Interleukin 6 and cortisol in acute musculoskeletal disorders: results from a case‐referent study in Sweden

According to modern stress theory, the hypothalamo–pituitary–adrenocortical system (HPA axis) is an important part of the body's arousal system in physically straining (such as in infections) as well as in psychologically arousing situations. When demands for arousal have been excessively high for a long time, the HPA may show disturbance in its regulatory ability. Interleukins (IL) constitute an important part of the communication between the HPA axis and the immune system. The aim of the present study was to explore part of the circadian serum cortisol variation as well as interleukin 6 (IL-6) in relation to acute low back and neck/shoulder pain and potential psychosocial stressors. In a defined geographical area, men and women who consulted any caregiver (traditional as well as alternative) for an acute spine pain condition preceded by six months without consultations constituted the case group. Age and gender matched men and women from the population register constituted the referent group. During an examination day all subjects went through ergonomic and psychosocial examinations (questionnaires, interviews and clinical examinations). Blood samples were drawn in the morning (8 am) as well as midday (noon) in a subsample of 243 individuals (86 cases and 157 referents) and analyzed for IL-6 (midday sample) and cortisol (morning and midday sample). Female cases had higher IL-6 levels (p<0.05) and those seeking care for low back pain had a smaller cortisol variation between morning and midday values than referents. In men, low self-reported decision latitude at work (possibility to issue control) was significantly associated with higher IL-6 concentration and low social support at work with low morning cortisol values. In women, high job satisfaction was associated with low IL-6 concentrations and lower midday cortisol levels. Statistically strong correlations were found between IL-6 and the degree of cortisol decrease between morning and midday (p<0.01). Reduced cortisol variation among female low back pain cases may indicate a disturbance in the HPA axis. A high IL-6 level may arise in the course of a long-lasting aroused psychosocial situation with concomitant impaired cortisol regulation. It could be speculated that the hormonal disturbances found reflect an impaired psychosocial state. Serum IL-6 may be a useful serum marker for psychosocial adverse conditions in epidemiological studies. Copyright © 2000 John Wiley & Sons, Ltd.