Asthma, a disease of the human respiratory system, which narrows the airways, commonly in response to a "trigger" such as an exposure to an allergen, exercise, cold air, or emotional stress. This narrowing can cause symptoms like shortness of breath, wheezing, chest tightness, and coughing. Between asthmatic episodes, most people with the condition feel fine. This disease is a chronic inflammatory condition wherin the airways develop an increased responsiveness to certain stimuli, shown by bronchial hyper-responsiveness, increased mucus production, inflammation, and intermittent airway obstruction. Asthma can be anywhere from mild to life threatening, but can generally be controlled with a combination of drugs, inhalers and changes in lifestyle. People have focused on asthma recently because of its rapidly increasing number of patients, affecting up to one in four urban children. Genetic factors can contribute to cases of asthma, but there is no clear pattern of inheritance found. It is a very complex disease which is influenced by many various developmental, genetic, and environmental factors, which work togetherto create the widespread condition. Breast-fed babies have proved to be less susceptible to asthma. Current research indicates that the prevalence of asthma in children has been increasing. According to the Centers for Disease Control and Prevention's National Health Interview Surveys, around 9.2% of US children under 18 years old had asthma in 2001, in comparison with just 4% in 1980. The World Health Organization (WHO) reports that 8% of the population of Switzerland suffer from asthma today, compared to 1.9% in 1983. Asthma is more common in countries outside North America, but is by no means a problem restricted to location. "WHO" estimates that there are between 15.3 and 20.1 million asthmatics in India. In the U.S., urban residents, African Americans and Hispanics are affected moreso than the population as a whole. Around the globe, asthma is the cause of approximately 175,000 deaths per year. Asthma and AthleticsAsthma appear to be more common in athletes than in the general population. One particular survey of participants in the 1996 Summer Olympic Games revealed that 16% had asthma, and 10% were on medication for asthma. There seems to be a high number of asthmatics in sports like mountain biking, cycling, and long-distance running, and a somewhat low percentage in weightlifting. It is not clear how much of these cases are results of the effects of training in the sport.