EDITORIAL

 

Gastro-esophageal reflux disease and irritable bowel syndrome - why are they associated?

Enfermedad por reflujo gastroesofágico y síndrome de intestino irritable, ¿por qué se asocian?

 

 

E. Rey and M. García-Arredondo

Department of Digestive Diseases. Hospital Clínico San Carlos. Universidad Complutense. Madrid, Spain

 

 

Gastroesophageal reflux disease (GERD) and irritable bowel syndrome (IBS) are the most prevalent gastrointestinal disorders in the general population. In Spain around 10% of the population have typical reflux symptoms for at least one day a week, and 20% have them on an occasional basis (1); incidence is around 4% annually (2), whereas the prevalence of IBS is around 2-12% (3) depending on the defining criteria. Moreover, around 28% of people with GERD symptoms (4) and two thirds of people with IBS (5) consult a doctor each year. From a worldwide perspective both GERD (6) and IBS (7) exhibit similarly high prevalence scores, even though regional differences exist.

Given the high prevalence of both diseases among the population their common association is hardly surprising; in fact, patients with heartburn as well as abdominal pain and bowel transit changes are common in our practices. To date we have considered these patients as carriers of two unrelated diseases, with the diagnostic and therapeutic complications this entails. However, population-based studies show that the association of GERD and IBS does occur much more commonly than would be expected by random causes (8). A recent systematic review of the literature suggests that the prevalence of GERD in subjects with IBS is 30%, much higher than the 19% seen in the general population, whereas the prevalence of IBS in individuals with GERD is 60%, notably higher than 12% of the population (9). This fact suggests a number of questions, most of them as yet unanswered: should we still consider them two unrelated diseases? Which factor may explain the above-mentioned association? Has this association any diagnostic or therapeutic implications?

While it has been suggested that IBS symptoms may be a component of GERD´s clinical expression (10), based on the improvement of abdominal symptoms in patients diagnosed with GERD on antireflux therapy, most of the available scientific evidence suggests that these are separate disorders sharing some common factor.

The search for this shared factor is a scientific challenge with dramatic diagnostic and therapeutic implications; however, it has just begun and several years will probably go by until data apt to be translated into clinical practice will be available.

Major factors explored include genetic and psychological aspects, motility disorders, and sensitivity changes. Lembo et al. (11) have shown, in a study with twins, that genetic contributions to GERD and IBS development are different; while this is only a study to be subsequently confirmed by further research, individual studies performed to explore susceptibility to GERD or IBS also suggest no shared genes. A gastrointestinal tract smooth muscle disorder has been suggested to support this association, but data available thus far are scarcely convincing (12). Some studies suggest that a shared factor could be visceral hypersensitivity, and generalized (non-organ-specific) hypersensitivity has been found in functional GI disorders (13) while esophageal hypersensitivity was seen in patients with IBS (14). Finally, psychological factors play a relevant role both in GERD (2,15) and IBS (16), and population-based studies have been suggested for potential explanations (17); however, at least from a clinical point of view, these do not seem determinant in the association of both disorders (15).

In this issue of Revista Española de Enfermedades Digestivas, Max Schmulson et al. (18) report novel data on this search for factors, and focus on the hypothesis that obesity may explain it. Obesity is a Western world epidemics (19,20); its prevalence progressively increased during the last few decades, is clearly associated with GERD (21), and is linked to abdominal symptoms such as diarrhea and distension (22). Using adequate methods, their results reinforce both the GERD and IBS superposition, and an association between obesity and reflux symptoms, but also clearly show that obesity provides no explanation why GERD and IBS are associated more commonly than expected by chance. Even a negative result detracts no value from this report, particularly bearing in mind that we just set out in our way to explain something that is extremely common in our practices on a daily basis.

 

References

1. Diaz-Rubio M, Moreno-Elola-Olaso C, Rey E, Locke GR, III, Rodriguez-Artalejo F. Symptoms of gastro-oesophageal reflux: prevalence, severity, duration and associated factors in a Spanish population. Aliment Pharmacol Ther 2004; 19: 95-105.        [ Links ]

2. Rey E, Alvarez-Sanchez A, Rodriguez-Artalejo F, Moreno Elola-Olaso C, Almansa C, Diaz-Rubio M. Onset and disappearance rates of gastroesophageal reflux symptoms in the Spanish population, and their impact on quality of life. Rev Esp Enferm Dig 2009; 101: 477-82.        [ Links ]

3. Mearin F, Badia X, Balboa A, Baro E, Caldwell E, Cucala M, et al. Irritable bowel syndrome prevalence varies enormously depending on the employed diagnostic criteria: comparison of Rome II versus previous criteria in a general population. Scand J Gastroenterol 2001; 36: 1155-61.        [ Links ]

4. Rey E, Moreno-Elola-Olaso C, Rodriguez-Artalejo F, Diaz-Rubio M. Medical consultation for gastro-oesophageal reflux symptoms: reasons and associated factors. Digestion 2004; 70: 173-7.        [ Links ]

5. Badia X, Mearin F, Balboa A, Baro E, Caldwell E, Cucala M, et al. Burden of illness in irritable bowel syndrome comparing Rome I and Rome II criteria. Pharmacoeconomics 2002; 20: 749-58.        [ Links ]

6. Dent J, El-Serag HB, Wallander MA, Johansson S. Epidemiology of gastro-oesophageal reflux disease: a systematic review. Gut 2005; 54: 710-7.        [ Links ]

7. Rey E, Talley NJ. Irritable bowel syndrome: novel views on the epidemiology and potential risk factors. Dig Liver Dis 2009; 41: 772-80.        [ Links ]

8. Jung HK, Halder S, McNally M, Locke GR, III, Schleck CD, Zinsmeister AR, et al. Overlap of gastro-oesophageal reflux disease and irritable bowel syndrome: prevalence and risk factors in the general population. Aliment Pharmacol Ther 2007; 26: 453-61.        [ Links ]

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15. Rey E, Garcia-Alonso M, Moreno-Ortega M, Almansa C, Alvarez-Sanchez A, Diaz-Rubio M. Influence of psychological distress on characteristics of symptoms in patients with GERD: the role of IBS comorbidity. Dig Dis Sci 2009; 54: 321-7.        [ Links ]

16. Rey E, Moreno OM, Garcia Alonso MO, Diaz-Rubio M. Constructive thinking, rational intelligence and irritable bowel syndrome. World J Gastroenterol 2009; 15: 3106-13.        [ Links ]

17. Lee SY, Lee KJ, Kim SJ, Cho SW. Prevalence and risk factors for overlaps between gastroesophageal reflux disease, dyspepsia, and irritable bowel syndrome: a population-based study. Digestion 2009; 79: 196-201.        [ Links ]

18. Schmulson M, Pulido D, Escobar C, Farfan-Labone B, Gutierrez-Reyes G, Lopez-Alvarenga JC. Heartburn and other related symptoms are independent of body mass index in IBS. Rev Esp Enferm Dig 2010; 102: 229-33.        [ Links ]

19. Wang Y, Beydoun MA. The obesity epidemic in the United States -gender, age, socioeconomic, racial/ethnic, and geographic characteristics: a systematic review and meta-regression analysis. Epidemiol Rev 2007; 29: 6-28.        [ Links ]

20. Schroder H, Elosua R, Vila J, Marti H, Covas MI, Marrugat J. Secular trends of obesity and cardiovascular risk factors in a Mediterranean population. Obesity (Silver Spring) 2007; 15: 557-62.        [ Links ]

21. Corley DA, Kubo A. Body mass index and gastroesophageal reflux disease: a systematic review and meta-analysis. Am J Gastroenterol 2006; 101: 2619-28.        [ Links ]

22. Delgado-Aros S, Locke GR, III, Camilleri M, Talley NJ, Fett S, Zinsmeister AR, et al. Obesity is associated with increased risk of gastrointestinal symptoms: a population-based study. Am J Gastroenterol 2004; 99: 1801-6.        [ Links ]