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47 Prevalence of functional defecation disorders 1 Associated factors FNRFI Two studies described factors associated with the presence of FNRFI. Although quality of school life (QOSL) in children with FNRFI was found to be low, it was not statistically different compared to children with other functional gastrointestinal disorders. 26 Using the PedsQL4.0 Generic Core Scale, Lewis et al . found significantly lower HRQoL scores in 17 children with FNRFI as compared to children without a functional gastrointestinal disorder. 46 DISCUSSION This is the first systematic review describing the prevalence of FDDs in children based solely on the Rome III criteria. No epidemiological studies utilizing the Rome IV criteria were identified. Our systematic review is the first to provide a meta-analysis on this subject which revealed a pooled FC prevalence of 9.5% and a pooled FNRFI prevalence of 0.4% in children worldwide. Pooled data analysis did not reveal a sex-related or age-related predominance for FC; for FNRFI this analysis was not performed due to scarcity of data. Significant geographical differences were observed for the prevalence of FC but not for FNRFI. Our results are in line with a previous systematic review on the prevalence of FC, which included 17 pediatric studies, 3 of which are also included in the current systematic review. 6 In that systematic review, Mugie et al . described the prevalence of FC in both children and adults and reported the prevalence of FC in children to range between 0.7% and 29.6%, with a median of 12%. 6 However, the authors included studies which applied various criteria for the diagnosis of FC, ranging from self-report to the Rome II and III criteria. 6 The authors refrained from performing a meta-analysis, therefore, the reported median prevalence rate did not take sample sizes of included studies into account. Moreover, the authors described amedian female/male ratio of 1.5:1, including both pediatric and adult studies. After pooling the data in the current systematic review, we found an OR of 0.99 (95% CI 0.9-1.4) for boys, suggesting that no sex-related predominance of FC occurs in children. Since the current study is the first systematic review on the prevalence of FNRFI, it is difficult to compare our results with previously published literature, but the results seem to confirm previous assumptions that FNRFI occurs in approximately 1% of the general pediatric population. 7 Differences in the prevalence of FC were observed among continents, with the lowest pooled prevalence occurring in Asia. This suggests that cultural differences (e.g. lifestyle, environment, type of toilet) might play a role in the pathophysiology of FC. However, the number of studies varied strongly and for the grouped analysis we had to group continents with low numbers of studies together, so these results should be interpreted carefully. Historically, epidemiological data on FDDs from developing regions such as Africa have