Objective: The objective of this study was to examine differences in intellectual capacities between children with and without soiling, daytime wetting, and bed-wetting.
Methods: This study was based on a population of >6000 children (age range: 7 years 6 months to 9 years 3 months; median: 7 years 6 months) from the United Kingdom-based Avon Longitudinal Study of Parents and Children. Data on wetting and soiling were obtained from a questionnaire completed by parents. The Wechsler Intelligence Scale for Children-Third Edition was administered at a research clinic.
Results: Bed-wetting was associated with lower Wechsler Intelligence Scale for Children-Third Edition IQ scores compared with control subjects, particularly performance IQ. This difference remained after exclusion of children with an IQ of <70 and adjustment for gender, stressful life events, and sociodemographic background. There were fewer differences in IQ scores between children with and without soiling or daytime wetting. Co-occurring wetting and soiling were associated with lower IQ scores than isolated soiling, daytime wetting, or bed-wetting, but this was mostly attributable to an overrepresentation of children with an IQ of <70 in the co-occurrence group.
Conclusions: It is hypothesized that the differences in intellectual capacities between children with and without bed-wetting are associated with maturational deficits of the central nervous system. There was less evidence for differences in intellectual capacities between children with and without soiling and daytime wetting. The central nervous system is involved to a lesser extent in soiling and daytime wetting, because peripheral influences from the bladder and gut play a greater role.