Blunted diurnal cortisol variation has been associated with overt cardiovascular disease in adults. The relationship between the diurnal cortisol variation and subclinical atherosclerosis in youth has yet to be investigated. The objectives of this study were to: 1) determine the relationship between overnight cortisol measures and CIMT in overweight and obese, African-American and Latino children; 2) assess ethnic differences in these relationships and 3) explore whether overnight cortisol and CIMT relationships were independent of inflammatory markers, C-reactive protein (CRP), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α).
One hundred and fifty-six overweight and obese African-American and Latino children (ages 8–17, 86M/70F, 55 African-American /101 Latino) underwent measures of CIMT by B-mode ultrasound, nocturnal cortisol rise (NCR=salivary cortisol rise from 2200hrs to awakening at 0530hrs), cortisol awakening response (CAR=salivary cortisol from time of awakening to 30 min later), fasting serum cortisol and overnight urinary free cortisol.
Using linear regression, salivary cortisol0530hrs and NCR were negatively associated with CIMT (βstandardized = −0.215 and −0.220, p<0.01) independent of age, height, percent body fat, ethnicity and systolic blood pressure. Nocturnal salivary cortisol2200hrs, morning serum cortisol, and overnight urinary free cortisol were not associated with CIMT. Using ANCOVA, participants with LOW NCR (NCR <0.44µg/dL, n=52) had significantly greater CIMT than those with HIGH NCR (NCR ≥0.91 µg/dL, n=52; 0.632±0.008 vs. 0.603±0.008mm p=0.01) after controlling for covariates. Ethnicity was independently associated with CIMT, whereby African-American children had greater CIMT than Latino children (−0.028±0.009, p=0.006). The relationships between cortisol measures and CIMT did not differ between the two ethnic groups (all pinteraction=0.28–0.97). CRP, IL-6 and TNF-α were not associated with CIMT (p>0.05). IL-6 was inversely related to NCR (r=−0.186, p=0.03), but it did not explain the relationship between NCR and CIMT.
Salivary cortisol0530hrs and NCR, but not CAR, nocturnal salivary cortisol 2200hrs, morning serum cortisol or overnight urinary free cortisol, were associated with CIMT, independent of relevant covariates, including inflammatory factors. A low awakening salivary cortisol or a blunted NCR may be related to increased atherosclerosis risk in overweight and obese minority youth. These findings support adult studies suggesting flattened daytime diurnal cortisol variation impacts cardiovascular disease risk.