Trends of Co-Morbid Depression in Hospitalized Patients with Failed Back Surgery Syndrome: An Analysis of the Nationwide Inpatient Sample.

INTRODUCTION: Co-morbid depression has been associated with poor outcomes following spine surgery and worsening of low back pain symptoms leading to failed back surgery syndrome (FBSS). Given the increasing focus of healthcare utilization and value-based care, it is essential to understand the demographic and economic data surrounding co-morbid depression amongst patients with FBSS.

METHODS: Our study investigated the NIS database for FBSS patients who had co-morbid depression (ICD-9 CM codes 300.4, 301.12, 309.0, 309.1, 311; ICD-10 M96.1) between 2011 and 2015 across 44 states. We obtained demographic and economic data such as age, sex, ethnicity, location, number of in-patient procedures, hospital length of stay, cost of hospital stay, and frequency of routine discharge dispositions. The NIS database represents approximately a 20% sample of discharges from hospitals in the United States. These data are weighted to provide national estimates for the total United States population. National administrative databases (NADs) like National Inpatient Sample (NIS) are a common source of data for spine procedures. This database is appealing to investigators because of ease of data access and large patient sample. The NIS database is a de-identified database that consists of a collection of billing and diagnostic codes used by participating hospitals with the goal of quality control, population monitoring, and tracking procedures. The NIS does not require institutional review board (IRB) approval or exempt determination.

RESULTS: Between 2011 and 2015, a total number of 115,976 patients with FBSS were identified. Of these patients, about 23,425 had co-morbid depression. The rate of co-morbid depression in 2015 was 23% with the lowest reported rate being 20% in 2011. Females and Caucasians had consistently higher rates of co-morbid depression compared to males and other ethnic groups respectively. The average length of stay for patients with co-morbid depression fluctuated between 2011 and 2015, with the highest reported at 4.81 days in 2015. The number of procedures increased steadily from 2011 to 2015 with a dip in 2013. The highest number of procedures was reported as 3.94 in 2015. The mean total hospital charges remained stable over time with the largest change being the decrease from 2011 (mean $93,939; 95% CI $80,064-$107,815) to 2012 (mean 82,603; 95% CI $75,127-$90,079). Additionally, patients with FBSS and co-morbid depression were more often discharged home than home with healthcare or to another healthcare facility.

CONCLUSIONS: The occurrence of co-morbid depression in hospitalized patients with FBSS increased from 20% in 2011 to 23% in 2015. While direct hospital costs and length of stay remained relatively stable, the number of inpatient procedures performed trended upwards. The exact etiology for this increase in depression prevalence is unknown; additional studies are needed to shed further insight.