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Unformatted text preview: Chapter 10: PA and Osteoporosis Cross-sections of normal and osteoporotic bone- bone constantly remodelling in a breakdown-build-up process- osteoclasts break down bone and osteoblasts lay down new bone- osteoblasts rebuild by forming new bone cells from collagen to make an osteoid matrix matrix provides infrastructure for the mineralization of bone, and gives bone its mechanical, elastic, and tensile strength- bone mineral density depends on the balance of osteoclasts and osteoblasts “Porous Bone” – abnormally low bone mass and microstructural deterioration of bone tissue that leads to brittle bones and increased risk of fractures – osteopenia: BMD between 1 and 2.5 SD below young adults direct risk factor for osteoporosis – WHO Osteoporosis: – Bone mineral density (BMD) more than 2.5 SD below the average in young adults – Can’t withstand normal physical activities – Nontraumatic fractures – Physical inactivity a risk factor – PA contributes to peak bone mass during youth and young adulthood, retards bone loss with aging, and can help reduce the risks of osteoporotic fractures – Normal BMD within 1SD of the mean of a young adult – Osteopenia BMD between 1.0 and 2.5 SD of the mean – Osteoporosis BMD of 2.5+ SD of the mean – Severe osteoporosis osteoporosis with one or more fragility fractures – Each 0.5 SD decrease = 50-100% ⇑ risk of fracture – 1.0 SD at femur neck (hip) = 300% ⇑ risk of hip fracture – Direct cost of treating osteoporotic fractures: $17 billion/y for proximal femur, radius, & vertebrae – Woman’s lifetime risk of hip fracture is equal to her combined risk of breast, uterine, and ovarian cancer – ~ 1/5 patients who fracture a hip, most after age 75, dies in the year following the fracture, and 50% of the survivors become dependent on others for care Magnitude of the Problem (USA) – 10 million diagnosed osteoporosis – 80% women – ≥ 50 y old: – Bone mass is generally lowest among women who are white or Asian, thin framed, and sedentary – 44 million estimated w/osteoporosis or osteopenia • Expected to rise in nations w/increasing life expectancy (Dishman fig 10.1) – Women & race: osteoporosis • African American: 5% (35% w/osteoporosis) – Higher bone mass in Black, overweight, or obese • Latina: 10% (49% w/osteopenia) • non-Hispanic White or Asian descent: 20% Fractures and Mortality – 1.5 million fractures in USA per year – Osteoporosis-related fracture in lifetime • 1/2 of USA women ≥ 50 y; 1/8 of USA men ≥ 50 y – Hip fracture • North America & Europe: Increasing incidence (even if corrected for age of pop) • Greater ⇑ expected in Asia & Latin America by 2050 • 1/5 → dead within 1 y (men 2x mortality) • 1/2 → physically dependent • Women: 17.5% lifetime risk = combined breast, uterine, ovarian; Men: 6.0% lifetime risk N orm al B o ne O steo porotic B o ne C r o s s - s e c t io n s o f n o r m a l a n d o s t e o p o r o t ic b o n e...
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This note was uploaded on 08/13/2008 for the course EDKP 330 taught by Professor Koziris during the Fall '07 term at McGill.
- Fall '07