Abstract
BACKGROUND: Psychological stress is elevated in individuals with chronic medical conditions, including those with chronic obstructive pulmonary disease (COPD). Nail cortisol may have utility as a marker for testing the biologic effects of stress reduction interventions. The aim of this pilot study is to explore the use of nail cortisol as a marker of chronic psychological stress in individuals with COPD. METHODS: Pearson's correlation was used to test if nail cortisol was correlated with perceived stress, serum cortisol, or inflammatory biomarkers. A multivariable linear regression model was used to evaluate the association between perceived stress and nail cortisol. Stepwise logistic regression modeling was used to determine associations of psychobiologic measures of stress with demographic, clinical, and psychological variables. RESULTS: A total of 50 participants were included in the study. The mean (standard deviation [SD]) perceived stress score was 12 (+/-6) and mean (SD) nail cortisol level was 0.05 (+/-0.09) nmol/g. Nail cortisol was not correlated with perceived stress, serum cortisol, or inflammatory markers. There was no association between nail cortisol and perceived stress after controlling for confounders. Suboptimal health status and grit score were associated with perceived stress. Higher levels of serum fibrinogen were associated with higher levels of serum cortisol. Experiencing 3 or more negative lifetime events was associated with a decrease in nail cortisol. CONCLUSION: We found no correlation between nail cortisol and levels of perceived stress, serum cortisol, or inflammatory biomarkers and there were no similar associations of variables across psychobiologic measures of stress.