Lecture 24: Ageing and Musculoskeletal Health

AGEING AND MUSCULOSKELETAL HEALTH LECTURE 24 Mrs. B, an 80-year old women tripped and break her right hip while attempting to go to the bathroom in the middle of the night. Prior to this episode, she had been living alone and spent most of her days watching TV. She has a prior history of hip...

AGEING AND MUSCULOSKELETAL HEALTH LECTURE 24 Mrs. B, an 80-year old women tripped and break her right hip while attempting to go to the bathroom in the middle of the night. Prior to this episode, she had been living alone and spent most of her days watching TV. She has a prior history of hip fracture 20 years ago when she slipped on ice. She is unaware of any family history. She last presented 6 months ago when she had a fall at home. 1) What risk factor does she have for osteoporosis? 2) What measurements should the doctor perform? 3) What needs to be prescribed?  Changing Bone Density with Aging Osteopenia Low bone mineral density but not yet osteoporosis Osteoporosis Low bone mineral density microarchitectural deterioration of bone tissue ↑ skeletal fragility ↑ fracture susceptibility Osteoporosis = significant cause of morbidity and mortality  Osteoporosis – Etiology Bone is being constantly remodeled: Bone reabsorbed by osteoclasts New bone deposited by osteoblasts Disrupt old bone tissue Produce new bone tissue Imbalance between bone resorption and bone formation Osteoporosis – Etiology Inadequate peak bone mass (20-30 yrs) Estrogen suppresses osteoclast bone resorption Lack of estrogen = bone resorption > bone deposition How will you make the diagnosis? DXA scan (dual energy x-ray absorptiometry) 3 compartment model Bone mineral density Lean body mass Fat mass T-Score Diagnosis: (2.5 S.D. below comparison group) Comparison group: 20 yr old sex-matched healthy adult Vitamin D and Bone Health What may be the reasons related to this age group? - ↓ Intake - ↓ Time outside, institutionalized - ↓ Intestinal absorption Vitamin D and Bone Health ↓ in precursor 25 hydroxyvitamin D Who is at risk? - Non-Modifiable Factors  Advanced age  Female  European and Asian ancestry  Family history for fracture  Previous fracture > 2x  Rheumatoid arthritis  Gastrointestinal disorders: Crohn’s, Celiac, gastrectomy, severe liver disease Medications Glucocorticoids = ↑ bone resorption, ↓ bone formation Proton pump inhibitors= ↓ calcium absorption Who is at risk? – Modifiable Factors Tobacco smoking inhibits the activity of osteoblasts Low BMI being overweight protects by increasing load on bone Alcoholism can inhibit Ca absorption; liver disease can interfere with Vit D activation contain phosphoric acid Soft drink displacement of Ca containing drinks (i.e. milk) from the diet. Who is at risk? – Modifiable Factors bedrest with decrease bone Insufficient activity mass Physical activity (weight bearing) increase bone mass by 1-2% Physical fitness in later life = decreased risk of falling constant damaging insult to Excessive exercise bone which can cause exhaustion to structural elements Marathon runners develop severe osteoporosis later in life Who is at risk? – Modifiable ↓ Serum 25-OH vit D (< 20 ng/mL) ↓ Calcium intake RDA for Calcium 51-70 yr: 1000 mg/d for men, 1200 mg/d for women >70 yr: 1000 mg/d for men, 1200 mg/d for women Calcium should be taken throughout day since we only absorb 500 mg at a time  Osteoporosis - Treatment Bisphosphonates are predominately prescribed How do they work?  Preferentially bind calcium, forming strong bonds with bone mineral  Prevent bone resorption and increase bone formation for about a year (then bone formation plateau)  Increased bone mineralization resulting in stronger bone and a continued increase in bone mineral density Side Effects: GI reflux prevents usage Mrs. B, an 80 year old women tripped and break her right hip while attempting to go to the bathroom in the middle of the night. Prior to this episode, she had been living alone and spent most of her days watching TV. She has a prior history of hip fracture 20 years ago when she slipped on ice. She is unaware of any family history. She last presented 6 months ago when she had a fall at home. 1) What risk factor does she have for osteoporosis? 2) What measurements should the doctor perform? 3) What needs to be prescribed? Sarcopenia Age-associated ↓ in skeletal muscle mass and strength Appendicular muscle mass ≥ 2 standard deviations below the mean for young healthy adults (DXA scan) Sarcopenia Prevalence of Sarcopenia: % of population Men, 70 y 52.6 – 57.6 % Women, 70 y 43.2 – 60.0 %  Most powerful risk factor for frailty, loss of independence, and disability in older subjects.  Highly predictive of incident disability and all-cause mortality in advanced age. Sarcopenia – Etiology Causes - poorly understood Occurs independent of high activity May be attributed to:  Denervation of motor units  Net conversion of fast type II muscle fibers into slow type I fibers - Type I fiber: oxidative, aerobic exercise - Type II fiber: glycolytic, explosive exercises - II  I fiber: loss in muscle power  Lack of Physical Activity – intensity and load bearing  Sarcopenia - Prevention Resistance training (RT) Most powerful countermeasure 2 wks RT Positive influence on the Muscle protein neuromuscular system, hormone synthesis concentrations, and protein synthesis rates Studies: Increased protein Muscle protein synthesis synthesis rates with as little as 2 wks of RT in adults 76-92 yr ol Pre Post Older adults can grow muscle and synthesize muscle protein if given intense enough RT! Obesity in Older Adults – Sarcopenic Obesity Prevalence of older adults with sarcopenia and obesity ↓ RMR ↓ Physical activity Sarcopenia ↑ inflammatory cytokines Obesity ↓ Muscle mass Accelerated loss of ↑ Fat mass ↓ BMD muscle mass? ↑ Fat in muscle Frailty Muscle weakness Loss of endurance High muscle mass but ↓ quality Sarcopenic Obesity- Treatments Weight loss?  Exacerbate age-associated declines in FFM? Diet-induced: 75% fat mass, 25% FFM Exercise-induced: 88% fat mass, 12% FFM Exercise?  Improves physical functioning  Doesn’t always lead to large losses of body weight Appropriate treatment controversial