Plasma Homocysteine Levels in Obstructive Sleep Apnea: Association With Cardiovascular Morbidity

Abstract

ObjectivesObstructive sleep apnea (OSA) is associated with cardiovascular morbidity and mortality. Plasma levels of homocysteine are also associated with cardiovascular morbidity and mortality. We therefore investigated homocysteine and conventional cardiovascular risk factors in OSA patients with and without cardiovascular morbidity in comparison with normal control subjects and ischemic heart disease (IHD) patients without OSA. SettingTechnion Sleep Medicine Center, Haifa, Israel. Methods and participantsLevels of homocysteine, cholesterol, low-density lipoprotein, high-density lipoprotein, triglycerides, creatinine, vitamins B12 and B6, and folic acid were determined in 345 participants after overnight fasting. These included OSA patients with IHD (n = 49), with hypertension (n = 61), or without any cardiovascular disease (n = 127). Two control groups were employed: IHD patients without or with low likelihood for sleep apnea (n = 35), and healthy control subjects (n = 73). ResultsAfter adjustment for age, body mass index, creatinine, and existence of diabetes mellitus, OSA patients with IHD had significantly higher homocysteine levels (14.6 ± 6.77 μmol/L) than all other groups including the IHD-only patients. Hypertensive OSA patients had comparable homocysteine levels to IHD patients (11.80 ± 5.28 μmol/L and 11.92 ± 5.7 μmol/L, respectively), while patients with OSA only had comparable levels to normal control subjects (9.85 ± 2.99μ mol/L and 9.78 ± 3.49 μmol/L, respectively). No differences in conventional cardiovascular risk factors or in vitamin levels were found between groups. ConclusionsPatients with the combination of IHD and OSA have elevated homocysteine levels. We hypothesize that these results may be explained by endothelial dysfunction combined with excess free-radical formation in OSA patients.