How do patients sleep after orthopedic surgery? Changes in objective sleep parameters and pain in hospitalized patients undergoing hip and knee arthroplasty

<strong>Aim.</strong> Sleep impairment after hip and knee arthroplasty is multifactorial and still poorly understood and post-operative pain is a potential cause of sleep deprivation or disturbances. The aim of this study was to assess actigraphy-based sleep characteristics and pain scores in patients undergoing knee or hip joint replacement and hospitalized for ten days after surgery. <strong>Methods.</strong> In this observational cohort study, n=20 subjects (11 males and 9 females; age: 64.0±10.39 years old) completed a daily sleep diary and wore the Actiwatch 2 actigraph (Philips Respironics, Portland, OR) to record sleep parameters for 11 consecutive days, starting the day before surgery and ending the 10^th day after surgery. Subjective scores of pain, by a visual analog scale (VAS), were constantly monitored for the entire experimental protocol. The following evaluation time-points have been considered for the analysis: pre-surgery (PRE), the first (POST1), the fourth (POST4) and the tenth day (POST10) after surgery. A repeated-measures one-way analysis of variance followed by the Tukey-Kramer post hoc tests, or the equivalent nonparametric Friedman test followed by the Dunn’s multiple comparisons, was applied to test differences in sleep and pain among time-points. Test for correlation between mean VAS score and the sleep parameters at each post-operative time point were performed using Pearson’s method. <strong>Results.</strong> Sleep quantity and timing parameters did not differ from PRE to POST10, during the hospitalization. On the contrary, Sleep Efficiency (p=0.006; η²_p=0.45, large), Sleep Latency (p=0.039; η²_p=0.37, large), Wake After Sleep Onset (p=0.042; η²_p=0.34, large), Immobility Time (p=0.005; η²_p=0.47, large) and Fragmentation Index (p=0.016; η²_p=0.36, large) displayed significant differences. In detail, Sleep Efficiency and Immobility Time significantly decreased at POST1 compared to PRE by 10.8% (p=0.003; ES: 0.9, moderate) and 9.4% (p=0.005; ES: 0.86, moderate) respectively. Overall, all sleep quality parameters showed a trend of constant improvement from POST1 to POST10. VAS scores were higher in the 1^st day post-surgery (4.58 ± 2.46; p=0.0011 and ES: 1.40, large) compared to POST10 (1.68 ± 1.58) and in POST4 (3.85 ± 2.31) compared to POST10 (-2.18; p=0.0087 and ES: 1.09, moderate). During time, mean VAS showed significant negative correlations with mean Sleep Efficiency (r = -0.71; p=0.021) and mean Immobility Time (r = - 0.83; p=0.003) and a significant positive correlation with Fragmentation Index (r = 0.70; p=0.023), highlighting that high scores of pain were associated with lower overall sleep quality. <strong>Conclusion.</strong> Sleep quantity and timing parameters were stable during the entire hospitalization whereas sleep quality parameters significantly worsened the 1^st night after surgery compared to the pre-surgery night and, overall, these parameters showed a trend of constant improvement until discharge. Pain scores were at the highest level the 1^st day after surgery and at the lowest level before discharge with a negative correlation between pain and sleep quality parameters during time. The present study confirms the important impact of surgery on sleep parameters, especially on the first few post-operative days.