Indirect effect of sleep on abdominal pain through daytime dysfunction in adults with irritable bowel syndrome

Abstract

Study objectives: Sleep deficiency, psychological distress, daytime dysfunction, and abdominal pain are common in adults with irritable bowel syndrome. Prior research on individuals with chronic pain has identified the indirect effect of sleep on pain through psychological distress or daytime dysfunction; however, this effect is less clear in irritable bowel syndrome. The purpose of this study was to examine potential indirect effects of sleep on abdominal pain symptoms simultaneously through psychological distress and daytime dysfunction in adults with irritable bowel syndrome.

Methods: Daily symptoms of nighttime sleep complaints (sleep quality and refreshment), psychological distress, daytime dysfunction (fatigue, sleepiness, and difficulty concentrating), and abdominal pain were collected in baseline assessments from 2 randomized controlled trials of 332 adults (mean age 42 years and 85% female) with irritable bowel syndrome. Structural equation modeling was used to examine the global relationships among nighttime sleep complaints, psychological distress, daytime dysfunction, and abdominal pain.

Results: The structural equation modeling analyses found a strong indirect effect of poor sleep on abdominal pain via daytime dysfunction but not psychological distress. More than 95% of the total effect of nighttime sleep complaints on abdominal pain was indirect.

Conclusions: These findings suggest that the primary impact of nighttime sleep complaints on abdominal pain is indirect. The indirect effect appears primarily through daytime dysfunction. Such understanding provides a potential avenue to optimize personalized and hybrid behavioral interventions for adults with irritable bowel syndrome through addressing daytime dysfunction and sleep behaviors. Additional study integrating symptoms with biological markers is warranted to explore the underlying mechanisms accounting for these symptoms.

Clinical trial registration: Registry: ClinicalTrials.gov. Name: Nursing Management of Irritable Bowel Syndrome: Improving Outcomes, Nursing Management of IBS: Improving Outcomes. URLs: https://ichgcp.net/clinical-trials-registry/NCT00167635, https://ichgcp.net/clinical-trials-registry/NCT00907790. Identifiers: NCT00167635, NCT00907790.

Keywords: daytime dysfunction; irritable bowel syndrome; pain; psychological distress; sleep.

© 2020 American Academy of Sleep Medicine.

Figures

Figure 1. Initial hypothesized structural model of direct and indirect effects of sleep on pain through psychological distress and daytime dysfunction.

Latent variables are represented in ovals.

Figure 2. Initial structural model of nighttime sleep complaints, psychological distress, daytime dysfunction, and abdominal discomfort/pain symptoms in adults with irritable bowel syndrome.

Latent variables are represented in ovals, and indicators of latent variables are represented in rectangles. Standardized factor loadings (in light blue) of symptom indicators within their latent variables from confirmatory factor analyses were all statistically significant and > 0.6, suggesting that the latent variables were measured adequately by their respective symptom indicators. The standardized estimates (in dark blue) represent structural pathway relationships between the latent variables from SEM analyses. However, this initial SEM model yielded inadequate model fit. Solid lines indicate significant paths; dashed lines indicate nonsignificant paths. SEM = structural equation modeling. *P < .05, ***P < .001.

Figure 3. Final structural model of nighttime sleep complaints, psychological distress, daytime dysfunction, and abdominal discomfort/pain symptoms in adults with irritable bowel syndrome.

Given inadequate model fit of the initial SEM model, a direct path between psychological distress and daytime dysfunction was added to create this SEM model, which then yielded relatively good model fit. Nighttime sleep complaint was a significant predictor for psychological distress (β = 0.26) and daytime dysfunction (β = 0.31) but not for abdominal discomfort/pain (β = 0.04). Psychological distress was a significant predictor for daytime dysfunction (β = 0.59) but not for abdominal discomfort/pain (β = 0.08). Daytime dysfunction was significantly predictive for abdominal discomfort/pain (β = 0.48). Latent variables are represented in ovals, and indicators of latent variables are represented in rectangles. The standardized estimates (in dark blue) represent structural pathway relationships between the latent variables from SEM analyses. Solid lines indicate significant paths; dashed lines indicate nonsignificant paths. SEM = structural equation modeling. *P < .05, ***P < .001.