This study confirms the high prevalence of IBS in the US population and its impact on the working life, social activities and well-being of sufferers. The overall prevalence of IBS in this population was 14.1%, with only 3.3% being medically diagnosed. This compares with a prevalence rate of 11.5% in a previous European study, and is consistent with other large US-based epidemiological studies, where prevalence estimates cluster around 10-15%.[25,26] Expected variations in diagnostic rates according to Manning, Rome I and Rome II criteria were seen, as previously noted.[21,27,28] Clearly, IBS prevalence can vary substantially depending on the diagnostic criteria employed. This comprehensive, representative survey used specific, validated IBS diagnostic criteria to estimate prevalence and symptom patterns, and also assessed impact of IBS on work, lifestyle and health. In this study, prevalence rates were highest among those aged 25-54 years, and the prevalence of IBS among women was approximately two times higher than that recorded for men in individuals medically or not medically diagnosed with IBS. These findings corroborate previously published reports, which demonstrated a higher IBS prevalence in women than in men.[30,31] In patients medically diagnosed with IBS, 25% had visited a health professional at least five times before being formally diagnosed, suggesting that diagnostic criteria are not being properly utilized, IBS symptoms are not always recognized or are misdiagnosed, and/or that the diagnosis of IBS is not being communicated to the patient.
This US population study adopted a survey methodology similar to that used in a recent European study of IBS prevalence and impact. That study comprised approximately 5000 respondents from each of eight countries with a total sample population of 41 984, whereas in the US, the total sample population was 5000. Thus, comparisons between the two studies remain limited. The only other US study using random-digit dialling to assess IBS included 1014 adult women with IBS.[28,32]
The clinical presentation of IBS is quite varied, with sufferers in the present study reporting a wide range of symptoms. IBS sufferers also reported that their symptoms rarely improve and were fairly or very painful, as highlighted in previous studies.[2,34] In this study, the prevalence of individual IBS symptoms was higher in medically diagnosed IBS patients than in current IBS sufferers who were not medically diagnosed. This finding may be related to IBS severity, which is likely to be greater in patients presenting for treatment. Medically diagnosed patients may also have a greater awareness of IBS and its associated symptoms. Data confirmed that IBS is a long-term condition, with one-third of IBS sufferers having experienced IBS symptoms for over 10 years, a figure comparable with that in Europe (40%).
It is well documented that IBS can have a considerable impact on sufferers' lives,[16,21,26,35,36,37] and this is compounded by the condition's chronic and episodic nature. This study reinforces that IBS has a substantial impact on quality of life. There was a large impact on absenteeism and work productivity, confirming previous findings in both US[1,2,20,34] and European populations. Additionally, ill health was recorded for an average of 6.4 days in current IBS sufferers, compared with 3.0 days in non-IBS sufferers. One in six current IBS sufferers in the US had changed their work schedule and one in four had worked fewer hours. These data support findings from Drossman et al., who reported that IBS patients missed three times more days from work than non-sufferers. Time management, the ability to concentrate and commuting time were also negatively affected in IBS sufferers in the present study. Regular social activities such as going out for a meal, long journeys or holidays were also hindered. Thus, the symptoms of IBS appear to affect the ability to live a normal life. This is further compounded by the fact that other functional GI disorders often coexist with IBS. Although this was not fully assessed in this study, 24% of IBS sufferers had also suffered from GERD or dyspepsia.
Substantial health care use because of IBS was recorded in this US population. Sufferers used a wide range of medications for relief of IBS symptoms. Medically diagnosed IBS patients with current symptoms appeared to take fewer antisecretory medications and laxatives than those not medically diagnosed, presumably due to the availability of these medications over the counter. This finding contradicts data from Shih et al., who reported that 89% of doctor visits generated prescriptions. At the time of the present study, treatment options for abdominal pain/discomfort, bloating and constipation were only viewed as being completely effective in a small proportion of users. As IBS symptoms are intermittent, treatment was often restricted to times when patients experienced symptoms.
A varying perception of IBS-A was highlighted in this study. Most IBS sufferers (74% medically diagnosed, 63% not medically diagnosed) had alternating symptoms of constipation and diarrhoea as defined by doctors and diagnostic criteria. However, when sufferers were asked to categorize themselves, only approximately one-third of medically and not medically diagnosed respondents with IBS defined themselves as having IBS-A (33% and 27%, respectively) compared with IBS-C (17% and 30%, respectively) and IBS-D (45% and 29%, respectively). This finding is in contrast to other published data, which reported equal prevalence rates of IBS-C, IBS-D and IBS-A.[25,34] A possible explanation for this discrepancy is the use of more strict criteria for IBS-A in the current study than in the Rome II subclassification.
In conclusion, IBS is a prevalent disorder that significantly impacts work, lifestyle and social well-being. Diagnosing and managing IBS can be challenging due to the lack of a diagnostic marker and effective treatment options. Individuals with IBS who are not formally diagnosed reported a significant prevalence of GI symptoms, which impacted on their work and other daily activities, although in some instances to a lesser degree than medically diagnosed individuals. All IBS sufferers face the challenge of their condition on a daily basis and this study highlights the huge unmet therapeutic need in IBS.
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Prof. A. P. S. Hungin, Centre for Integrated Health Care Research, Wolfson Research Institute, University of Durham, Stockton-on-Tees TS17 6BH, UK. E-mail: email@example.com .
Aliment Pharmacol Ther. 2005;21(11):1365-1375. © 2005 Blackwell Publishing
Cite this: Irritable Bowel Syndrome in the United States: Prevalence, Symptom Patterns and Impact - Medscape - Jun 01, 2005.