It would interest you to know how a Neurologist would tell the story of sleep apnea (OSA) in Singapore.

Physicians have seen sleep apnea centuries ago but did not know what this disease was. Graves the Dublin physician wrote in the Dublin Journal of the man who fell asleep in his soup. What should have been an almost inevitable discovery of a disease by a respiratory physician had to be described by a Neurologist for the simple reason that traditionally it was the Neurologist rather than a Pulmonologist who would observe patients breathing during sleep. Sleep apnea as we know it now was described in 1965 by a French Neurologist (Gastaut). This was the background for our interest in sleep apnea as neurologists.

Gastaut was a Neurologist with interest in EEG from France. His description of sleep apnea was ignored in America initially. Later, with Guilleminault the Frenchman who went over to Stanford, they became leaders in OSA research.

Here in Singapore it was a similar story. While doing sleep-deprived EEG (this brings out epileptic activities), we often observed patients who would stop breathing in sleep. We used to wake the patient up lest they would not breathe again. However it never occurred to us that this was sleep apnea because this condition had not been in our textbooks of medicine. Symptomatic sleep apnea was being diagnosed only rarely in the UK probably from lack of recognition.

We researched in this field at a time when the hospitals were not interested. The ceaseless regular donations by the Shaw Foundation helped us to pioneer sleep disorders in this region. We traced the story of sleep and apnea research from the early 1980s to the 21st century by which time sleep lab has become a vogue and pride to almost every hospital in Singapore. The virtue of running sleep disorder units as multidisciplinary is exemplified.

Singapore – Sleep Apnea ResearchTop

The earliest sleep lab in Singapore (Year 1987) was in Ward 48, Singapore General Hospital (SGH), which was modifed to a Sleep Laboratory. We used a SIEMENS 16 channel EEG machine (now a museum piece) for our initial recordings. Our sleep study technologist was Mr.Ang our EEG technician. We performed paper recording of a whole night’s sleep(a big stack of recorded paper). The EEG signals were AC signal written by pen. For slow signals like oximetry and chest movement recording, DC amplifiers were later used with respiratory interphase. Initially we counted the apneas as the EEG recording went. Sleep staging was a tiring process.

We were doing Sleep Latency but not in the way Carskadon (who described the Multiple Sleep Latency Test, the gold standard objective test of sleepiness) & Dement defined it.

There were only 3 sleep centres in USA in 1977 and 92 centres in 1987, and only 40 when we started sleep research. Technological improvement came along in the late 80’s (1986) when we were able to record overnight sleep signals on a cassette tape. We started dedicated sleep monitoring initially using an ambulatory Oxford medical system (an improvement from the bulky Siemen EEG), initially a 4 channel 24-hour recorder which we bought in 1986, then upgraded to an 8 channel recorder with audio-visual playback. This Oxford medilog 9000 was an 8-channel recorder and playback. For rapid sleep scoring the physiologic data was converted to audio signals. Later medilog sleep stager became available and then the medilog sleep analysis computer (SAC) system came in with the polygraph. A respiratory interphase was able to time-lock other parameters like breathing and oximetry.

Digital recording overtook analogs sometime in the late 1980s. The next advancement was video time-locked to the polysomnogram. Our early split screen recording was on the telefactor. Here patients behavior was seen on a video which was time-locked to the recording parameters. With donations from Shaw Foundation, we had an up-to-date 4 sleep labs. SGH supported this and we expanded to 6 labs and a Sleep Disorders Clinic. We ran it as multi-disciplinary: ENT, Respiratory, Neurology, and Psychiatry. Technician training was the next concern. 3 sleep technologists obtained board certification RPSGT initially, and others followed suit. By now the Shaw Foundation had steadily, yearly since 1985, supported sleep research by way of donations totalling more than $700,000.00. We owe them a tremendous debt of gratitude.

The 1st case description of OSA in Singapore was by Dr TK Lim and Dr WC Tan (Annals Academy of Medicine, July 1985, Vol.14, No.3). This was a clinical description of 6 cases. No EEG, EMG or airflow were measured. The authors spent many hours at the bedside, observing the breathing. All their patients were obese and males. Dr YT Wang and Dr Poh SC (SMJ 1989, No.30:12-14) detected only 10 cases of OSA in 2 years. They speculated that the lower incidence of obesity locally accounted for the low prevalence of OSA. Dr WC Tan studying snorers in Singapore using respiratory monitors but No Airflow concluded that OSA is not uncommon in Asians (1991). In Stanford University, USA where Guilleminault studied and defined OSA, there were only about 150 cases in 1978, about 450 cases in 1980, and 800 cases in 1984. Not many cases were known outside Stanford.

We recognized that not all OSA patients are Pickwickian (ie. middle-aged male, obese, sleepy snorers), a stereotype that emerged from clinical observations in earlier years. Pulmonologists believed respiratory failure was the cause of excessive daytime sleepiness, until Gastaut (1966) showed it was from the repeated arousals associated with OSA.

Our local study of patients highlighted for the first time that OSA syndrome is much more common than was thought and drew attention to the enormous public health burden it caused (Sleep Res Online. 1999). Initially the results from our study, showing a 15% prevelance seemed unbelievable, compared to the initial Israel study showing a prevalence of 0.5%. When this problem was highlighted in our SGH bulletin (1997), the size of the problem invited disbelief. There were letters to the author that these figures were over-exaggerating this problem.

Unlike snoring and other sleep disorder symptoms, OSA syndrome has not been the subject of any sound epidemiological surveys in the general population. None of the studies to date used a true random sample of subjects to be monitored polysomnographically. Most were cohort studies and studied abnormal breathing without an objective measure of sleep. This is a major flaw. Recent generations of sleep physiologists have assumed that sleep apnea is a relatively uncommon problem.

Ancoli-Israel in 1991 found that AHI>5 occurred in 24.0% of a population (65-95 years). Considerable surprise greeted the finding by Young et al (1993) that 24% men and 9% women in Wisconsin had AHI>5. Of these, 4% males and 2% females had OSA syndrome characterised by AHI>5 plus hypersomnia.

In our local study we sampled our population in 2 stages. It was known that almost all apneic patient snores. We initially sampled randomly a middle aged, otherwise healthy population (30-60 years) to study prevalence of snoring. Couples were interviewed: 24.1% were habitual snorers. In a 2nd stage we studied 106 consecutive cases of loud habitual snorers of the same age and ethnicity mix using full polysomnography.

Estimates of sleep disordered breathing (SDB) in our population was 0.241 x 0.87 x 100 = 20.8%. This is only slightly higher than the 16.5% estimate in the much-quoted paper from Wisconsin (Young et al, 1993). Our figure was comparable to another American study which showed AHI>5 in 24.0% population aged 65-95 years (Ancoli-Israel, 1991) Young’s estimate of sleepiness is 19% compared to our 72%, thus contributing to the almost 3 fold higher prevalence locally. Their stringent questionnaires for hypersomnolence compared to our MSLT validated sleepiness could have accounted for the difference. It is well known that clinical evaluation underestimates sleepiness.

For some reason, the local population showed or suffered more hypersomnia with OSA than the much-quoted Wisconsin study.

In a subsequent paper (Sleep Medicine 2004) we tried to find out whether hypersomnia as a symptom was commoner in our population for the amount of apnea. 195 cases of OSA were studied with MSLT and it appears that the hypersomnia is more related to factors other than AHI such as snoring and total arousals in the night. This also confirmed the same high prevalence of EDS in our local cases of OSA.

CPAP for OSA in SingaporeTop

The earliest patient to get CPAP was our patient Mr.P. who had severe OSA initially diagnosed in 1987. He had a twin brother in Sydney who also had severe OSA and happened to be on Dr.Colin Sullivan’s CPAP trial. Thus the first CPAP machine came in to Singapore. At that time there were no agents to import CPAP into Singapore. Dr Sullivan’s machine was very hardy and did not give any problems. Mr. P. only changed to a new CPAP in year 2003, the only reason being that the old machine got stale. When we repeated the sleep study in year 2003, the apnea index remained about the same (90 AHI). His response to CPAP was remarkable.

Residual Sleep In OSATop

OSA – NARCOLEPSY SYNDROME: OSA can co-exist with narcolepsy. We encounter this problem when we see patients in whom CPAP alone is ineffective in treating the OSA. Such patients are very sleepy by day and multiple sleep latency testing (MSLT) shows very short sleep onset latency and many sleep-onset REM periods (SOREMPs). These cases of OSA associated with Narcolepsy are often missed if MSLT is not done. In our series, 7 of 195 OSA patients also had clinical Narcolepsy, 28.2% OSA had SOREMPs on MSLT. Stimulants like modafinil and methyphenidate are useful in these patients.

Upper Airway Surgery for OSATop

Local surgeons have done various operations for OSA. Dr KK Loh performed uvulopalatopharygoplasty (UPPP) surgeries in 1991. Dr YH Goh and Dr KA Lim performed the first maxillo- mandibular advancement surgery in Singapore in 2000.

OSA in SingaporeTop

Our early research had shown the peculiarly high prevalence of OSA locally and the enormous public health burden, at a time when sleep researchers around the world played it down.

We made use of the press, TV and public forums to educate the doctors and public on OSA. Hospital referrals of OSA increased and we saw an explosive increase in sleep laboratories in Singapore. While others were satisfied with documenting only apnea, we were able to see apneas within objective measures of sleep, sleepiness and behavior. We stressed the importance of comprehensive monitoring as many narcolepsy cases were being missed if multiple sleep latency tests are not done. They present as the problem of CPAP being ineffective when treating OSA.

With OSA management taken care of, we discuss the sociolegal aspect that looms over us.

OSA – Sociolegal Aspect in SingaporeTop

Motor car accidents – 6 cases in our study had motor car accidents. There is no legislation barring drivers with OSA in Singapore.

Pilots – There is no requirement to declare snoring in the initial medical examination. The 1st pilot to my knowledge to be taken off was only recent, where the SIA pilot himself complained of sleepiness while piloting and driving a motor car.

Violence – It is known that OSA cases when woken out of deep sleep by an apnea could go into automatism and if violent can fall into trouble. The case of Mr.Butler (1963) who shot and killed his wife while experiencing confusional arousal after he was woken out of deep sleep by an apnea is well known. The jury found him guilty.

Confusional Arousal locally has been seen. A National Serviceman with sleep walking was woken out of deep sleep and strangled his mate.

Future of Sleep Medicine in SingaporeTop

The formation of the Singapore Sleep Society was a milestone in the history of Sleep Medicine in Singapore. We hope to translate the medical model of clinical service to improving health and quality of life among Singaporeans by dissemination of knowledge of the disease and implementation of clinical practice guidelines. Our goal is to improve public awareness and health literacy in sleep disorders, such that terms like “sleep apnea” and “CPAP” become common parlance to the layman.

In the future, we expect to see new surgical approaches for OSA and other novel therapeutic strategies. As awareness of sleep disorders and the number of sleep laboratories (and, of concern, unattended portable/home sleep studies) increase locally, maintaining high standards in Sleep laboratories and in the management of sleep disorders becomes even more of a priority for us. We need to improve recognition of common sleep disorders like OSA, just as we highlight related problems like the rise in obesity. Good sleep needs to be identified as important, just like proper nutrition and regular exercise.

Our future goals include:

  • Increasing awareness of sleep disordered breathing since OSA is so common in Singapore
  • National education programmes on the impact of lack of sleep on cognition and performance and the importance of good sleep health
  • Improving safety in occupational groups at risk of chronic sleep loss and/or involved in transportation safety eg. shift workers, drivers, pilots, health care workers
  • Ensuring adequate training and certification of sleep technologists in Singapore