Evidence That Independent Gut-to-Brain and Brain-to-Gut Pathways Operate in the Irritable Bowel Syndrome and Functional Dyspepsia

A 1-Year Population-Based Prospective Study

N. A. Koloski; M. Jones; N. J. Talley


Aliment Pharmacol Ther. 2016;44(6):592-600. 

In This Article


Response Rate

In the original survey, a total 3260 people returned a completed survey of 8981. The denominator was reduced by 13 people who had died and 466 return to senders. Responders were significantly more likely to be aged over 45 years compared with nonresponders (68.3% vs. 40.5%, P < 0.001). Responders were also more likely to be female vs. nonresponders; although this was statistically significant, it was numerically very small due to the study power (53.4% vs. 48.0%, P < 0.001). There were no statistically significant differences between responders and nonresponders with respect to socioeconomic status with the SIEFA Advantage–Disadvantage scores being similar for responders vs. for nonresponders (M = 965.8 vs. M = 965.5, P = 0.89). Hence, the only trait on which responders and nonresponders differ by an amount large enough to have a practical consequence is age and the response bias is actually towards the older age group, which is likely to bias towards the null if at all and so does not limit the generalisability of our findings.

For the 1-year follow-up, we mailed out the survey to 2885 people who had responded to the original survey and had also agreed to being recontacted for future research. The denominator was reduced by 69 returns to senders and five people who had died. A total of 1900 completed surveys were returned and used in the analyses, giving a response rate of 67.6%.

Sample Characteristics

Among the 1900 individuals with responses at both baseline and follow-up, the mean age was 57 (s.d. = 14), 53% (n = 1010) were female and the mean body mass index was 28 (s.d. = 6).

Incidence and Disappearance of FGID, IBS and Functional Dyspepsia

We found 6.4% developed new onset IBS, with about 2% developing new onset IBS-C and IBS-D. Slightly more people developed FD (7.2%) with the new onset of FD- PDS more common than FD-EPS (Table 1). Almost half of those people with IBS and FD at baseline lost their symptoms at the 1-year follow-up (Table 1).

FGID Brain-to-gut Pathways

Among those people free of IBS and FD at baseline, we found higher levels of anxiety and depression were significant predictors of developing IBS and FD at a 1-year follow-up (Table 2), implicating brain–gut interactions in these disorders, but not among those who already had IBS or FD.

FGID Gut-to-brain Pathways

Among those people who did not have elevated levels of anxiety and depression at baseline, people with documented IBS and FD at baseline reported significantly higher levels of anxiety and depression at the 1-year follow-up (Table 3), but not among those who already had elevated anxiety or depression, implicating primary gut-to-brain pathways operate in a major subset with these disorders.

Association Between Change From Baseline to Follow-up for Mood and Quality-of-life Scores vs. Change in FGID Status

We also examined change from baseline to follow-up for mood and quality-of-life scores vs. change in IBS and FD status. We only found a change in mental functioning was significantly associated with developing FD at follow-up compared with people who did not have FD at baseline or follow-up (P = 0.01, see Table S1). In IBS, we found that a change in physical functioning was significantly associated with those people who developed IBS at follow-up vs. those who continued to have IBS from baseline to follow-up (P = 0.04, see Table S2).

Proportions of Brain-to-gut and Gut-to-brain

For this purpose, we consider only those who (i) met criteria for a mood disorder at baseline (but not an FGID) and who then reported a mood disorder 1 year later or (ii) who met criteria for an FGID at baseline (but not a mood disorder) and who then reported an FGID 1 year later. Of 215 individuals with mood disorder at baseline 30 met criteria for FGID 1 year later and of 309 individuals with an FGID at baseline 60 met criteria for a mood disorder 1 year later. Hence, it is only in the 90 (30 plus 60) individuals who meet criteria (i) or (ii) above in whom the order of incidence in this study could be determined, yielding 1/3 of individuals in whom mood disorder precedes FGID and 2/3 in whom FGID precedes a mood disorder.