In this clinic-based case-control design, we studied demographic factors in Rome III confirmed IBS patients. Because the diagnosis of IBS depends on criteria used, estimation of true prevalence of IBS may be limited.[2
] Compared to previous guidelines, Rome III criteria is more specific and restrictive,[5
] The time period for diagnosis has been reduced from 12 months, using Rome II criteria to 3 months in Rome III.[20
] Using Rome III criteria might have led to the low estimation of IBS in this study.
We found that IBS-C (about 52%, 80/153) with alternating features of mixed subtype (IBS-M) and diarrhea (IBS-D) was the most common form of IBS. A female pre-dominance was seen in our patients diagnosed using Rome III criteria. D No differences were seen among male and female regarding to subtype of IBS (P > 0.05).
In Sorouri et al
] in Iranian general population using Rome III criteria, the majority of cases were IBS-C (45.3%), while the cases with IBS-D (13.4%) were the least common. Another Iranian study on university students using Rome II criteria found IBS-C (50%) as the most frequent and IBS with an alternating stool pattern (IBS-A) as the least frequent subtype (21%).[6
] Similarly, in other Asian countries reported that IBS-C was the most frequent subtype (77.4%), and IBS-A and IBS-D comprised 15.5% and 7.1% of IBS patients, respectively.[21
] Mearin, et al
] in a study conducted in Spain by using Rome II criteria on 2,000 subjects showed that IBS-C (37%) was the most common subtype, followed by IBS-D and IBS-A. Hungin, et al
] in their study in USA revealed that IBS-A comprised the majority (66%) of IBS cases, followed by IBS-D (21%) and IBS-C (13%). An international study also found that IBS-A (63%), IBS-D (21%) and IBS-C (16%) to be the most frequent subtypes, respectively.[24
] A report from China noted IBS-D to be the most prevalent (74.1%) and IBS-A as the least frequent (10.8%) subtype.[25
] In Iran, among IBS patients referred to gastroenterology clinic, Roshandel, et al
] reported IBS-A as the most frequent (60%) and IBS-C and IBS-D to be 29.1% and 10.9%, respectively. It seems that in Asia there is no consistency among different studies but in USA and European nations IBS-A maybe the most frequent IBS.
Comparable to other studies we found that about half of male patients and two third of female patients were below the age of 45 years.[26
] One Iranian study revealed that prevalence of IBS was more common in the young decreasing with increasing in age.[13
] A similar age trend was identified in a Nigeria population.[29
] In contrast, no associations have been found between IBS and age China and England.[25
While IBS is more frequent in females than males in Iran[5
] and many European countries;[17
] no consistent differences however have been observed in Asian studies. Whereas, a number of studies conducted in Asia have not revealed a gender difference in the prevalence of IBS, others has been reported a female pre-dominance.[19
] The reason for this controversial sex difference is unknown. It has been suggested that female preponderance is selection bias due to females more likely to seek health care or differences in psychological responses and clinical symptoms between males and females.[38
Consistent with other studies, we found that being single was more common in female patients with.[5
] Sedentary lifestyle, changing in food habit, psychological factors may account for this finding.
In the present study, IBS was related to unemployed, lower monthly income and low educated. While Andrews, et al
] shown a higher prevalence of IBS among persons of lower income, employment and education in the general population, Khoshkrood-Mansoori, et al
] found no relationship between the prevalence of IBS and the education level. Unemployment is a risk factor for IBS possibly related to (1) lower income (2) more severe psychological distress compared to employed individuals.
While we have found no association between BMI and IBS in males, a significant association was seen among BMI < 25 and female gender (P
< 0.05). Khademolhosseini, et al
] in study on 1,978 individuals over 35 years in Shiraz, southern Iran, found no association between IBS and BMI. In contrast, Sorouri, et al
] in a population-based study from Tehran, capital of Iran, reported that all subtypes except IBS-D increase with increasing BMI. It is possible that the use of self-reported information may account for differences in BMI score.
Some studies have shown that smoking habit and alcohol consumption is significantly associated with gastrointestinal disorders such as gastroesophageal reflux disease,[41
] uninvestigated dyspepsia,[44
] abdominal pain[45
] and IBS, especially, in female and diarrhea-pre-dominant IBS.[45
] Halder et al
] shown a relationship between alcohol consumption and IBS. We found no association between smoking and alcohol use in patient sibs. These conflicting results might be attributed to the study design, diagnostic criteria used, cultural differences, environmental factors, and small sample size.
This study limitation was that most exposures and outcome measures (such as height, weight) of the study were based on subjective reports. Diagnosis based on patients’ symptoms may lead to an under recognition or misdiagnosis of the disease.
Because of the cross-sectional design and other limitations mentioned above, we believe that these results should be interpreted with caution. Frequency of IBS defined by Rome III criteria was relatively higher in females and younger peoples. Marital status, educational level, occupation, income and BMI were the most important related factors to IBS especially in females. Additional research is required to clarify the role of demographic factors in IBS patients with a larger sample size.