Melatonin and Cortisol Concentration Before and After CPAP Treatment of Obstructive Sleep Apnea

This study investigated changes in salivary melatonin and cortisol concentrations before and after Continuous Positive Airway Pressure (CPAP) therapy in patients with OSA. Underlying these hormonal changes is a key mechanism involving dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and circadian rhythm.

A prospective before-and-after study was conducted on 59 adults with OSA, of whom 27 completed an 8-week follow-up after CPAP therapy. Salivary melatonin and cortisol were measured via ELISA in morning and afternoon samples. Other habits that affect sleep were also assessed. Hormonal changes were analyzed using Wilcoxon signed-rank tests, and correlations with clinical variables were evaluated using Spearman correlation.

At baseline, mean melatonin concentration was 80.80 ± 52.48 pg/mL, higher in the afternoon, and mean cortisol concentrations was 7.58 ± 5.45 ng/mL, higher in the morning. After CPAP treatment, melatonin concentration decreased to 63.78 ± 39.85 pg/mL, with a reduced difference between morning and afternoon concentrations. Cortisol concentration increased slightly to 8.06 ± 8.08 ng/mL. These hormonal changes were not statistically significant (p>0.05). Notably, melatonin concentrations correlated negatively with tea consumption (rho = -0.43, p<0.05) after adjustment.

This research investigated salivary melatonin and cortisol as biomarkers for CPAP efficacy in OSA patients. Although no significant changes were detected, trends indicated reduced sleep pressure, including lower afternoon melatonin and higher cortisol levels. The substantial dropout rate limits how these results can be interpreted. More studies with larger sample sizes, longer treatment durations, and more comprehensive hormonal evaluations at various times of the day are needed to elucidate the potential significance of salivary biomarkers in understanding circadian control in OSA.