2.4.3. Sleep Disturbances

Quality of sleep was assessed by using four items adapted from the widely used Pittsburgh Sleep Quality Index [33]. Scoring ranges from 4 to 20.

## 2.4.4. Chronic Pain

Participants diagnosed with chronic pain were asked to complete the Brief Pain Inventory Short Form (BPI-SF). The BPI-SF is validated in patients with both cancer and non-cancer pain and is one of the most used measurement tools for evaluating clinical pain, including both pain severity and the interference of pain on feelings and function [34]. Therefore, items from this scale were used to assess two distinct dimensions of pain: (i) severity of pain; and (ii) the extent to which pain interferes with daily activity. Patients scored both dimensions on a 0–10 scale.
