Sample Sizes and Participants’ Ages
There were 3811 respondents who met the study criteria. Women in the control group, the IBS group, the FM group, and the IBS plus FM group numbered 3213 (84.3%), 366 (9.6%), 161 (4.2%), and 71 (1.9%), respectively, with a mean (SD) age of 62.4 (13.6), 64.9 (13.7), 63.2 (10.8), and 61.1 (10.9) years, respectively.
Age and Education Comparisons
Age comparisons are shown as mean (SD) in . The overall ANOVA was statistically significant (P<.05), but the only statistically significant pairwise difference was that women in the control group on average were 2.5 years younger than those in the IBS group (Tukey-Kramer post hoc test, P<.05). Sample numbers and percentages for the education (high school or less, some college, college graduate or higher) comparisons also are shown in . The overall 3 × 4 χ2 test was statistically significant (P<.05). The only statistically significant post hoc differences, however, were between women in the control group and the FM group (Tukey post hoc tests for proportions, P<.05); the proportion of college graduates was higher in the control group. On the basis of these results, we re-ran the comparisons adjusting for age and education; there were no material differences, and thus we present the unadjusted analyses.
Age and Education of Women In the Control Group and Women With Irritable Bowel Syndrome, Fibromyalgia, or Both Disorders (N=3811)a
We predicted that reports of comorbidities would increase from control participants to IBS to FM to IBS plus FM participants. reveals this pattern in the group comparisons on medical and pain diagnoses and CES-D (depressive symptom) scores. Details about the statistically significant (P<.05) pairwise differences are given in the next 4 sections.
Diagnoses and Trauma/Stressors of Women in the Control Group and Women With Irritable Bowel Syndrome, Fibromyalgia, or Both Disorders (N=3811)a
Control and Clinical Group Comparisons
shows the sample numbers and means (SDs) for the continuous physical health and symptoms, sleep quality, and mental health measures. All overall 1-way ANOVA tests were statistically significant With 2 exceptions, women in the control group reported better physical and mental health, less pain, fewer physical symptoms, and better sleep quality, as determined by post hoc pairwise tests. Differences in mean BMI between the control group (26.4) and the IBS group (27.0) and mean (SD) incontinence scores between the control group and the FM group (1.7 [1.3] for both groups) were not statistically significant. The mean physical health composite score for women aged 55 to 64 years in the normative sample was 46.28. The mean mental health composite score for the same population in the normative sample was 50.14.
Physical Health and Symptoms, Sleep Quality, and Mental Health Scores of Women in the Control Group and Women With Irritable Bowel Syndrome, Fibromyalgia, or Both Disorders (N=3811)a
displays sample numbers and percentages for the medical, pain, and psychiatric diagnoses and trauma/stressor variables (all categorical or yes/no). All overall χ2 tests were statistically significant. With the exception of type 2 diabetes mellitus and rheumatoid arthritis, the control group showed statistically significant lower rates of general medical, pain, and psychiatric diagnoses than the IBS group. The percentage point differences were substantial, particularly between the control group and the IBS plus FM group. The widest percentage point differences were recorded for hypothyroidism (16.1% [control] and 52.2% [IBS plus FM]) and sleep apnea (3.8% [control] and 24.6% [IBS plus FM]).
Compared with the FM group, the control group reported lower rates of physical, sexual, and emotional trauma and lower major life stressor rates than those in the FM group (range, 10.2%–15.7%). Except in the category of type 2 diabetes mellitus, the control group reported lower rates of general medical, pain, and psychiatric diagnoses than the FM group.
Comparisons across all variables between the control and FM groups and the control and IBS plus FM groups were similar, with 2 exceptions. We observed no statistically significant differences between the control and IBS plus FM groups for variables in the emotional abuse/neglect category and for rheumatoid arthritis rates. There were no statistically significant differences between the control and IBS groups for the trauma/major life stressor variables.
IBS and FM Group Comparisons
Regarding physical health and symptoms, sleep quality, and mental health (), the IBS group reported lower BMI, better physical health, and lower pain scores than the FM group. There were no statistically significant differences between the IBS and FM groups in headache score, sleep score, or the 3 mental health scores. As predicted, the IBS group compared with the FM group reported more symptoms of the following conditions, expressed as mean (SD): indigestion (2.9 [1.4] vs 2.5 [1.4]), constipation/diarrhea (2.9 [1.5] vs 2.0 [1.3]), and incontinence (2.4 [1.6] vs 1.7 [1.3]).
Percentages for diagnoses and trauma/stressors in were similar between the IBS and the FM groups. There were, however, 3 statistically significant differences: lower rates of diagnosed degenerative disk disease (22.4% vs 40.5%), sciatica/arthritis back (30.6% vs 43.8%), and depression (28.4% vs 40.9%) among women with IBS than those with FM.
IBS and IBS Plus FM Group Comparisons
Pairwise comparisons between IBS and IBS plus FM groups () were statistically significant, with the exception of the incontinence and sleep quality categories. Respondents in the IBS plus FM group generally reported worse physical and mental health, more pain, and more physical symptoms than those in the IBS group. In , the IBS plus FM group reported higher rates of hypothyroidism, sleep apnea, degenerative arthritis, degenerative disk disease, sciatica/arthritis back, and depression diagnoses than those with IBS only. In general, the differences were substantial but not as large as between the control group and the IBS plus FM group.
FM and IBS Plus FM Group Comparisons
There were no statistically significant between-group differences on the physical health or sleep measures (). Women in the FM plus IBS group, however, reported more physical symptoms (ie, headaches, indigestion, constipation/diarrhea, and incontinence) and worse mental health scores than the FM group. Statistically significant differences were found between the IBS plus FM group and the FM group for hypothyroidism (52.2 vs 30.8) and depression (64.3 vs 40.9) ().