Association between primary nocturnal enuresis and habitual snoring in children with obstructive sleep apnoea-hypopnoea syndrome frequency of arousals that are correlated with respi- ratory obstructive events [1, 16]. Moreover, Harvey et al. [20] classified OSAS in children based on AHI value: as mild (1 > AHI < 5/h), moderate (5 > AHI < 9/h) and severe (AHI > 10/h). Nocturnal enuresis refers to the involuntary loss of urine after the age of 4 to 5 years, when children are expected to have achieved full bladder control at night. It is classified as primary when the child has never achieved night-time dryness and secon- dary when bedwetting occurs after dryness for at least 6 months [3, 10, 21]. The minimal frequency of nocturnal urine loss required to diagnose the condition as nocturnal enuresis has varied in different studies from once in the previous year [20] to twice a week [22]. In our study a child was characterized as having urine incon- tinence when it appears at least one night per week in children older than 4 years of age [3, 4, 20, 23]. Ethical approval Our study was approved by the Ethical Committee of the Medical School of Aristotle University of Thes- saloniki, Greece, and written informed consent was obtained from parents of all subjects. Statistical analysis The statistical analysis was performed using SPSS 11.2 for Windows; SPSS; Chicago, IL (SPSS Inc, Chicago IL). Frequencies and descriptive statistics were used primarily in order to assess the sample’s overall attri- butes. χ2 test and Fisher’s exact test were used be- tween qualitative variables in order to calculate p values. Mann-Whitney and Kruskal-Wallis tests were used for variables that were not normally distri- buted. Values of p below 0.05 were considered signif- icant. Moreover, since the p value depends on the size of the data set, the statistical inference was assessed using estimation with confidence intervals (CI) and odds ratios (OD). If the 95% CI excludes 1, there is a significant difference between the groups and when the 95% CI includes one, there is no signif- icance at p = 0.05. Table I. Demographic and clinical features and poly- somnographic results of children with OSAHS Sex Age [years] (Mean ± standard deviation) BMI [kg/m2] Snoring Restless sleep Fatigue Mouth breathing Nasal congestion Nocturnal enuresis 7 (16.7%) Difficulty in arousal 22 (52.4%) 38 (90.5%) 34 (81%) 14 (33.3%) 30 (71.4%) 32 (76.2%) 28 males (66.7%) : 14 females (33.3%) 2 : 1 ratio 3.5-14.5 (7.63 ±2.90) 13.66-18.52 (18.52 ±4.24) Apnea-hypopnoea 1.30-94.20 (10.54 ±15.67) index (AHI) [events per hour of sleep] Apnea index (AI) [apnoeic events per hour of sleep] Total sleep time [h] 7.15 ±1.07 0.8-21.10 (4.27 ±3.30) Results Forty-two children were evaluated for possible SDB, and polysomnography sleep study was perfor- med on them. Their demographic and clinical fea- tures and polysomnographic results are presented in Table I. Comparisons between the presence of nocturnal enuresis and patients’ clinical features and symptoms are recorded in Tables II and III. Mild degree of OSAHS was presented by 14/42 children (33.3%), 16 (38.1%) moderate and 12/42 (28.6%) severe. Children who snore had higher levels of AHI (11.02 ±16.37 events per hour of sleep) compared with non-snorers (6.05 ±4.81 events per hour of sleep), but there was no statistical significance (p = 0.33, z = –0.96). Moreover, no significant association (p = 0.68, z = –0.40) was found between patients’ age and sex Table II. Correlations between the presence of nocturnal enuresis and clinical features of patients with OSAHS Parameter Age [years] (Mean ± standard deviation) Sex AHI AI Arch Med Sci 3, June / 2012 Without NE 7.77 ±3.06 10.96 ±16.49 4.42 ±3.58 Children with OSAHS 3.5-14.5 (7.63 ±2.90) 25/28 males : 10/14 females 3/28 males : 4/14 females 28 males (66.7%) : 14 females (33.3%) 2 : 1 ratio NE 6.92 ±1.98 8.45 ±11.51 3.57 ±2.36 p = 0.54 z = –0.61 p = 0.14 p = 0.70 p = 0.62 z = –0.49 p = 0.19 OD = 0.37 95% CI = 0.09-1.45 523