Asthma is a condition in which one airways get narrow and swells and produces extra mucus. This can makes breathing difficult and trigger coughing, wheezing and shortness of breath. For some people, asthma is a minor problem. For some others, it can be a major problem that can interferes with daily activities and may lead to a life-threatening asthma attack. Asthma can't be cured, but its symptoms can be controlled. Asthma is caused by inflammation of the airways. While there is no cure for asthma, there are a number of treatments that can help effectively control the condition. Treatment of asthma is based on two important aspects: relieving symptoms, preventing future symptoms and attacks from developing. Treatment and prevention involves a combination of medicines, lifestyle advice, and identifying and then avoiding potential asthma triggers. People with asthma often suffer from night time coughing, wheezing and breathlessness that disturb their sleep. It is not clear whether there is a circadian rhythm factor responsible for these nighttime disturbances or whether sleep in some way contributes to them, but studies designed to uncover the exact influence of sleep or circadian rhythms on asthma have been largely inconclusive. Even so, many researchers believe that asthmatic symptoms are at least partly due to circadian rhythms and use the term "nocturnal asthma" to describe the phenomenon of asthma symptoms worsening at night. Not all asthma sufferers experience nocturnal asthma.