The Pittsburgh Sleep Quality Index (PSQI) is a validated and commonly used questionnaire ranging in scores from 0 to 21 that aims to determine the subjective sleep disturbance in a given clinical scenario [8,9]. A PSQI score greater than or equal to 5 is indicative of “poor” sleep, with a sensitivity of 0.90 and a specificity of 0.87 [9]. Longo et al. [10] established the patient acceptable symptom state (PASS) to be 5.5 for PSQI. Use of a validated questionnaire like PSQI is important, as self-reports of sleep quality are prone to error.

In patients who present to an orthopedic surgeon for shoulder pain relating to RC pathology, the rate of sleep disturbance is very high. Several studies have found that around 90% of these patients have significant sleep disturbance, as assessed by the PSQI [6,11-13]. These sleep disturbances can be severe, with average preoperative PSQI scores of 11.7 and 9.5 in studies by Horneff et al. [11] and Khazzam et al. [12], respectively. In a study conducted by Ansok et al. [14], 18 patients with full-thickness RCT were monitored using wearable sleep trackers to obtain objective data on the impact of RCT on sleep. The study revealed a substantial impact of RCT on sleep as the affected cohort exhibited decreased total sleep time, more frequent awakenings, and delayed sleep onset compared to unaffected controls. Notably, patients in the study were not aware of the extent of their sleep deficit and underestimated their sleep disturbance by 90 minutes [14]. Tanik et al. [15] found greater pressure-pain sensitivity in the affected limb of patients with partial thickness RCT, a factor that is hypothesized to contribute to discomfort during sleep. Given the relationship between adequate sleep and overall physical and mental health, it is important that such patients receive timely definitive management of their RCT.

The evidence for the effect of RCT-related sleep disruption on daytime wakefulness is mixed based on studies reporting scores from the Epworth Sleepiness Scale (ESS), a validated survey used to evaluate daytime sleepiness [16]. While Ansok et al. [14] reported elevated ESS scores as a result of RCT, Gumina et al. [17] did not find a significant difference between RCT patients and healthy controls. Ansok et al. [14] found no correlation between objective actigraphy measurements and PSQI or ESS [8,9,16]. Instead, only pain visual analog scale (VAS) score correlated with actigraphy measurements, which aligns with the findings of Khazzam et al. [12,14].

Furthermore, studies have demonstrated that healthier patients tend to overestimate their sleep quality, while patients with diagnosed depression and anxiety tend to underestimate their sleep quality [14,18]. In addition, several patient-level factors have been identified as independent risk factors for sleep disturbance in the context of RCT, as defined by the PSQI. These factors include pain VAS, depression, female sex, comorbid low back pain, and concurrent cervical pathology [12]. This highlights the complexity of assessing sleep disturbances and the need to consider multiple factors in preoperative evaluation.

Conflicting evidence exists on the association between magnetic resonance imaging (MRI) characteristics of RCT and sleep disturbances. In a cross-sectional study of 208 patients, Reyes et al. [19] found no correlation between PSQI score and tear size, number of tendons involved, tendon retraction, Goutallier classification, muscle atrophy, or humeral head rise. Some researchers have questioned the reliability of subjective sleep measures, such as the PSQI, and have opted for more objective measurements of sleep quality. For example, MacConnell et al. [20] prospectively studied the sleep of 36 RCT patients with a waist-worn accelerometer and found no association between tendon retraction and sleep efficiency. Taken together, these results suggest no association between either subjective or objective measures of sleep impairment and structural characteristics of RCT. These findings oppose those of Gumina et al. [17], who found higher PSQI and ESS scores in patients with small tears compared to large and massive tears in a case-control study of 324 RCT patients. That study also found significant correlations between tear size and sleep latency and sleep disturbances [17]. The authors hypothesize that this could be attributed to greater bursal inflammation with smaller tears, which may reflect insufficient time for nociceptor desensitization in more acute tears [17].

Studies investigating the association between inflammation and night pain in RCT have yielded more consistent results and have provided several insights. In a prospective study of 63 patients, Cho et al. [21] performed enzyme-linked immunosorbent assay to measure the concentrations of inflammatory cytokines in blood samples obtained prior to RC repair (RCR). They found significantly higher levels of tumor necrosis factor (TNF)-⍺ in patients who reported sleep disturbances compared to those without sleep disturbances and controls without an RCT [21]. They suggested that TNF-⍺ could be a potential therapeutic target for sleep disturbances associated with RCT [21]. Terabayashi et al. [22] used Doppler ultrasonography to assess blood flow and found that RCT patients who reported night pain had higher peak systolic velocities in the anterior humeral circumflex artery of the affected side compared to the unaffected side. This was not observed in RCT patients without night pain or in controls without RCT [22]. Notably, they only included RCT patients who reported aching pain at night and excluded patients reporting night pain related to movement or compression [22]. These findings suggest several pathological mechanisms that can result in night pain and sleep disturbances in RCT patients. Future studies should seek to characterize RCT-related night pain as there may be several distinct underlying processes contributing to such symptoms, and that may require more nuanced treatment. Another explanation is the shoulder stiffness experienced by patients with RCT. In addition, pain from the injury can result in joint disuse and contracture of the joint capsule, leading to secondary adhesive capsulitis that itself could lead to sleep disturbances [23,24].

Behavioral factors also have been implicated in the pathophysiology of night pain experienced by RCT patients. In a cohort of 20 healthy volunteers, Werner et al. [25] observed significant variation in subacromial pressure between sleep positions. They found that individuals preferring to sleep supine had lower subacromial pressure than those favoring side or prone positions. These findings suggest that sleep position preferences should be assessed in the evaluation of RCT patients with night pain as modifications may help mitigate tear propagation and promote the healing of RCRs. Several studies have suggested that psychobehavioral factors such as mental health, preoperative narcotic use, and coping strategies have a significant impact on pain and sleep quality [19-17,26]. Studies assessing the influence of these factors are limited and warrant further investigation as they may play a role in the pathophysiology of RCT-related sleep disturbances and may provide novel therapeutic approaches.