Hair Cortisol, Obesity and the Immune System: Results From a 3 Year Longitudinal Study

Background: Long-term glucocorticoid levels measured in scalp hair (HairGC) are positively correlated to obesity in cross-sectional studies, however it is unclear whether this reflects a state of obesity or an actual maintaining or contributing factor to obesity. Objectives: To investigate whether hair cortisol (HairF) and hair cortisone (HairE) predict changes in body mass index (BMI) and waist circumference (WC) over time, and to assess whether HairGC are linked to immune parameters. Methods: We measured HairGC in 1604 participants of the Netherlands Study of Depression and Anxiety (NESDA), and correlated these to BMI, WC, and immune parameters (interleukin-6 (IL-6), high-sensitive C-reactive protein (CRP), total leukocyte, monocyte and lymphocyte counts and the neutrophil-to-lymphocyte ratio). Also, we assessed whether baseline HairGC predict changes in BMI and WC at the follow-up visit, three years later, and whether immune parameters influenced this correlation. Results: In cross-sectional analyses, HairF and HairE were positively correlated to BMI (β=2.06 and β=2.84kg/m(2) respectively) and WC (β=5.36 and β= 8.54cm respectively, all p<0.001). HairF was related to IL-6 (adjusted β=0.15, p<0.05) and leukocyte count (adjusted β=0.57, p<0.01), and HairE to IL-6 (adjusted β=0.21, p<0.05). In the adjusted longitudinal analyses, baseline HairF was associated with a yearly increase in BMI (β=0.58%, p=0.009) and baseline HairE with a yearly increase in WC (β=0.84%, p=0.049). Adjusting for baseline IL-6 or leukocytes did not affect the found associations between GC and WC or BMI change. Conclusions: HairGC levels are related to BMI, WC, IL-6 and leukocytes in cross-sectional analyses. Moreover, chronically higher HairGC may be a relevant risk factor for the development of obesity in the future, although causality is yet to be proven.