Obesity and the impact of chronic pain.

OBJECTIVE: To evaluate obesity as a marker for increased pain severity, disability, and psychologic distress in treatment-seeking, mixed chronic pain patients.
METHODS: Three hundred seventy-two consecutive chronic pain patients seeking evaluation at a university pain clinic were divided into 3 weight categories, based on body mass index (BMI): normal (BMI < 25 kg/m2), overweight (BMI between 25 kg/m and 30 kg/m2), and obese (BMI > or = 30 kg/m2). Patients completed questionnaires to identify pain severity, disability, depression, anxiety, and quality of life.
RESULTS: Pain severity and days per week with pain were similar among the weight groups. Disability was related to increasing weight status, with increased BMI associated with more days per week with both reduced activity and complete disability. Depressive symptoms were also related to weight category, with an average Beck Depression Inventory score of 11.81 +/- 7.55 in normal, 12.88 +/- 11.64 in overweight, and 15.78 +/- 9.88 in obese patients. Anxiety scores were similar among the weight categories. Physical function domain of quality of life was also reduced in relation to weight.
CONCLUSIONS: Weight is associated with co-morbid disability, depression, and reduced quality of life for physical function in chronic pain patients. Calculation of the BMI should become a routine part of the screening evaluation for chronic pain patients, with additional screening for disability and psychologic distress in patients with elevated BMIs.