| Irritable bowel syndrome (IBS) is a functional disorder of the intestines, afflicting between five to twenty percent of the population. There are few epidemiologic studies addressing possible component causes of IBS and the prevalence of other disorders suspected to be commonly associated with IBS. The purpose of this thesis was to quantify the association of risk factors and IBS onset and to quantify the prevalence of other disorders thought to be related to IBS. The context was data from United Healthcare, a large, national managed care plan during the period January 1995 through June 2002 for the first study, and January 1996 through June 2002 for the second and third studies. The specific hypotheses addressed in this thesis were as follows: (1) The incidence of IBS is increased following hysterectomy in comparison to the period before hysterectomy. The study was conducted using a sequence symmetry analysis. (2) The incidence of IBS is elevated among people with asthma in comparison to people without asthma. Since oral steroids are used by asthmatics to reduce systemic inflammation, it was also hypothesized that the incidence of IBS among oral steroid users within the asthma cohort would be reduced in comparison to compared with non-users of oral steroids. A cohort study, with a nested case-control study, of people with and without asthma was conducted. (3) The prevalence of migraine, fibromyalgia and depression is greater among people with IBS in comparison to people without IBS. A cohort study of people with and without IBS was conducted.; The first study showed no association between hysterectomy and IBS. The second study showed a 20% increase in the incidence of IBS among people with asthma in comparison to people without asthma. Among people with asthma, there was no association between dispensing of oral steroids and IBS. The third study showed a 60% increase in the prevalence odds of migraine, fibromyalgia, or depression among people with IBS compared to people without IBS. This research provides further insight of a condition affecting a large number of patients, particularly women, often resulting in a significantly decreased quality of life. |
