Depression Trends in Patients with Chronic Pain: An Analysis of the Nationwide Inpatient Sample

Background: Depression remains a major public health issue that affects the lives of many worldwide, including patients with chronic pain. Comorbidities like depression have been associated with decreased quality of sleep, decreased enjoyment of life activities, increased anxiety, and decreased efficacy in treatments among patients with chronic pain. Despite these associations, the trends and demographic characteristics of patients with chronic pain with depression is yet to be investigated. Objectives: To investigate the trends and demographic characteristics of hospitalized patients with chronic pain with comorbid depression from years 2011 to 2015 in the United States. Study Design: This was an observational study. Setting: Patients were identified from a Healthcare Cost and Utilization Project database called National Inpatient Sample (NIS) documentation. Methods: Patients were identified from the NIS database using International Classification of Diseases, Ninth and Tenth Revision (ICD-9 and ICD-10) diagnosis codes for chronic pain and comorbid depression from years 2011 to 2015. Results: Between 2011 and 2015, an estimated 9.3 million patients with chronic pain were identified. Of this cohort, 2.2 million patients (22.9%) were diagnosed with comorbid depression. The estimated number of patients with depression varied from 399,865 (22.6%) in 2011 to 421,490 (23.1%) in 2015 (P = 0.13). From 2011 to 2015, there was a significant upward trend of depression among blacks (8.1 +/- 0.42% to 9.7 +/- 0.27%), patients aged 65 to 84 years (29.0 +/- 0.39% to 32.4 +/- 0.23%), Medicare insured patients (56.1 +/- 0.54% to 58.5 +/- 0.29%), Medicaid insured patients (14.7 0.4% to 17.1 +/- 0.24%), and patients from zip code areas with lowest annual household income (29.2 +/- 1.3% to 32.0 +/- 0.59%). Among patients with depression, the adjusted total hospitalization cost increased from $43,584 in 2011 to $49,923 in 2015 (P < 0.001), with average length of hospital stay stable around 5.05 +/- 0.02 days. Most patients were discharged home or with self-care compared with short-term facility (57.9 +/- 0.14% vs. 2.0 +/- 0.03%). Limitations: Large database research comes with several limitations. The NIS database does not contain variables that can evaluate disease severity such as depression. In addition, the NIS database is highly dependent on the selection and report accuracy of the appropriate diagnostic ICD codes. These estimates could be imprecise from over or underestimation of the number of patients with chronic pain with comorbid depression. Conclusions: These findings from the present investigation suggest that depression in patients with chronic pain remained stable from 2011 to 2015, with the majority of patients identified as women, white, and ages 45 to 65 years.