Dietary habits and salivary cortisol levels as an early predictor of metabolic syndrome in children: a case-control study

Introduction:
Dysregulation of the hypothalamic-pituitary-adrenal axis is an essential factor in developing metabolic syndrome. Dysregulation of the hypothalamic-pituitary-adrenal axis increases cortisol levels, which is associated with increased abdominal body fat accumulation, triglyceride storage in the adipose cell, insulin resistance, and development of hypertension.

Aim:
To understand the relationship between dietary habits, salivary cortisol levels and metabolic syndrome in children.

Material and methods:
This case-controlled study included 46 subjects selected from primary schools in Ismailia city, Egypt. The study subjects were divided into two matched age and gender groups: Group 1: Children with metabolic syndrome as a patient group. Group 2: Normal age- and sex-matched children as a control group. All children were subjected to history taking, measurements, and laboratory investigations (total lipid profile, fasting blood sugar, circadian salivary cortisol in the day and at night).

Results:
There was a statistically significantly lower HDL level in the patient group compared to the control group, while there were statistically significantly higher levels of triglycerides, cholesterol, and fasting blood sugar in the patient group compared to the control group (p < 0.05). There was a statistically significant positive correlation between salivary cortisol level in the day and both systolic and diastolic blood pressure levels in the patient group (r = 0.554, p = 0.006 and r = 0.485, p = 0.019, respectively). Similarly, there was a statistically significant positive correlation between salivary cortisol level in the day and waist circumference in the patient group (r = 0.500, p = 0.018). On the other hand, in the control group there was no statistically significant correlation between salivary cortisol level and triglycerides, low-density lipoprotein, high-density lipoprotein, FBS, body mass index, waist circumference, and blood pressure.

Conclusions:
Dietary habits, family history, and salivary cortisol levels during the day are more strongly correlated with components of metabolic syndrome, especially central obesity and blood pressure. Dietary habits have a great impact on developing metabolic syndrome; thus a healthy lifestyle is advised. Further studies, with a larger number of participants, are encouraged to confirm our observations.