Water fluoridation and osteoporotic hip fracture

Hillier, Sharon Lee (1998) Water fluoridation and osteoporotic hip fracture. University of Southampton, Doctoral Thesis.

Abstract

Ecological studies suggest a positive association between water fluoridation and hip fracture incidence. However, few studies have been performed to relate water fluoride content to hip fracture risk in individuals. This issue was addressed in a case-control study of hip fracture.

The study was located in the county of Cleveland, comprising three districts: Hartlepool (natural fluoride 1-2ppm) Middlesbrough and Stockton (fluoride 0.15ppm). In each district all patients aged 50 years and over who had sustained a fracture of the proximal femur and able to pass a mental test score were interviewed. Controls were selected from general practice listings for the county. Information on risk factors was obtained using a structured questionnaire. Cumulative exposure to fluoride in water was estimated from a residential history, and data on fluoride content of water supplied by local water companies. Excised femoral heads were collected from cases who had undergone surgery. The fluoride content of the bones were ascertained and used as a biological marker for fluoride exposure.

The study comprised 424 cases and 281 controls. Independent risk factors for hip fracture included body mass index (OR 3.1, 95% CI 2.0 - 4.8, lowest v. highest third of distribution); recent physical inactivity (OR 6.3, 95% CI 3.8 - 10.5); diagnosis of rheumatoid arthritis (OR 2.3 95% CI 1.1 -5.1) and age at menarche (OR 1.8 95% CI 1.1 - 3.0, 15 years or older v. 13 years or younger). After adjusting for age, sex and these variables, there was no increase risk of hip fracture associated with lifetime exposure to fluoride in water (OR 0.6, 95% CI 0.4 -1.0). Water fluoride was associated with higher fluoride in the femoral heads.

In conclusion, no increase in the risk of hip fracture was observed with water fluoride at levels of up to 2 ppm.

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