In 1997 Wright and colleagues1 published a systematic review on the health effects of obstructive sleep apnoea syndrome (OSA) and the effectiveness of treatment with continuous positive airway pressure (CPAP). They concluded that there was limited evidence of increased mortality or morbidity in patients with OSA, and that the evidence linking the condition to cardiovascular risk factors and motor vehicle crashes was conflicting and inconclusive. They also concluded that, although CPAP had been shown to improve daytime sleepiness, there were insufficient data to determine its effect on quality of life, morbidity or mortality. This review generated much controversy, but was a wake-up call to investigators in this field that all were not convinced that OSA was an important condition that always warranted treatment.2 At that time, our understanding of OSA and the impact of CPAP treatment was at a similar stage to where we were with cardiovascular risk factors such as systemic hypertension, diabetes and hypercholesterolaemia several decades ago. Considerable progress has been made since this review, and many of the issues which it raised have subsequently been addressed in papers published in Thorax . Systemic hypertension has been reported in epidemiological and hospital-based studies of patients with OSA, and is independent of obesity and the other common risk factors for hypertension which are also frequently present in this patient population. There have been conflicting data as to whether nasal CPAP can effectively reduce blood pressure in patients with OSA. Hui and associates3 performed a randomised controlled study in 56 patients with moderate to severe OSA and daytime sleepiness which showed that 12 weeks of therapeutic CPAP reduced 24 h mean and diastolic blood pressure by 3.8 mmHg and 3.5 mmHg, respectively. No …