The influence of a high fluoride content in the drinking water on the bone mineral mass in man

Fluoride in drinking water and risk of hip fracture in the UK: a case-control study

BACKGROUND

Although the benefits of water fluoridation for dental health are widely accepted, concerns remain about possible adverse effects, particularly effects on bone. Several investigators have suggested increased rates of hip fracture in places with high concentrations of fluoride in drinking water, but this finding has not been consistent, possibly because of unrecognised confounding effects.

METHODS

We did a case-control study of men and women aged 50 years and older from the English county of Cleveland, and compared patients with hip fracture with community controls. Current addresses were ascertained for all participants; for those who agreed to an interview and who passed a mental test, more detailed information was obtained about lifetime residential history and exposure to other known and suspected risk factors for hip fracture. Exposures to fluoride in water were estimated from the residential histories and from information provided by water suppliers. Analysis was by logistic regression.

FINDINGS

914 cases and 1196 controls were identified, of whom 514 and 527, respectively, were interviewed. Among those interviewed, hip fracture was strongly associated with low body-mass index (p for trend <0.001) and physical inactivity (p for trend <0.001). Estimated average lifetime exposure to fluoride in drinking water ranged from 0.15 to 1.79 ppm. Current residence in Hartlepool was a good indicator for high lifetime exposure to fluoride. After adjustment for potential confounders, the odds ratio associated with an average lifetime exposure to fluoride > or =0.9 ppm was 1.0 [95% CI 0.7-1.5].

INTERPRETATION

There is a low risk of hip fracture for people ingesting fluoride in drinking water at concentrations of about 1 ppm. This low risk should not be a reason for withholding fluoridation of water supplies.

Water fluoridation, bone mass and fracture: a quantitative overview of the literature

OBJECTIVE

To use the technique of meta-analysis to address the following research questions: Is water fluoridation associated with altered fracture risk at a population level and are the differences between studies consistent with confounding or chance variation between studies?

METHOD

The data sources utilised were Medline 1966-97, reviews and bibliographies. The search terms were fluoridation, bone mass and/or fracture. We included all observational studies published in English relating water fluoridation to bone mass and/or fracture in the initial assessment.

RESULTS

Water fluoridation had no evident effect on fracture risk (RR 1.02, 95% CI 0.96-1.09, n = 18 studies). There was marked heterogeneity between studies which could be explained, in part, by the combination of gender, urbanicity and study quality (R2 0.25, p = 0.05, weighted analysis).

CONCLUSIONS

Water fluoridation both at levels aimed at preventing dental caries and, possibly, at higher naturally occurring levels appears to have little effect on fracture risk, either protective or deleterious, at a population level. The small effect on bone mass seen in studies performed at the individual level is consistent with this finding. Variation between studies is also likely to be due to differences in the distribution of other recognised fracture risk factors between different populations. Confirmation of these findings is required in large studies performed at the individual level.

Drinking water fluoridation: bone mineral density and hip fracture incidence

The role of drinking water fluoride content for prevention of osteoporosis remains controversial. Therefore, we analyzed the influence of drinking water fluoridation on the incidence of osteoporotic hip fractures and bone mineral density (BMD) in two different communities in eastern Germany: in Chemnitz, drinking water was fluoridated (1 mg/L) over a period of 30 years; in Halle, the water was not fluoridated. BMD was measured in healthy hospital employees aged 20-60 years (Halle: 214 women, 98 men; Chemnitz: 201 women, 43 men, respectively) using dual-energy X-ray absorptiometry. Hip fractures in patients > or = 35 years admitted to the local hospitals in the years 1987-1989 were collected from the clinic registers. There was no difference in age, anthropometric, hormonal, or lifestyle variables between the two groups. Mean fluoride exposure in Chemnitz was 25.2 +/- 7.3 years. No correlation was found between fluoride exposure and age-adjusted BMD. We found no significant difference in spinal or femoral BMD between subjects living in Halle and Chemnitz [lumbar spine: 0.997 +/- 0.129 (g/cm2) vs. 1.045 + 0.171 (g/cm2), p = 0.08, for men; 1.055 +/- 0.112 (g/cm2) vs. 1.046 +/- 0.117 (g/cm2), p = 0.47, for women]. The fracture incidence showed an exponential increase with aging in men and women with an incidence about 3.5 times higher for women. In Chemnitz, we calculated an age-adjusted annual incidence of 142.2 per 100,000 for women and 72.5 per 100,000 for men, respectively. In Halle, the incidences were 178.5 per 100,000 for women and 89.2 per 100,000 for men. There was a lower hip fracture incidence after the age of 85 in women in Chemnitz (1391 per 100,000 in Chemnitz vs. 1957 per 100,000) in Halle, p = 0.006). Using the age-adjusted incidences, significantly fewer hip fractures occurred in Chemnitz in both men and women. In conclusion, our study suggests that optimal drinking water fluoridation (1 mg/L), which is advocated for prevention of dental caries, does not influence peak bone density but may reduce the incidence of osteoporotic hip fractures in the very old.

Hip fracture incidence before and after the fluoridation of the public water supply, Rochester, Minnesota

Recent ecological comparison studies have suggested a positive association between fluoridation and hip fracture. Using data from the Rochester Epidemiology Project, we found the incidence of hip fracture for the 10 years before the fluoridation of the Rochester, Minn, public water supply was 484 per 100,000, compared with 450 per 100,000 in the following 10 years. When the effects of calendar time and age were controlled for, the relative risk associated with fluoridation was 0.63. These ecologic trend data suggest that the fluoridation of public water supplies is not associated with an immediate increase in rates of hip fracture. Further studies of this association at the individual level are clearly required before public policy decisions can be made.

The association between water fluoridation and hip fracture among white women and men aged 65 years and older. A national ecologic study

For the past 45 years, there has been a great deal of debate regarding the health issues surrounding the fluoridation of public water supplies. In order to assess the association between fluoridation and hip fracture, we identified 129 counties across the United States considered to be exposed to public water fluoridation and 194 counties without exposure. Data from the Health Care Financing Administration and the Department of Veterans Affairs were used to calculate the incidence of hip fracture among white persons, aged 65 years or older, in fluoridated and nonfluoridated counties. There was a small statistically significant positive association between fracture rates and fluoridation. The relative risk (95% confidence interval) of fracture in fluoridated counties compared to nonfluoridated counties was 1.08 (1.06 to 1.10) for women and 1.17 (1.13 to 1.22) for men. As comparisons were made at the grouped level, it may be inappropriate at this time to draw inferences at the individual level. The relationship observed at the county level needs to be duplicated at the individual level with more precise measures of fluoride exposure.

Fluoride in the prevention of osteoporosis and fractures

Age-related fractures, especially hip fractures, produce sufficient morbidity and mortality to make osteoporosis a disease worth preventing, and accurate techniques exist to identify groups at high risk of fracture by virtue of low bone mass. While the need for prevention is evident, no specific program of fluoride use for this purpose has been devised, and epidemiologic data provide little support for the notion that exposure to fluoride reduces hip fracture incidence. At present, fluoride cannot be recommended as a prophylactic agent for the fractures that are the primary adverse health outcome of osteoporosis.

Skeletal fluorosis. A report of two cases

Two illustrative cases of patients with skeletal fluorosis and classic radiographic changes are presented. One patient demonstrated a progressive paraparesis, while the other was diagnosed incidentally on routine radiographs. A review of the literature, treatment, and histologic findings are presented.

Fluoride therapy for osteoporotic lesions

The clinical research and the metabolic and therapeutic concerns related to the administration of fluoride for osteoporotic lesions are reviewed. Two or three daily administrations of 22.4 mg of sodium fluoride (NaF) have been shown to stimulate osteoblastic activity. When accompanied by supplemental calcium (Ca) new normal bone is deposited leading to an increase in total bone mass. The Ca should be given daily in 600 to 1,000 mg quantity at times separate from the fluoride ingestion to avoid formation of insoluble calcium fluoride. Vitamin D may also be prescribed to aid Ca absorption. The precise mechanism of action is not yet known. Promising clinical results have been obtained with a variety of osteoporotic conditions including “otosclerosis.”