Nocturnal pain, is the pain different compared with pain during the day? An exploratory cross-sectional study in patients with hip and knee osteoarthritis

Objective To explore characteristics of nocturnal pain and to identify differences in participants' characteristics and osteoarthritis (OA) symptoms between hip and knee OA participants with and without nocturnal pain. Methods Data for this exploratory cross-sectional study were obtained from an online survey, distributed through social media and patient associations in the period from April 2020 until May 2020, which was conducted in 101 participants with (self-reported) hip or knee OA. Descriptive statistics were used to provide insight into the characteristics of the study population. Pain intensity, localization, dimension, and impact of (nocturnal) pain on sleep were described and compared with daytime pain. Results Nocturnal pain was reported by 76/101 (75%) participants. Participants with nocturnal pain scored higher visual analogue scale (VAS) scores for their nocturnal pain compared with their pain at the moment (respectively: median VAS score 49.5 vs. 40.0). Their day pain rating indexes of sensory-discriminative dimension were higher compared with their nocturnal pain. Comparison between participants with and without nocturnal pain showed that participants with nocturnal pain were affected by intermittent, constant, and radiating pain. Pain had more impact on their sleep and they scored their pain at its worst higher compared with participants without nocturnal pain. Conclusion In participants with nocturnal pain (75%), we found that their VAS pain scores were not in harmony with their pain expressed in words. This study increases awareness of nocturnal pain in OA patients in general practice. More research is needed to provide general practitioners possible interventions for patients with OA and nocturnal pain. Lay Summary Nocturnal pain is an important part of the pain experience in osteoarthritis (OA) and highlighted as key concern by patients with hip and knee OA. Reports have shown a wide range in prevalence of nocturnal hip and knee pain in OA patients (14%-85%). We found that participants with nocturnal pain (76/101 = 75%) were more often affected by both intermittent and constant pain, reported higher pain scores for pain at its worst and pain had more impact on their sleep compared with those without nocturnal pain. Participants with nocturnal pain scored higher visual analogue scale (VAS) scores for their nocturnal pain compared with their pain at the moment. On the other hand, they scored the pain expressed in words higher for their day pain than for their nocturnal pain. More research is needed to explore factors that associate with nocturnal pain and to explore how healthcare professionals can support people with nocturnal pain.