Physiology of Aging

1. Physiology of Aging Min H. Huang, PT, PhD, NCS

2. Reading assignments • Guccione: Ch 3, Ch 7 (pp. 104-113 only), (Ch 15, pp. 272-278 prn)

3. Learning objectives • Identify and interpret physiologic changes that occur with aging. • Adapt physical therapy management to address age-related and life-style related declines in physiological systems.

4. A geriatric client at ICU 73-year-old, active woman with a past history of hypertension and atrial fibrillation. She underwent a routine cardioversion for atrial fibrillation but developed multiple complications, including sepsis and respiratory failure. The patient spent 3 weeks of limited activity in the ICU and was transferred to long-term acute care hospital.

5. Questions to consider • What is your assumption about this patient’s expected outcomes? • How might your personal biases/assumptions affect your interview with this patient? • How might your knowledge of age-related declines in physiological systems affect your clinical decision making?

6. Overview of aged-related physiological changes

7. Ropper 2009 (in Adams and Victor’s)

8. Age-Related Changes in Body Composition/Metabolism

9. Age-Related Changes in Body Composition/Metabolism • Most of the fat increase occurs inside the peritoneum • Fat significantly contribute to increased whole body inflammation, age-related declines, and diseases • Exercise increases metabolic rate and can burn fat as energy sources

10. Age-Related Changes in Body composition/Metabolism • Decreases • Lean body mass • Strength ↓ about 8% per decade after 30 y.o, not linear but slow in the beginning and accelerates as age • Healthy 80-90 y.o. have shown 20-40% ↓ n in max isometric force • Increases • Fat Mass (contributes to strength and mobility limitations) • LDL cholesterol

11. Sarcopenia vs. Cachexia Sarcopenia Cachexia Muscles will NOT respond to exercises Complex pathophysiology including changes in body metabolism Ongoing loss of muscle loss, loss of nutrition, caused by negative balance between protein and energy. • Age-related loss of muscle mass; decreased muscle strength and rate of force production • Amenable to change • Strengthening exercise can significantly ↑ muscle mass and strength • Contribute to the decline in functional ability and frailty

12. Cachexia “… a multifactorial syndrome defined by an ongoing loss of skeletal muscle mass (with or without loss of fat mass) that cannot be fully reversed by conventional nutritional support and lead to progressive functional impairment..………. pathophysiology is characterized by a negative protein and energy balance driven by ↓food intake and abnormal metabolism.” Fearon, 2011

13. Stage of Cachexia Fearon, 2011

14. Age-Related Changes in Skeletal Tissue • Basic metabolic unit (BMU) • Osteoclast, osteoblast, osteocyte • Aging • ↑ bone breakdown rate (osteoclast activity) • ↓ bone accretion rate (osteoblast activity) • Decline in bone mineral with age • Begins in the 3rd decade at a rate 0.5% to 1% yearly • ~ 2% yearly for the 5-year peri- and menopausal era

15. Non-modifiable risk factors for bone loss • Modifiable risk factors for bone loss

16. Hip Fracture: How big is the problem in people age 65+ years? • In 2007, 281,000 hospital admissions for hip fractures • Over 90% of hip fractures are caused by falling, most often by falling sideways • In 1990, it was estimated that by 2040, the number of hip fractures would exceed 500,000, although the rate of hip fracture has in fact, declined in recent years. • In 1991, Medicare costs for hip fractures were estimated to be $2.9 billion.

17. Age-Related Changes in Collagenous Tissues and Clinical Consequences

18. Age-Related Changes in Cardiovascular Tissues and Clinical Consequences

19. Age-Related Changes in Nervous System and Clinical Consequences

20. Age-Related Changes in Immune System and Clinical Consequences

21. Age-Related Changes in Hormonal Axis • Loss of sex hormones with age ↓ muscle mass and muscle strength • Testosterone levels gradually decline at ~ 1% a year after age 30. By about age 70, the decrease can be as much as 50%. • Testosterone replacement in men ↑ lean muscle mass, but resistance exercise + testosterone replacement is required to ↑ muscle strength

22. Age-Related Changes in Hormonal Axis • Estrogen replacement in women ↑ in strength and lean mass in postmenopausal women • Findings from the Women’s Health Initiative (WHI), a 15-year study launched in 1991 • Hormone medication (whether estrogen + progestin or estrogen only) resulted in an increased risk of stroke and blood clots • Estrogen + progestin resulted in an increased risk of heart attack and breast cancer http://nccam.nih.gov/health/menopause/menopausesymptoms#hed1

23. Estrogen Loss and Manifestationsof Health Risks Over Time

24. Menopause Is Associated With anAccelerated Loss of Bone Mass • Decreased cortical thickness is associated with hip fracture

25. After adjustment for age and race, the women not using Hormone Therapy in the previous year had a 55% increased risk of hip fracture http://www.medscape.com/viewarticle/752892_3

26. Age-related changes in sensorimotor and nervous system

27. http://www.youtube.com/watch?v=HmuBnYVh6xE

28. Neuro-ophthalmologic Signs • Progressive smallness of pupils • Decreased reactions to light and accommodation • Far-sightedness (hyperopia or presbyopia) • Insufficiency of convergence (problem with focus and depth perception) • Restricted range of upward conjugate gaze • Diminished dark adaptation • Increased sensitivity to glare

29. Age-Related Visual Changes • Visual acuity & field decrease with aging • Increased difficulty seeing blues & greens • Spatial visual changes occur making it difficulty to see slow moving objects • Changes with accommodation, contrast, & depth perception • Control of smooth pursuits and saccade is decreased

30. Problems in Vision • Glaucoma (98% blindness preventable) • Peripheral vision lost 1st then central • Cataracts: opacity of the lens • Medicare: #1 surgery • Central vision lost 1st • Sunglasses for prevention • Macular Degeneration • Risk increases with age 28% those older than 75 • Central vision primarily affected • Quality of life with reading, tv, sewing

31. What is this an example of? J. Blackwood

32. J. Blackwood

33. What is this? J. Blackwood

34. Other areas of visual loss • Diabetic retinopathy • Retinal detachment • Legal blindness J. Blackwood

35. PT Considerations in Visual Deficits Associated with Aging • Adaptation of HEP instructions • PT gym/room, hallways with deco • Patterns of flooring • Safety in environment, provide adequate light • Use of contrasting colors for safety • Avoid abrupt changes in light, nightlights • Large print, low vision aids, assistance both verbal and tactile J. Blackwood

36. Hearing Loss with Aging • May be masked as dementia • More loss with high tones • Peripheral hearing loss (conduction hearing loss) • Sensorineural loss • Presbycusis • decrease in auditory acuity resulting from degenerative changes in the inner ear with age (a reduction of the number of hair cells) • Tinnitus J. Blackwood

37. Communication Aids • Hearing aids, amplification devices • Written word • What PTs can do • Be sure to have the Pt’s attention • Place yourself between 2-3 feet in front of the Pt • Speak slowly & clearly. Do NOT shout. • Talk naturally with a slower pace & more pauses • Lower the pitch of your voice • Avoid background noise • Write

38. Vestibular System Changes • Disequilibrium and dizziness • Hair cell receptors decline begins at age 30 • 20% decrease in hair cells of saccule and utricle • 40% decrease in hair cells of semicircular canals • Vestibular receptor ganglion cells decrease by age 55-60

39. PNS Sensory System Changes with Aging • Decreased number of unmyelinated and myelinated nerve fibers • Blood vessels become atherosclerotic • Loss of blood supply to nerve fibers • Major factor of the increased prevalence of peripheral neuropathies with age • Sensory conduction velocity slows by 2–4 m/s after age of 20 years

40. Impairment or Loss of Vibratory Sense in the Toes and Ankles • Proprioception impaired very little or not at all • ↑ thresholds for the perception of cutaneous stimuli such as touch, tactile sensitivity • requires refined methods of testing for detection (e.g. monofilament, 128 Hz tuning fork) • Sensory changes correlate with • loss of sensory fibers on sural nerve biopsy • ↓amplitude of sensory nerve action potentials • loss of dorsal root ganglion cells

41. Motor Signs • ↓ speed and amount of motor activity • Slowed reaction time • Impaired fine coordination and agility • ↓ muscular power • legs more than arms • proximal muscles more than distal ones • Thinness of muscles • particularly the dorsal interossei, thenar, anterior tibial muscles, due to a progressive ↓ in the # of anterior horn cells

42. Changes in Tendon Reflexes • ↓ Ankle DTR compared to Knee DTR in persons >70+ years • Loss of Achilles DTR in people >80+ years • +Palmomental reflexes in ~50% people >60+ years • An involuntary contraction of the mentalis muscle of the chin caused by stimulation of the thenar eminence. • Its presence may suggest cerebral pathology • ? sensitivity and specificity

43. Effects of Aging on Stance and Gait • Motor agility begins to decline by the 3rd decade • decrease in neuromuscular control • Changes in joints and other structures • Gait with normal aging • Steps shorten • Slower • Stooping • More cautious • Habitually touches (relaying on sensory cues)

44. Differential Diagnosis of Gait Abnormalities • Abnormal gait patterns associated with degenerative disease of the brain are mostly accompanied by mental changes • e.g. frontal lobe–basal ganglionic degeneration, normal-pressure hydrocephalus • Other neurologic symptoms and signs present

45. Effects of Aging Other Motor Impairments • Urinary incontinence • Compulsive, repetitive movements • Mouthing, stereotyped grimacing, protrusion of the tongue, side-to-side or to-and-fro tremor of the head • Odd vocalizations (sniffing, snorting, and bleating) • Some of these may resemble tics but they are not really voluntary • ↓ forward trunk angular displacement during stand to sit • Increased risk of anterior disequilibrium Dubost 2005

46. PNS Motor System Changes with Aging • Loss of αMN • remaining αMN will innervate the muscle cells • remaining MU become larger which can reduce motor coordination for finely tuned movements • Signs of reinnervation • space between nodes in myelin was reduced • ↓ in the NCV • Motor conduction slows by 0.4–1.7 m/s per decade after 20 years (sensory by 2–4 m/s)

47. PNS Changes with Aging • Wallerian degeneration is delayed • Regeneration takes longer because secretion of trophic factors is slower than in younger adults • Density of regenerated neurons is reduced • Less collateral sprouting

48. ANS Changes with Aging • Sympathetic control of dermal vasculature is reduced, resulting in reduced wound repair efficiency • In aging animal models, TENS improved vascular response through increasing activity of sympathetic nerves

50. Benign Senescent Forgetfulness • Other terms • age-associated memory impairment (AAMI) • minimal cognitive impairment • Worsens very little or not at all over years • Does not interfere significantly with work or ADL