Biomarkers May Help Predict OSA, Effective CPAP Tx
SEATTLE, WA—Serum glucose is not a reliable biomarker for predicting obstructive sleep apnea (OSA) or whether treatment is effective with continuous positive airway pressure (CPAP), a pilot study of biomarkers presented at SLEEP 2015 concluded.
Noting that only a limited number of clinical randomized trials have evaluated the effect of CPAP on metabolic variables—and “even they remain inconclusive,” Edith Mensah-Osman, MD, PhD, MBA, of EENA Comprehensive Neurology and Sleep Center in Boynton Beach, FL, hypothesized that “OSA is associated with impaired glucose tolerance as a result of modifications of factors involved in glucose homeostasis or dysregulation of glucose homeostasis due to chronic sleep deprivation.”
The team aimed to identify biomarkers with measureable biochemical characteristics linked to the severity of OSA and to examine the effect of CPAP on these variables.
The study recruited adult volunteer patients and assessed overall well-being via a questionnaire at baseline and follow-up. Blood pressure, body weight, serum glucose and lipids, and urine glucose data were collected from health records at initial diagnosis of OSA and before and after treatment with CPAP. In addition, “data from volunteers without diagnosis of OSA were analyzed and used for sensitivity and specificity determination,” Dr. Mensah-Osman noted.
Patients were assessed using a questionnaire for socio-demographics factors; anthropometric measures evaluated height, body weight, neck or waist circumference, and blood pressure. Saliva samples were collected for biochemical analysis.
The study found a “greater correlative variation of neck circumference with systolic and diastolic pressures in the general pool of patients compared to patients with primary diagnosis of OSA,” she noted. Although patients with a primary diagnosis of OSA had a BMI >27.53kg/m2, this BMI was not correlated with high blood pressure.
In addition, the Epworth Sleepiness Scale was not a good predictor of OSA in patients; however, a high BMI and blood pressure were both associated with a high AHI. The study also found that “levels of DHEA, afternoon cortisol, and 17-OH progesterone in saliva of patients diagnosed with OSA were significantly lower when compared to normal reference ranges for each marker.”
Since preliminary data have shown changes in products of the adrenal cortex, this suggests that regulation of gluconeogenesis may be involved in the pathophysiology of OSA, Dr. Mensah-Osman concluded, adding that “ongoing research is currently focused on a central regulator of glucose homeostasis as a biomarker and diagnostic tool to evaluate effectiveness of CPAP treatment of OSA.”