Biologic Aging Theories and Longevity Chapter 2 Mc
Biologic Aging Theories and Longevity Chapter 2 Mc. Graw-Hill/Irwin © 2013 Mc. Graw-Hill Companies. All Rights Reserved.
Living Long and Well l Life Span – theoretical limit on the length of life l l 115 -120 years Life Expectancy – the number of years an individual can expect to live l l Can be calculated for any age Based on year of birth and other factors 2
Life Expectancy l l Improvements in public health Variations l l l Within and among countries Between groups Morbidity l l Period of reduced function, disability and illness Compression morbidity 3
Factors Influencing Longevity l l Actuarial Data Animal Studies Longitudinal Studies Centenarian Studies 4
Heredity l Parenting styles l l l Diet, activity level, stress management Centenarians often have very old first-degree relatives Human genome l Group of genes on chromosome 4 may be related 5
Gender l Females live longer than males l Average life expectancy in the U. S. l l l Males: 75. 4 Females: 80. 4 Males participate in more risky behavior X Chromosome Hormonal influences 6
Race and Ethnicity l Difficult to research in America l Socio-economic factors are tied to race l l Minorities are often poor, less educated, have poorer living situation, less insurance, worse diet and worse jobs Minorities/poor may face higher stress levels and discrimination 7
Cigarette Smoking l l l Leading cause of preventable death in the US Men lose 13. 2 years. Women lose 14. 5 years. In older people smoking: l l l Reduces bone density in postmenopausal women Increases risk of hip fractures Increases risk of cataracts Increases risk of chronic obstructive pulmonary disease Quitting decreases the risks l 65 -year old smoker who quits gains two years life expectancy 8
Genetic and Acquired Disease l l In general, the more diseases an individual has and the number of body systems affected, the more likely they are to die. Genetic diseases affect life expectancy l l l Down’s Syndrome Huntington’s Disease Acquired diseases l Cancer 9
Body Weight and Height l Obesity is correlated with an increased risk of premature death and disability l l Increased likelihood of diseases that negatively affect mortality rate Shorter people reportedly live longer than those who are taller 10
Physical Activity l High levels of physical activity are associated with low death rates from all causes of mortality l l Exercise strengthens the heart, decreases the likelihood of obesity, increases the good cholesterol in the blood No study has conclusively documented the effect of physical activity, the type, frequency or duration which promote long life. l Confounding factors 11
Alcohol Use l l l Light consumption (1 -2 drinks/day) may be associated with cardiovascular benefits. Heavy drinking (3+drinks/day) is associated with reduced life expectancy. Are moderate drinkers just healthier all around, or does alcohol have an effect on longevity? 12
Marital Status l l People married at the time of their deaths lived longer than those widowed or divorced Marriage may help promote longevity because: l l l You have a friend for help and reduction of stress Marriage promotes healthful habits Sex is more frequent in a married relationship 13
Psychological Factors l Personality traits may influence longevity l l A negative personality is comparable to high blood pressure A negative person may also chose life-shortening behaviors A calm person may live longer Personality may effect hormones, immune function, cholesterol level, etc. 14
Social Class: Education, Income, and Occupation l High education and occupation level are correlated with long life l l l People in middle and upper classes live longer than those in the lower classes More income may mean more money spent on health, better living conditions Higher education may mean more healthful habits 15
Cultural Factors l l People from developed countries have higher life expectancy than those from less-developed countries l Often associated with high rates of infant and maternal morality Other factors – sanitation, prevalence of infectious disease, dietary factors, access to health care – affect longevity 16
The Physical Environment l l l Radiation can impair cell function and accelerate the aging process Air pollution is inversely related to longevity Our environment will be more polluted in the future and have a greater effect on longevity 17
Overview of Cell Reproduction and Repair l l l Cells are the basic building blocks of all life Each cell is somewhat self-contained and selfmaintaining There are more than 200 types of cells in the human body Genes are located on chromosomes (DNA) inside each cell nucleus Almost every cell has an identical and complete set of genetic information 18
Cell Reproduction and Repair (cont. ) l l l A mutation is any alteration in the genetic code Mutations can be insignificant or lethal to the cell Most cells reproduce by mitosis Damaged cells can divide and replace themselves, or repair the damage When the processes of damage and repair no longer work, they have a great impact on cellular aging 19
Biological Theories of Aging l There are two phenomena in aging: l l l A physiological decline in many body systems An increased prevalence of disease Two theories explain aging l l Random Theory of Aging Programmed Theory of Aging 20
Random Aging: Cross Linking and Wear and Tear l l The environment causes mutations in cells leading to errors and damage to the cells that weaken the ability to function and divide, thus causing aging Cross linking of DNA makes the chromosomes function less efficiently l l Caused by radiation and UV light Wear and Tear Theory suggests that years wear cells out l Is wear and tear the cause of aging or the result of it? 21
Random Aging: Free Radical Theory l Damage from highly reactive molecules within the cell causes aging l l Free radicals are the toxic byproduct of cell metabolism Also created through our diet or environment The body produces enzymes to inactivate free radicals Free radical damage to the cell’s DNA and less ability to repair damage can lead to errors in the genetic material 22
Random Aging: Rate of Living l l l Do we have a finite amount of life? Can we use it all up? Animal studies show that slower metabolisms increase longevity But… exercise is associated with longevity 23
Random Aging: Accumulation of Errors l l Cell mutations disrupt normal function Too much mutation and the cell is inefficient or dead Accumulation of mutations causes aging Regardless of how the mutation occurs, random theory of aging says “eventually we wear out” 24
Programmed Aging: Born to Die l Biological Clock (Pacemaker) Theory suggests we are programmed from birth to shut down at a specific time l l l Hypothalamus Immune System Cells may have a finite life as well 25
Programmed Aging: Telomere Shortening l Telomere are protective caps of DNA fragments l l May protect the genetic information during cell division Each division shortens the telomere When the telomere is too short the cell cannot divide Are Telomeres our Biological Clock? 26
Theories of Aging l l l Any single theory of aging is insufficient Genetic theorists acknowledge the external influences, and vise versa It is difficult to determine what causes aging and what is a result of aging 27
Attempts to Extend the Length of Life l l Caloric Restriction: Eat less and live longer Antioxidant Therapy: Just take vitamins DHEA: The wonder hormone? Human Growth Hormone: Expensive, but effective? 28
Biologic Aging Theories and Longevity Chapter 2
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