title: Hypothalamic-pituitary-adrenal axis function: relative contributions of perceived stress and obesity in women.
abstract: OBJECTIVE
  A range of behavioral and psychosocial factors may contribute to a chronically stimulated hypothalamic-pituitary-adrenal (HPA) axis and subsequently altered diurnal patterns. The goal of this cross-sectional study was to examine associations among diurnal cortisol levels, perceived stress, and obesity patterns.
  
  
  METHODS
  Seventy-eight women (aged 24-72 years) employed in a rural public school system completed the perceived stress scale, collected diurnal saliva samples, and underwent anthropometric assessments. Reduced peak-to-nadir cortisol values across the day were considered a sign of impairment in HPA function. A series of linear regression models determined the best predictors of diurnal cortisol variation.
  
  
  RESULTS
  There was a marginal linear trend in stress levels across body mass index (BMI) categories, with obese women reporting the highest levels of stress (p = 0.07). Perceived stress was the only significant predictor of the degree of flattening of the diurnal cortisol curve in the sample as a whole (beta = -0.042, R(2) = 0.11, F = 8.6, p = 0.005), indicating reduction in the normal diurnal pattern. Among overweight women (BMI = 25-29.9 kg/m(2)), stress and waist circumference combined predicted 35% of the variability in diurnal cortisol. In contrast, among obese women (BMI > or = 30 kg/m(2)), BMI predicted 31% of the variability in diurnal cortisol (F = 13.8, p = 0.001), but stress was no longer significantly related to diurnal cortisol.
  
  
  CONCLUSIONS
  Psychological stress predicts a significant portion of HPA axis functioning. In overweight women, perceived stress and waist circumference were of approximately equal importance in predicting adrenal cortisol secretion. However, among obese women, a major portion of the diurnal cortisol variation was predicted by BMI alone, not stress or waist circumference. This may help elucidate the mechanisms linking obesity to increased risk of cardiovascular disease (CVD).
authors.affiliation: University of Oklahoma Prevention Research Center, Oklahoma City, Oklahoma, USA. noha-farag@ouhsc.edu
authors.forename: Noha H
authors.initials: NH
authors.lastname: Farag
authors.forename: William E
authors.initials: WE
authors.lastname: Moore
authors.forename: William R
authors.initials: WR
authors.lastname: Lovallo
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Mills
authors.forename: Srikrishna
authors.initials: S
authors.lastname: Khandrika
authors.forename: June E
authors.initials: JE
authors.lastname: Eichner
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D002940:Circadian Rhythm; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism*; D007030:Hypothalamo-Hypophyseal System / Q000503:physiopathology*; D016014:Linear Models; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism*; D010913:Pituitary-Adrenal System / Q000503:physiopathology*; D012463:Saliva / Q000378:metabolism*; D013315:Stress, Psychological / Q000378:metabolism*
chemical_list: D006854:Hydrocortisone