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Pathogenesis of Osteoporotic Fracture

Pathogenesis of Osteoporotic Fracture. Pathogenesis of Osteoporotic Fracture. LOW PEAK BONE MASS. LOW PEAK BONE MASS. POSTMENOPAUSAL BONE LOSS. POSTMENOPAUSAL BONE LOSS. AGE-RELATED BONE LOSS. AGE-RELATED BONE LOSS. LOW BONE MASS. LOW BONE MASS. Other Risk Factors. Other

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Pathogenesis of Osteoporotic Fracture

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  1. Pathogenesis of Osteoporotic Fracture Pathogenesis of Osteoporotic Fracture LOW PEAK BONE MASS LOW PEAK BONE MASS POSTMENOPAUSAL BONE LOSS POSTMENOPAUSAL BONE LOSS AGE-RELATED BONE LOSS AGE-RELATED BONE LOSS LOW BONE MASS LOW BONE MASS Other Risk Factors Other Risk Factors Nonskeletal factors (propensity to fall) Nonskeletal factors (propensity to fall) Poor bone quality (architecture) Poor bone quality (architecture) FRACTURE FRACTURE Adapted from Melton LI, Riggs BL, eds. Osteoporosis: Etiology, Diagnosis, and Management. Raven Press, 1988,New York, pp 155-179 Adapted from Melton LI, Riggs BL, eds. Osteoporosis: Etiology, Diagnosis, and Management. Raven Press, 1988,New York, pp 155-179

  2. Objective • To investigate the influence of dietary intake on bone mineral density in women aged 30-39

  3. Design: cross sectional study • Volunteers (n=139) aged 30-39 • Recruitment from: mailing, newspaper, health fairs, fliers, referrals • Exclusions: diseases or medications known to affect BMD; pregnancy; non-white race

  4. Nutrient Intake • Current- for year preceding BMD measurement • Teenage- for ages 13-17 • Nutrients of interest were assessed by modified Block (NCI) FFQ (self administered): • Calcium • Phosphorus • Protein • Vitamin C • Caffeine • Alcohol • Fiber

  5. Food Frequency Questionairre • Self administered- 94 questions; 30 minutes • Original for NCI therefore questions concerned fat, vitamin A etc; (n=35) of these were deleted. • Other foods high in calcium were added (n=23) • Beverage list was expanded to determine caffeine in mg/day (n=15)

  6. Covariates: • Physical measurements: • Height • Weight • Skinfold thickness • Waist circumference • Bioelectric impedence • Grip strength

  7. Covariates: • Interview: • Demographics • Menstrual function • Pregnancy and lactation • Oral contraceptive use • Disease and medication history • Fracture history • Smoking • Physical activity

  8. Outcome: • Bone mineral density by dual x-ray absorptiometry (gm/cm2) • Lumbar Spine (L2-L4) • Hip – femoral neck- trochanter- wards traingle • Forearm- proximal and distal

  9. Multivariate regression analysis • BMD= nutrient+ age + height + weight+ grip strength

  10. Results • Bone mineral density was not related to current intake of: • Caffeine • Vitamin D • Protein • Fiber • Phosphorus

  11. Strengths and Limitations • Dietary interview detailed and planned for 2 time periods • BMD is a reliable measure • Able to control for many confounders • Power 77% to detect r=0.20 • Measurement error • Multicollinearity • Generalizability • Multiple comparisons

  12. Conclusion • A change in calcium intake from 800 to 1200 mg per day will increase hip BMD by approximately 6% • Fiber • Supplemental calcium • Phosphorus (r=0.95 with calcium) • Protein (r=0.84 with calcium) • Alcohol

  13. Calcium and BMD • Strength: moderate r~0.2 • Probably stronger due to RME of dietary calcium • Teenage intake • Specificity • problem in diet due to high nutrient correlations • stronger effect with supplements added • stronger effect after correct for fiber

  14. Calcium and BMD • Temporality • Problem with design • BMD now diet in past year or teenage • Biological Plausability • 30% of bone is calcium • Bone calcium maintains serum calcium • Greater amount of calcium in cortical bone where stronger effect is observed • Consistency

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