Purpose: Reduced slow wave sleep (SWS) has been linked to hypertension in some studies. The aim of the study is to investigate the association between SWS and office blood pressure (BP) in non-hypertensive obstructive sleep apnea (OSA). Methods: This is a retrospective study of 3350 patients who underwent polysomnography (PSG) in our hospital. Based on quartiles of percent SWS, participants were classified into four groups. BP was measured manually on the randomly chosen arm in a seated position with sphygmomanometer after PSG in the morning, and the average of the second and third measurements was used for this analysis. Elevated office BP was defined as a systolic BP >= 140 mmHg or diastolic BP >= 90 mmHg. Results: There were 1365 patients with OSA and 597 primary snorers included in our study. In OSA group, OSA patients with SWS <13.5% had a significant elevated risk with elevated office BP (OR,1.49[95%CI 1.05-2.10], P=0.025), compared to the highest quartile (percent SWS >39.2%). However, no significant relationship between decreased SWS and elevated office BP was found in primary snorers group. Conclusion: In non-hypertensive OSA patients, decreased SWS is associated with elevated office BP. Plain language summary This is the first study to investigate the association between decreased SWS and incident elevated office BP in non-hypertensive OSA patients. Our results found that in non-hypertensive OSA patients, decreased SWS is associated with elevated office BP. The relationship between decreased SWS and elevated office BP in OSA patients was evident especially in men and in those