Water hardness and eczema at 1 and 4 y of age in the INMA birth cohort

Abstract

Background: Exposure to hard water has been suggested as a risk factor for eczema in childhood, based on limited evidence from two ecologic and two cross-sectional studies.Objectives: We evaluate this hypothesis for the first time in early infancy using prospective data from a mother–child cohort study.Methods: We used data from the INMA cohorts in Gipuzkoa, Sabadell and Valencia, Spain (N=1638). Current and ever eczema, bathing frequency and duration and covariables were collected by questionnaires at 14 months (14m) and 4 years (4y). Calcium carbonate (CaCO3) level in municipal water was assigned to home addresses at birth, 14m and 4y. We calculated Odds Ratio (OR) of eczema related to CaCO3 at home, bath exposure and a combination of both.Results: Prevalence of eczema ever was 18.4% at 14m and 33.4% at 4y. Mean CaCO3 ranged from 51.6 to 272.8mg/L among areas. No association was detected between water hardness at home and current or ever eczema. Adjusted OR was 0.79 (95%CI=0.45, 1.39) at 14m and 0.93 (0.56, 1.52) at 4y among children in the highest vs. lowest tertiles of CaCO3. Bath exposure alone or in combination with water hardness did not increase the OR of eczema at 14m or 4y either.Conclusions: We did not find an association between eczema and water hardness at home or bathing exposure during the first four years of life. This first cohort study in a critical age period with improved exposure assessment does not confirm the association suggested among children by previous studies.