Aging of the Skeletal System Mindy Millard-Stafford, Ph.D. February 5, 1998 Chapter 9- DiGiovanna Underlying question- Aging vs. disuse, abuse?

Age (yrs) Bone Mineral Density (BMD) Females Males 30 70

BONE Growth Factors Genetics Hormones Nutrition Alcohol Exercise/loading Smoking Medications

Fragility Bone fracture Low Ca +2 Reduced Bone Mass Excessive loss Low intake Poor absorption Fatigue stress Poor architecture other heredity Low Ca +2 intake Estrogen deficiency Inactivity stability fallsForce Environmental hazards

I. Bone composition changes A. Bone cells, marrow (few changes known) B. Bone matrix change 1. Mineralization - more brittle, breakable 2. Quantity of matrix 3. Trabeculae thin, weaken - first to be lost 4. Cortical bone - differential loss ( after 45 yrs)

Age (yrs) Bone mass % Trabecular Compact MENOPAUSE

C. Bone cells?- repair of fractures maintained - old osteons remain, new ones appear, fusion points (weakness) - new osteons fail to fill old space, gaps weaken matrix

D. Effects of menopause 1. Increases rate of loss in women - ~ yrs, estrogen % trabecular loss 10 yr post menopausal % cortical loss - elder women have 1/2 BMC of that in their 20s

E. Variability in bone loss 1. Trabecular earlier, faster than cortical 2. Some anatomical sites more susceptible - vertebral crush fractures (mostly trabecular bone) - Colles fracture - femoral neck (hip fracture)

F. Health implications 1. Weakening results in greater risk for fracture when large force applied 2. Hip fracture most debilitating - prolonged immobility blood clots, pneumonia, bedsores immobility reduces matrix further

II. Aging problems of skeleton/joints A. Osteopenia- routine loss of bone ( all individuals) B. Osteoporosis- “bones with pores” 1. postmenopausal (type I) - trabecular bone sites 2. senile (type II)- cortical bone C. Osteoarthritis

D. Osteoporosis- 1. >24 million cases - 80% women - 60% of all women over 60 yrs 2. Results in > 1 million fractures 50% vertebral crush 25% femoral neck

3. Screening for low BMD - use of dual-energy xray absorptiometry (DXA) - scan the spine (L2-L4), Ward’s triangle (femur)

4. Potential Effects - vertebral crush fracture mobility, stature, Dowager’s hump posture breathing,circulation - hip fractures (1/3 women by 90 yr) 12-15% die of complications

E. Osteoarthritis 1. cartilage breaks down in joint, resulting in “bone on bone” - most common type of arthritis - most common disease of elderly (second to CHD for Dr. visit) - different etiology from rheumatoid arthritis (RA)

2. Physiological effects: - osteophyte formation - reduced range of motion - synovial membrane thick, stiff - swelling,pain 3. Treatment - anti-inflammatory drugs, joint replacement,

F. Rheumatoid arthritis 1. Lower frequency than OA 2. Autoimmune disease - cartilage pannus 3. Pain, immobility in joints (extremities) but also damage to other fibrous connective tissue 4. Treatment - similar to OA, no cure/ prevention

Class activity: 1.Total the # of Yes responses in Osteoporosis screening for yourself 2. Determine the average score for the entire class 3. Determine the average score for males, and females

III. Prevention of bone loss A. Build the maximum BMC before age 30 - Physical activity (weight bearing) - Adequate calcium intake (1000 mg/d pre-menopausal 1500mg/d post menopausal) - Adequate Estrogen - Avoid excess alcohol

- Avoid smoking - Avoid excess caffeine B. Reduce bone mass loss after 30 - Exercise

Age (yrs) Bone Mineral Density (BMD) Females Males exercise

B. Reduce bone mass loss after 30 - All of the above plus: HRT Fosamax use of Calcium carbonate antacid limit corticosteroid treatment avoid excess protein, insoluble fiber

C. Avoid injury (falls) - strengthen muscles - improve neuromuscular facilitation, flexibility - architectural considerations osteoarthritis prevented with surgical repair of torn ligaments (physical therapy, maintain strength)

Age related changes affecting musculoskeletal system & strength changeresult joint stiffness arc of motion connective tissue flexibility muscle mass strength activity (disease) disuse atrophy appetite/food intake fatigability

Age related changes (cont’d) changeresult proprioception impaired balance motor neurons strength/coordination atrophy Type II fibers strength, power motivation to move more disuse atrophy