Plasma homocysteine in obstructive steep apnoea

Aims Whether increased homocysteine is one mechanism linking obstructive steep apnoea (OSA) to cardiovascular abnormalities is unclear. We hypothesised that plasma homocysteine would be higher in OSA patients than in control subjects, would increase further during steep, and decrease after treatment with continuous positive airway pressure (CPAP). Methods and Results For study A, homocysteine was measured in 22 OSA patients and 20 controls first before steep, then after 5 h of untreated OSA, and then in the morning after CPAP treatment. Homocysteine was similar in the OSA and control subjects at at[ three time points, and declined overnight in both groups (P = 0.0017, P = 0.036, respectively). To further assess this diurnal variation, we studied plasma homocysteine under a full-night protocol in 10 OSA patients and 12 controls (study 13). Homocysteine was measured before steep, in the morning after steep, and at noon. Results in both OSA and control groups showed an overnight decline in homocysteine which was reversed by noon (repeated measures ANOVA: OSA, P = 0.04; controls, P = 0.02). Study C showed that disturbed steep did not affect homocysteine levels in normal subjects. Conclusion There is a significant diurnal variation in plasma homocysteine, so that homocysteine is lower in the morning after waking. Neither OSA nor disturbed steep elicit acute or chronic changes in homocysteine. (C) 2004 Published by Elsevier Ltd on behalf of The European Society of Cardiology.