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

Aim. 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. Methods. 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. Results. 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. Conclusion. 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.