P R E S S   R E L E A S E

        A recent study conducted by the Department of Medicine and Therapeutics of The Chinese University of Hong Kong on a group of middle-aged commercial drivers (n=216, mean age 45 yrs, BMI 25 kg/m² ) revealed that 40% and 13.4% admitted to have daytime sleepiness and having fallen asleep during driving respectively.  Sleep studies were performed on 51 subjects, and 61% and 20% were found to have sleep-disordered breathing (SDB) and obstructive sleep apnoea (OSA) respectively.  Overall, it is estimated that at least 14.4% and 4.6% of the commercial drivers are suffering from SDB and OSA respectively (Hui et al. Intern Med J 2002, in press).

        Sleep-disordered breathing briefly means cessation of breathing at least 5 times per hour during sleep.  Obstructive sleep apnoea syndrome means SDB with associated daytime sleepiness.  Overseas studies have shown that drivers with SDB have at least 6 times the risk of having a motor vehicle accident compared to those without SDB.

        "Many of the subjects are overweight and have limited time for exercise due to their job nature and long shift.  SDB and the associated sleepiness may impair their alertness and concentration during driving," Professor David Hui Shu-Cheong, Head of Division of Respiratory, Department of Medicine and Therapeutics, CUHK, explained the accident-proneness of SDB patients.

        Besides sleepiness, SDB is also associated with many diseases, particularly in the long term.  SDB is not only an independent risk factor for hypertension but it is also strongly associated with heart failure and stroke.  A more recent CUHK study has shown the prevalence of SDB is much higher among patients following acute ischaemic stroke (age 64 yrs, BMI 24 kg/m²) at 49% compared to 24% in a control group.  Many of the stroke patients have had symptoms of OSA before stroke (Hui et al. Chest 2002, in press).  This suggests that sleep apnoea may predispose to stroke through high blood pressure and other mechanisms.  Recently we have shown with echocardiography in 68 consecutive patients that severe OSA is associated with diastolic dysfunction (i.e. abnormality of heart muscle relaxation) (Fung et al, Chest 2002, in press) .

        Moreover, the prevalence of OSA in renal failure patients on Continuous Ambulatory Peritoneal Dialysis (age 57 yrs, BMI 25 kg/m²) was high at 14% (Hui et al. Am J Kidney Dis 2000) while in contrast, the prevalence of SDB and OSA was low among freshmen enrolled at the CUHK (n=1910, age 19 yrs and BMI 20 kg/m²) at 2.3% and 0.1% respectively (Hui et al. Chest 1999).

        OSA is a treatable disorder and the best treatment is with nasal continuous positive airway pressure (CPAP).  Our HK Chinese patients have better CPAP compliance (72% of our patients using CPAP at least 5 nights per week and at least 4 hrs per night) than the American (46%) and nearly as good as the European (79%).  Our experience at the Prince of Wales Hospital has shown that patient compliance is related to the severity of OSA (Hui et al. Chest 2001).