Asthma is a serious, long-term illness that affects around 15% of children in the United States. During adolescence, up to 50% of teenagers stop experiencing symptoms and are able to discontinue treatment. However, asthma symptoms often reoccur in adulthood for many of these people. It is not known exactly what causes this recurrence, but potential risk factors may include obesity, elevated serum leptin levels, early onset of puberty, exposure to pollutants, parental smoking habits, and lack of breastfeeding. Additionally, it is not known why childhood asthma is initially more prevalent in boys, but during adolescence it becomes more prevalent in girls. Beginning in 1989, a group of children born on the Isle of Wight in the United Kingdom has been followed by study researchers to provide long-term information on asthma. These children have been periodically evaluated over the years and are now 18 years old. The purpose of this study is to analyze participants' data collected over a span of 18 years to identify factors that may increase a person's risk of experiencing persistent or recurrent asthma in adulthood.