There is a continuum in sleep disordered breathing (SDB) from chronic snoring to upper airway resistance syndrome to obstructive sleep apnoea (OSA) that is associated with progressively increasing consequences. The reported prevalence of SDB depends on the recognition threshold. In a landmark community based study, Young and coworkers1 found that 2% of women and 4% of men had both daytime sleepiness and an apnoea-hypopnoea index (AHI) of >5/hour. In this month’s ThoraxKnuistingh Neven and colleagues2 present data from a small Dutch town which suggest that the prevalence of OSA with associated daytime sleepiness is at least 0.9% in men of 35 years or older. Thus, SDB is common, but how clinically significant is it? In their provocative systematic review Wright et al 3 concluded that there is limited evidence of increased mortality or morbidity in patients with OSA. To put these conclusions in context, it needs to be recognised that our understanding of SDB has only recently moved from its infancy to its adolescence. We are only at a similar stage in our knowledge of the natural …