Pathogenesis of Osteoporotic FracturePathogenesis of Osteoporotic Fracture

LOW PEAKBONE MASSLOW PEAKBONE MASS

POSTMENOPAUSALBONE LOSS

POSTMENOPAUSALBONE LOSS

AGE-RELATEDBONE LOSS

AGE-RELATEDBONE LOSS

LOW BONEMASS

LOW BONEMASS

OtherRisk Factors

OtherRisk Factors

FRACTUREFRACTURE Poor bone quality(architecture)

Poor bone quality(architecture)

Nonskeletal factors(propensity to fall)Nonskeletal factors(propensity to fall)

Adapted from Melton LI, Riggs BL, eds. Osteoporosis: Etiology, Diagnosis, and Management. Raven Press, 1988,New York, pp 155-179Adapted from Melton LI, Riggs BL, eds. Osteoporosis: Etiology, Diagnosis, and Management. Raven Press, 1988,New York, pp 155-179

Pathogenesis of Osteoporotic FracturePathogenesis of Osteoporotic Fracture

LOW PEAKBONE MASSLOW PEAKBONE MASS

POSTMENOPAUSALBONE LOSS

POSTMENOPAUSALBONE LOSS

AGE-RELATEDBONE LOSS

AGE-RELATEDBONE LOSS

LOW BONEMASS

LOW BONEMASS

OtherRisk Factors

OtherRisk Factors

FRACTUREFRACTURE Poor bone quality(architecture)

Poor bone quality(architecture)

Nonskeletal factors(propensity to fall)Nonskeletal factors(propensity to fall)

Adapted from Melton LI, Riggs BL, eds. Osteoporosis: Etiology, Diagnosis, and Management. Raven Press, 1988,New York, pp 155-179Adapted from Melton LI, Riggs BL, eds. Osteoporosis: Etiology, Diagnosis, and Management. Raven Press, 1988,New York, pp 155-179

Objective

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

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

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

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)

Covariates:

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

Covariates:

• Interview:– Demographics

– Menstrual function

– Pregnancy and lactation

– Oral contraceptive use

– Disease and medication history

– Fracture history

– Smoking

– Physical activity

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

Multivariate regression analysis

• BMD= nutrient+ age + height + weight+ grip strength

Results

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

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

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

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

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