Differential association between biomarkers of subclinical inflammation and painful polyneuropathy: results from the KORA F4 study.

OBJECTIVE Inflammatory processes have been implicated in the pathogenesis of painful neuropathy in rodents, but the relationship between inflammatory biomarkers and painful distal sensorimotor polyneuropathy (DSPN) has not been assessed in population-based studies. Therefore, we investigated whether circulating levels of seven pro- and anti-inflammatory immune mediators were associated with painful DSPN in older individuals in a large population-based study. RESEARCH DESIGN AND METHODS The study population consisted of individuals with painless (n = 337) and painful DSPN (n = 54) from a source population (n = 1,047) of men and women aged 61-82 years who participated in the German KORA F4 survey (2006-2008). We measured circulating levels of seven immune mediators and assessed their associations with the presence of painful DSPN using multiple logistic regression models. RESULTS After adjustment for age and sex, we found positive associations between serum concentrations of the cytokine interleukin (IL)-6 and the soluble intercellular adhesion molecule (sICAM)-1 and painful DSPN (P = 0.004 and P = 0.005, respectively), whereas no associations were observed for C-reactive protein, IL-18, tumor necrosis factor-α, adiponectin, and IL-1 receptor antagonist (IL-1RA, P = 0.07-0.38). Associations between IL-6 and sICAM-1 and painful DSPN remained significant after additional adjustment for waist circumference, height, hypertension, cholesterol, smoking, alcohol intake, physical activity, history of myocardial infarction and/or stroke, presence of other neurological conditions, and use of nonsteroidal anti-inflammatory drugs (P = 0.005 and P = 0.016, respectively). CONCLUSIONS Painful DSPN is linked to systemic subclinical and vascular inflammation in the older population independent of anthropometric, lifestyle, and metabolic confounders.