Association between drinking water hardness and incidence of hospitalization for childhood fracture: an ecological study of England

Bone fracture during childhood is a common injury, with rates in early adolescence equivalent to that of older age. Nutrition is profoundly important for healthy skeletal development, although data are scarce on the extent to which bone-forming minerals in drinking water might contribute to musculoskeletal health. The aim of this study was to describe the association between the hardness of local domestic drinking water across England with rates of hospitalization for childhood fracture, while adjusting for sociodemographic characteristics. Total water hardness (CaCO₃) and calcium and magnesium concentrations were obtained de novo from water companies. Counts of hospitalizations for fracture in patients aged under 18 yr were extracted from the Hospital Episode Statistics database (April 1, 2012, to March 31, 2020). Sex-specific Poisson regression was used to describe the association between water hardness and rates of fracture hospitalizations aggregated at the neighborhood level (lower-level super output areas [LSOAs]), adjusted for age, deprivation, rurality and latitude. We included 29 776 LSOAs and identified 298 929 hospital admissions for fracture, at an estimated rate of 3.50/1000 person-years. Water hardness was associated with a significant reduction in fracture admissions: covariate-adjusted incidence rate ratio of 0.87 (95% CI, 0.86-0.89) and 0.84 (95% CI, 0.82-0.86) comparing very hard to soft water areas, for boys and girls, respectively. The reduction was consistent across commonly fractured skeletal sites and for secondary fractures within the same child. Concentrations of either calcium or magnesium were independently associated in a dose-response manner with fewer hospital admissions for fracture. Future research is needed to confirm and further elucidate these findings, although they are suggestive that achieving adequate dietary intake of these bone-forming minerals may be especially important for children in areas with soft drinking water. We conclude that hospital admissions for childhood fracture are approximately 10%-15% lower in hard water areas of England.