Epidural Fat and Its Association with Pain, Physical Function, and Disability Among Older Adults with Low Back Pain and Controls

Objective. To examine epidural fat and its relationship to pain, physical function, and disability among older adults with chronic low back pain, chronic low back pain plus leg pain, and controls. Design. Cross-sectional, comparative study. Setting. Standardized examinations were conducted in a research laboratory, and magnetic resonance images were obtained. Subjects. A total of 93 adults age 60 to 85 years (24 with chronic back pain, 25 with chronic back pain plus leg pain, and 44 controls). Methods. Reliability for assessment of epidural fat diameter, averaged across spinal levels, was established (intraclass correlation coefficient = 0.95). Linear regression was used to explore how epidural fat diameter related to self-reported (Short Form-36 Health Survey: physical component summary score) and performance-based (stair climb performance) measures of physical function among adults with chronic back pain with and without leg pain, as compared with controls, while controlling for age, sex, and body mass index. Associations between epidural fat and pain intensity and low back pain-related disability were also explored (P <= 0.050). Results. Epidural fat helped explain self-reported function (P < 0.001); adults with axial low back pain (LBP) may have a relationship between epidural fat and self-report function that is different from controls (P = 0.015). Relationships between epidural fat and stair performance were significantly different from controls for those with LBP (P = 0.000) but not for those with LBP plus leg pain (P = 0.366). Relationships between epidural fat and pain intensity and/or disability were not found. Conclusions. Increased epidural fat may help explain better function among older adults with chronic axial back pain, but not among those who also report leg pain.