Natural fluoride in drinking water and myocardial infarction: A cohort study in Sweden.
Large geographical variation in the coronary heart disease (CHD) incidence is seen worldwide and only a part of this difference is attributed to the classic risk factors. Several environmental factors, such as trace elements in the drinking water have been implicated in the pathogenesis of CHD. The objective was to assess the association between drinking water fluoride exposure and myocardial infarction in Sweden using nationwide registers. This large cohort consisted of 455,619 individuals, born in Sweden between January 1, 1900 and December 31, 1919, alive and living in their municipality of birth at the time of start of follow-up. Estimated individual drinking water fluoride exposure was stratified into four categories: very low (<0.3mg/l), low (0.3-<0.7mg/l), medium (0.7-<1.5mg/l) and high (≥1.5mg/l). In Cox regression analyses, compared to the very low fluoride group, the adjusted Hazard Ratio for the low fluoride group was 0.99 (95% confidence interval, 0.98-1.00), for the medium fluoride group 1.01 (95% confidence interval, 0.99-1.03) and 0.98 (95% confidence interval, 0.96-1.01) for the highest fluoride group. Adding water hardness to the model did not change the results. We conclude that the investigated levels of natural drinking water fluoride content does not appear to be associated with myocardial infarction, nor related to the geographic myocardial infarction risk variation in Sweden. Potential misclassification of exposure and unmeasured confounding may have influenced the results.
Clinical Epidemiology Unit, Department of Medicine, Karolinska Institutet and Karolinska University Hospital, Solna, Sweden; Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden. Electronic address: Peggy.Nasman@ki.se.
Peggy
P
Näsman
Clinical Epidemiology Unit, Department of Medicine, Karolinska Institutet and Karolinska University Hospital, Solna, Sweden.
Fredrik
F
Granath
Clinical Epidemiology Unit, Department of Medicine, Karolinska Institutet and Karolinska University Hospital, Solna, Sweden.
Jan
J
Ekstrand
Clinical Epidemiology Unit, Department of Medicine, Karolinska Institutet and Karolinska University Hospital, Solna, Sweden.
Anders
A
Ekbom
Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden.
Gunilla
G
Sandborgh-Englund
Clinical Epidemiology Unit, Department of Medicine, Karolinska Institutet and Karolinska University Hospital, Solna, Sweden.
C Michael
CM
Fored
D000074341:Dietary Exposure / Q000706:statistics & numerical data*; D060766:Drinking Water / Q000737:chemistry*; D005459:Fluorides / Q000032:analysis*; D006801:Humans; D009203:Myocardial Infarction / Q000453:epidemiology*; D013548:Sweden / Q000453:epidemiology; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014881:Water Supply / Q000706:statistics & numerical data
D060766:Drinking Water; D014874:Water Pollutants, Chemical; D005459:Fluorides
Cardiovascular disease; Cohort study; Coronary heart disease; Drinking water; Environmental exposure; Fluoride; Myocardial infarction; Water hardness