LAUSR

Australian Aboriginal and Torres Straight Islanders (ATSI) are noted to have a higher burden of chronic health conditions. However, there is a paucity of data on Obstructive Sleep Apnoea (OSA) in this population. In this retrospective study, we evaluated the clinical and polysomnographic (PSG) characteristics of ATSI and non- ATSI adult patients who underwent diagnostic PSG between 2011 and 2015. There were a total of 3078 patients. Of the total, 403 (13%) were of ATSI origin. Amongst those of ATSI origin, 61% were male and 39% females, while amongst the non-ATSI cohort, 66% were males. The median age was 47.8 years in ATSI and 51.5 years in the non- ATSI cohort. In the combined cohort, body mass index was >30 kg/m2 ( 61%), hypertension (14.4%), diabetes ( 17.8%) and heart disease ( 23.3%). The ATSI patients had higher rates of class III obesity (27 v 15%), hypertension (26 v 14%), cardiac disease (34 v 23%) and diabetes (37 v 17%). Among all the study participants, the PSG confirmed 83.7% of the patients had an apnoea-hypopnea index (AHI) more than 5/hour, mild (AHI 5-15/hour) in (28.4%), moderate (AHI 15-30/hour) in (22.3%), and severe (AHI > 30/hour) in (33.0%). Among the ATSI patients, 46% had severe OSA. The median total AHI value was higher in the ATSI population (25, IQR: 11 - 58) compared to the non-ATSI (17, IQR: 7 - 36), and in rural/remote population (19, IQR: 8 - 42) compared to urban (17, IQR: 7 - 37). This trend was similar for NREM (Non Rapid Eye Movement)-AHI and REM (Rapid Eye Movement) AHI scores, although statistically significant difference was found only with ATSI status. In the combined cohort the probability of (OR= 1.62, 95% CI: 1.32-2.00, p<0.001) of severe OSA was 62% higher in individual with hypertension , however, when stratified by ATSI status, the association was only significant in the non-ATSI population (OR=1.53 95% CI: 1.21 - 1.94, p<0.001). The odds of severe AHI was also significantly associated with heart disease (1.37; 95%CI: 1.14,1.63, p<0.001), diabetes (1.74; 95%CI: 1.43,2.10; p<0.001) and smoking (1.28; 95%CI: 1.09,1.50, p=0.0023) in the overall study cohort. In both ATSI and non- ATSI patients, BMI, neck circumference, sleep efficiency, wake after sleep onset and respiratory arousal index were significantly higher and independently associated with severe AHI.