From snoring to sleep apnea in a Singapore population.

We have no information on snoring and obstructive sleep apnea (OSA) in our population, which is predominantly Chinese. Our perception is that sleep apnea syndrome is more common than the 2-4% prevalence (Young et al., 1993) often quoted, judging from the experience in our sleep disorder unit. We studied the snorers in an adult population in Singapore and then went on to see how many snorers suffer pathological apnea and sleep apnea syndrome. Room partners, 220 of them aged 30-60 years, were interviewed for their observation of snoring among each other. 106 consecutive habitual loud snorers of a similar age group in the same population were studied with polysomnography in our sleep laboratory. An apnea index greater than 5 was considered pathological. 24.09% were loud habitual snorers. 87.5% of loud habitual snorers had significant obstructive apneas on the polysomnogram and 72% of these apneics complained of excessive daytime sleepiness (EDS). Given the clinical observation that all apneics snored, by extrapolating these figures, we guess that sleep apnea syndrome affects about 15% of the population. Multiple Sleep Latency Tests validated EDS in our cases with clinical hypersomnia. Hypersomnolence was significantly related to the poor delta wave sleep. Contrary to what was believed, OSA occurred predominantly in stage 1 and 2 non-rapid eye movement (NREM) sleep rather than in REM sleep. The frequent arousals prevented sleep going beyond stage 1 and 2.