Objective: To determine whether fluoridation influences bone mineral density and fractures in older women. Design: Multicentre prospective study on risk factors for osteoporosis and fractures. Setting: Four community based centres in the United States. Participants: 9704 ambulatory women without bilateral hip replacements enrolled during 1986-8; 7129 provided information on exposure to fluoride. Main outcome measures: Bone mineral density of the lumbar spine, proximal femur, radius, and calcaneus plus incident fractures (fractures that occurred during the study) of vertebrae, hip, wrist, and humerus. Results: Women were classified as exposed or not exposed or having unknown exposure to fluoride for each year from 1950 to 1994. Outcomes were compared in women with continuous exposure to fluoridated water for the past 20 years (n = 3218) and women with no exposure during the past 20 years (n = 2563). In women with continuous exposure mean bone mineral density was 2.6% higher at the femoral neck (0.017 g/cm2, P < 0.001), 2.5% higher at the lumbar spine (0.022 g/cm2, P < 0.001), and 1.9% lower at the distal radius (0.007 g/cm2, P = 0.002). In women with continuous exposure the multivariable adjusted risk of hip fracture was slightly reduced (risk ratio 0.69, 95% confidence interval 0.50 to 0.96, P = 0.028) as was the risk of vertebral fracture (0.73, 0.55 to 0.97, P = 0.033). There was a non-significant trend toward an increased risk of wrist fracture (1.32, 1.00 to 1.71, P = 0.051) and no difference in risk of humerus fracture (0.85, 0.58 to 1.23, P = 0.378). Conclusions: Long term exposure to fluoridated drinking water does not increase the risk of fracture.
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