Because there were no previous studies reporting IBS prevalence in Chile, the estimate presented at the Latin American Consensus on Irritable Bowel Syndrome, corresponding to a maximum prevalence of 18%, was used to calculate sample size.15 According to the formula used for this calculation, we established a minimum sample size of 391 surveys to reach 80% power and an alpha level of 0.05.

All the eligible surveys were given a correlated code number, keeping the identity of the subjects confidential. The STATA 9.0 software was used for the data analysis. Age and IBS presence (with and without the variable of sex) were compared using the Student's t test. The Pearson chi-square test or the Fisher exact test were used to compare the categorical variables. Possible risk factors, such as female sex, a family history of IBS, and occupational level were determined through the logistic regression analysis. Odds ratio was calculated with a 95% confidence interval.

Data were presented as mean ± standard deviation. All the calculations were two-tailed p values and statistical significance was considered with a p<0.05.

This study was approved by the Scientific Ethics Committee of the Hospital Clínico Universidad de Chile.

Upon comparing the demographic data of the subjects with IBS symptoms and the asymptomatic ones, a greater proportion of women was observed in the IBS group (65.6%), whereas the percentage of women was 42.9% in the asymptomatic subjects. On the other hand, there were no differences in the ages of the patients in the two groups (45.2 years vs-. 41.1 years).

The sex distribution percentage of the different patient ages in the IBS group is shown in Figure 2: the percentage of women patients with IBS symptoms progressively increased with age, reaching a maximum 46-60 years; there were significant differences with men from the same age group and with older or younger women (p<0.05). In contrast, there were no age-related variations in men.

Figure 2.

Distribution percentage of men and women with irritable bowel symptoms in different age groups. Significant differences can be seen when comparing men and women in the 46-60 year age group with those under 30 years of age and above 60 years of age.

* p < 0.05.

(0.08MB).

Regarding the educational level (Table 1), the majority of the surveyed subjects, whether presenting IBS symptoms or asymptomatic, were in level 4 (technical studies). When comparing the percentage distribution of the subjects with IBS symptoms and the asymptomatic ones, a lower IBS percentage was seen in the group with a higher level of education; there were no differences in the other groups. In relation to the area of residence, the majority of the subjects lived in areas 1 and 5; there were no differences in the distribution percentage between the subjects with and without IBS symptoms in the different areas of residence (Table 1).

A family history of IBS was present in 40% of the IBS subjects, whereas only 14.9% of the asymptomatic subjects stated having such a history (p<0.001) (Table 1).

The univariate analysis of the evaluated factors showed that women had a greater risk for IBS, but it was not statistically significant (p=0.057). The presence of family history was significant (p<0.01). Having a university education was associated with a lower presence of IBS symptoms and was statistically significant (p<0.02).

A past history of surgery was found in 107 subjects and the number of surgeries was 108 (38.7%). The most frequent procedures were cholecystectomy, appendectomy, and gynecologic interventions. Table 2 shows that more than twice the number of subjects with IBS underwent cholecystectomy compared with the asymptomatic subjects (p<0.05). This difference was maintained when only women were taken into account. In contrast, appendectomy presented with a similar frequency in both groups.

A very low proportion of other surgical procedures was observed in the two groups.

In the concomitant pathology analysis (Table 2), high blood pressure and diabetes mellitus stood out and their frequency was significantly greater in the patients with IBS symptoms (p<0.05).

The mean age for IBS symptom onset was 30.4 years, with a range of 11 to 69 years.

Forty-nine (39.2%) of the subjects with IBS had seen a physician. Of those subjects, tests were ordered for 28 of them; the most frequent was endoscopy, performed in 13 of the subjects, blood tests in 8, abdominal ultrasound in 4, and abdominal ultrasound plus endoscopy in 3 subjects.

Of the 49 subjects with IBS that had a medical consultation, 37 (75.5%) reported having received some kind of treatment for their symptoms (Table 3) and the most frequently used drug was a proton pump inhibitor in 35.1% of the cases.

In Latin America, a prevalence of IBS between 9 and 18% has been described,15 which is similar to that reported for the Hispanic population in the United States.17

In Europe, a telephone survey encompassing a large number of participants, revealed an overall prevalence of 11.5%; it was higher in Italy and in the United Kingdom.18 A survey of 5,000 patients in the United States reported a 14.1% prevalence.19 Two recent studies in Mexico showed an IBS prevalence of close to 16%,20,21 in Colombia a somewhat higher figure of 19.9% was reported,22 and in Uruguay this prevalence was 10.9%.23

In Chile, a survey was applied to Chilean gastroenterologists in which they were asked if they thought they presented with IBS. There was an affirmative response in 22% of those surveyed.24

From the data obtained in the present study, we can say that the population visiting shopping malls in different areas of Santiago has a high prevalence of IBS symptoms at 28.6%, one of the highest in the world, similar to that observed in Nigeria.25

It is difficult to establish the factors that could be related to this greater IBS prevalence in Chile. Unlike other pathologies, such as cholelithiasis, the ethnic factor does not seem to be relevant, given that a recent communication26 reported a prevalence of 22% in a rural mapuche population, only slightly lower than the figure observed in the present study. Taking into account that there are no previous studies that would enable variability over periods of time to be established in relation to IBS prevalence, it can only be speculated that the very relevant socioeconomic changes have been the main variant in the last decades in the Chilean environment.

Age at the time of onset is within the ranges that have been established in other studies, even though this variable is not clearly defined in the main studies.27–29 A mean of 42 years has been estimated in Latin America.15

Regarding the IBS-D and IBS-C subgroups, the low prevalence in our study of the alternating group in which both symptoms are present is striking, compared with that observed in a European study in which this presentation form was observed in 63% of the cases.18 Nevertheless, the results observed in different reviews indicate much variability in this respect in the different populations studied, a fact that is partially dependent on the methodology employed for establishing the diagnosis.18,27,28

When analyzing the characteristics of the group of patients with IBS, it should be taken into account that a percentage of them probably are organic pathology carriers, especially those of the IBS-D group. Their evaluation could lead to establishing other diagnoses such as: microscopic colitis, celiac disease, and inflammatory bowel disease. The percentage of organic pathology with these characteristics that could be present in this group of patients was not analyzed in the present study.

Some studies have reported a greater number of surgeries in IBS patients,27,39 especially cholecystectomy, but also appendectomy and gynecologic surgery, and this phenomenon was also observed in our survey.

It is interesting that 33.6% of the subjects with IBS had undergone cholecystectomy, compared with 13% of the asymptomatic subjects. This proportion was maintained only in the analysis of the female patients. It is possible that the presence of gastrointestinal symptoms in patients with IBS is a determining factor in a more frequent diagnosis of cholelithiasis that results in cholecystectomy, even as a prophylactic measure. This is a widely accepted criterion in the Chilean medical environment. The association with organic pathologies such as high blood pressure that do not compromise the gastrointestinal tract is not clear.

The percentage of patients that visited a physician was similar to that described in another study.28 It is conspicuous that the majority of the tests done (upper gastrointestinal endoscopy) and the therapy administered (proton pump inhibitors) had little relation to the symptoms the patients most likely described to their attending physicians; this can have an important economic impact on local health organizations.40

It is possible that, depending on the respective speciality of the attending physician, fewer diagnostic criteria of functional gastrointestinal disorders, in accordance with the symptoms reported by the patient, are employed. As a result, a greater difference between the question asked by the attending physician and the interpretation of the patient's response would be observed.

In conclusion, according to the results of our survey, the group being studied presented with one of the highest frequencies of IBS-type symptoms. Even if only some of these patients seek medical attention for their symptoms, the required information and orientation in relation to their adequate management should be reflected in the undergraduate study programs in general medicine and in the postgraduate courses for specialists.