Investigation of the Relationship Between Chronic Stress and Insulin Resistance in a Chinese Population

BACKGROUND Chronic stress may facilitate the development of metabolic diseases. Insulin resistance is present long before the clinical manifestations of individual metabolic abnormalities. To explore whether chronic stress is an independent risk factor of insulin resistance, we investigated the relationship between the stress system, selected parameters of energy homeostasis, and insulin resistance in a Chinese population. METHODS We recruited 766 workers employed at four companies in Beijing. The degree of insulin resistance was determined using the homeostasis model assessment of insulin resistance (HOMA-IR). The highest quartile of HOMA-IR among all study subjects was further defined as insulin resistance in our study. The short standard version of the Copenhagen Psychosocial Questionnaire (COPSOQ) was used to assess job-related psychosocial stress. Pearson's correlation coefficients were calculated between cortisol level and HOMA-IR and components of metabolic syndrome, with stratification by gender. The relationship between cortisol and HOMA-IR independent of obesity was analyzed using a linear mixed model with company as a cluster unit. RESULTS The values of the two scales of COPSOQ, including "demands at work" and "insecurity at work", were significantly associated with insulin resistance and cortisol concentration (P < 0.05). Cortisol was significantly positively correlated with glucose, HOMA-IR, and waist circumference in males and females (P < 0.05). After adjusting for potential confounders, cortisol was an independent positive predictor for HOMA-IR (P < 0.05). CONCLUSIONS These findings showed that chronic stress was associated with insulin resistance and may contribute to the development of insulin resistance.