Lecture 22: Biology of Ageing Part I PDF

BIOLOGY OF AGEING PART I LECTURE 22 Learning Objectives  Describe methods to define ageing  Describe physiological changes with ageing What is Aging? Healthy cell Deteriorated cell Leonard Hayflick Cell Senescence What is Aging? Cellular Senescence Process...

BIOLOGY OF AGEING PART I LECTURE 22 Learning Objectives  Describe methods to define ageing  Describe physiological changes with ageing What is Aging? Healthy cell Deteriorated cell Leonard Hayflick Cell Senescence What is Aging? Cellular Senescence Process of accumulative changes to cellular structure that disrupts metabolism with the passage of time, resulting in deterioration What Counts as Old? There is no one age that defines “old”  51-70 yr and >70 yr – DRI category  65yr - Eligibility for Medicare  60 yr - World Health Organization U.S. Census Bureau uses: “young old”: 65-74y “aged”: 75-84y “oldest old”: 85+y So how do you define old? Functional status - Activities of Daily Living used to determine independent living ability Katz ADL scale Bathing Transferring Dressing Continence Toileting Feeding https://www.youtube.com/watch?v=zs2B4DZarOM Global Population Trends: Life Expectancy and Life Span Life expectancy Average number of years expected to live in a population cohort or group Commonly reported as life expectancy from birth Life span Maximum number of years a person can live Human life span projected to range from 110 - 120 yrs  Life Expectancy at Birth and at Age 65 ↑ Largely due to ~80 yr fewer deaths from CVD, stroke, accidents ↑ with age as the indiv ~85 yr survives > mortality rates associated w/diseases Physiological Changes with Aging Shifts in body composition & subsequent loss of physical resilience  ↓ Fat free mass (bone, muscle, water)  Muscle most affected = Sarcopenia  ↑ Body fat mass  Overall ↓ in body weight What factors support body composition change with aging? Physical activity, Hormones, Food intake, Lower metabolism Changing Sensual Awareness: Taste and Smell What affects taste and smell making it difficult to determine if decline is due to aging?  Disease  Medications Changing Sensual Awareness: Oral Health  Tooth loss  Oral health is not necessarily affected by aging but by -GI secretions -Skeletal system -Mucous membrane -Muscle in the mouth -Olfactory neurons -Taste buds Changing Sensual Awareness: Appetite and Thirst Appetite Thirst Hunger & satiety cues Thirst-regulating weaken mechanisms ↓ Appetite-regulating Dehydration occurs more mechanisms may be quickly after fluid blunted = ↓ food intake deprivation & rehydration is less effective Mini Nutritional Assessment Senescence Cellular senescence Phenomenon by which normal diploid cells cease to divide, normally after about 50 cell divisions in vitro Theories of Aging –Programmed aging Hayflick Limit: replicative senescence (1961) All cells contain genetic code to divide certain number of times (50-60 times) Evidence: population doublings of fibroblasts Number of times cells have doubled since their isolation in vitro Age of donor # population doublings Fetal 60-80 Middle-aged 20-40 80 year-old 10-20 Theories of Aging- Programmed aging Molecular Clock Theory Chromosome Telomere Repetitive nucleotide sequences at each end of a chromatid Telomere Protects the end of the chromosome from deterioration Telomere shortening? Shortens upon each cell division Reach point were too short and can no longer divide Theories of Aging- Wear and Tear Theory Free Radical Theory Build up of unstable oxygen compounds (ROS) Endogenous: metabolism (mitochondria), inflammation Exogenous: smoking, solar radiation ↑ Oxidative damage ↑ DNA damage Summary  Aging is related to changes in cellular structure and metabolic disruption Better way to define old age is by functional status, than chronological status Several physiological changes accompany old age There are multiple theories of aging, but they are theories