Chest
Volume 122, Issue 4, October 2002, Pages 1162-1167
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Clinical Investigations
Increased 8-Isoprostane and Interleukin-6 in Breath Condensate of Obstructive Sleep Apnea Patients

https://doi.org/10.1378/chest.122.4.1162Get rights and content

Study objectives

Obstructive sleep apnea (OSA) is characterized by repeated episodes of upper airways obstruction during sleep that result in episodes of hypoxia. An increase of systemic biomarkers of inflammation and oxidative stress has been found in patients with OSA and obesity.

Design

The aim of this study was to measure the levels of markers of inflammation (interleukin [IL]-6) and oxidative stress (8-isoprostane) in the exhaled breath condensate of OSA and obese patients.

Patients and methods

Eighteen OSA patients (13 men; mean [ŷ SEM] age, 44 ŷ 7 years), 10 obese subjects (4 men; mean age, 39 ŷ 8 years), and 15 healthy age-matched subjects (8 men; mean age, 42 ŷ 4 years) were recruited. IL-6 and 8-isoprostane were measured in exhaled breath condensate by a specific enzyme immunoassay kit.

Measurements and results

Higher concentrations of IL-6 were found in OSA patients (8.7 ŷ 0.3 pg/mL) than in healthy control subjects (1.6 ŷ 0.1 pg/mL; p < 0.0001). Obese subjects also had higher levels than healthy control subjects, but lower levels than OSA patients (2.1 ŷ 0.2 pg/mL, p < 0.05 and p < 0.0001 respectively). Furthermore, 8-isoprostane levels were found to be higher in OSA patients (7.4 ŷ 0.7 pg/mL) than in obese subjects (5 ŷ 0.3 pg/mL; p = 0.4) and healthy subjects (4.5 ŷ 0.5 pg/mL; p < 0.005). We found a positive correlation between these two markers and neck circumference and apnea/hypopnea index.

Conclusions

These findings suggest that inflammation and oxidative stress are characteristic in the airways of OSA patients but not in obese subjects, and that their levels depend on the severity of the OSA. The measurement of IL-6 and 8-isoprostane levels may prove to be useful in screening and monitoring obese patients who have a high risk of developing OSA.

Section snippets

Patients

The study population consisted of 18 OSA patients, 10 subjects matched for obesity who did not have OSA, and 15 age-matched normal control subjects (Table 1). All subjects were white and were recruited from the sleep laboratory of the Respiratory Disease Institute at University of Bari (Italy). Written informed consent was obtained from all subjects, and the institutional ethics committee approved the study. A complete physical examination was performed, including neurologic, cardiopulmonary,

IL-6

IL-6 was measurable in the breath condensate of all subjects. Concentrations were significantly greater in obese patients (2.1 ŷ 0.2 pg/mL; p < 0.05) and in OSA patients (8.7 ŷ 0.3 pg/mL; p < 0.0001) than in healthy subjects (1.6 ŷ 0.1 pg/mL) [Fig 1, left, A]. There was a significant difference between OSA and obese patients (p < 0.0001). A positive correlation was found between IL-6 and AHI levels (r = 0.6; p < 0.0005) [Fig 2, left, A] and IL-6 and neck circumference (r = 0.5; p < 0.01) [Fig 2

Discussion

This study shows that IL-6 and 8-isoprostane are detectable in breath condensates and that their concentrations are higher in OSA patients, are intermediate in obese subjects without sleep apnea, and are lower in healthy subjects. A relationship between the two markers and the severity of OSA also was found. The positive correlation between neck circumference and the concentrations of the two markers may be useful to screen obese subjects who are at high risk for developing sleep apnea.

Our

ACKNOWLEDGMENT

We gratefully acknowledge the assistance of Dr. F. Carpagnano, without whose dedicated and expert technical assistance this study would not have been possible.

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