Chronic Pain Without Clear Etiology in Low- and Middle-Income Countries: A Narrative Review.

Globally, 8 of the top 12 disabling conditions are related either to chronic pain or to the psychological conditions strongly associated with persistent pain. In this narrative review, we explore the demographic and psychosocial associations with chronic pain exclusively from low- and middle-income countries (LMICs) and compare them with current global data. One hundred nineteen publications in 28 LMICs were identified for review; associations with depression, anxiety, posttraumatic stress, insomnia, disability, gender, age, rural/urban location, education level, income, and additional sites of pain were analyzed for each type of chronic pain without clear etiology. Of the 119 publications reviewed, pain was described in association with disability in 50 publications, female gender in 40 publications, older age in 34 publications, depression in 36 publications, anxiety in 19 publications, and multiple somatic complaints in 13 publications. Women, elderly patients, and workers, especially in low-income and low-education subgroups, were more likely to have pain in multiple sites, mood disorders, and disabilities. In high-income countries, multisite pain without etiology, female gender, and association with mood disturbance and disability may be suggestive of a central sensitization syndrome (CSS). Because each type of prevalent chronic pain without known etiology reviewed had similar associations in LMICs, strategies for assessment and treatment of chronic pain worldwide should consider the possibility of prevalent CSS. Recognition is especially critical in resource-poor areas, because treatment of CSS is vastly different than localized chronic pain.