Pain sensitivity after Roux-en-Y gastric bypass - associations with chronic abdominal pain and psychosocial aspects.

Objectives: The aims of this study were to investigate modifications in pain sensitivity after RYGB and to explore associations between pain sensitivity and weight loss, chronic abdominal pain, total body pain, anxiety, depression, and pain catastrophizing.

Methods: In total, 163 patients with obesity were examined with a cold pressor test for pain sensitivity before and two years after RYGB. Two aspects of pain sensitivity were registered: Pain intensity (numeric rating scale, range 0-10) and pain tolerance (seconds). Associations between pain sensitivity and the explanatory variables were assessed with linear regression.

Results: Two years after RYGB the pain intensity increased (mean ± SD 0.64 ± 1.9 score units, p<0.001). Pain tolerance decreased (7.2 ± 32.4 s, p=0.005). A larger reduction in body mass index was associated with increased pain intensity, β=-0.090 (95 % CI -0.15 to -0.031, p=0.003), and decreased pain tolerance β=1.1 (95 % CI 0.95 to 2.2, p=0.03). Before surgery, participants with chronic abdominal pain reported 1.2 ± 0.5 higher pain intensity (p=0.02) and had 19.2 ± 9.3 s lower pain tolerance (p=0.04) than those without abdominal pain. No differences in pain sensitivity were observed between participants who did or did not develop chronic abdominal pain after RYGB. Pain sensitivity was associated with symptoms of anxiety but not with pain catastrophizing, depression or bodily pain.

Conclusions: The pain sensitivity increased after RYGB and was associated with larger weight loss and anxiety symptoms. Changes in pain sensitivity were not associated with development of chronic abdominal pain after RYGB in our study.