RESEARCH ARTICLE Prevalence and long-term

Full list of author information is available at the end of the articleBackground Chronic pain is common in the general population with a prevalence ranging from 20 % to 55 % [1-5]. Chronic pain persists beyond three months and is characterized by repeated or continuous pain episodes [6]. Other pain dimensions are quantitative (intensity) [7,8], qualitative (burning, pressing pain) [9], and spatial measures (whether the pain is local, regional or widespread) [10-12]. Chronic widespread pain (CWP) is an important measure of the global burden of pain [1,13], with a reported prevalence of 4 % to 18 % [14,15]. These various aspects of chronic pain have been assessed extensively and studied together as one entity, but rarely separately. Wolfe et al. [16] have defined CWP as pain in the left and right sides of the body, above and below the waist, plus pain in the axial skeleton. CWP seems to be more prevalent in females than in males [17,18], but it appears to be constant between age groups