Asthma is characterised by breathlessness, cough, wheeze and chest tightness especially at night or in early morning. The severity of these symptoms is variable. Symptoms occur in episodes. These may occur suddenly or may develop over a period of days or weeks. Some patients complain of attacks of symptoms mainly at night or in early morning. These episodes typically occur between 4 am and 6 am, and these episodes of breathlessness disturb their sleep.