep apnea testing, and a willingness to use PAP therapy. Exclusion criteria were major medical illness with anticipated survival less than 6 months or inability to travel to follow-up appointments. The diagnosis of OSA was established using the NOX-T3 system (Carefusion, Yorba Linda, CA). As part of routine clinical care, all participants completed a group class where they received education about OSA and treatment with PAP therapy from a sleep technologist and were instructed on how to apply the recording device. Comprehensive self-report sleep questionnaires were also completed at that time. Events were scored according to American Academy of Sleep Medicine criteria, with an AHI of 3% greater than or equal to 5 events/h considered significant. Participants were enrolled following interpretation of their sleep test but prior to initiating PAP treatment. Auto-titrating PAP devices (ResMed S9 or Philips Remstar Auto with A-flex) were used for therapy (ResMed, San Diego, CA, and Respironics, Murrysville, PA). Minimum pressures were empirically selected by the interpreting sleep physician based on body mass index, overall AHI, and dominant event type (apnea vs hypopnea). Maximum pressures were set at 20 cm H₂O. Following informed consent, participants underwent baseline evaluations, which included a face-to-face interview with a board-certified sleep physician, completion of questionnaires, and 1-week sleep diaries. Participants were scheduled for follow-up visits at 3 and 6 months. Statistics on demographics and PAP usage are reported in Table 1.

Table 1.

Demographic characteristics at baseline.

Characteristics	Values
Age, mean (SD), y	51.90 (13.47)
Sex, n (%)
Men	37 (90.2)
Women	4 (9.8)
Ethnicity, n (%)
Hispanic	10 (24.4)
Non-Hispanic	31 (75.6)
Race, n (%)
White	32 (78.0)
Black	8 (19.5)
Other	1 (2.4)
Era, n (%)
Vietnam	17 (41.5)
Persian Gulf	23 (56.1)
Other	1 (2.4)
PAP usage in last 6 months, mean (SD), %
Nightly usage	50.0 (39.8)
Used > 4 hours	44.8 (36.6)
Average hours per night	3.51 (2.57)
PCL-S ≥ 50, n (%)	35 (85.4)
BMI, mean (SD), kg/m2	31.24 (4.79)
Sleep medications, n (%)	18 (43.9)
Mood medications, n (%)	24 (58.5)
Mood and sleep medications, n (%)	13 (37.1)
Hours of sleep, mean (SD)	6.53 (2.12)

n = 41. BMI = body mass index, PAP = positive airway pressure, PCL-S = Posttraumatic Stress Disorder Checklist—Specific, SD = standard deviation.

Measures

PAP data

PAP device downloads were performed at 3- and 6-month follow-up visits. PAP data downloads included 0–3 months, 3–6 months, and 0–6 months of aggregated data. Data abstracted included percentage of nights used (number of days PAP was used divided by total number of days in download), average hours used per night (average number of hours PAP was used on the nights it was worn), percentage of nights used more than 4 hours (number of days PAP was used more than 4 hours divided by total number of days in download), and residual device AHI.

PTSD

Participants completed the 17-item Posttraumatic Stress Disorder Checklist—Specific (PCL-S),²⁶ which asks about PTSD symptoms in the past month and maps directly onto Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV), diagnostic criteria. This measure was completed at baseline, 3 months, and 6 months. Items ranged from 1 (not at all) to 5 (extremely), with total scores ranging from 17 (no symptoms) to 85 (severe symptoms). Subcategories are made up of re-experiencing (5 questions; subscale score ranges from 5 to 25), avoidance (7 questions; subscale score ranges from 7 to 35), and hyperarousal (5 questions; subscale score ranges from 5 to 25). A PCL-S score of 50 or higher indicates probable PTSD in a military population.²⁶

Medications

Baseline medications were classified in groups of sleeping medication (eg, trazodone, sedating antihistamines, or nonbenzodiazapine sedative hypnotics), antidepressants (eg, sertraline, escitalopram), pain medications (eg, opioids, gabapentin), and other. Each class of medications was included as a potential covariate.

Statistical analysis

Data were analyzed using descriptive statistics, paired-sample t tests, and mixed models. Longitudinal data were analyzed using mixed-model procedures²⁷ in SPSS version 25 (IBM Corporation, Armonk, NY), which allowed for maximum available data to be used in the analyses. This approach requires only 2 datapoints, and estimates any missing data, reducing the analytic problem presented by missing data over 6 months. Outcome variables included PCL-S and each of the subscales (Intrusions, Avoidance, Hyperarousal). PAP-use variables (percentage of nights used in the last 6 months, number of hours per night used, on average, in the last 6 months, and percentage of days used at least 4 hours or more) were examined and showed that the percentage of nights used in the last 6 months was the strongest predictor of PTSD change and was used in the longitudinal analyses. Main fixed-effects predictors were PAP-use variables (percentage of nights PAP was used in the last 6 months), time (baseline, 3 months, 6 months), and the interaction of PAP-use variables by time on PTSD scores (baseline, 3 months, and 6 months). To examine how PTSD changes over time (eg, all in the first 3 months or equally over 6 months) we examined linear and quadradic models. Several random-factor models using slope and intercept were tested and we present the best-fitting model as indicated by a significant chi-square difference test of the log-likelihood values; all models converged successfully. All models were tested with the full PCL-S and subscores, and outcomes without the 2 sleep items. There were no differences in outcome analyses between the full PCL and the PCL with the sleep items removed; as such, only the results using the fully validated measures are reported. Chi-square analyses showed that controlling for age and use of sleep medication as covariates resulted in significantly better fitting models based on lower log likelihoods. Figure 1 and Figure 2 present a mean split for percentage of days used in the past 6 months, with a high-use group (n = 19) and a low-use group (n = 22). We present full score PTSD data previously published by Orr and colleagues⁵ for context of the subscore reanalyses.

Figure 1. Observed change in PTSD scores overtime as a function of high/low mean split percentage of days PAP was used over 6 months.

PAP = positive airway pressure, PTSD = posttraumatic stress disorder.

Figure 2. Observed re-experiencing, avoidance, and hyperarousal scores over time as a function of high/low mean split % number of days PAP used over 6 months.

*Significant (P < .05). NS = nonsignificant, PAP = positive airway pressure, PCL-S = Posttraumatic Stress Disorder Checklist—Specific.

RESULTS

Attrition analyses

Of the 58 veterans who consented, 17 veterans only had baseline data and were not included in the longitudinal analyses. We compared included and excluded veterans on baseline body mass index, PCL-S, age, sex, AHI, weight, and sleep medications. There were no differences between groups on any variables (P > .05). Including only veterans with at least 2 data points, the final sample comprised 41 participants.

Adherence variables

We examined the percentage of nights used, average hours used per night, and percentage of nights used more than 4 hours (see Table 2 for observed means at baseline and 6 months and Table 3 for correlations in change in PTSD and PAP use). We examined correlations of adherence rates and change in PTSD scores and found that the percentage of nights used had the highest correlation with change in PTSD scores; as such, we used percentage of nights used in the last 6 months in the longitudinal analyses.

Table 2.

Change in symptoms over time.

Characteristics	Baseline (n = 41) Mean (SD)	3 Months (n = 41) Mean (SD)	6 Months (n = 32) Mean (SD)	Paired t Tests (Baseline to 6 Months)	Effect Size (Cohen’s d)
AHI, events/h	24.47 (20.66)	3.81 (7.40)	2.03 (1.75)	t(31) = 4.24, P < .001	0.50
PTSD checklist5	61.02 (14.75)	52.00 (17.43)	52.34 (17.89)	t(31) = 4.24, P < .001	0.50
Re-experiencing subscore	17.71 (4.18)	15.20 (5.51)	15.03 (5.60)	t(31) = 3.72, P < .001	0.47
Avoidance subscore	24.37 (7.62)	21.17 (7.83)	21.34 (8.91)	t(31) = 3.09, P = .004	0.35
Hyperarousal subscore	18.95 (4.73)	15.63 (5.49)	15.97 (5.17)	t(31) = 4.37, P < .001	0.56

AHI = apnea-hypopnea index, PTSD = posttraumatic stress disorder.

Table 3.

Change in PTSD and PAP-use correlations between baseline and 6 months.

	1.	2.	3.
1. Change in PTSD between BL and 6 months	—
2. Percentage of nights used between BL and 6 months	.43*	—
3. Average hours used per night	.34*	.83***	—
4. Percentage of nights used more than 4 hours	.37	.94***	.92***

***P < .001. *P < .05. BL = baseline, PAP = positive airway pressure, PTSD = posttraumatic stress disorder, SD = standard deviation.

Baseline PTSD scores and subscores predicting PAP adherence

We examined multiple models of baseline PTSD and PTSD subscores, controlling for age, sleep medications, and sex, on 6-month PAP adherence. In separate models, regressions indicated that more severe PTSD total score (β = −.36, P = .03), re-experiencing (β = −.44, P = .007), and hyperarousal (β = −.45, P = .008) predicted lower PAP adherence, but avoidance subscores did not (β = −.19, P = .27).

Change in PTSD over time

A random intercept and random slope mixed-effects model fit the PTSD data best with a quadratic time variable (Figure 1). Results showed, on average, that PTSD scores significantly decreased between 0 and 3 months (average 8.02-point decrease) and were maintained between 3 and 6 months (average 0.34-point increase). Age, sex, and use of sleep medication added to the data fit and were included in analyses. The random intercept and random slopes suggest that individuals have significantly different intercepts (starting PCL-S scores) and significantly vary from the mean change over time.

PAP adherence on change in PTSD

A random intercept mixed-effects model fit the PTSD data best with a linear time variable (see Figure 1). Results showed, on average, that PTSD scores significantly decreased as a function of percentages of nights PAP was used between baseline and 6 months, such that more nights used showed larger decreases in PTSD symptoms (time by PAP use interaction [b = −0.07, standard error (SE) = 0.03, t(53.87) = −2.13, P = .04; 95% confidence interval −0.14, −0.004]). Age, sex, and use of sleep medication added to the data fit and were included in analyses. Observed means in Figure 1 used a mean split for percentage of days used in the past 6 months, with a high-use mean equal to 91.12% (standard deviation [SD] = 11.65%) days used and low-use mean equal to 18.04% (SD = 17.57%) days used. The high-use group averaged a 14.36-point decrease on the PCL-S (SD = 11.26), while the low-use group averaged a 3.67-point decrease on the PCL-S (SD = 8.75).

PAP adherence on change in PTSD re-experiencing

The mixed-effects models (linear or quadratic time) showed that PAP adherence did not predict changes in re-experiencing subscores (Figure 2; time by PAP use interaction [b = −0.02, SE = 0.01, t(52) = −1.47, P = .15; 95% confidence interval −0.04, 0.01]).

PAP adherence on change in PTSD avoidance

A random intercept mixed-effects model fit the PTSD data best with a linear time variable (see Figure 2). Results suggest that the more days of PAP use over 6 months leads to larger decreases in avoidance symptoms (time by PAP use interaction [b = −0.03, SE = 0.01, t(52) = −2.29, P = .03; 95% confidence interval −0.06, −0.001]).

PAP adherence on change in PTSD hyperarousal

A random intercept mixed-effects model fit the PTSD data best with a linear time variable (Figure 2). Results show that more days of PAP use over 6 months leads to larger decreases in hyperarousal symptoms (time by PAP use interaction [b = −0.02, SE = 0.01, t(52.13) = −1.90, P = .05; 95% confidence interval −0.04, −0.00]).

DISCUSSION

These findings are a reanalysis of Orr and colleagues⁵ longitudinal PAP-use and PTSD paper. Our findings reaffirm the importance of PAP use among patients with comorbid PTSD and sleep apnea, as well as the difficulty in achieving adherent PAP use in this population. Previous research showed lower rates of PAP use among patients with PTSD compared with those without PTSD.^10,11 This study replicates that finding and builds on it by specifying the types of symptoms that are most associated with lower levels of PAP use. First, we found that higher levels of baseline PTSD re-experiencing and hyperarousal symptoms, but not avoidance, predicted reduced PAP adherence. Second, we found that the number of days using PAP was the strongest predictor of change in PTSD, with veterans tending to be either adherent, with 91.12% of days used in the past 6 months, or nonadherent, with only 18.04% of PAP use in the past 6 months. While, on average, PAP use predicted an 8.34-point decrease on the PCL-S over a 6-month period, when examining high vs low adherence the numbers are staggering; the high-adherent group showed a 14.36-point decrease on the PCL-S (a clinically meaningful change) while the low-adherent group averaged just a 3.66-point decrease. Third, we found that more PAP use over a 6-month period predicted significant decreases in PTSD avoidance and hyperarousal, but not re-experiencing.

While further research is needed to investigate specific aspects of why higher re-experiencing and hyperarousal symptoms predicted lower PAP use, there are a few plausible explanations. For hyperarousal, it is possible that higher hyperarousal increases the feeling of claustrophobia, thus decreasing PAP adherence. Similarly, using a PAP mask could remind patients of traumatic events (eg, combat while wearing gas mask) or the sensation of having something on the face itself heightens arousal, thus creating somatic arousal similar to the traumatic event. Of note, a recent study found that a low arousal threshold (waking up easily in the night) was not associated with adherence to PAP therapy in patients with PTSD,²⁸ suggesting that hyperarousal is more likely associated with avoidance of putting on a PAP mask before initiating sleep or is interfering with falling asleep, rather than increasing the middle of the night awakenings from a low arousal threshold.

In explaining re-experiencing, it is possible that nightmares lead to waking up and removing the mask for the rest of the night. Another possibility is increased rapid eye movement (REM) rebound, frequently observed with initial PAP use, may worsen nightmares in a subset of patients. One study found REM rebound at the first time of PAP exposure actually predicted higher 30-day and 60-day (but not 120-day) PAP adherence, but this study only focused on first-night PAP exposure and did not focus on patients with PTSD or nightmares.²⁹ Interestingly, we did not find a relationship between avoidance and PAP adherence. It may be that PTSD avoidance scores are specific to stimuli associated with the traumatic event(s) and external reminders (people, places, conversations, activities, objects, situations) that arouse distressing memories associated with the traumatic event(s). As such, PTSD avoidance may not accurately predict lower PAP adherence that re-experiencing and increased hyperarousal do.

Taken together, we suggest that patients with high levels of PTSD symptoms receive objective overnight OSA testing due to the high co-occurrence of the 2 disorders.³⁰ We also recommend the individuals with PTSD, especially with significant re-experiencing or hyperarousal symptoms, receive extra clinical attention at the time of PAP therapy initiation. Education, including normalization of an arousal/anxiety response, as well as careful mask and pressure selection, may facilitate initial success using PAP. Further, specific discussion of how to use the machine after a nightmare will increase the number of hours used but also limit the negative association of the PAP device and nightmares. While currently untested, it is possible that, for both high hyperarousal and re-experiencing, using desensitization protocols (eg, wearing a PAP mask while watching television, practicing mindfulness while wearing a PAP mask) and how to successfully use the Ramp function (decreasing initial PAP pressure for 5 to 45 minutes while the veteran falls asleep or recovers from a nightmare) may have large effects on adherence and treatment outcomes.

This study’s results also demonstrated improvement in PTSD symptoms as being dependent on PAP adherence. The percentage of nights that PAP was used over 6 months was more strongly correlated with improvement in PTSD symptoms than the percentage of nights of greater than 4 hours’ use or the average number of hours use per night. Thus, we recommend focusing on a goal of starting each night with PAP to maximize the dose–response of PAP use, rather than emphasizing the sheer number of hours or a particular goal of a certain number of hours of sleep. The latter goal may be particularly unattainable for patients with insomnia, which is among the most common complaints of patients with PTSD.³¹ This finding also heightens the concern that Medicare PAP-adherence guidelines (ie, 4+ hours’ use for 70% of nights)³² may not represent a clinically meaningful measure of adherence, particularly among patients with PTSD. Further, we generally found veterans to either be adherent or nonadherent to PAP. Importantly, studies showed that adherence to PAP therapy at 1 month was predictive of adherence rates at 1 year, suggesting that early PAP adherence is vital for continued use at follow-up,^16,17 especially for veterans with PTSD.

Similar to Orr and colleages,⁵ El-Solh and colleagues^11,20 found that greater PAP use was associated with a global reduction in PTSD symptoms. In analyzing the subscores, we found that increased number of days of PAP use predicted improvements in the avoidance and hyperarousal symptom clusters, but not re-experiencing. This may be due to decreases in fragmentation from effective PAP use that leads to more daytime energy, increased concentration, and better emotional coping, making engaging people, places, and emotions easier to handle. Further, decreasing fragmentation has been shown to have a direct effect on physiological hyperarousal. Hyperarousal may play a unique role in that higher hyperarousal predicts less PAP use, but effective PAP use has the largest effect on decreasing hyperarousal. Ullah and colleagues⁶ found improvement across all symptom clusters, albeit with slightly lower effect sizes than the present study. In both Ullah et al’s and our study, the avoidance cluster of symptoms had the smallest effect size from baseline to 6 months among patients with PTSD, compared with other symptom clusters. Future research is needed to systematically evaluate these potential mechanisms in the context of PAP use among patients with PTSD and OSA.

There are a number of limitations of this study. First, this study took place at 1 VA Sleep Medicine Clinic. The education and follow-up support provided to these patients may not be representative of that provided at other VA clinics or in the private sector. Second, while the possibility that sleep apnea treatment improved PTSD symptoms, which would be in alignment with other studies in this area, we cannot rule out other potential causes of improvement, including trauma-focused psychotherapy, behavioral sleep treatment, or implementation of other sleep-related strategies (eg, sleep hygiene). While medication use was included as a covariate, use of behavioral strategies and treatment was not collected as part of this study. Third, we used the PCL-S, which is based on the DSM-IV, and not the updated Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5). The DSM-5 updates PTSD to include “negative alterations of cognition and mood” as a fourth symptom cluster. As such, we are unable to examine all 4 of the subscales that future research should examine. Fourth, our relatively small sample size likely accounts for nonsignificant quadratic findings, where much of the observed change occurs in the first 3 months of PAP use. Increasing the number of participants over time would allow more robust analyses to be run. Finally, PTSD symptoms were evaluated based on self-report; future studies might improve measurement of PTSD symptoms with the use of structured clinical interviews with the clinician-administered PTSD scale (CAPS).

CONCLUSIONS

Among veterans with PTSD who were newly diagnosed with sleep apnea, higher levels of PTSD symptoms, especially re-experiencing and hyperarousal, were associated with reduced PAP use. A greater number of days of PAP use was associated with greater improvement in PTSD symptoms, and symptom clusters of re-experiencing and avoidance were most improved. Future research is needed to identify other factors influencing PAP adherence among patients with PTSD, as well as interventions to facilitate PAP use in this population.

DISCLOSURE STATEMENT

All authors have seen and approved this manuscript. This study was funded by a Veteran Affairs Rehabilitation Science Research and Development Career Development Award, 1lK2Rx002120-01, granted to Peter Colvonen, PhD; a Veteran Affairs Rehabilitation Science Research and Development Career Development Award, IK2RX002952, granted to Lizabeth Goldstein, PhD; and an American Academy of Sleep Medicine Award, granted to Kathleen Sarmiento, MD MPH. The views expressed in this paper are those of the authors only and do not reflect the official policy or position of the institutions with which the authors are affiliated, the Department of Veterans Affairs, or the US Government. The authors report no conflicts of interest.

ABBREVIATIONS

AHI,

apnea-hypopnea index

OSA,

obstructive sleep apnea

PAP,

positive airway pressure

PCL-S,

Posttraumatic Stress Disorder Checklist—Specific

PTSD,

posttraumatic stress disorder

SD,

standard deviation