Is obstructive sleep apnoea syndrome really one of the causes of secondary polycythaemia?

This is the authors' abstract. We don't add key points for this paper.

BACKGROUND: It is widely believed that sleep apnoea syndrome leads to polycythaemia, but the evidence is largely anecdotal. We believe that polycythaemia is not commonly seen in patients with sleep apnoea syndrome. Therefore, we aimed to determine the relationship between polycythaemia and sleep apnoea syndrome. METHODS: The study included 335 patients diagnosed with obstructive sleep apnoea (OSA) syndrome, all of whom underwent standard nocturnal polysomnography. RESULTS: There were no significant differences in haemoglobin levels or haematocrit (P > 0.05) between the OSA groups in all patients. Of the 335 patients, only 1 male patient with severe OSA (0.3%) had clinically significant polycythaemia. According to regression analysis, there was a weak linear correlation between haemoglobin levels and lowest oxygen saturation levels in female patients (r = -0.242, P = 0.021). CONCLUSION: We think that OSA is very rarely the reason for secondary polycythaemia.