High-protein meal challenge reveals the association between the salivary cortisol response and metabolic syndrome in police officers

Objectives: Policing is considered a high-stress occupation and officers have elevated cardiovascular morbidity and mortality. To investigate a potential connection, we evaluated the association between salivary cortisol response to a high-protein meal challenge and the metabolic syndrome (MetSyn), a subclinical disorder associated with increased cardiovascular risk. Methods: Cross-sectional data were from the Buffalo Cardio-Metabolic Occupational Police Stress (BCOPS) Study (2004-2009). MetSyn was defined as having ≥3 components: abdominal obesity, hypertension, elevated triglycerides, reduced high-density lipoprotein cholesterol, and glucose intolerance. Officers provided five saliva samples for cortisol analysis, one before challenge (high-protein shake) and four at 15-min intervals thereafter, where the usual response is increase. Regression models were used to examine trends in mean number of MetSyn components across quartiles of area under the curve (AUC) salivary cortisol. Patterns of mean cortisol response were assessed by MetSyn status using repeated-measures analysis of covariance. Results: Prevalence of MetSyn was 25.7% among 373 officers (74.0% male). The mean count of MetSyn components decreased (1.89, 1.75, 1.55, 1.37; P<0.01) across increasing quartiles of AUC salivary cortisol. Mean salivary cortisol decreased from baseline (5.55, 4.58, 4.47, 4.79, 4.75 nmol/l) in officers with MetSyn and increased (5.08, 5.82, 5.92, 5.82, 5.60 nmol/l) in their counterparts. The test for interaction between MetSyn status and time of saliva collection was statistically significant (P<0.001). Conclusions: Reduced cortisol response to a high-protein meal challenge may be associated with MetSyn. Future longitudinal studies could provide useful evidence for planning intervention studies on cardiovascular risk among police officers.