Objective:
Persons with chronic pain suffer from additional symptoms and deficits that are directly or indirectly related to their condition. Attentional deficits are a common problem in these individuals. The same is true for sleep disturbances. It is well-known that night sleep affects attention the next day. Therefore, sleep disturbances might be responsible for the association between chronic pain and deficits in attention.

Methods:
We studied the gaze behaviour (absolute and relative fixation times, i.e., attentional biases) in patients with chronic musculoskeletal pain (N = 20) and pain-free individuals (N = 28). For that purpose, we used an eye-tracker to monitor gaze behaviour during the presentation of affective stimuli, that is, pictures of faces displaying joy, anger, pain, and neutral expressions. In addition, we assessed subjective/wellbeing parameters, as well as objective sleep parameters with a portable polysomnography (PSG) device during two nights at home, with the aim of testing the mediating role of sleep for the relationship between chronic pain and alterations of attention.

Results: Patients with chronic pain exhibited overall shorter fixation times (on average ∼160 ms shorter fixation times). With respect to the attentional biases, all participants looked longer at the affective faces compared to the neutral ones, independent of group or type of affective stimulus. Several subjective sleep/ wellbeing parameters, together with two PSG parameters (sleep efficiency and duration of awakenings), were significantly worse in patients with chronic pain. Despite this, only subjective sleep quality and sleep efficiency mediated the association of chronic pain and attentional processes. Conclusions: Our findings confirm previous studies showing attentional deficits and sleep disturbances in patients with chronic pain. However, our results only partially support the hypothesis that the relationship between chronic pain and altered attentional processes is due to disturbed sleep. Other mechanisms might be involved, highlighting the need for further studies.