The Prevalence, Humanistic Burden, and Healthcare Impact of Irritable Bowel Syndrome (IBS) Among United States Veterans

Abstract

Background & Aims:

Irritable bowel syndrome (IBS) in Veterans is understudied. We aimed to investigate (1) prevalence of IBS; (2) phenotypic, environmental, and psychosocial factors associated with IBS; and (3) associations of IBS with health-related quality of life (QOL) and healthcare utilization.

Methods:

From June 2018 to April 2020, we invited Veterans to complete the Rome IV IBS questionnaire, Short Form-12, Post-Traumatic Stress Disorder (PTSD) checklist, Hospital Anxiety and Depression Scale, and questionnaires on general health, antibiotic-use, infective enteritis (IE), and healthcare utilization.

Results:

Among 858 Veteran respondents, 244 (28.4%) met Rome IV IBS criteria (47.5% IBS with diarrhea [IBS-D], 16.8% IBS with constipation [IBS-C], 33.6% mixed-IBS [IBS-M]). IBS was associated with greater anxiety and depression and lower QOL (all p<0.001). Provisional PTSD, IE, and bowel problems after antibiotics were more common in IBS (all p<0.001) as were multiple doctor visits (p<0.01) and hospitalizations (p=0.04). Comparisons across non-IBS and IBS subgroups revealed overall associations of psychological comorbidities (p<0.01), multiple doctor visits (p<0.01), hospitalizations (p=0.03), IE (p<0.01) and bowel problems after IE (p=0.03) or antibiotics (p<0.01) with subgroup. Highest anxiety and depression scores, PTSD, multiple doctor visits, hospitalizations, and bowel problems after IE were observed in IBS-C. In adjusted analyses, IBS was associated (all p<0.001) with anxiety (odds ratio [OR]=3.47), depression (OR=2.88), lower QOL, PTSD (OR=3.09), IE (OR=4.44), bowel problems after antibiotics (OR=1.84), multiple doctor visits (OR=2.08), and hospitalizations (OR=1.78).

Conclusion:

IBS is prevalent among Veterans and has a measurable impact on individuals and healthcare resources. Veterans with IBS may experience significant psychological impairment.

Graphical Abstract

In a survey of over 800 Veterans, almost 1 in 3 meet Rome IV IBS criteria

IBS is associated with anxiety and depression; provisional PTSD; prior infectious enteritis; history of bowel problems after antibiotics; lower quality of life; and higher healthcare utilization

Compared to Veterans without IBS, psychological comorbidities are higher in Veterans with any IBS subtype

INTRODUCTION

Irritable bowel syndrome (IBS) is a disorder of gut-brain interaction with a substantial burden¹ on patients and healthcare resources.² Observational studies have identified individual (e.g. genetics, ethnicity, sex, gut microbiome, psychological comorbidities) and environmental (e.g. diet, enteric infection, stress) risk factors.^{3, 4} Prevalence across geographically-defined populations varies due to differences in genetic, cultural, and dietary factors; subsets within populations may exhibit additional variation because of individual risk factors.

Veterans are exposed to environmental and psychosocial factors that could elevate the risk for IBS. Among female Veterans, the prevalence of IBS is as high as 38%⁵, and IBS is associated with higher levels of anxiety or depression and rates of post-traumatic stress disorder (PTSD). A recent study⁶ observed that rates of Rome III-defined IBS increased from 10.9% to 30.5% from pre- to post-deployment periods, suggesting that environmental factors such as infectious enteritis (IE) and the deployment experience may be important. In contrast, others have reported much lower rates. Retrospective studies utilizing ICD coding have reported prevalence rates as low as 2.07%.⁷ An epidemiologic study⁸ exploring IBS incidence and risk factors in the US military demonstrated a lower-than-expected IBS incidence of 141 per 100,000 person-years using military medical encounter data. However, risk of IBS was 2 to 3-fold higher after an episode of IE; this risk was further modified by co-existing depression or anxiety, suggesting an interaction between psychological distress and acute IE.

Although select studies suggest that IBS places a significant health burden on Veterans, estimates of IBS prevalence in the Veteran population according to more recent iterations of Rome criteria (Rome IV) and among both sexes are lacking. Moreover, its impact on quality of life (QOL) and healthcare utilization is unclear. Improved characterization of IBS among Veterans using validated Rome IV criteria could identify opportunities to address Veterans’ healthcare needs; quantify the humanistic toll (i.e., psychological burden and QOL) of IBS; improve recognition among clinicians; provide insight on mechanisms and pathways to target for treatment; and estimate health care services required for treatment. The aims of this study were to: (1) estimate the prevalence of IBS in Veterans; (2) identify host, environmental, and psychosocial factors associated with IBS; and (3) examine relationships between IBS and both health related QOL and healthcare utilization among Veterans.

METHODS

Study design:

This cross-sectional survey study was approved by the Indiana University Institutional Review Board. All survey responses were anonymous. Unique study identification numbers were used and linked to a separate mailing database to track individuals who received the invitation, responded, did not respond, or opted out. Survey components included the Rome IV IBS Diagnostic Questionnaire Module for IBS, Short-Form Health Survey (SF-12)⁹ for health-related QOL, a 20-item self-report checklist to screen for DSM-5 Post-traumatic Stress Disorder (PTSD) symptoms (PCL-5),¹⁰ Hospital Anxiety and Depression Scale,¹¹ and questions about sociodemographic features, general health, antibiotic use, IE, and healthcare utilization (Supplement).

Study participants:

From June 2018 to April 2020, Veterans ages 18–65 years at the time of the database search and receiving outpatient care at the Indianapolis Veterans Affairs Medical Center were invited by mail to participate in an online survey study on gastrointestinal conditions. Exclusion criteria were active hospitalization, chronic digestive diseases other than IBS, and regular use of opioids. Eligible individuals received a letter containing study information, instructions for accessing the online survey or for requesting paper surveys, and the informed consent document (implied consent with no signature required).

Individuals participated by accessing a secure web-based environment and entering a unique study identification number. Survey completers were entered into a drawing for one of ten $50 Amazon gift certificates. Study information flyers informing Veterans of a general research survey on gastrointestinal symptoms were placed in VA clinics, public spaces, and were posted on the VA intranet and VA Facebook page.

Study endpoints:

Primary endpoints were prevalence of IBS and IBS subtypes. IBS was defined by scoring responses to the Rome IV IBS Diagnostic Questionnaire Module for IBS. Secondary endpoints were psychological comorbidities (anxiety or depression scores, PTSD); health-related QOL; and frequency of self-reported antibiotic-use, prior IE, new bowel problems after IE or antibiotics, and healthcare utilization. Provisional PTSD was defined by applying DSM-5 criteria to symptom cluster severity scores. Covariates were determined a priori and included age, sex, and body mass index (BMI). A sample size of 865 survey respondents was sufficient to estimate the prevalence of IBS with no more than 2% margin of error at the 95% confidence level assuming a baseline prevalence of 10%.⁶

Statistical analysis:

Data were summarized using means and standard deviations (SD), medians and interquartile range (IQR), or frequencies (%). Participants with missing questionnaires were excluded. Unadjusted comparisons of participants with and without IBS were performed using the Pearson’s chi-square or Fischer’s exact test for categorical variables and t-test or Wilcoxon rank sum test for continuous variables. Comparisons across non-IBS and IBS subtype groups were performed using the Pearson’s chi-square or Fisher’s exact tests and ANOVA F-test or Kruskal-Wallis test for categorical and continuous variables, respectively, to determine overall associations of endpoints with group. Multivariable logistic and general linear regression were performed to evaluate associations of IBS status or phenotype with study endpoints after adjusting for covariates, with non-IBS as the reference group. Participants reporting “do not know” to individual survey items were excluded in the analysis of that item.

RESULTS

Patient characteristics and IBS prevalence:

A total of 36,449 survey invitations were mailed, of which a large number were returned due to invalid addresses. Of 1,286 respondents, 858 (66.7%) completed the survey (Figure 1). Mean (SD) age of the 858 responders was 53.6 (10.7) years, mean (SD) BMI was 31.2 (6.5) kg/m², 170 (19.8%) were female, 749 (87.3%) were Caucasian, 25 (2.9%) were Hispanic, and 244 (28.4%) met Rome IV IBS criteria (47.5% IBS with diarrhea [IBS-D], 16.8% IBS with constipation [IBS-C], 33.6% mixed-IBS [IBS-M], 2% unsubtyped).

Figure 1:

Study Flow Chart

Clinical characteristics and psychological comorbidity:

Participants with IBS (Table 1) were younger (p<0.001) and more frequently female (p<0.001). Race/ethnicity, education, BMI, or current tobacco or alcohol use did not significantly differ between participants with and without IBS. In univariable analyses, IBS was associated with higher anxiety and depression scores (p<0.001) (Table 2). A higher proportion of participants with IBS had abnormal anxiety and depression scores (both p<0.001) and provisional PTSD (all p<0.001).

Table 1:

Clinical Characteristics in Veterans With and Without Irritable Bowel Syndrome (IBS)

	Without IBS (N = 614)	With IBS (N = 244)	p-value
Age (years), mean (SD)	55.6 (9.8)	48.3 (11.2)	<0.001
Females, N (%)	104 (16.9%)	66 (27.0%)	<0.001
Race, N (%)			0.71
Caucasian	534 (87.0%)	215 (88.1%)
African American	42 (6.8%)	13 (5.3%)
Other	38 (6.2%)	16 (6.6%)
Hispanic, N (%)	15 (2.4%)	10 (4.1%)	0.19
Married, N (%)	415 (67.6%)	158 (64.8%)	0.43
Highest education level, N (%)			0.6
High school degree or other	197 (32.1%)	86 (35.2%)
Bachelor’s or technical/vocational degree	287 (46.7%)	112 (45.9%)
Master’s or Doctorate degree	130 (21.2%)	46 (18.9%)
Body mass index (kg/m2), mean (SD)	31.0 (6.4)	31.7 (6.7)	0.16
Current tobacco use, N (%)	107 (17.4%)	48 (19.7%)	0.44
Alcohol use, N (%)			0.12
Never	110 (17.9%)	42 (17.2%)
Rarely	200 (32.6%)	100 (41.0%)
Occasionally	208 (33.9%)	72 (29.5%)
Regularly or frequently	96 (15.6%)	30 (12.3%)

Table 2:

Psychological Characteristics, Antibiotic use, Infectious Enteritis, Quality of Life, and Healthcare Utilization in Veterans by Irritable Bowel Syndrome (IBS) Status

	Without IBS (N = 614)	With IBS (N = 244)	P-value
HADS anxiety score, median (IQR)	5.0 (2.0–9.0)	10.5 (6.0–14.0)	<0.001
HADS anxiety			<0.001
Normal (0–7)	419 (68.2%)	85 (34.8%)
Borderline abnormal (8–10)	87 (14.2%)	37 (15.2%)
Abnormal (11–21)	108 (17.6%)	122 (50.0%)
HADS depression score, median (IQR)	6.0 (4.0 –10.0)	10.0 (7.0–13.5)	<0.001
HADS depression			<0.001
Normal (0–7)	350 (57.0%)	70 (28.7%)
Borderline abnormal (8–10)	117 (19.1%)	60 (24.6%)
Abnormal (11–21)	147 (23.9%)	114 (46.7%)
SF-12 physical component score, mean (SD)	44.2 (11.0)	40.0 (10.0)	<0.001
SF-12 mental component score, mean (SD)	49.0 (10.9)	41.1 (12.1)	<0.001
PCL-5 total score, median (IQR)	10.0 (3.027.0)	28.5 (12.547.5)	<0.001
Provisional PTSD, N (%)	109 (17.8%)	109 (44.7%)	<0.001
History of antibiotic use, N (%)	581 (94.6%)	226 (92.6%)	0.26
New bowel problems within 3 months of taking antibiotics, N (%)	96 (21.8%)	56 (35.7%)	<0.001
History of reported infectious enteritis, N (%)	108 (22.5%)	86 (54.1%)	<0.001
New bowel problems within one year of infectious enteritis, N (%)	36 (42.9%)	38 (65.5%)	0.008
Seen a doctor in the last 2 years, N (%)	595 (97.1%)	232 (95.1%)	0.15
Multiple doctor visits in last 2 years, N (%)	375 (61.2%)	174 (71.3%)	0.005
Received emergency department care, N (%)	488 (79.9%)	203 (83.5%)	0.22
Hospitalization within the previous 10 years, N (%)	279 (45.7%)	129 (53.3%)	0.044

IQR, interquartile range; HADS, Hospital Anxiety and Depression Scale; SF-12, Short Form 12, PCL-5, Post-Traumatic Stress Disorder Checklist for DSM-5

Analysis by IBS subtype revealed significant associations of age and sex with subtype (overall p<0.001, [Table 3]). Participants without IBS had a higher mean [SD] age (55.6 [9.8] y) than participants with IBS-C (48.9 [11.8] y), IBS-D (47.9 [10.8] y), or IBS-M (48.2 [11.7] y). Participants with IBS-C were more frequently female (46.3%, overall p<0.001) and Hispanic (9.8%, overall p=0.04) than participants without IBS (16.9% females, 2.4% Hispanic) and those with IBS-D (15.5% female, 1.7% Hispanic). IBS subtype was significantly associated with anxiety, depression, and PTSD (overall p<0.001). Numerically higher anxiety, depression, and PCL-5 scores and highest prevalence of abnormal anxiety or depression scores and PTSD were observed in IBS-C, although they were not statistically significantly higher than scores and prevalence for other IBS subtypes (Figure 2).

Table 3:

Multiple Logistic Regression Analysis of Associations between IBS status or IBS Subtype and Secondary Endpoints^*

	Anxiety		Depression		Provisional PTSD
	aOR (95% CI)	p-value	aOR (95% CI)	p-value	aOR (95% CI)	p-value
IBS	3.47 (2.55–4.72)	<0.001	2.88 (2.13–3.89)	<0.001	3.09 (2.19–4.37)	<0.001
Subtype
No IBS	Reference	N/A	Reference	N/A	Reference	N/A
IBS-C	4.90 (2.59–9.25)	<0.001	4.55 (2.41–8.61)	<0.001	5.45 (2.77–10.74)	<0.001
IBS-D	3.17 (2.13–4.72)	<0.001	2.70 (1.82–3.99)	<0.001	2.76 (1.77–4.31)	<0.001
IBS-M	3.96 (2.49–6.29)	<0.001	3.07 (1.95–4.83)	<0.001	3.11 (1.88–5.14)	<0.001
IBS subtypes
IBS-C vs. IBS-D	1.55 (0.76–3.13)	0.23	1.69 (0.84–3.41)	0.14	1.98 (0.93–4.17)	0.075
IBS-C vs. IBS-M	1.24 (0.59–2.58)	0.57	1.48 (0.71–3.08)	0.29	1.75 (0.81–3.80)	0.16
IBS-D vs. IBS-M	0.8 (0.46–1.38)	0.42	0.88 (0.51–1.51)	0.64	0.89 (0.49–1.60)	0.69
	Infectious Enteritis (IE)		Bowel dysfunction after IE		Bowel dysfunction after antibiotics
	aOR (95% CI)	p-value	aOR (95% CI)	p-value	aOR (95% CI)	p-value
IBS	4.44 (2.95–6.69)	<0.001	3.235 (1.52–6.90)	0.002	1.84 (1.20–2.81)	0.005
Subtype
No IBS	Reference	N/A	Reference	N/A	Reference	N/A
IBS-C	2.87 (1.24–6.66)	0.014	14.95 (1.63–137.52)	0.017	1.55 (0.66–3.68)	0.32
IBS-D	4.60 (2.73–7.73)	<0.001	2.43 (0.86–6.82)	0.093	1.68 (0.97–2.92)	0.065
IBS-M	5.42 (2.93–10.01)	*<0.001	2.73 (1.05–7.10)	0.04	2.24 (1.20–4.19)	0.011
	Multiple doctor visits		Hospitalization
	aOR (95% CI)	p-value	aOR (95% CI)	p-value
IBS	2.07 (1.45–2.95)	<0.001	1.78 (1.28–2.47)	<0.001
Subtype
No IBS	Reference	N/A	Reference	N/A
IBS-C	4.611 (1.85–11.50)	0.001	2.55 (1.29 –5.06)	0.007
IBS-D	1.67 (1.07–2.61)	0.025	1.36 (0.89–2.09)	0.15
IBS-M	2.39 (1.37–4.16)	0.002	2.51 (1.52–4.15)	<0.001

^*Models adjusted for age, sex, BMI

Figure 2:

Psychological Characteristics of Veterans with Irritable Bowel Syndrome (IBS). P-values shown for overall comparisons across groups; pairwise comparisons of IBS subtypes with non-IBS performed using multivariable logistic regression; *p<0.001

Multivariable associations of IBS subtype with anxiety, depression, and provisional PTSD are summarized in Table 3. After adjusting for covariates (age, sex, BMI), IBS was significantly associated (all p<0.001) with anxiety (odds ratio [OR]=3.47, 95% CI: 2.55, 4.72), depression (OR=2.88, 95% CI: 2.13, 3.89), and PTSD (OR=3.09, 95% CI: 2.19, 4.37). Participants with any IBS subtype were more likely to have higher levels of anxiety or depression and PTSD (all p<0.001) than those without. Highest OR values for psychological comorbidities were associated with IBS-C. Comparisons between pairs of IBS subtypes based on the adjusted model showed no statistically significant differences in anxiety, depression or PTSD (Table 3); higher OR for PTSD in IBS-C compared to IBS-D were of borderline significance (p=0.08).

Antibiotic use and infective enteritis:

History of IE (p<0.001), new bowel problems after IE (p=0.008), and new bowel problems after antibiotics (p<0.001) were more common in IBS in both unadjusted (Table 2) and adjusted (Table 3) analyses. Analysis by IBS subtype demonstrated that prior IE (overall p<0.001) and bowel problems after antibiotics (overall p=0.005) were most common in IBS-M and new problems after IE (overall p=0.03) were most common in IBS-C (Figure 3). Significant associations were observed in multivariable analyses by subtype (Table 3). All subtypes (IBS-M, p<0.001; IBS-D, p<0.001; IBS-C, p=0.01) were more likely to report IE than non-IBS participants. Those with IBS-M (p=0.04) and IBS-C (p=0.02) were more likely to report new bowel problems after IE. Those with IBS-M (p=0.01) were more likely to report new bowel problems after antibiotics.

Figure 3:

Antibiotic Use and Infectious Enteritis in Veterans with Irritable Bowel Syndrome (IBS). P-values shown for overall comparisons across groups; pairwise comparisons of IBS subtypes with non-IBS performed using multivariable logistic regression [pairwise comparisons between IBS subtypes not performed]; *p<0.001; **p<0.05

Health-related QOL and Healthcare Utilization:

Participants with IBS had lower mental and physical health-related QOL scores (both p<0.001) in univariable analysis than those without IBS (Table 2). Multiple doctor visits (p=0.005) and hospitalizations in the past 10 years (p=0.044) were more common in IBS (Table 2). Significant associations were observed across subtypes. Lowest physical and mental QOL scores (both overall p<0.001) and higher frequency of multiple doctor visits (overall p=0.003) and hospitalizations (overall p=0.027) were observed in IBS-C (Supplemental Figure).

In multivariable analyses, IBS status and all IBS subtypes were associated with lower physical health-related QOL than those without IBS (IBS effect estimate=[−5.36], 95% CI: −6.98, −3.74; IBS-C effect estimate=[−7.08], 95% CI: −10.40, 3.76; IBS-D effect estimate=[−4.71], 95% CI: −6.83, −2.59; IBS-M effect estimate=[−6.19], 95% CI: −8.63, −3.75) and lower mental healthrelated QOL scores (IBS effect estimate=[−6.47], 95% CI: −8.22, −4.72; IBS-C effect estimate=[8.50], 95% CI: −12.07, −4.92; IBS-D effect estimate=[−5.64], 95% CI: −7.93, −3.36; IBS-M effect estimate=[−7.79], 95% CI: −10.42, −5.16). Compared to participants without IBS, those with IBS and any IBS subtype were more likely to report multiple doctor visits; those with IBS, IBS-C, and IBS-M were more likely to have been hospitalized (Supplemental Figure).

DISCUSSION

We observed high rates of IBS among Veterans and clinically-important and statistically significant associations of IBS with anxiety, depression, and PTSD. Novel aspects include the use of Rome IV criteria, which are based on general U.S. population thresholds,¹² assessment of outcomes by IBS subtype, and examination of health care utilization and QOL in a Veteran population. Veterans with IBS commonly reported prior IE, particularly those meeting IBS-D or IBS-M criteria. IBS was associated with lower physical and mental health-related QOL along with more frequent provider visits and hospitalizations.

The prevalence of Rome IV-defined IBS in this study is much higher than previously reported global prevalence rates of 1.5 to 5% when using the same Rome IV criteria.^{13, 14} Prevalence rates of 25% overall and 39% among females Veterans in this study are comparable to the 38% prevalence reported among female Veterans by Savas et al.⁵ who defined IBS using modified Rome II criteria. Others¹⁵ have estimated lower rates of 17% and 8.2% in female and male Gulf War Era Veterans,¹⁵ respectively, when relying on clinical diagnosis or rates as low as 2–4%^{7, 16} when using ICD codes. Higher prevalence of IBS in this study and in the study by Savas et al. when using validated Rome criteria compared to studies that used physician-based diagnoses or coding suggests that IBS could be under-recognized among Veterans. The high prevalence of Rome IV-defined IBS in our cohort, even after excluding individuals with other gastrointestinal diseases, is especially notable as prior data has shown Rome IV to be more restrictive than Rome III.¹⁴ Findings suggest that Veterans are at elevated risk of IBS including severe IBS compared to the general population.

Similar to other studies, we observed that IBS was significantly associated with anxiety, depression, and PTSD.^{5, 17} Among non-Veterans, anxiety and depression are at least twice as common¹⁸ in IBS compared to controls, while those with PTSD have a 3–4 fold increase in odds of IBS¹⁷. Savas et al.⁵ reported a four-fold increase in odds of IBS in female Veterans with PTSD. In their study, anxiety and depression were significantly associated with IBS. We observed elevated anxiety or depression scores and PTSD in almost half of Veterans with IBS; associations were seen with all IBS subtypes. Scores were highest in IBS-C, although differences between IBS subtypes were not statistically significant. Results underscore the importance of biopsychosocial factors in IBS. Although associations of anxiety and depression with IBS are well-established,¹⁹ it is not fully known whether associations are due to effects of mood on symptom perception, negative effects of gastrointestinal symptoms on mood, or interactions of psychological stress with environmental or individual factors. Is it also unclear if these relationships differ by IBS subtype. Some studies suggest that constipation may correlate with psychological comorbidity^20–22 and higher rates of depression have been described in IBS-C compared to other subtypes.²⁰

In general, PTSD rates are higher among Veterans^{23, 24} than in the general population. In our cohort, associations of IBS with PTSD imply that dysregulation of the brain-gut axis could be influenced by abnormal emotional-arousal circuits or psychosocial factors such as experiential avoidance.²⁵ These pathways may represent treatment targets for Veterans and should be further explored.

In addition to psychosocial factors, we examined other factors linked to IBS. Acute IE is a well-recognized IBS risk factor²⁶ and diarrheal illnesses are among the most common noncombat conditions experienced by military personnel.²⁷ Like others,²⁸ we observed that prior IE was more common in IBS, with antibiotic use possibly increasing the risk of IBS.²⁹ Prior IE was reported by 54% of participants with IBS and was most commonly reported in IBS-M or IBS-D, consistent with previous studies.^{30, 31} New bowel problems were more common in IBS-M and IBS-C. However, the nature and type of bowel problems, whether bowel problems represented new or changing symptoms, and if bowel problems occurred during service and/or deployment could not be determined from this cross-sectional study. Overall, our findings suggest that IE may be an important risk factor for IBS in Veterans. Tuteja et al. recognized the potential importance of IE and studied the effect of rifaximin in Gulf War Veterans with IBS-D or IBS-M, showing no treatment benefit.³² Whether Veterans with PI-IBS are more likely to respond to rifaximin due to a microbial origin for symptoms or less likely to respond due to other factors (e.g. microbial dysbiosis, psychosocial factors) requires further study.

Upon evaluating the impact of IBS on QOL, we observed that all IBS subtypes were associated with lower health related QOL. Additionally, IBS was associated with more frequent provider visits and those with IBS-C and IBS-M were more likely to have been hospitalized. However, the reasons for visits and hospitalizations are not known. Results confirm that IBS is common among Veterans and is associated with impaired QOL and greater healthcare utilization. Results warrant increased clinician awareness of IBS to ensure timely recognition and treatment.

Study strengths include the use of validated questionnaires, a large sample size, and unbiased recruitment of eligible men and women receiving care at the VA Medical Center in Indianapolis. Our findings extend the current body of knowledge by demonstrating that the clinical burden imposed by IBS is substantial among Veterans. This study is the first to show that relationships of IBS with psychological factors, QOL, IBS risk factors, and interactions with the healthcare system may differ depending on IBS subtype. Findings suggest that putative pathophysiological IBS mechanisms may be differentially linked to subtype.

Study limitations include the potential for recall or responder bias due to the opt-in study design and the potential for selection bias given the low survey response rate. However, much of the low response rate was due to invalid addresses rather than a lack of interest. Compared to the demographic characteristics of Indiana Veterans according to the 2017 American Community Survey (ACS ³³), our cohort included a higher percentage of females (22.3% vs. 11.6%) and Veterans with higher education (48.5% vs. 20.0% with Bachelor’s degree or higher). Age (45.7% ages 35–54 years; 46.1% ages 55–65) and race distributions (87% Caucasian) were similar to the ACS population (47.2% ages 35–54 years; 38.4% ages 55–65 years; 85.3% Caucasian). We did not have access to participants’ full medical records to verify responses and diagnoses. The study was conducted at a single, large VA and results may not generalize to Veterans nationwide. We did not have a civilian population as a comparator. Although the Rome IV criteria have excellent specificity for IBS¹², individuals can fluctuate between bowel disorder groups³⁴ over time. Yet, a recent report³⁵ demonstrated that 85% of individuals who met Rome IV IBS criteria at baseline continued to meet either Rome IV (70%) or Rome III (15%) for IBS at 12 months. It is also possible that participants with IBS-type symptoms were more willing to respond to a survey about gastrointestinal symptoms. To minimize the impact of potential biases, participants were blinded to research hypotheses and questions were non-leading. Survey invitations were distributed to all eligible Veterans. In addition to using Rome IV criteria, we excluded individuals with other gastrointestinal diseases using both self-reported history and screening filters during the initial database search. Pairwise comparisons between IBS subtypes may have been limited by sample size. Although the cross-sectional design precludes our ability to determine temporality of the observed associations, our findings may guide future prospective studies.

In conclusion, we demonstrate that IBS is prevalent among Veterans survey respondents and IBS in Veterans is associated with psychological symptoms and places a measurable burden on health and healthcare utilization. Effects may differ by subtype. Increased IBS awareness and identification of IBS risk factors including IE and PTSD is required. Future studies are needed to explore the role of biopsychosocial factors in IBS pathophysiology and IBS subtype among Veterans.

WHAT YOU NEED TO KNOW.

Background:

The prevalence of IBS among Veterans is not well-described.

Veterans may be at higher risk of IBS due to unique environmental and individual factors.

Findings:

Prevalence of IBS is high among Veterans.

Psychological symptoms and prior enteric infection are associated with IBS in Veterans.

The humanistic and socioeconomic burdens of IBS among Veterans are substantial.

Implications for Patient Care:

Clinicians caring for Veterans should be aware that IBS is common and may be associated with specific risk factors including infectious enteritis and PTSD.