Diurnal salivary cortisol is associated with body mass index and waist circumference: the Multiethnic Study of Atherosclerosis

Abstract

Objective: Neuroendocrine abnormalities, such as activation of the hypothalamic-pituitary-adrenal (HPA) axis, are associated with obesity; however, few large-scale population-based studies have examined HPA axis and markers of obesity. We examined the cross-sectional association of the cortisol awakening response (CAR) and diurnal salivary cortisol curve with obesity.

Design and methods: The Multiethnic Study of Atherosclerosis Stress Study includes 1,002 White, Hispanic, and Black men and women (mean age 65 ± 9.8 years) who collected up to 18 salivary cortisol samples over 3 days. Cortisol profiles were modeled using regression spline models that incorporated random parameters for subject-specific effects. Cortisol curve measures included awakening cortisol, CAR (awakening to 30-min postawakening), early decline (30 min to 2-h postawakening), late decline (2-h postawakening to bedtime), and the corresponding areas under the curve (AUC). Body mass index (BMI) and waist circumference (WC) were used to estimate adiposity.

Results: For the entire cohort, both BMI and WC were negatively correlated with awakening cortisol (P < 0.05), AUC during awakening rise, and early decline and positively correlated to the early decline slope (P < 0.05) after adjustments for age, race/ethnicity, gender, diabetes status, socioeconomic status, β-blockers, steroids, hormone replacement therapy, and smoking status. No heterogeneities of effects were observed by gender, age, and race/ethnicity.

Conclusions: Higher BMI and WC are associated with neuroendocrine dysregulation, which is present in a large population sample, and only partially explained by other covariates.

Figure 1

Summary of Diurnal Cortisol Curve Parameters Derived from Mixed Model Linear Regression Key: A=awakening cortisol at time zero; B=cortisol awakening response (CAR) denoting rise from awakening to 30 minutes post-awakening; C=early decline from 30 minutes post-awakening to 2 hours post-awakening; D=late decline from 2 hours post-awakening to bedtime; E=area under curve (AUC) for CAR; F=AUC for early decline; G=AUC for late decline; the full AUC is the sum E+F+G

Figure 2

Diurnal Curve for entire sample set

Figure 3

Diurnal Curve during awakening hours