The correlation of sleep disorders with postoperative outcomes in spine surgery: A narrative review

Abstract

Background

Sleep hygiene plays a pivotal role in maintaining good health, yet nearly 30% of adults face sleep disorders such as sleep apnea, insomnia and circadian rhythm disruptions. These disturbances are associated with worse patient-reported health outcomes and higher risk of complications following surgery. In orthopedics, sleep disorders increase readmission rates and prolong hospital stays, yet their correlation with outcomes following spine surgery remains poorly understood.

Methods

We conducted a literature search using Pubmed, Embase and Scopus databases to identify studies reporting on the correlation of sleep-related disorders on spine pathologies and postoperative outcomes.

Results

Sleep disorders contribute to systemic inflammation, impaired tissue repair and hormonal dysregulation, adversely affecting spinal health and recovery. Patients with untreated sleep disturbances experience higher pain levels, delayed rehabilitation and increased dependency on analgesics. Improved management of sleep disturbances has shown potential to improve clinical and functional outcomes after surgery.

Conclusions

Managing sleep disorders in patients undergoing spine surgery is vital to optimize outcomes. Future research should prioritize prospective studies and the integration of comprehensive sleep-focused perioperative care strategies to minimize complications and improve recovery.

Introduction

Proper sleep is essential to achieving optimal health-related outcomes [1]. Yet, sleep disorders remain prevalent and often go undiagnosed, affecting nearly 30% of all adults and increasing in prevalence with age [2]. Examples of these disorders include sleep apnea, insomnia, parasomnia, hypersomnia, circadian rhythm disorder, and sleep-related movement disorders [3]. Sleep disorders have frequently been associated with a variety of adverse health conditions such as cancer, obesity, hypertension, type 2 diabetes, and increased mortality [[4], [5], [6], [7]]. In addition, sleep disturbances prior to surgery also increase the risk of postoperative complications including hypoxic injury, increased pain, and cardiovascular problems [[8], [9], [10]]. In orthopedics, in particular, they have also been shown to increase hospital stays and readmission rates within 90 days after surgery [11,12].

Over the past 15 years, there has been a 2.4-fold increase in the frequency of annual spine surgeries performed [13]. However, the correlation of sleep disorders on postoperative outcomes in patients undergoing spinal surgery remains poorly understood. Given the rise in spinal surgeries and the potential for postoperative complications, understanding the effects of sleep disorders on surgical outcomes is clinically relevant and essential for preoperative medical optimization and postoperative patient management. As such, this review aims to summarize the effects of sleep disorders on spine pathologies and postoperative spine surgery outcomes, with emphasis on the importance of treating sleep disorders.

Methods

We conducted a literature search using PubMed, Embase and Scopus databases. The search included the following keywords; “Sleep Disorder”, “Sleep Disturbance”, “Sleep Apnea”, “Insomnia”, “ Circadian Rhythm Disorder”, “Spin* Patholog*”, “Spin* Surger*”, “Lumbar Surger*” and “Cervical Surger*”. These terms were combined using Boolean operators “AND” and “OR” to identify articles reporting on the correlation of sleep-related disorders with spine pathologies and postoperative outcomes after surgery. Our inclusion criteria were limited to comparative studies evaluating the correlation of sleep disorders with spine pathologies and outcomes after spine surgery. Exclusion criteria included case reports, narrative reviews and noncomparative studies (Fig. 1).

Fig. 1.

PRISMA flow chart.

Pathophysiological mechanism linking sleep disturbances to spinal disorders and degenerative changes

Sleep disturbances are increasingly being recognized as significant contributors to the development and progression of spinal disorders, including degenerative changes in spinal structures [[14], [15], [16]]. While sleep disturbances directly impact quality of life by impairing physical and mental well-being, they also trigger several pathophysiological processes that negatively impact spinal health [17].

Systemic inflammation and tissue degradation

Chronic sleep deprivation is a well-documented inducer of systemic inflammation [18]. Along with sleep disturbances, it elevates the levels of pro-inflammatory cytokines such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) which are associated with degenerative processes in musculoskeletal structures [[19], [20], [21], [22], [23]]. Inflammation contributes to the breakdown of the extracellular matrix within intervertebral discs which eventually accelerates degenerative disc disease [24,25]. It also promotes oxidative stress, further damaging cellular components and disrupting the homeostasis required to maintain the integrity of the spine [26,27] (Fig. 2).

Fig. 2.

The role of sleep disturbance in systemic inflammation and tissue degradation. Chronic sleep disturbances can lead to an increase in proinflammatory cytokines, such as IL-6 and TNF-α, that can lead to degenerative changes in musculoskeletal structures. These changes can accelerate disc pathology and disrupt homeostasis within the spine.

Impaired tissue repair and regeneration

Sleep plays a vital role in tissue repair and cellular regeneration which are essential processes in order to maintain the health of the spine [28,29]. During restorative sleep, anabolic hormones such as growth hormone are secreted which facilitates protein synthesis, collagen formation and bone remodeling [30]. Chronic disruptions in sleep impair these regenerative processes and renders musculoskeletal tissues vulnerable to microtears, structural weakening and eventually to degeneration [28,29]. For instance, the failure to adequately repair the ligaments and muscles that surround the spine could lead to a gradual loss of spinal stability and to an increased risk of deformities [31,32].

Hormonal dysregulation

Sleep disturbances significantly affect hormonal balance and disrupts the circadian secretion of cortisol and growth hormone [33,34]. Due to poor sleep, cortisol becomes elevated and exerts catabolic effects on bone and muscle tissue which ends up weakening the spine over time [33]. Moreover, insufficient levels of growth hormone impair bone remodeling and the maintenance of the disc integrity [35]. These hormonal imbalances collectively predispose individuals to conditions such as osteoporosis and spinal deformities which further exacerbate the impact of spinal degeneration [[36], [37], [38]] (Fig. 3).

Fig. 3.

The role of sleep disturbances in hormonal dysregulation. Sleep disturbances can disrupt the circadian secretion of cortisol and growth hormone, creating significant hormonal imbalance. Cortisol may become elevated and exert catabolic effects on bone and muscle while decreases in growth hormone impair bone remodeling and disc integrity. This may predispose individuals to the development of osteoporosis or spinal deformity.

Neural pathways and melatonin dysregulation

The neural pathways directing sleep and circadian rhythms pass through the cervical spinal cord which makes it a critical region to understand the interplay between sleep disturbances and spinal disorder [39]. Studies have shown that reduced melatonin levels, the hallmark of disrupted sleep, are linked to impaired circadian regulation [40]. Melatonin is essential for initiating and maintaining restorative sleep cycles and its deficiency can amplify the effects of sleep disturbances. In conditions such as cervical myelopathy, the proximity of the pathology to these neural pathways may contribute to the observed prevalence of sleep disturbances in these patients [41]. Furthermore, the reduction in melatonin levels and the interruption of circadian rhythms may have downstream effects such as an increased pain sensitivity and altered neurovascular regulation that can exacerbate the spinal conditions [15,42,43].

Pain, postural changes and biomechanical stress

The relationship between pain and sleep is bidirectional. Sleep disturbances impair the body's ability to modulate pain through endogenous mechanisms which results in a heightened pain sensitivity [[44], [45], [46]]. In patients with spinal disorders, an increased pain perception can lead to chronic muscle tension, compensatory postural changes and reduced mobility [[47], [48], [49]]. These biomechanical adaptations place uneven stress on spinal structures which accelerates wear and tear in intervertebral discs, facet joints and the surrounding soft tissues [50]. Over time, this can also lead to conditions such as degenerative disc disease, spondylolisthesis and spinal deformities [50].

Correlation of sleep-disordered breathing and hypoxia

Sleep-disordered breathing such as OSA introduces intermittent hypoxia and hypercapnia which have profound effects on spinal health [51]. Hypoxia induces oxidative stress and endothelial dysfunction which impairs the vascular supply to intervertebral discs and other spinal tissues [52]. This compromised nutrient delivery can accelerate degenerative changes and reduce the spine's ability to repair itself following injury [[53], [54], [55], [56]]. Moreover, disrupted sleep due to apnea-related awakenings exacerbates systemic inflammation and hormonal dysregulation which creates a vicious cycle that perpetuates degeneration of the spine [57,58].

Broader implications for spinal health

Patients suffering from cervical myelopathy and other spinal disorders often report a poor quality of sleep, which leads to increased pain susceptibility, depression and functional limitations [44,[59], [60], [61], [62]]. Atypical symptoms including headache and shoulder pain often accompany these conditions and present additional risk factors for sleep disturbances [[63], [64], [65], [66], [67], [68]]. In fact, patients with cervical spine injuries or conditions report worse sleep quality compared to their counterparts at the level of the thoracic or lumbar region which is likely due to the involvement of neural pathways and the increased pain sensitivity in cervical diseases [43,69]. Therefore, it is important to manage sleep disturbances in these patients as untreated sleep disorders could worsen the spinal pathology by contributing to systemic inflammation, hormonal imbalances and delayed tissue repair.

Incidences of sleep disturbances in spine pathologies

Degenerative spine conditions

Several studies have examined the prevalence and correlation of sleep disturbances in degenerative spine disorders. For instance, Guo et al. investigated the causal effects of modifiable risk factors on intervertebral disc degeneration and found that individuals who experience sleeplessness have 1.8 times higher odds of developing disc degeneration compared to those who do not [14]. Similarly, Tarnoki et al. reported that patients with obstructive sleep apnea (OSA) had double the number of lumbar disc bulges and almost 4 times the severity of disc degenerations compared to individuals without OSA [70]. Kim et al. further investigated the prevalence of sleep disturbances in patients with lumbar spinal stenosis (LSS) and reported a prevalence fo 73% in these patients [71]. Shi et al. also reported a high prevalence of sleep disturbances reaching 60% in patients with cervical radiculopathy, with the majority being female patients [72].

Deformity-related spine conditions

Sleep disturbances are also prevalent in deformity-related spine conditions including adult spinal deformities (ASD). Kim et al. additionally investigated the prevalence of sleep disturbances in patients with ASD and reported a prevalence of 75% [71]. They also looked at the correlation of this high prevalence with patient-reported outcomes and found that those with worse sleep had a higher visual analogue scale (VAS) scores for back pain compared to getting sufficient sleep [71].

These findings shed light on the reciprocal relationship between sleep disturbances and spinal deformities with pain and the changes in posture potentially worsening sleep disruption.

Finally, Zarrabian et al. examined the relationship between sleep, pain, and disability in patients suffering from spine pain of different etiologies, and reported that the quality of sleep could independently predict both disability and pain [44]. These findings suggest a high prevalence of sleep disturbances in patients with spine pathologies and a strong association with worse patient outcomes, highlighting the need for an emphasis on sleep hygiene in this challenging patient population.

Assessment of sleep disturbances

It is important to evaluate sleep disorders in order to better understand the severity of the condition and hence tailor treatment strategies accordingly. Different approaches are available to assess sleep disturbances including taking a detailed sleep history, administering sleep questionnaires and conducting polysomnography (PSG).

Sleep questionnaires

Several validated scales and questionnaires have been shown to effectively screen for sleep disturbances. These included the Epworth Sleepiness Scale (ESS) that assesses daytime sleepiness; the Pittsburgh Sleep Quality Index (PSQI) that evaluates the quality of sleep; the Berlin Questionnaire (BQ) and the STOP-BANG Questionnaire (SBQ) which identify OSA [[73], [74], [75], [76]]. Among these, the SBQ has shown a greater accuracy in detecting OSA compared to ESS and BQ across all severity levels ranging from mild, moderate and severe [77]. Moreover, the REM Sleep Behavior Disorder Screening Questionnaire is highly sensitive in detecting patients with idiopathic REM sleep behavior disorder [78,79].

Polysomnography

Polysomnography (PSG) remains the gold standard for the comprehensive evaluation of sleep disturbances. In insomnia, it identifies prolonged latency to fall asleep, reduced overall sleep duration, and lower sleep efficiency [80]. Alternatively, narcolepsy is marked by reduced sleep efficiency, shortened sleep onset latency, and the occurrence of sleep-onset REM periods [81,82]. For REM sleep behavior disorder (RBD), PSG findings typically show a decreased percentage of REM sleep, the absence of normal muscle atonia during REM, and episodes of vigorous, jerky movements [83]. In comparison, NREM parasomnias primarily occur during the first half of the night and are characterized by vocalizations and either simple or complex motor behaviors [84].

Sleep disorders and spine surgeries

Based on the aformentioned findings, numerous studies have assessed the correlation of proper sleep on outcomes following spine surgeries.

Patient-reported outcome measures

Sleep disturbances are highly correlated with patient-reported outcomes following spine surgery, specifically in terms of pain, functionality, sleep quality, and overall well-being [41,85]. Patients with sleep disturbances frequently report higher levels of postoperative pain, greater difficulties in functionality, and impaired cognitive performance, all of which may make it harder for patients to participate in physical therapy. This can significantly hinder their recovery and reduce their ability to perform daily activities following surgery as well [41,85]. The bidirectional relationship between sleep and pain likely contributes to the development of these challenges: poor sleep increases pain sensitivity which can further disrupt sleep, thus creating a vicious cycle that complicates pain management [[86], [87], [88]]. As a result, these patients have greater dependance on analgesics to optimize pain control, which can lead to hyperalgesia and further increase pain intensity, prolong recovery duration, and delay rehabilitation efforts [[89], [90], [91], [92]].

In contrast, patients who had sleep disturbances due to their spinal pathology prior to surgery and experienced improvement in their sleep patterns after surgery report significantly improved clinical outcomes [41,42,[93], [94], [95], [96]]. These patients often experience better pain management, quicker functional recovery, and improved sleep quality. Furthermore, the resolution of sleep disturbances may facilitate a smoother recovery process by allowing patients to engage more effectively in rehabilitation and daily activities [97,98]. Interestingly, these patients also report better improvements in outcomes compared to those who did not have sleep disturbances prior to surgery, suggesting that the resolution of sleep issues can provide an important boost in terms of postoperative recovery and overall well-being [96].

The fact that sleep disturbances resolve in some instances and not in others suggests that the etiology and primary driver of sleep disturbances is often multifactorial, extending beyond the underlying spinal pathology itself. However, the retrospective nature of most studies in this area, the methods employed for selection of patients, and the incorporation of potential confounders into the analyses make it difficult to draw definitive cause-effect conclusions on whether the sleep disturbance was due to the spine pathology itself or due to other underlying factors [99]. Among those, obesity is a well-established contributor to poor sleep quality as excess weight adversely affects different aspects of sleep physiology [100]. In patients undergoing spine surgery, the interaction between obesity and surgical outcomes may further exacerbate sleep disturbances. Understanding the combined influence of these factors is essential for evaluating postoperative sleep quality and addressing potential challenges in this patient population [100]. In turn, it is difficult to determine if resolution of the spine pathology through surgery will directly lead to improvements in sleep quality or if other concomitant factors such as comorbidity burden, obesity and higher American Society of Anesthesiologists (ASA) scores play a more significant role. These findings underscore the importance of a comprehensive perioperative care, with emphasis on patients suffering from sleep disturbances prior to spine surgery in order to ensure optimal surgical outcomes.

Postoperative complications

Several studies have assessed the correlation of sleep disturbances, specifically OSA diagnosis, with outcomes following spine surgery. Chung et al., for instance, have previously demonstrated a 3-fold increase in major complication rates such as myocardial infarctions, cardiac arrests and septic shock while Stundter et al. have reported 1.3 times the odds of increased hospital costs in OSA patients undergoing elective spine surgeries [101,102]. Likewise, Chung et al. have also demonstrated an increase in hospital stays in this population as well [101]. However, while most studies agree that poor sleep can contribute to adverse postoperative outcomes, some studies have also demonstrated conflicting findings. Nistal et al., in particular, reported no clinically significant difference in complication rates or hospital costs in patients undergoing posterior cervical decompression and fusion [103]. Moreover, Lin et al. have also refuted the increase in length of hospital stay observed by Chung et al. [101,104].

The discrepancy in literature findings may be attributable to the creation of standardized OSA protocols in 2006 that has since been proven to be effective in treating OSA in other surgical contexts [[105], [106], [107]]. These preoperative protocols were published by the American Society of Anesthesiologists (ASA) and include comprehensive screening with tools like the STOP-Bang questionnaire to evaluate for the risk of OSA through questions on snoring, tiredness, observed apnea, high blood pressure, body mass index (BMI), age, neck circumference, and gender, thus aiding in surgical decision-making by identifying high risk patients [75] (Fig. 4). They also include the initiation of preoperative continuous positive airway pressure (CPAP) therapy, optimization of an anesthetic management plan, and close postoperative monitoring [108,109]. These protocols aim to mitigate the risks associated with OSA to ensure better oxygenation and reduced airway obstruction during the perioperative period [108,109]. Already, many studies have highlighted the impact of CPAP initiation on postsurgical outcomes. In their meta-analyses, for instance, Nagappa et al. found that CPAP significantly reduced the postoperative apnea-hypopnea index in patients with OSA from 37±19 events per hour preoperatively to 12±16 events per hour postoperatively. It also reduced the length of hospital stay, with patients on CPAP staying on average for 4.0±4 days compared to 4.4±8 days for those not on CPAP [110]. Moreover, Mutter et al. revealed that the odds of adverse cardiac events was significantly lower in patients with OSA treated with CPAP preoperatively compared to those with undiagnosed and untreated OSA [111]. However, not all institutions adopt these protocols or implement them consistently in their routine practice, and specifically in complex spine surgeries. Moreover, most studies reporting postoperative complications in patients with sleep disturbances following spine surgery were conducted retrospectively and involved patients who were registered at varying time points in relation to the protocols being created and updated [[101], [102], [103], [104],112]. This variation in protocol adoption and implementation timing likely contributes to the inconsistent findings regarding the correlation of OSA with spine surgical outcomes.

Fig. 4.

STOP-BANG sleep apnea questionnaire.

Nonetheless, all studies found that OSA was either not associated with increased mortality or even protective against mortality following surgery [[101], [102], [103], [104]]. One possible explanation for the survival benefit of OSA is ischemic conditioning, which is a key characteristic of OSA. This phenomenon consists of repeated lung collapse and obstruction that leads to intermittent hypoxia and could provide a protective effect from any ischemic injury [[113], [114], [115], [116]]. Another explanation for this advantage might be the careful preoperative medical optimization and postoperative care given to patients diagnosed with OSA.

Best practices for addressing sleep disturbances in the postoperative period

Sleep disturbances are a significant concern for spine surgery patients during the postoperative period [117]. These are often excacerbated by pain, stress, environmental factors and the effects of medications. It is therefore essential to address these issues adequately during the in-hospital stay in order to promote recovery and optimize patient outcomes [[118], [119], [120]].

Effectively managing pain is important to minimize sleep disruptions in the postoperative setting. In fact, pain is primary driver of poor sleep and multimodal analgesic strategies including the use of acetaminophen, NSAIDs and low-dose opioids have proven to control pain with improvements in sleep patterns [69,121]. Moreover, techniques including epidural anesthesia and nerve blocks can provide pain relief which could reduce the need for systemic opioids and transitioning to nonopioid management as soon as feasible can further support the restoration of normal sleep patterns [122,123].

The hospital environmnent often disrupts sleep due to noise, lighting and frequent interruptions [124]. Therefore, creating a more sleep-friendly environment can significantly improve rest. Noise reducing strategies including the implementation of quiet hours, sound-absorbing materials and the provision of earplugs have been shown to improve sleep quality [125,126]. Similarly, controlling light exposure by dimming lighting at night and the use of eye masks could help set a more restful environment [127,128]. Moreover, ensuring an adequate room temperature can also positively impact sleep [129].

The timing and side effects of medications should also be carefully managed in order to reduce their impact on sleep [130,131]. For instance, corticosteroids could disrupt sleep when administered too late in the day [132,133]. Therefore, adjusting dosing schedules or considering alternatives when it is appropriate could improve sleep quality. In the case of persistent sleep disturbances, short-term pharmacologic interventions such as melatonin or low-dose trazodone can also be used under close supervision to avoid dependency or adverse effects [134,135].

Moreover, nonpharmacologic interventions have an essential role in addressing postoperative sleep disturbances [136]. These include relaxation techniques such as guided imagery, progressive muscle relaxation, physical therapy and cognitive behavioral therapy for insomnia (CBT-I), which have been found to be effective in reducing anxiety and hence would yield a better sleep environment [[137], [138], [139], [140], [141]]. When possible, light physical activity during the day such as short walks can also help regulate circadian rhythms and would result in better sleep outcomes [142].

For patients with OSA, the adherence to CPAP therapy is essential during the hospital stay. Preoperative screening for undiagnosed OSA with the use of the STOP-BANG questionnaire would help identify patients at-risk [76,101]. Clinicians should also remain vigilant for postoperative respiratory symptoms that are suggestive of OSA as early intervention is critical to minimize its impact on recovery [76,101].

Moreover, education and engagement of patients are important factors to manage sleep disturbances [143]. Therefore, discussing the importance of sleep for healing and involving patients in their care plans can improve adherence to interventions. Also setting realistic expectations and addressing common concerns including hospital-related disruptions can further reduce anxiety and promote better sleep [117,144,145].

Future directions

In order to gain a better understanding of the causal association between sleep disturbances and postoperative outcomes in spine surgery, future research should be conducted as prospective studies. Moreover, proper application of standardized preoperative screening procedures, such as the STOP-Bang questionnaire, and uniform application of CPAP therapy amongst facilities are critical. Further awareness can be obtained by looking into the effects of individualized perioperative care programs for patients with sleep disorders. Additionally, examining the possible advantages of novel therapy approaches targeted at enhancing the quality of sleep prior to and during surgery may help improve patient outcomes. Finally, creating comprehensive solutions to reduce the risks associated with sleep disturbances in spine surgery patients will need combining multidisciplinary approaches involving sleep specialists, anesthesiologists, and spine surgeons.

In summary, although findings on the effects of sleep disturbances on spine surgery outcomes are conflicting, standardized preoperative protocols such as those recommended by the ASA, including CPAP therapy and thorough screening, may be helpful in mitigating risks. Maintaining compliance with these guidelines is, hence, essential to maximizing postoperative spine surgery outcomes in patients with sleep disorders.

Conclusion

Sleep disorders are highly prevalent in patients with spine pathologies. Preoperative sleep disturbances that persist postoperatively can negatively correlate with patient-reported outcomes, whereas resolution of sleep disturbances after surgery results in better functional outcomes. Although the available literature findings on postoperative complications following spine surgery are conflicting, institutional implementation of the OSA protocols may be beneficial in improving surgical outcomes. Therefore, it is recommended to adopt comprehensive and standardized management protocols similar to those used for OSA to optimize outcomes in spine surgery patients.

CRediT authorship contribution statement

Joseph E. Nassar: Conceptualization, Data curation, Writing – original draft, Writing – review & editing. Manjot Singh: Writing – original draft, Writing – review & editing. Ashley Knebel: Writing – original draft. Mohmmad Daher: Writing – review & editing. Daniel Alsoof: Writing – review & editing. Bassel G. Diebo: Writing – review & editing. Alan H. Daniels: Conceptualization, Supervision, Writing – review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.