“…Cross-sectional univariate associations between higher pain and higher fatigue levels were significant, with a median correlation of 0.51 (range 0.22–0.75) in all studies [10, 12, 13, 15, 17–20, 24, 31, 39, 40, 50, 60–69], but there was one in which only one of two correlations was significant [8]. The multivariate association was significant after controlling for variables such as demographics, disease activity, depression, sleep and physical functioning in all studies [10, 17, 18, 32, 39, 50, 61, 63, 66, 70], but there was one that included another pain measure as a covariate [27].…”