How do we define normal bowel frequency from newborn to teens? A Bayesian meta-analysis

Objectives: Defecation disorders are a common pediatric problem and bowel frequency is crucial in identifying them. The aim of this analysis is to define normal bowel frequencies in healthy children ranging from newborns to adolescents. Methods: A literature search was conducted using MEDLINE, SCOPUS, EMBASE, Cochrane Library, and Web of Science from their inception to February 2024, aiming to identify studies reporting bowel habits of healthy children (0–18 years). A Bayesian distribution modeling approach was adopted to pool the mean frequency of bowel opening using inverse-variance weighing. A subgroup analysis and a meta-regression were performed with Bayesian generalized additive mixed distributional models. The methodological quality of the articles was evaluated using the Newcastle–Ottawa Scale modified for cross-sectional studies. Results: Seventeen studies were included in the analysis, including 22,698 children aged from 0 to 18 years. The subgroup meta-analysis showed mean bowel frequencies for newborns, 1–6 months, 6–12 months, 1–2 years, 2–5 years, and over 5 years are 3.24 (95% credible interval [CrI]: 2.83–3.63), 1.99 (95% CrI: 1.77-2.19), 1.66 (95% CrI: 1.45–1.88), 1.53 (95% CrI: 1.37–1.7), 1.15 (95% CrI: 0.99–1.31), and 1.02 (95% CrI 0.88–1.18), respectively. Between studies, heterogeneity demonstrated a near-normal distribution with a mean of 0.16 and a 95% CrI of 0.04–0.28. The variance of the distribution of mean bowel frequency reduced with age. Discussion: In this Bayesian meta-analysis, we found that younger children have a higher bowel frequency. The reported bowel frequencies for each age group could serve as normal values in clinical practice to differentiate health and disease.