The fluoridation of drinking water and hip fracture hospitalization rates in two Canadian communities

[Effects of long-term fluoride in drinking water on risks of hip fracture of the elderly: an ecologic study based on database of hospitalization episodes]

OBJECTIVES

Fluoridation of drinking water is known to decrease dental caries, particularly in children. However, the effects of fluoridated water on bone over several decades are still in controversy. To assess the risk of hip fracture related to water fluoridation, we evaluated the hip fracture-related hospitalizations of the elderly between a fluoridated city and non-fluoridated cities in Korea.

METHODS

Cheongju as a fluoridated area and Chungju, Chuncheon, Suwon, Wonju as non-fluoridated areas were chosen for the study. We established a database of hip fracture hospitalization episode based on the claims data submitted to the Health Insurance Review Agency from January 1995 to December 2002. The hip fracture hospitalization episodes that satisfied the conditions were those that occurred in patients over 65 years old, the injuries had a hip fracture code (ICD-9 820, ICD-10 S72) and the patients were hospitalized for at least 7days. A total of 80,558 cases of hip fracture hospitalization episodes were analyzed.

RESULTS

The admission rates for hip fracture increased with the age of the men and women in both a fluoridated city and the non-fluoridated cities (p<0.01). The relative risk of hip fracture increased significantly both for men and women as their age increased. However, any difference in the hip fracture admission rates was not consistently observed between the fluoridated city and the nonfluoridated cities.

CONCLUSIONS

We cannot conclude that fluoridation of drinking water increases the risk of hip fracture in the elderly.

Osteoporosis: the role of micronutrients

Osteoporosis and low bone mass are currently estimated to be a major public health threat. Adequate nutrition plays a major role in the prevention and treatment of osteoporosis; the micronutrients of greatest importance are calcium and vitamin D. Calcium has been shown to have beneficial effects on bone mass at all ages, although the results are not always consistent. Higher doses than the current US recommendation (600 IU) of vitamin D in the elderly (age > or = 65 y) may actually be required for optimal bone health (800-1000 IU/d). The elderly can clearly benefit from increased vitamin D intakes; however, the potential importance of vitamin D in peak bone mass is just being investigated. Vitamin D has been related to falls, with supplementation reducing the number of falls. There are clear fracture benefits demonstrated in randomized clinical trials of calcium and vitamin D supplementation. The other micronutrient needs for optimizing bone health can be easily met by a healthy diet that is high in fruits and vegetables to ensure adequate intakes for magnesium, potassium, vitamin C, vitamin K, and other potentially important nutrients. Healthcare professionals need to be aware of the importance of adequate calcium and vitamin D intakes (easily monitored by serum 25(OH)D) for optimal bone health, as well as the prevention of falls and fractures. In addition, a healthy diet that includes 5 servings a day of fruits and vegetables should optimize the intake of micronutrients required for bone health.

Calcium, vitamin D, and nutrition in elderly adults

The nutritional needs for optimizing bone health easily can be met by a diet that is high in fruits and vegetables (five or more servings/day), adequate in protein but moderate in animal protein, and with adequate calcium and vitamin D intakes through the consumption of low fat dairy or calcium-fortified foods. Foods are a preferred source to maintaining calcium balance because there are other essential nutrients that are found in high-calcium foods. For those individuals in whom there is inadequate calcium intake from diet, supplemental calcium can be used. Supplemental or dietary calcium should be spread out throughout the day, with 500 mg or less being consumed at each meal to optimize absorption. In all individuals older than 70 years, vitamin D intakes of at least 600 IU per day (up to 1000 IU/day) are recommended, in addition to the calcium requirement of 1200 mg per day. Vitamin D from foods, supplements, and/or multivitamins can be used to meet the vitamin D requirement. In frail elderly individuals with malabsorption and alcoholics, there may be a need to supplement magnesium. Some elderly individuals with indications of poor nutritional status (low albumin levels) or after hip fracture might benefit from protein supplementation and a multivitamin to ensure adequacy of other nutrients.

Practitioner's guide to fluoride

The current health care trend is to provide evidence-based recommendations and treatment. Many literature reviews have shown fluoride's effectiveness against caries. The current use of fluoride in the prevention of dental caries is based on community, professional, and individual strategies. Personalized fluoride regimens should include a risk analysis and a review of the patient's current fluoride exposure. The future of fluoride may be found in its slow release and retention in the oral cavity through various modalities. Because of the many uncertainties still associated with fluoride, further research is needed.

Water fluoridation, osteoporosis, fractures--recent developments

BACKGROUND

Optimal (1ppm) water fluoridation is seen as the most socially equitable way to prevent dental caries, however concerns about the safety of fluoridation are periodically raised.

METHODS

Research on effects on bone published since the 1991 National Health and Medical Research Council report on water fluoridation was reviewed.

RESULTS

Thirty-three studies were identified. Adverse effects in animal feeding studies were only seen at doses much greater than those currently used in artificial water fluoridation. The majority of animal studies showed no effect or a beneficial effect of low fluoride doses. The results of ecological studies were conflicting. One of the two cohort studies showed an increase in fracture incidence at fluoride levels four times greater than optimal water fluoridation and the other showed no effect after 20 years' optimal fluoridation. The cross-sectional studies showed a favourable effect on bone mineral density. The clinical trials predominantly showed increased bone density in several sites associated with fluoride treatment of 9-22.6mg fluoride per day for one-four years.

CONCLUSION

These studies provide a substantial body of evidence that fluoride at up to 1ppm does not have an adverse effect on bone strength, bone mineral density or fracture incidence.

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.

Bone-fracture incidence rate in two Italian regions with different fluoride concentration levels in drinking water

The effect of the fluoride concentration in drinking water on the prevention of fractures related to osteoporosis has been questioned or contradicted in several recent studies. These studies have been mostly performed using water with artificially added fluoride, at the optimum level of about 1 mg/l. In the present study authors have investigated the effect of equal or greater fluoride concentrations (mean 1.45 mg/l) naturally present in waters supplied for human consumption to a population of 72.756 (Bracciano county), in comparison with a population of 126.189 (Avezzano county), supplied with low fluoride concentration water (mean 0.05 mg/l). The incidence of fractures in the years 1990 and 1991 was evaluated in the two areas (Bracciano and Avezzano), which are located in central Italy and where population have a similar life style, economic and social level and employment structure. The incidence data were obtained from the registers of the public hospital taken as a reference in each district. The authors noticed a significantly greater rate of fracture incidence at several parts of the body, in particular femur fractures (relative risks for males 4.28 and for females 2.64), in the population of the district of Avezzano than in the population of Bracciano. The greater concentration of fluoride in waters distributed for human consumption in Bracciano district seems to have the effect of protecting its inhabitants against fractures.

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.

The effect of water fluoridation on the bone mineral density of young women

INTRODUCTION

Osteogenic effects of therapeutic fluoride have been reported; however, the impact of exposure to low level water fluoridation on bone density is not clear. We investigated the effect of long-term exposure to fluoridated water from growth to young adulthood on bone mineral density (BMD).

METHODS

BMD was measured in 24 healthy women from Regina (fluoride 0.1 mg/L) and 33 from Saskatoon (fluoride 1.0 mg/L), with no differences between groups for height, weight, lifestyle or dietary factors.

RESULTS

Saskatoon women had significantly higher mean BMD at total anterior-posterior lumbar spine (APS) and estimated volumetric 1.3 (VLS), with no difference at total body (TB) or proximal femur (PF).

CONCLUSION

Exposure to water fluoridation during the growing years may have a positive impact on axial spine bone density in young women.

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.

New, or biased, evidence on water fluoridation?

The recent review, 'New evidence on fluoridation', by Diesendorf, Colquhoun, Spittle, Everingham and Clutterbuck (Aust N Z J Public Health 1997; 21: 187-90) claims a consistent pattern of evidence pointing to fluoride damaging bone, a negligible benefit in dental caries reduction from ingested fluoride, and any small benefit from fluoride coming from the action of fluoride at the tooth surface. Public health authorities are allegedly reluctant to pursue such evidence. In the interest of scholarly debate, invited by Diesendorf et al., this reaction paper examines six separate areas raised in the original paper: fluoridation and hip fracture; fluoridation and osteosarcomas; pre-eruptive and posteruptive benefits in dental caries reduction; fluoride ingestion; benefit in dental caries reduction for contemporary Australian children; and bias of health authorities and responsible science. Numerous examples of bias in the identification, selection and appraisal of the evidence on water fluoridation presented by Diesendorf et al. are developed. Further, this reaction paper puts forward both studies and appraisal indicating that water fluoridation should continue to be regarded as a safe and effective public health measure.

Salt fluoridation and general health

Salt fluoridation is a systemic form of fluoride supplementation, leaving it to the consumer whether he wants fluoride supplements or not, but thereafter not requiring special dependability for daily compliance. Most German drinking water has low fluoride concentrations. The estimated fluoride intake in German children is between 100 and 300 micrograms/day, and in adults, between 400 and 600 micrograms/day. Male subjects have higher mean intakes than females. From 70 to 90% of the salt intake of 10 to 13.5 g/day in German adults comes from commercially prepared foods. This leaves about 1 to 4 g of salt to be added as table salt at the individual level and to become the source of supplementary fluoride. To increase fluoride intake by at least 500 micrograms/d, and to prevent an additional intake of more than 3000 micrograms/day, it may be necessary to have salt at a fluoride level of around 500 micrograms/g or to include one commercial food to be prepared with fluoridated salt, e.g., bread. A salt fluoride concentration of 250 micrograms/g does not present a risk of dental fluorosis. However, clear recommendations about systemic fluoride supplementation must be given as long as there are fluoride tablets, fluoride-rich mineral waters, and fluoridated table salt available simultaneously. Persons at risk for hypertension from salt consumption require different means of fluoride supplementation. By and large, in areas of low drinking water fluoride, fluoridated table salt has the potential to become a means of systemic supplementation comparable with drinking water fluoridation.

Effects of fluoridated drinking water on bone mass and fractures: the study of osteoporotic fractures

To determine if optimal fluoridation of public water supplies influences bone mass and fractures, we studied 2076 non-black women, all aged > or = 65 years recruited into the Study of Osteoporotic Fractures at the Pittsburgh clinic. Information on fluoride exposure was limited to community water supplies. The variable used in the analysis was years of exposure to fluoridated water in community drinking water supplies. Bone mineral density (BMD) was measured at the spine and hip using dual energy X-ray absorptiometry and at the midpoint and ultradistal radius and calcaneus using single photon absorptiometry. Prevalent and incident vertebral fractures were determined by morphometry. Incident nonspine fractures were ascertained every 4 months and confirmed by radiographic report. Exposure to residential fluoridated water had no effect on bone mass. Women exposed to fluoride for > 20 years had similar axial and appendicular bone mass to women not exposed or women exposed for < or = 20 years. There was some suggestion that women exposed to fluoride for > 20 years had a lower relative risk of nonspine fractures (relative risk, RR, = 0.73; 95% confidence interval [CI] 0.48-1.12), osteoporotic fractures, RR = 0.74 (CI 0.46-1.19), and hip fractures, RR = 0.44 (CI 0.10-1.86), compared with women not exposed, but none of these relative risks was statistically significant. There was no association with wrist or spinal fractures. Our results do not support the findings from recent ecological studies which showed an increased risk of hip fracture among individuals exposed to fluoridated public water.

Dietary factors related to preservation of oral and skeletal bone mass in women

Skeletal bone loss in adults increases the risk of bone fractures and may contribute to the loss of teeth in healthy postmenopausal women. The relationship of skeletal osteopenia to residual ridge resorption is unclear. Low bone mass in women is attributed to heredity, estrogen deficiency, a low lifetime calcium intake, and lack of regular physical activity. A high calcium intake will promote optimal bone growth in youth and decrease the rate of bone loss in the later postmenopausal period. In early menopause, estrogen is the only effective therapy for conserving bone in women. In older women, a high plasma level of vitamin D enhances calcium absorption, whereas high sodium, protein, alcohol, and caffeine intakes will cause increased urinary losses and negative calcium balance. Women who have a low intake of dairy foods may benefit from a refined calcium carbonate supplement that contains vitamin D. This article focuses on the nutritional factors that influence bone health.