Open Journal of Gastroenterology, 2013, 3, 55-63 OJGas
http://dx.doi.org/10.4236/ojgas.2013.31009 Published Online February 2013 (http://www.scirp.org/journal/ojgas/)
Irritable bowel syndrome in Chinese nursing and medical
school students—Related lifestyle and psychological factors
Yukiko Okami1,2*, Gyozen Nin2, Kiyomi Harada3, Sayori Wada3, Tomiko Tsuji1, Yusuke Okuyama4,
Susumu Takakuwa5, Motoyori Kanazawa6, Shin Fukudo6, Akane Higashi3
1Department of Health and Nutrition, Nagoya Bunri University, Inazawa, Japan
2Ex-Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, Japan
3Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, Japan
4Department of Gastroenterology, Japan Red Cro ss Kyoto Daiichi Ho spital, Kyoto , Japan
5Department of Education, K yoto Women’s University, Kyoto, Japan
6Department of Behavioral Medicine, Graduate School of Medicine, Tohoku University, Sendai, Japan
Received 17 December 2012; revised 19 January 2013; accepted 25 January 2013
ABSTRACT
Background: Previous studies have shown that the
prevalence of irritable bowel syndrome (IBS) is 10% -
15% in the general population. IBS is a functional
gastrointestinal disorder characterized by abdominal
pain, abdominal discomfort and disordered defeca-
tion associated with a stressful lifestyle. However, the
cause of IBS has not been clarified yet. Based on a
similar, previous study in Japan, this study investi-
gated the prevalence of IBS and the relationship be-
tween IBS and stress, lifestyle and dietary habits
among nursing and medical school students in China.
Methods: Designed to investigate IBS symptoms, life-
style, dietary intake, life events, anxiety and depress-
sion, a blank self-administrated questionnaire was
used to survey 2500 nursing or medical students in
China. Questionnaires were collected from 2141 stu-
dents (85.6%) and responses obtained from 1934 stu-
dents (90.3%) were analyzed. Results: On the whole,
the prevalence of IBS was 32.1% in this study, 26.6%
in males and 33.6% in females. In females, the IBS
group showed a bedtime later than that in the
non-IBS group, and the length of time asleep in the
IBS group was shorter than that in the non-IBS
group (p < 0.001, p = 0.005). In females, the IBS group
showed a frequency for the intake of vegetables and
potatoes that was lower than that of the non-IBS
group (p = 0.007, p = 0.023). The prevalence of IBS
among nursing and medical school students in China
(32.1%) was significantly lower than that in Japan
(35.5%). Especially, the number of females in the
constipation dominant IBS subgroup in China (11.8%)
was less than that found in Japan (20.4%). Conclu-
sions: The prevalence of IBS was high among nursing
and medical students in China, but lower than that
shown in Japan.
Keywords: China; Irritable Bowel Syndrome; Nursing
School; Medical School; Lifestyle; Food Frequency;
Dietary Habits
1. INTRODUCTION
A functional disorder of the gastrointestinal (GI) tract,
irritable bowel syndrome (IBS) is associated with ab-
dominal pain or discomfort, with a concurrent distur-
bance in bowel habits [1]. The mechanism and cause of
IBS remain unknown. However, it has been clarified that
most of the reported disorders, for example, dysregula-
tion of the nervous system, altered intestinal motility,
and increased visceral sensitivity, result from dysregula-
tion of the bidirectional communication between the gut
with its enteric nervous system and the brain (the brain-
gut axis) [2]. The neural network of the brain that gener-
ates this stress response is called the central stress cir-
cuitry [3], and it receives input from the somatic and
visceral afferent pathways and also from the visceral
motor cortex. The output of this central stress circuit is
known as the emotional motor system, and it includ es the
autonomic efferents, such as the hypothalamus-pituitary-
adrenal axis and pain modulatory systems [3].
In Western countries, the prevalence of IBS is 15% -
24% in the general population, regardless of age or eth-
nicity, with a males/females ratio of 1:1.5 [4,5]. In most
Asian countries, the prevalence of IBS is 5% - 10% [6],
lower than that found in Western countries. The preva-
lence of IBS was found to be 5.7% in Korean college and
university students [7], 10.4% in undergraduates in South-
*Corresponding a uthor.

Y. Okami et al. / Open Journal of Gastroenterology 3 (2013) 55-63 56
east China [8,9], and 7.9% in college and university stu-
dents in North China [10]. The incidence rate per year is
between 1% and 2% [11,12]. The frequency of young
females with defecation problems has been increasing
recently. In general, more females have IBS than males
[14,15] and the prevalence of females with IBS is 1.5 to
2 times higher than that shown for males in many coun-
tries [7,15-17].
Reports have been published on IBS in China since
1990. The prevalence of IBS was reported to be 0.82% in
1996 [18], 5.6% in 2001 [19], and 20.2% in 2006 [20].
In a study conduc ted in Japan between 2006 and 2007
[21], we investigated the prevalence of IBS and the rela-
tionship between IBS and stress, lifestyle, and dietary
habits in nursing and medical students, who were se-
lected as the subjects of the study because they had a
more stressful life than students with other majors or the
general population due to their demanding schedule with
the university curriculum and clinical practice. The re-
sults of that study showed that the prevalence of IBS was
35.5% on the whole, 25.2% in males and 41.5% in fe-
males. In addition, IBS was related to anxiety and de-
pression, dietary habits including less intake of fish, fruit,
milk and green-yellow vegetables, and much intake of
retort food products, as well as with unhealthy lifestyles,
including irregular meals and sleep disturbances [21].
Based on these results, we investigated the prevalence
of IBS and the tendency in China, which is located close
to Japan. In addition, we also chose nursing and medical
students as the subjects of this study in order to compare
the results with the Japanese study [21]. The purpose of
this study was to clarify the prevalence of IBS and the
relationship between IBS and stress, lifestyle and dietary
habits in nursing and medical school students in China,
and to compare the results obtained from the Chinese
subjects with data obtained from our previous Japanese
study [21]. Therefore, the hypothesis of this study was
sufficiently different from the Japanese study [21].
2. METHODS
In order to compare the results obtained from the Chi-
nese subjects with data previously obtained from our
Japanese study [21], we used similar subjects and the
same questionnaires (in Chinese, rather than Japanese),
the same IBS definitions and the same assessment crite-
ria as in the Japanese study [21]. From the copyright
holder, we obtained permission to show the data in the
previously published Japanese study [21] as the refer-
ence.
2.1. Study Population
Initially, questionnaires were issued to a total of 2500
students for participation in this study, selected from the
3169 university students majoring in nursing or medical
technology at Zhengzhou University in Henan Province.
A total of 2141 students answered the self-administered
questionnaires. According to our eligibility criteria, un-
der the age of 30 years old, no diagnosis of inflammatory
bowel diseases, and no data inadequacy, 207 students
were considered inelig ible. Therefore, we analyzed ques-
tionnaires obtained from a total of 1934 students aged
16- to 24-year-old (19.7 ± 1.4), including 414 (21.4%)
males and 1520 (78.6%) females.
Study participants were asked to sign an informed
consent form before they participated in the study. This
study was approved by the Ethical Board of Kyoto Pre-
fectural University and Zhengzhou University. This was
an observational and cross-sectional study conducted fr om
October through November in 2007.
2.2. IBS Definitions
Patients with IBS were diagnosed with Rome II criteria
[22]. Subjects were classified into three subgroups as
follows: The diarrhea-predominant IBS (IBS-D), the
constipation-predominant IBS (IBS-C), and th e alteration
type IBS (IBS-A). We used a modified Chinese version
of the Rome II modular questionnaire, including 15 items
complied by Shinozaki et al. [23].
2.3. Questionnaire Information (Table 1)
In order to obtain a questionnaire suitable for our pur-
pose, we combined well-known criteria with some origi-
nal items. The questionnaire con tained 67 items, with the
Table 1. The questionnaire information items (n).
Bowel habits (Rome II criteria) 15
Psychological factors (HADS*) 14
Stressful life events 1
Lifestyle
Sleeping
Habitation
Drinking
Smoking
Desire to be thin
Dieting experience
Exercise frequency
Exercise items
Time spent sitting
Use of laxatives
1
1
1
1
1
1
1
1
1
1
Dietary habits and food frequency 20
Subjective factor for physical condition 1
Physical characteristics
Sex
Age
Height
Weight
Hometown
1
1
1
1
1
Treatment of d is e a s e 1
Total 67
*Hospital anxiety and depression scale.

Y. Okami et al. / Open Journal of Gastroenterology 3 (2013) 55-63 57
following sections; bowel habits (Rome II criteria) (15
items), psychological factors (Hospital anxiety and de-
pression scale: HADS) (14 items), stressful life events (1
item), subjective physical condition factors (1 item), life-
style (10 items), dietary habits and food frequency (20
items), physical characteristics (5 items), and treatment
for disease (1 item).
There were six optional answers in the subjective
physical condition factors section; stress, sleep, diet, ir-
regular mealtimes, smoking and drinking.
2.4. Psychological Assessments
In order to evaluate the stress situation correctly, we as-
sessed both the stress response and the stressor.
2.5. Stress Response
The hospital anxiety and depression scale (HADS) [24]
was employed, a scale proven to be reliable and valid
when screening for mood disorders. HADS can be di-
vided into a subscale for anxiety (HAD-A) and a sub-
scale for depression (HAD-D). In either of the HAD
subscales, a score above 10 indicates definite clinically
significant anxiety or depression, respectively, up to a
maximum score of 21. Respectively, a score of more
than 11 points is regarded as a definite type, a score be-
tween 8 and 10 is doubtful and a score of less than 7
points indicates no mood disorder.
2.6. Stressor
A stressor is a life event considered to be a stressful and
subjective event. The subjects were asked whether or not
such an event had occurred within the past three months
as defined in the IBS definitions and the HADS. They
answered “YES” if they thought it was such a life event
in their subjective viewpoint, because the form of per-
ception is different from person to person. The subjects
provided a free description of the content of the life
event. Two examples of a life event were provided in the
questionnaire, such as the divorce of parents or a roman-
tic breakup.
2.7. Exercise Assessment
The exercise guideline for health in Japan published in
2006 [25] used “METS” as the unit for the intensity of
exercise and “Exercise” as the amount of exercise.
“METS” indicates a multiple number of 1 MET, which is
the intensity of ex ercise in the resting state. “Exercise” is
“METS” multiplied by time. The questionnaire asked
about the kind of exercise done and the exercise time
period. These items were calculated and “Exercise” was
used a s a unit.
2.8. Statistical Analysis
Values were expressed as mean ± SD. An an alysis of the
proportions among the IBS diagnostic groups was per-
formed using Pearson’s chi-square test. Statistical analy-
ses for significant differences in parameters were per-
formed using the nonparametric Mann-Whitney U test
between two groups. The Kruskal-Wallis test was used to
measure differences among the three groups. All statisti-
cal computations were performed using SPSS (version
11.5 for Windows). A two-sided p value of less than 0.05
(p < 0.05) was considered statistically significant.
3. RESULTS
3.1. Prevalence of IBS
Out of 1934 students, 110 (26.6%) males and 511 (33.6%)
females were diagnosed as having IBS. The predominant
type was IBS-A in both males (14.5%) and females
(12.5%) (Table 2). The prevalence of IBS and IBS-C in
females was higher than that found in males (IBS: p =
0.006, IBS-C: p < 0.001) (Table 2).
3.2. Characteristics of the Subjects by IBS Status
In males, there were no statistically significant differ-
ences in age, height, weight, BMI or hometown between
the IBS and the non-IBS groups (age: p = 0.208, height:
p = 0.752, weight: p = 0.944, BMI: p = 0.572, home-
town: p = 0.294). In females, age and height were higher
in the IBS group than those in the non-IBS group (age: p
Table 2. IBS prevalence among nursing and medical school students in China.
Males Females Total p*
Total 110 (26.6) 511 (33.6) 621 (32.1) 0.006
IBS-D 27 (6.5) 141 (9.3) 168 (8.7) 0.078
IBS-C 23 (5.6) 180 (11.8) 203 (10.5) <0.001
IBS subgroup
IBS-A 60 (14.5) 190 (12.5) 250 (12.9) 0.284
Non-IBS subgroup 304 (73.4) 1009 (66.4) 1313 (67.9)
To tal 414 (100.0) 1520 (100.0) 1934 (100.0)
Data are pres ented as n (% ). IBS ir ritable b owel s yndro me, IBS- D diarrh ea predo minan t IBS, I BS-C con stipat ion pr edominan t IBS , IBS-A
alteration type IBS, *Chi-square test (m ales vs. females).

Y. Okami et al. / Open Journal of Gastroenterology 3 (2013) 55-63 58
< 0.001, height: p = 0.021). However, there were no sta-
tistically significant differences in weight, BMI or home-
town between the IBS-group and the non-IBS group
(weight: p = 0.059, BMI: p = 0.697, hometown: p =
0.573). The average weight for males subjects in the
IBS-A subgroup was heavier, compared with the other
subgroups (p = 0.039).
3.3. The Relationship between Psychological
Factors and IBS
In females, the anxiety scores were significantly higher
in the IBS group, compared with the non-IBS group (p <
0.001) (Figure 1). Females in the IBS-C subgroup had
higher anxiety scores than the other subgroups (p = 0.015)
and the average scores were over 10 points. Conse-
quently, for females, the IBS group showed a more defi-
nite anxiety type, compared with the non-IBS group (p <
0.001). Females in the IBS-C subgroup showed a more
definite anxiety type than the other subgroups.
In both males and females, there were more life events
in the IBS group than in the non-IBS group (males: p =
0.015, females: p = 0.013) (Table 3). In males, the IBS-C
subgroup had more life events than the other subgroups
(p = 0.012).
3.4. Lifestyle
In females, the IBS group had more sleep disturbances
than the non-IBS group (p < 0.001) (Figure 2). In fe-
males, the bedtime of the IBS group was later than
shown for the non-IBS group (p < 0.001) (Ta ble 4). In
females, the number of sleeping hours in the IBS group
was less than that shown in the non-IBS group (p =
0.005). In females, the IBS-C subgroup used more laxa-
tives than the other subgrou ps (p = 0.030) (Figure 3). In
males, the rate of students using lax atives more than one
time a week was 5.4% in the IBS group and 1.9% in the
non-IBS group. In f emales, it was 3.5% in the IBS group
Figure 1. Anxiety and depression scores on the hospital anxiety
and depression scale (HADS) in the IBS group and the non-IBS
group among nursing and medical school students in China. *p
< 0.001, Mann-Whitney U test.
Table 3. Life events in the IBS and the non-IBS groups among
nursing and medical school students in China.
Males Females
IBS Non-IBSp* IBS Non-IBSp*
Positive17 (15.7)23 (7.6)0.015 63 (12.3) 84 (8.3)0.013
Negative91 (84.3)278 (92.4) 924 (91.7) 448 (88.7)
Total 108 (100.0)301 (100.0) 1008 (100.0) 511 ( 1 00.0)
Data are pr esented asn (%). IBS irritable b owel syndrome, *Chi-square test.
*
Figure 2. Sleep disorder in the IBS group and the non-IBS
group among nursing and medical school students in China. *p
< 0.001, Chi-square test.
and 2.6% in the non-IBS group. In females, the IBS
group had more di et experiences than the non-IBS group
(p < 0.001). There were no statistically significant dif-
ferences shown for either males or females between the
IBS group and the non-IBS group in drinking, smoking,
exercise and time spent sitting.
3.5. Dietary Habits and Food Frequency of
Intake
In females, the intake of less leafy vegetables, other vege-
tables, and potatoes wa s less in the IBS group, compared
with the non-IBS group (p = 0.007, p = 0.023) (Table 5).
Females in the IBS-C subgroup ate less beans or bean
products, and mushrooms, and drank less milk (p = 0.012,
p = 0.006, p = 0.005). Females in the IBS group had more
irregular meals and skipped meals more frequently than
the non-IBS group (p = 0.002, p = 0.018) (Figures 4 and
5). Especially in males, the rate of missing meals almost
everyday was 33.3% in the I B S-D su b- gro u p.
3.6. Subjective Factors Affecting the Body
In females, more students in the IBS group thought that
the factors affecting their bodies were stress, food, and
sleeping time, compared with those in the non-IBS group
(p = 0.043, p = 0.032, p = 0.006). More males in the
IBS-C subgroup thought the factor affecting their bodies
was food, co mp ar ed with th e ot h er su bg rou ps ( p = 0.005).
More females in the IBS-C subgroup thought the factor

Y. Okami et al. / Open Journal of Gastroenterology 3 (2013) 55-63 59
Table 4. Sleep time and exercise in the IBS and the non-IBS groups among nursing and medical school students in China.
Males (n = 414) Females (n = 1520)
IBS Non-IBS p* IBS Non-IBS p*
Hours of sleep (h/day) 6.9 ± 0.8 7.0 ± 0.9 0.617 7.0 ± 0.8 7.1 ± 0.9 0.005
Bedtime (time (AM) ± min) 23:43 ± 5523:39 ± 520.254 23:11 ± 5023:01 ± 57 <0.001
Amount of exercis e n (exercise/day) 8.8 ± 7.2 9.4 ± 7.6 0.591 6.6 ± 6.2 6.1 ± 5.7 0.264
Time spent sitting (h/day) 8.2 ± 2.7 8.6 ± 2.5 0.222 8.4 ± 2.2 8.2 ± 2.3 0.139
IBS: irritable bowel syndrome. Data are presented as mean ± SD, *Mann-Whitney U test.
Figure 3. Use of laxatives in the IBS group and the non-IBS group among
nursing and medical school students. *p = 0.030 (IBS-D, IBS-C vs. IBS-A),
Chi-square test.
Table 5. Frequency of intake in the IBS and the non-IBS groups among nursing and medical school students in China.
Milk Meat Fish Eggs Leafy vegetables
Other vegetables
and potatoes
Everyday 12 (10.9) 33 (30.0) 4 (3.6) 32 (29.1) 68 (61.8) 60 (54.5)
1 - 5 times a week27 (24.5) 52 (47.3) 26 (23.6) 56 (50.9) 38 (34.5) 40 (36.4)
IBS
Nothing 71 (64.5) 25 (22.7) 80 (72.7) 22 (20.0) 4 (3.6) 10 (9.1)
Everyday 39 (13.0) 91 (30.4) 12 (4.0) 105 (35.1) 177 (59.2) 160 (53. 5)
1 - 5 times a week80 (26.8) 139 (46.5) 99 (33.1) 149 (49.8) 104 (34.8) 124 (41.5) Non-IBS
Nothing 180 (60.2) 69 (23.1) 188 (62.9) 45 (15.1) 18 (6.0) 15 (5.0)
Males
p
* 0.728 0.925 0.163 0.362 0.782 0.234
Everyday 48 (9.5) 38 (7.5) 6 (1.2) 90 (17.8) 208 (41.1) 185 (36.6)
1 - 5 times a week109 (21.5) 182 (35.9) 101 (19.9) 261 (51.5) 251 (49.6) 283 (55.9) IBS
Nothing 350 (69.0) 287 (56.6) 400 (78.9) 156 (30.8) 47 (9.3) 38 (7.5)
Everyday 95 (9.5) 83 (8.3) 26 (2.6) 192 (19.2) 493 (49.3) 433 (43.3)
1 - 5 times a week228 (22.8) 357 (35.7) 196 (19.6) 507 (50.8) 415 (41.5) 483 (48.3) Non-IBS
Nothing 676 (67.7) 559 (56.0) 777 (77.8) 300 (30.0) 91 (9.1) 83 (8.3)
Females
p
* 0.821 0.803 0.184 0.773 0.007 0.023
Data are pr esented asn (%). IBS irritable bo wel syndrome, *Chi-square test.

Y. Okami et al. / Open Journal of Gastroenterology 3 (2013) 55-63 60
Figure 4. Meal time in the IBS group and the non-IBS group
among nursing and medical school students in China. *p =
0.002, Mann-Whitney U test.
Figure 5. Skipping meals in the IBS group and the non-IBS
group among nursing and medical school students in China. *p
= 0.018, Chi-square test.
affecting their bodies was stress, compared with the other
subgroups (p = 0.025).
3.7. Comparison between Chinese and Japanese
(Figure 6)
The prevalence of IBS among nursing and medical
school students in China (32.1%) was lower than that
found in Japan (35.5%) [21] ( p = 0.028). More Japanese
females’ subjects had IBS than their Chinese counter-
parts (p < 0.001). In females, the prevalence of the
IBS-D subgroup was higher in China than that in Japan
(p = 0.014), and the prevalence of the IBS-C subgroup in
China was lower than that in Japan (p < 0 .001). In males,
there were no statistically significant differences between
China and Japan in the prevalence of IBS or the sub-
groups.
4. DISCUSSION
The results of this study showed that the general preva-
lence of IBS was 32.1% in nursing and medical school
students in China, 26.6% in males and 33.6% in females.
Two major findings were revealed in the results.
First, the prevalence of IBS was higher than that
*
**
Preval ence of IBS (% )
Figure 6. Prevalence of IBS (%) between nursing and medical
school students in China and those in Japan [21] (printed with
permission). *p = 0.014, **p < 0.001, Chi-square test.
shown in other Asian studies [6-10]. One of the reasons
for this difference was that the subjects were nursing and
medical school students, who wor ked irregular hours du e
to their studies and clinical practice schedules. Some
studies [26,27] have shown that there are a variety of
stressors in clinical practice. Jimenez et al. [28] identi-
fied three types of stressors (clinical, academic and ex-
ternal) and two categories of symptoms (physiological
and psychological) linked to clinical practice. The sub-
jects of the study perceived clinical stressors more in-
tensely than academic or external stressors. In general,
most students don’t have any practical experience in the
clinical field. Timmins et al. [29] reported that one third
of the students in their study felt some degree of stress in
their relationships with teachers and staff in the ward,
and that the clinical experience and the death of patients
were independent sources of stress. Thus, these students
might feel more stress than other students or people in
general. In support of this hypothesis, other studies that
targeted nursing or medical school students also showed
a high prevalence of IBS, 35.5% in Japan [21], 15.8% in
Malaysia [15], 26.0% in Pakistan [30], and 26.1% in
Nigeria [31]. Especially, the prevalence of IBS in nursing
and medical school students in Japan [21] and China
were both higher than that found in other countries. Prior
to recent studies, no large-scale research studies on nurs-
ing and medical school students have been conducted.
These recent studies have made it clear that nursing and
medical school students in the Asian region have a high
prevalence of IBS. However, Chang et al. [6] reported
that more than 90% of nurses have very limited knowl-
edge in regard to IBS, and are unable even to explain it
clearly. It is important to expand their knowledge of their
own symptoms.
Second, the prevalence of IBS in females was higher
than that shown in males. This result was consistent with
other studies [4-10,21]. The difference between China
and Japan was the prevalence of the IBS-C subgroup in
females (China: 11.8%, Japan: 20.4%), showing that Ja-

Y. Okami et al. / Open Journal of Gastroenterology 3 (2013) 55-63 61
panese females were more constipated than Chinese fe-
males. When the food frequency was compared be-
tween Chinese females and Japanese females, each food
study showed significant differences. Chinese females
ate more beans, bean products, and fruit than Japanese
females. On the other hand, Japanese Females ate more
meat, eggs, milk, dairy products, mushrooms, instant
noodles, retort products, confectionery, juice, coffee and
tea than Chinese females. These results indicate that the
consumption of fiber prevents Chinese females from
having constipatio n. However, in addition to dietary hab-
its, other elements could also be factors in this difference.
For example, the number of females living in a dormi-
tory was 1403 (92.4%) in China and 192 (17.3%) in Ja-
pan and, the number of females living at a home of their
own was 105 (6.9%) in China and 608 (54.6%) in Japan
(p < 0.001).
The Japanese study [21] showed that students with
IBS felt more anxiety than tho se without IBS, which was
consistent with the findings of other studies [10,15,21].
Therefore, it can be inferred that anxiety is a predictor of
IBS diagnosis, and that psychological factors play an
important role in the development of IBS [32-35]. In
addition, Drossman [36] reported that psychological fac-
tors themselves influence motor abdominal functions, the
sensory threshold and the stress reactivity of the intes-
tines. The PSLES score, indicating stressful life events,
was higher in the IBS group (p < 0.001) in a study con-
ducted by Pinto et al. [37]. Furthermore, in that study,
both males and females in the IBS group had more life
events than the non-IBS group.
As mentioned above, more than ninety percent of the
subjects of this study were living in a dormitory at the
university and they took their meals in the dormitory
dining room. Thus, the lifestyles of the subjects were
similar. That could be the reason why the results were
similar for hometown and habitation between the IBS
group and the non-IBS group, despite the fact that life-
styles in the urban and rural areas in China are so differ-
ent.
In the IBS group, females went to bed later, had less
sleeping time and more experienced difficulty in falling
asleep than the females in the non-IBS group. It is said
that peptides synthesized by intestinal bacteria act as a
sleeping substance and bowel flora affects non-REM
sleep [38]. On the other hand, Burr et al. [39] reported
that differences in neuroendocrine levels during sleep
were great between the IBS group and the non-IBS group
in females. Jarrett et al. [40] also reported that the sym-
pathetic/parasympathetic nervous system balance across
sequential non-REM periods and REM cycles was mo du-
lated differently among the subgroups. The results of
these studies inferred that there is an interaction between
the sleeping state and abnormal defecation, especially in
females.
Compared with the non-IBS group, in females, the in-
take of leafy vegetables, other vegetables, and potatoes
was less in the IBS group. In the Japanese study [21],
females in the IBS group also showed a lack of fruit and
vegetables. Especially, females in the IBS-C group
showed a lack of fruit. These results were consistent with
the results shown in this study. Furthermore, both the
Japanese study [40] and the Korean study [7] sh owed th e
same results for meal times. In females, the IBS group
tended to have meals irregularly and to skip meals fre-
quently. It is said that skipping meals causes a decrease
in the gastro-colonic reflex and restrains defecation [38].
Regardless of the IBS, this study revealed that about
20% of the students skipped meals almost everyday. Re-
cently it has been said that young people show a lack in
the intake of fruit and vegetables [41,42]. Not only for
IBS patients, but also for young students, it is important
to regulate their lifestyles, including meal times and the
content of meals. More females in the IBS-group chose
food as their subjective factors affecting the body, com-
pared with those in the non-IBS gro up. This result shows
that they recognized their current situation. IBS is asso-
ciated with many complicated factors. Sakata et al. [43]
reported that the factors affecting IBS differed greatly in
individuals. Furthermore, in a study on QOL [44], it was
shown that the manner in which people accept situations
is different between the races. For example, people in
Switzerland considered disease to be more serious than
people in Greece did, and it affected their mental health.
Treatments are also different, depending on the individ-
ual, such as medical therapy, hypnotherapy, cognitive
behavioral therapy, and so on.
This study was limited in three respects. First, it is dif-
ficult to view the results of the study as being valid for
the whole country, because this questionnaire was con-
ducted in one university. Another limitation was the fact
that the students were not living in a general environment,
since most of them were living in a dormitory at the uni-
versity. Thirds, the number of females was more than
three times than that of males, because nursing students
are mostly females. We analyzed all data by sex.
In conclusion, the prevalence of IBS in nursing and
medical school students in China was high, and almost
the same as that found in Japan. In females, subjects in
the IBS group showed more anxiety than those in the
non-IBS group. In both males and females, subjects in
the IBS group experienced more life events than those in
the non-IBS group. In females, the IBS group had more
sleep disturbances, showed more irregular and skipped
meals, and intake of leafy vegetables, other vegetables,
and potatoes was less than that in the non-IBS group.
Because this study was a cross-sectional study, however,
the cause and effect relationship was not clarified. Fur-

Y. Okami et al. / Open Journal of Gastroenterology 3 (2013) 55-63 62
ther intervention studies are needed to clarify the cause
of IB S in th e future.
5. ACKNOWLEDGEMENTS
We would like to express our thanks to the staff at Zhengzhou Univer-
sity, including Y. Shi, and all of the students that collaborated in this
research.
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Abbreviations
BMI: body mass index;
HADS: hospital anx iety and depression scale;
HAD-A: subscale for anxiety;
HAD-D: subscale for depression;
G
I: gastrointestinal;
IBS: irritable bowel syndrome;
IBS-A: alteration type IBS;
IBS-C: constipation-predominant IBS;
IB S - D : di arrhea-predominant IBS;
METS: metabolic equivalents;
SD: standard deviation.