Journal des troubles du sommeil et de la thérapie
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The Association of Troponin I Levels with Severity of Obstructive Sleep Apnea Syndrome

Nalan Demir, Oğuz Köktürk, Tansu Ulukavak Ciftçi, Ozlem Gülbahar, Neslihan Celik Bukan and Kenan Köse

Background: As a result of repeated nocturnal hypoxemia, pulmonary arterial vasoconstriction, acute right ventricular dilatation and hypokinesia and myocardial injury may occur in patients with Obstructive Sleep Apnea Syndrome (OSAS). As it is known, Cardiac Troponin I (cTnI) is an important marker of myocardial injury. Objectives: The aim of this study is to investigate the degree of myocardial injury which is created with nocturnal hypoxemia by measuring cTnI levels in patients with OSAS and to evaluate the association between cTnI levels and severity of OSAS.

Methods: Seventy-six subjects who had OSAS symptoms were examined with standard polysomnography (PSG) and classified according to their Apnea-Hypopnea Index (AHI). Forty-seven patients with AHI ≥ 5 were considered as OSAS and 29 subjects with AHI<5 were included into control group. OSAS patients were divided into three groups according to their AHI values as mild (AHI=5-15) (n:13), moderate (AHI=15-30) (n:14) and severe (AHI>30) OSAS (n:20). Serum cTnI levels were measured twice in all subjects after the PSG.

Results: When the levels of cTnI were compared, there was no significant difference between patients and controls (OSAS=3.6 ± 2.7 ng/ml and controls=3.1 ± 1.8 ng/ml, p=0.3). Also no significant difference was detected between mild-moderate OSAS (2.93 ± 1.67 ng/ml), severe OSAS (4.57 ± 3.47 ng/ml) and controls comparing with their cTnI levels (p=0.053). But cTnI levels in severe OSAS patients were significantly higher than controls (p=0.01). According to the logarithmic transformation, log-cTnI was 0.49 ± 0.21 ng/ml and 0.47 ± 0.21 ng/ml in OSAS subjects and controls, respectively (p=0.74). Severe OSAS patients had higher log-cTnI levels (0.59 ± 0.22 ng/ml) than mildmoderate OSAS subjects and controls (p=0.018, f=4.26). There was a positive correlation between AHI and cTnI levels in patients with OSAS (r=0.276, p=0.019, R2=0.076).

Conclusion: Cardiac troponin I measurements may be useful to show the degree of myocardial injury in severe OSAS.