Drinking water composition and childhood-onset Type 1 diabetes mellitus inDevon and Cornwall, England

Aims Previous studies have reported inconsistent results on the association between some compositions (e.g. nitrate) in domestic water and the risk of childhood-onset Type 1 diabetes mellitus. This study aimed to examine the relationship between nitrate, zinc and magnesium in drinking water and the risk of childhood-onset Type 1 diabetes mellitus. Methods The study covers the Cornwall and the former Plymouth Health Author ity Regions in the far south-west of England. Five hundred and seventeen ch ildren, aged 0-15 years, diagnosed with Type 1 diabetes mellitus between 19 75 and 1996, were identified for inclusion in the study. Domestic water dat a (nitrate, Zn, Mg, Cu, Al, Ca, Fe and Mn) between 1993 and 1997 were provi ded by South-west Water Plc, UK, for each of the 40 Water Supply Zones in w hich the subjects had been resident at the time of diagnosis. The standardi zed incidence ratio (SIR) of the disease was calculated for each Water Supp ly Zone using the UK 1991 census population data. The relationship between the SIR of the disease and the water quality indicators in thirds (three st rata of low, medium and high concentrations) was examined by chi (2) test f or trend and Poisson regression analysis. Results The initial analyses by chi (2) test for trend on the relation of S IRs and drinking water compositions suggested that copper, magnesium and ni trate might have some protective effects, but Poisson regression analyses s howed that only zinc and magnesium were significant factors. The data sugge st that the incidence rate of childhood diabetes is significantly lower whe n the concentrations of zinc and magnesium in the domestic drinking water a re in the range 22.27-27.00 mug/l (incidence rate ratio (IRR), 0.76; 95% CI , 0.59-0.97) and greater than 2.61 mg/l (IRR, 0.72; 95% CI, 0.58-0.91), res pectively. Conclusions Our findings suggest evidence of a possible association between zinc and magnesium in the domestic drinking water and childhood diabetes i n the far south-west of England. However, these possible protective effects of zinc and magnesium in domestic drinking water warrant further confirmat ion.