The study included 335 patients diagnosed with obstructive sleep apnoea (OSA) syndrome, all of whom underwent standard nocturnal polysomnography.
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).
We think that OSA is very rarely the reason for secondary polycythaemia.