Circulating cell-derived microparticles in patients with minimally-symptomatic obstructive sleep apnoea

¹ Dept of Clinical Immunology, Churchill Hospital, Oxford, UK
² Oxford Centre for Respiratory Medicine, Churchill Hospital, Oxford, UK
³ Oxford Centre for Respiratory Medicine, Churchill Hospital, Oxford, UK; and Pulmonary Division, University Hospital of Zurich, Zurich, Switzerland

^* To whom correspondence should be addressed. E-mail: Malcolm.K{at}bluewin.ch.

	Abstract

Moderate-severe obstructive sleep apnoea (OSA) has been associated with several pro-atherogenic mechanisms and increased cardiovascular risk but it is not known if minimally-symptomatic OSA has similar effects. Circulating cell-derived microparticles have been shown to have pro-inflammatory, pro-coagulant and endothelial function impairing effects, as well as to predict subclinical atherosclerosis and cardiovascular risk.

In 57 patients with minimally-symptomatic OSA, and 15 closely-matched control subjects without OSA, AnnexinV+, platelet-, leukocyte- and endothelial-cell derived microparticles were measured by flow-cytometry.

In patients with OSA, levels of AnnexinV+ microparticles were significantly elevated, 2586 (1566–3964) µl^-1 compared to control subjects, 1206 (474–2501) µl^-1 (medians and interquartile range, p=0.007). Levels of platelet-derived and leukocyte-derived microparticles were also significantly higher in patients with OSA 2267 (1102–3592) µl^-1 and 20 (14–31) µl^-1 respectively, compared to control subjects, 925 (328–2068) µl^-1 and 15 (5–23) µl^-1 respectively (p=0.009 and p=0.02 respectively). Endothelial-cell-derived microparticle levels were similar in patients with OSA, 13 (8–25) µl^-1, compared to control subjects, 11 (6–17) µl^-1 (p=0.21).

In patients with minimally-symptomatic OSA, levels of AnnexinV+, platelet- and leukocyte-derived microparticles are elevated when compared to closely-matched control subjects without OSA. These findings suggest that these patients may be at increased cardiovascular risk, despite being minimally-symptomatic.