Pathogenesis of Osteoporotic Fracture

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Pathogenesis of Osteoporotic Fracture
Pathogenesis of Osteoporotic Fracture
LOW PEAK BONE MASS
POSTMENOPAUSAL BONE LOSS
AGE-RELATED BONE LOSS
LOW PEAK BONE MASS
POSTMENOPAUSAL BONE LOSS
AGE-RELATED BONE LOSS
LOW BONE MASS
Other Risk Factors
LOW BONE MASS
Other Risk Factors
Poor bone quality (architecture)
Nonskeletal factors (propensity to fall)
Poor bone quality (architecture)
Nonskeletal factors (propensity to fall)
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
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Objective

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

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Design cross sectional study

• Volunteers (n139) aged 30-39
• Recruitment from mailing, newspaper, health
  fairs, fliers, referrals
• Exclusions diseases or medications known to
  affect BMD pregnancy non-white race

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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

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Food Frequency Questionairre

• Self administered- 94 questions 30 minutes
• Original for NCI therefore questions concerned
  fat, vitamin A etc (n35) of these were deleted.
• Other foods high in calcium were added (n23)
• Beverage list was expanded to determine caffeine
  in mg/day (n15)

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Covariates

• Physical measurements
• Height
• Weight
• Skinfold thickness
• Waist circumference
• Bioelectric impedence
• Grip strength

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Covariates

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

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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

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Multivariate regression analysis

• BMD nutrient age height weight grip
  strength

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Results

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

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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 r0.20
• Measurement error
• Multicollinearity
• Generalizability
• Multiple comparisons

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Conclusion

• A change in calcium intake from 800 to 1200 mg
  per day will increase hip BMD by approximately 6
• Fiber
• Supplemental calcium
• Phosphorus (r0.95 with calcium)
• Protein (r0.84 with calcium)
• Alcohol

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Calcium and BMD

• Strength moderate r0.2
• 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

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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