The relationship between diurnal variation of cytokines and symptom expression in mild obstructive sleep apnea

To identify the relationship between (1) cytokines and everyday symptoms and (2) cytokine diurnal variation and everyday symptoms in mild obstructive sleep apnea (OSA).

An observational, single-night study of 20 adults with mild to moderate OSA undergoing diagnostic polysomnography. Everyday symptoms included sleepiness measured by Stanford Sleepiness Scale, fatigue and energy levels measured by Lee Fatigue Scale, and cytokine plasma concentrations including interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor-α (TNF-α) measured concurrent with symptoms at presleep (8 pm to 10 pm; time 1) and postsleep (5 am to 6 am; time. 2) Cytokine diurnal variation was calculated as [time 2 - time 1]. Wilcoxon signed-rank tests and Spearman partial rank correlations adjusted for age, body mass index, cardiovascular disease, and type 2 diabetes were used.

Twenty patients (50% male, obese, median age = 51.0 years) with mild OSA (apnea-hypopnea index, AHI; median 9.5 events/h) were evaluated. Evening IL-6 was associated with evening symptoms, including sleepiness (r = .69, P = .002) and energy level (r = -0.68, P = .003); morning IL-8 (r = .73, P = .001), and TNF-α (r = .59, P = .015) were associated with morning fatigue. Only morning IL-8 (r = -0.57, P = .022) and diurnal variations in IL-8 (r = -0.60, P = .014) were associated with morning energy level.

There is scant evidence addressing the diurnal variation of inflammatory biomarkers and the relationship with symptom expression in mild OSA. The present findings provide preliminary mechanistic findings for symptom expression in OSA and contribute insight to mild OSA symptom phenotypes.