Dziewas and colleagues1 report that patients with Charcot–Marie–Tooth disease type 1A (CMT1A) have an increased prevalence of obstructive sleep apnoea (see page 829). Sleep apnoea can be caused by CNS abnormalities; in these cases there is decreased respiratory effort. In obstructive sleep apnoea, also known as the obstructive sleep apnoea–hypopnoea syndrome (OSAHS), the cause is not from the CNS but from a physical obstruction to breathing. The obstruction can be an anatomical abnormality in the upper airway—for example, enlarged tonsils. Obesity, being male, advanced age and hypertension are all associated with OSAHS. The obstruction site is usually in the collapsible portions of the pharynx: the velopharynx, oropharynx or hypopharynx. Sleeping patients can overcome the obstruction by increasingly forceful inspiration which eventually creates enough inspiratory pressure to re-open the occluded airway. However, this crescendo respiratory pattern disrupts NREM/REM sleep causing daytime sleepiness and fatigue. OSAHS also causes an increased afterload in both ventricles of the heart, decreased left ventricular compliance, increased pulmonary artery pressure, decreased coronary blood flow and increased myocardial oxygen consumption. Taken together, these abnormalities predispose patients to develop cardiovascular disease. Whether patients with CMT1A with sleep apnoea …