What Are the Associations Between Sleep and Pain in Osteoarthritis?

Osteoarthritis is the most common type of arthritis, most often affecting the hips and knees. Apart from pain and disability, many people with osteoarthritis anecdotally report sleep disturbances. The prevalence of self-reported sleep problems in osteoarthritis varies widely ranging from 11.9% (Gore et al., 2011) to 81% (Wilcox et al., 2000), however, these figures have not been supported by studies using objective sleep measures. While the relationship between sleep and pain is bidirectional (Frohnhofen, 2018), there is increasing evidence that sleep disturbance may impact pain, more than pain impacts sleep (Finan et al., 2013). In addition, patients with hip osteoarthritis believe that if they have better subjective sleep, their pain will improve (Blagestad et al., 2016). Sleep quality before hip and knee joint replacement is also one of the most crucial factors determining both immediate and longer-term post-operative pain (Bjurström et al., 2021; Boye Larsen et al., 2021).

There are theoretical reasons to explain why poor sleep could affect pain in osteoarthritis. Fragmented sleep may activate immune and inflammatory pathways which can increase central pain processing, as well as via an effect on mood (Smith et al., 2009). Meta-analyses have shown that sleep deprivation increases pain sensitivity in healthy controls (Schrimpf et al., 2015), and both short sleep duration and insomnia are causally linked to the development of chronic widespread pain (Williams et al., 2024). In osteoarthritis, participants with both pain and insomnia have increased central sensitisation on Quantitative Sensory Testing compared to controls (Campbell et al., 2015). Emerging evidence suggests that chronotype, an individual preference for "morningness" or "eveningness" may influence sleep quality, with "morning" types reporting better sleep quality (Yazdi et al., 2014). In addition, "evening" types may be more susceptible to musculoskeletal pain (Zhang et al., 2018), although the mechanisms for this are unclear. Qualitatively, patients with osteoarthritis describe difficulty getting to sleep, due to pain and positioning problems, as well as frequent waking during the night and difficulty getting back to sleep (Whale & Rachael, 2022). Self-reports of poor sleep in osteoarthritis are also associated with an increased level of pain catastrophizing (Campbell et al., 2015), a tendency to constantly think about pain and the negative consequences of pain (Quartana et al., 2009). A meta-analysis of plasma C-Reactive Protein (CRP) levels, a protein produced by the liver in response to the presence of inflammatory cytokines that is involved in immune activation and a biomarker for a peripheral inflammatory state, has shown a modest but significant increase in people with osteoarthritis (Jin et al., 2015). Experimental sleep deprivation is associated with higher levels of plasma CRP (Irwin et al., 2016) and cross-sectional population studies show that both shorter and longer than average sleep duration is associated with higher levels of plasma CRP (Lee et al., 2020; Zhang et al., 2023).

Potentially, as objective sleep data is time consuming and expensive to collect, most sleep studies in osteoarthritis favour subjective, self-report measures of sleep quality, such as the Pittsburgh Sleep Quality Index (PSQI) 1989) and the Insomnia Severity Index (ISI). Quantitative objective measurements, such as actigraphy or polysomnography (PSG) are much less commonly used and are typically used for only a few days. In two of the very few PSG studies of sleep in osteoarthritis, one showed more sleep-stage transitions suggestive of sleep fragmentation in people with osteoarthritis compared to controls (Yeung et al., 2018), another showed more light than deep sleep, implying worse sleep quality in people with osteoarthritis compared to controls (Leigh et al., 1988), although this study is limited by a sole recruitment of male participants. Whether this would replicate in a mixed sample remains an empirical question. In many sleep studies, it is common to find a disparity between subjective and objective measures of sleep quality, in particular, worse self-reported sleep efficiency and total sleep time, compared to objective sleep measures (Bean et al., 2021; Heitkemper et al., 2005). This phenomenon is often called 'sleep misperception' (Hughes et al., 2018).

The extent of sleep misperception varies between different clinical populations and in one study, increasing pain levels, but not age, depression or dysfunctional sleep beliefs lead to the greatest difference between subjective and objective sleep measures, suggesting that pain can cause people to negatively interpret their sleep (Hughes et al., 2018). Sleep misperception has been reported in people with several different pain conditions including rheumatoid arthritis (Hirsch et al., 1994) but not so far in osteoarthritis. Due to a paucity of empirical literature, the mechanisms underlying sleep misperception are unclear. One theory is that people who underestimate their sleep may have more frequent brief nocturnal awakenings (Harvey & Tang, 2012), also suggested in a small objective study in osteoarthritis (Yeung et al., 2018).

Positive personality factors that may be protective of sleep or sleep misperception such as resilience or self-efficacy have not been widely studied. Resilience has been described as an important characteristic that can help individuals "bounce-back" from challenging situations allowing adaptation and personal growth and is considered important regarding outcomes related to chronic pain (Smith & Zautra, 2008). Sleep and resilience are positively correlated in healthy individuals (Arora et al., 2022) and people with knee osteoarthritis who have high levels of psychological resilience also have higher levels of self-rated health (Hsieh et al., 2023). Three personal characteristics have been considered key characteristics of increased pain resilience - optimism, pain acceptance, and purpose in life (Smith & Zautra, 2008). In addition, self-efficacy (Bandura, 1977) which in the context of health is a belief in one's abilities to control symptoms, as well as external factors such as emotional or social support are also likely influence recovery or "bounce-back" from setbacks. Optimists tend to report better subjective sleep (Lau et al., 2017), lower levels of clinical pain (Shanahan et al., 2021) and lower pain catastrophising scores (Hood et al., 2012). In osteoarthritis, optimism is associated with less clinical pain and less experimental pain sensitivity (Thompson et al., 2018). In addition, people with more optimistic traits tend to report better sleep quality and fewer insomnia symptoms than those with fewer optimistic traits, even if their objective sleep is impaired, demonstrating a favourable sleep misperception pattern (Hernandez et al., 2020). This suggests that optimism may be a protective factor against the negative impact of sleep misperception and subsequent pain. The broader concept of pain resilience related to sleep has yet to be investigated in clinical populations with osteoarthritis. Another factor that may contribute to sleep misperception in osteoarthritis could be pain catastrophising; a collection of negative cognitive and affective biases to pain associated with feelings of helplessness (Quartana et al., 2009). In people with osteoarthritis, sleep disturbance is associated with both pain catastrophising and the level of knee pain (Wang et al., 2023).