Table 2

Relative risk (95% CI) in heart disease mortality for a quadrupling in concentrations of constituents in drinking water (for example, 20 mg/l v 5 mg/l of magnesium) in north west England, 1990–92

Relative risks from separate models (95% CI)Relative risks from separate models adjusted for geographical gradients (95% CI)Relative risks from combined model adjusted for geographical gradients (95% CI)
Acute myocardial infarction (ICD 410)
Log magnesium (mg/l)1.01 (0.99 to 1.03)1.01 (0.98 to 1.03)1.01 (0.96 to 1.06)
Log calcium (mg/l)1.02 (0.99 to 1.04)1.00 (0.97 to 1.04)0.99 (0.94 to 1.05)
Log fluoride (mg/l)0.99 (0.96 to 1.02)1.00 (0.97 to 1.04)0.99 (0.96 to 1.02)
Log lead (μg/l)1.00 (0.96 to 1.03)0.94 (0.91 to 0.98)0.94 (0.91 to 0.98)
Ischaemic heart disease (ICD 410–414)
Log magnesium (mg/l)0.97 (0.96 to 0.99)1.00 (0.98 to 1.02)1.01 (0.96 to 1.05)
Log calcium (mg/l)0.96 (0.94 to 0.99)1.00 (0.97 to 1.02)0.98 (0.94 to 1.04)
Log fluoride (mg/l)1.00 (0.98 to 1.03)1.02 (0.99 to 1.05)1.02 (0.99 to 1.05)
Log lead (μg/l)0.98 (0.95 to 1.01)0.99 (0.96 to 1.02)0.99 (0.96 to 1.03)
  • Results from Poisson regression analyses with expected numbers standardised for age, sex, and Carstairs deprivation quintile. CIs are adjusted with overdispersion parameters (1.6 for acute myocardial infarction and 1.9 for ischaemic heart disease).