Prevalence of OSAS in Chinese Elderly and Its CPAP Compliance

Obstructive sleep apnea syndrome (OSAS) is a common form of sleep-disordered breathing (SDB) characterized by repetitive episodes of cessation of breathing during sleep due to upper airway collapse. It causes sleep fragmentation, disabling daytime sleepiness, impaired cognitive function and poor quality of life. In addition, OSAS is associated with non-fatal and fatal cardiovascular consequences including sudden death, in addition to an increased risk of road traffic accidents. OSAS is equally common among the middle-aged male Caucasian and Hong Kong (HK) Chinese populations with a prevalence of at least 4%. However, the prevalence of OSAS in the elderly in Southeast Asia is unknown. Sleep disturbances, such as daytime sleepiness, SDB and non-respiratory causes including insomnia, restless leg syndrome are common in the elderly. There are also more frequent and sometimes prolonged nocturnal awakenings, leading to a decline in sleep efficiency (total time asleep as percentage of time in bed). However, the disruption of sleep architecture can be exaggerated by the presence of OSAS. The associated hypersomnolence can exacerbate the normal tendency in older people to sleep during the day, affecting their functional independence.

While OSAS produces large negative impacts on health and quality of life, the recognition is not always straightforward because of the presence of co-morbidities and normal age-related changes in sleep quality and behavior. Once OSAS is suspected, it is not only relatively easy to diagnose, but usually responds well to treatment with CPAP.

Method A sleep questionnaire will be conducted for 1000 subjects aged at least 60 yrs in the elderly community centers focusing on symptoms of OSAS, subjective sleepiness, restless leg syndrome, and sleep-related habits and routines, in addition to past medical history and medications. Home sleep study with the EMBLETTA device capable of recording sleep (a single EEG channel), respiratory events, snoring, respiratory efforts and oximetry will be performed on 300 subjects randomly. Descriptions of the device and the validity of the methods used to collect and display data have been published previously among both local Chinese and other populations. It is a multi-channel screening tool that measures airflow through a nasal cannula connected to a pressure transducer, providing an AHI based on recording time. It also detects both respiratory and abdominal efforts through the effort sensor and can differentiate between obstructive and central events. The body position is detected by the built-in sensors. Respiratory events are scored when desaturations of at least 4% occurred in the absence of moving artifacts and irrespective of co-existing changes in snoring or heart rate. A hypopnea is defined as a decrease in airflow by 50% of baseline for at least 10 seconds. Data are included in the analysis if the total recorded evaluation time of 4 hrs or longer is obtained during the EMBLETTA study.

Those who have negative or technical inadequate EMBLETTA study with a high pre-test probability of moderate to severe OSA will be invited to undergo hospital-based polysomnography for confirmation of their sleep apnoea status.

As OSA may increase the risk of cardiovascular mortality, all elderly subjects with AHI ≥ 15 or those with AHI ≥ 5 plus either cardiovascular risk factors or Epworth Sleepiness Score (ESS) score ≥ 10 received patient education program. Subjects who agreed for CPAP therapy were offered basic CPAP education package consisting of a 10-min CPAP education programme by a respiratory nurse explaining the basic operation and care of the CPAP device and the mask, educational brochure on OSA and CPAP treatment in Chinese, and careful mask fitting, and a short trial of CPAP therapy with the an automatic CPAP machine (AUTOSET CPAP) device (RESMED, Sydney, Australia) for approximately 30 minutes for acclimatization in the afternoon. Attended CPAP titration will be performed with the AUTOSET auto-titrating device in our hospital. Throughout the night and the next morning the nurses on duty would deal with any discomfort related to the CPAP treatment. The CPAP pressure for each patient will be set at the minimal pressure needed to abolish snoring, obstructive respiratory events and airflow limitation for 95% of the night as determined by the overnight AutoSet CPAP titration study. The patients subsequently will be followed up by physicians and nurses at the CPAP clinic in 1 month and 3 months later to deal with any problem with the CPAP device or mask fit. Subjects who agreed for home CPAP treatment will be prescribed nasal CPAP units with time clocks to assess objective compliance (run time). ESS, sleep apnea-specific quality of life index (SAQLI), and cognitive function tests will be performed at baseline and at 3 months after CPAP treatment.