Drinking Water Fluoride Exposure and Risk of Hip Fracture

The cariostatic benefit from fluoride dentifrices is indisputable. Possible adverse effects of fluoride accumulation in hard tissues are, however, still unclear. We studied the incidence of hip fractures in a large cohort of Swedish residents chronically exposed to various fluoride levels in drinking water.

Methods:

We examined the risk of hip fracture in near 480 000 individuals using national health care registries. Swedish residents born between year 1900 and 1919 still living in their municipality of birth by 1960 were identified. Individual lifetime drinking water fluoride exposure was estimated for each subject on the basis of information on ground water fluoride measurements in public water supplies. Subjects were stratified in four exposure groups. Level A <0.3 ppm (57.0%), level B 0.3-<0.7 ppm (29.7%), level C 0.7-1.5 ppm (10.5%) and level D >1.5 ppm (2.7%).

Statistical analyses:

We used Cox regression to estimate the association between a fracture and fluoride exposure compared with the lowest fluoride exposure group using time since entry into the cohort as the underlying time-scale. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated.

Results:

During follow-up a total number of 64,615 hip fractures occurred among the individuals in our cohort. Compared with the lowest exposure group, no differences were seen in adjusted risk estimates of first hip fractures between subjects of different drinking water fluoride exposure levels. Hip fracture incidence was 7.9/1000 person-years in individuals in exposure level A, 6.7/1000 in level B (HR = 1.01; 95% CI = 0.98-1.03), 6.2/1000 in level C (HR = 1.01; 95% CI = 0.98-1.04), and 8.6/1000 in the highest exposure level D (HR = 1.00; 95% CI = 0.95-1.06).

Conclusion:

We conclude that, in the investigated fluoride range, fluoride exposure from drinking water seem unlikely to have any important effects on the risk of hip fracture.