Hair cortisol, obesity and the immune system: Results from a 3 year longitudinal study

Higher long-term glucocorticoid levels, measured in scalp hair (HairGC), are associated with obesity. This may represent the state of obesity (perhaps interrelated with chronic immune activation), but could also promote further weight gain. We studied whether hair cortisol (HairF) and hair cortisone (HairE) predict changes in body mass index (BMI) and waist circumference (WC) over time, and assessed the association between HairGC and common immune parameters.

We measured HairGC in 1604 participants of the Netherlands Study of Depression and Anxiety (NESDA), and investigated their associations to BMI, WC, and immune parameters (interleukin-6 (IL-6), C-reactive protein (CRP), and leukocyte subsets). Also, we assessed whether baseline HairGC predict changes in BMI and WC at follow-up (three years later).

In cross-sectional analyses, HairF and HairE were positively associated to BMI (β = 2.06 kg/m², 95% confidence interval (CI)= 1.22-2.90 kg/m²) and β = 2.84 kg/m² (95%CI 1.75-3.93 kg/m²) respectively) and WC (β = 5.36 cm (95%CI 3.09-7.62 cm) and β = 8.54 cm (95%CI 5.60-11.48 cm) respectively, all p < 0.001). HairF was also positively associated to IL-6 (β = 0.15 (95%CI 0.003-0.292) p < 0.05) and leukocyte count (β = 0.57 (95%CI 0.234-0.909), p < 0.01), and HairE to IL-6 (β = 0.21 (95%CI 0.016-0.399), p < 0.05). In the longitudinal analyses, higher HairF was associated with yearly increases in BMI (β = 0.58% BMI change per year (95%CI 0.14-1.01%), p = 0.009) and higher HairE with increases in WC (β = 0.84% WC change per year (95%CI 0.02-1.69%), p = 0.049). Adjusting for baseline IL-6 or leukocytes did not change the found associations between HairGC and WC or BMI change.

HairGC levels are positively associated to BMI, WC, IL-6 and leukocyte numbers in cross-sectional analyses, and to increases in BMI and WC in longitudinal analyses. Although causality is yet to be proven, higher long-term glucocorticoid levels could represent a relevant risk factor for the development of obesity.