<p>We statistically examined the effect of background conditions and coexisting conditions on nocturia with sleep apnea syndrome (SAS) patients. Thirty three Osaka Dental University Hospital patients who were examined using polysomnography (PSG) from April 2019 to December31, 2020, were recruited for this study. They were divided into two groups: the nocturia group (nocturnal urination was twice or more) and the non‐nocturia group (nocturnal urination was once or less). The effect of nocturia with SAS on background conditions such as age, gender, BMI, apnea hypopnea index (AHI), lowest SpO2, estimated glomerular filtration rate (eGFR), sleep latency, sleep efficiency, and Non Rapid Eye Movement(NREM) ratio, and the prevalence of coexisting conditions including hypertension, diabetes mellitus (DM), metabolic syndrome (MS) and chronic kidney disease (CKD), were examined with the χ2 test, Student's t‐test and multivariate analysis (p<0.05). In univariate analysis, nocturia was related to age, sleep efficiency, eGFR, prevalence of DM and prevalence of MS for male patients, and related to age, sleep efficiency, and eGFR for female patients. In multivariate analysis, nocturia was related to age and sleep efficiency for both genders. Age was to positively correlate to nocturia through circadian extracellular fluid change. Lower eGFR as a renal dysfunction index was also to correlate with age.</p><p>DM and MS were related to renal dysfunction through visceral fat in males but not in females, which was attributed to the higher BMI in males. (J Osaka Dent Univ 2024; 58: 321-325)</p>