Abstract
BackgroundSystemic inflammation has been associated with reduced pulmonary function in individuals with and without chronic medical conditions. Individuals with chronic spinal cord injury (SCI) have clinical characteristics that promote systemic inflammation and also have reduced pulmonary function. We sought to assess the associations between biomarkers of systemic inflammation with pulmonary function in a chronic SCI cohort, adjusting for other potential confounding factors.MethodsParticipants (n = 311) provided a blood sample, completed a respiratory health questionnaire, and underwent spirometry. Linear regression methods were used to assess cross-sectional associations between plasma C-reactive protein (CRP) and interleukin-6 (IL-6) with forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and FEV1/FVC.ResultsThere were statistically significant inverse relationships between plasma CRP and IL-6 assessed in quartiles or continuously with FEV1 and FVC. In fully adjusted models, each interquartile range (5.91 mg/L) increase in CRP was associated with a significant decrease in FEV1 (−55.85 ml; 95% CI: -89.21, −22.49) and decrease in FVC (−65.50 ml; 95% CI: -106.61, −24.60). There were similar significant findings for IL-6. There were no statistically significant associations observed with FEV1/FVC.ConclusionPlasma CRP and IL-6 in individuals with chronic SCI are inversely associated with FEV1 and FVC, independent of SCI level and severity of injury, BMI, and other covariates. This finding suggests that systemic inflammation associated with chronic SCI may contribute to reduced pulmonary function.
Highlights
Systemic inflammation has been associated with reduced pulmonary function in individuals with and without chronic medical conditions
Short expiratory efforts and excessive back extrapolation are common in spinal cord injury (SCI), but we have demonstrated that forced vital capacity (FVC) and Forced expiratory volume in 1 s (FEV1) are reproducible in this population [34]
All adjusted models were attenuated relative to the basic model (Additional file 1: Table S1), the associations were robust to adjustment for potential confounders
Summary
Systemic inflammation has been associated with reduced pulmonary function in individuals with and without chronic medical conditions. A growing literature supports inverse associations between levels of inflammatory markers and reductions in measures of pulmonary function in both the general population and among populations with chronic disease (e.g. chronic obstructive pulmonary disease (COPD), asthma, end-stage-renal disease) [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17] The majority of these studies have been cross-sectional; these findings have been reported in some, but not all, SCI is a chronic medical condition that is associated with a number of clinical characteristics that promote systemic inflammation, including increases in central fat, decreased mobility due to muscle paralysis, and recurrent infection mainly associated with skin ulcers and urinary tract infections [25,26,27,28,29,30,31,32]. Our objective was to determine if these findings were generalizable to another SCI cohort with a larger sample size and information on additional potential confounders
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