POTS GI symptoms meta-analysis — FM-POTS-MCAS overlap epidemiology

One-paragraph summary

Systematic review + meta-analysis of GI symptoms and systemic comorbidities in POTS, pooling 19 studies covering 8,268 POTS patients. Headline findings: 57.9% of POTS patients have at least one GI symptom; the most common is nausea (70.1%), followed by bloating (64.9%), abdominal pain (60.4%), postprandial fullness (60.4%). IBS prevalence is 26.8%. The systemic-comorbidity pattern is striking: anxiety 42.9%, chronic fatigue 40.9%, migraine 35.6%, depression 34.4%, fibromyalgia 21.6%, and mast cell activation syndrome 36.3%. This is the epidemiological grounding the project's autonomic_dysregulation chain needs — the FM-POTS-MCAS-IBS overlap is real, large, and well-quantified, supporting the H1/H2/H3 cross-chain framework's prediction that these conditions share core mechanism elements.

Claims as triples

• gi_symptoms — prevalent_in → pots [evidence: meta-analysis 57.9% any GI symptom, 95% CI 38.4-75.2; confidence: established]
• nausea — most_common_gi_symptom_in → pots [evidence: meta-analysis 70.1%, 95% CI 51.5-83.7; confidence: established]
• ibs — comorbid_with → pots [evidence: meta-analysis 26.8%, 95% CI 15.3-42.4; confidence: established]
• fibromyalgia — comorbid_with → pots [evidence: meta-analysis 21.6%, 95% CI 12.8-34.2; confidence: established]
• mast_cell_activation_syndrome — comorbid_with → pots [evidence: meta-analysis 36.3%, 95% CI 17.8-60.0; confidence: established]
• chronic_fatigue — comorbid_with → pots [evidence: meta-analysis 40.9%, 95% CI 21.1-64.2; confidence: established]
• anxiety — comorbid_with → pots [evidence: meta-analysis 42.9%, 95% CI 22.7-65.8; confidence: established]
• depression — comorbid_with → pots [evidence: meta-analysis 34.4%, 95% CI 19.0-54.0; confidence: established]
• migraine — comorbid_with → pots [evidence: meta-analysis 35.6%, 95% CI 27.0-45.2; confidence: established]

Methods note

Systematic review with random-effects meta-analysis pooling proportions. Searched electronic databases inception through May 2025. Sub-group analyses conducted. Final dataset: 19 studies, 8,268 POTS patients. Methodology is standard PRISMA. The 95% CIs are wide on some comorbidity estimates (especially MCAS 17.8-60.0) reflecting heterogeneity across the included studies' diagnostic approaches.

Limitations

• Heterogeneity in POTS diagnostic criteria across studies
• MCAS diagnostic criteria vary substantially across studies (the wide 95% CI 17.8-60.0 reflects this)
• Studies may be biased toward more severe POTS (referral cohorts) — community-prevalence may differ
• GI symptom assessment is heterogeneous (questionnaires vs structured assessment)
• No within-patient stratification by POTS subtype (hyperadrenergic vs neuropathic vs hypovolemic)
• The 21.6% FM comorbidity is from self-report / clinical-diagnosis screening; rigorous ACR-criteria-applied FM prevalence may differ
• No data on age stratification (POTS is typically young women)

Open questions raised

• Q-POTS-FM-1 (new): Is FM-POTS comorbidity bidirectional, i.e., is POTS prevalence in FM cohorts at the same ~22% level as FM prevalence in POTS cohorts? Symmetric prevalence would support shared-mechanism framing; asymmetric would suggest one is a downstream consequence of the other.
• Q-POTS-FM-2 (new): Do POTS subtypes (hyperadrenergic vs neuropathic vs hypovolemic) differentially overlap with FM subtypes (autoimmune vs central-only vs peripheral SFN)? Cross-subtype mapping would refine the H1/H2/H3 chain assignment.
• Q-POTS-FM-3 (new): Does the FM-POTS-MCAS triad share IgG-mediated mechanism? Sanchez 2025 (FM-IgG → MRGPRX2/MC), Mignolet 2026 (LC-IgG passive transfer), and the POTS autoantibody literature (anti-G-protein-coupled-receptor AAbs) jointly suggest an IgG-mediated convergence; this meta-analysis quantifies the comorbidity that demands the mechanistic explanation.

Triangulation notes

• Quantifies the FM-POTS-MCAS overlap that the project's H2 (MC) and autonomic_dysregulation chains depend on. 36.3% MCAS in POTS + 21.6% FM in POTS produces a sizeable triple-overlap subpopulation that should be the target of stratified-cohort mechanism studies.
• Reinforces B-Re-7 (Post-COVID SFN ↔ FM SFN diagnostic-modality concordance): the autonomic-dysregulation chain encompasses POTS, FM, PASC-SFN, and ME/CFS via shared neuroautonomic mechanisms. This paper adds POTS to the cross-condition mechanism framing.
• Compatible with Azcue 2026 (β2-AR / M3-muscarinic AAbs in PCC vs ME/CFS): both papers approach the autonomic-dysregulation chain from different angles (autoantibody dissection in Azcue; epidemiological overlap in this paper). Cross-method convergence supports the framework.
• No retinal-substrate angle from this paper but it indirectly supports the autonomic-symptom-driven choroidal-substrate hypothesis: if 57% of POTS patients have GI symptoms and 21.6% have FM, the choroidal-vascular-substrate-vs-autonomic-symptom hypothesis (Ekici Zincirci 2026 — same intake batch) deserves stratification by FM-POTS subtype.

Bridges

• B6 / autonomic_dysregulation chain reinforcement: cross-condition prevalence quantified. Update synthesis/bridges.md or autonomic-chain documentation with these prevalence anchors.
• No new bridges but supplies prevalence data for the FM-POTS-MCAS-IBS cluster.

Subtype-mapping implications

• The 21.6% FM-in-POTS subpopulation and 36.3% MCAS-in-POTS subpopulation suggest a stratification axis. The biomarker-mapping cohort design should include POTS-specific phenotyping (orthostatic vitals, COMPASS-31 minimum) so that FM patients with POTS phenotype can be analyzed separately.
• This is consistent with the autonomic-subtype axis already present in the project's subtype mapping.

Confidence-tier framing

• Prevalence figures: established (meta-analysis n=8,268)
• Mechanism interpretation (IgG-mediated convergence): inferred (cross-paper triangulation)
• FM-POTS-MCAS-IBS shared mechanism: bridging (the prevalence pattern is consistent with shared mechanism, but the mechanism itself is not directly evidenced by this paper)