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AGE IS A primary risk factor for cancer. According to the American Cancer Society (ACS) 77 percent of all cancers are diagnosed in people age 55 and older. Age is usually marked by a stage or degree of mental or physical development. In general, age is characterized by structure degeneration and maximal function reduction. The National Center for Health Statistics announced that U.S. life expectancy in 2004 was 77.9 years. Females live about 6–8 years longer than males. An average 20-year-old man has heart reservation about 9 times that needed to preserve his life. After 30, his cardiac index, maximal breath capacity, and power lifting decline about 1.0 percent, 1.2 percent, and 1.3 percent, per year respectively. At age 70, his cerebral blood flow falls to about 80 percent; his kidney blood flow and resting cardiac output retain about 60 percent; and his cardiac reserve remains 50 percent. Average brain weight increases up to age 30 and will fall below 90 percent by age 90.
The elasticity of blood vessels and airways declines with age. Blood volume usually stays steady till age 80. Fibrinogen concentration rises 25 percent by age 70, which raises blood viscosity. Most lymphoid tissues reach their maximum development at puberty and then slowly regress with age. As general immune response decreases and cancer risk increases, the number of T cells and the activity of B cell decline.
Cortisone, a stress hormone, intends to respond more to acute stress in aged by reducing lean mass and bone density, which may precede the onset of many age-related disorders. In contrast to acute stress that temporarily facilitates immune and memory, chronic stress damages body revival. At the cell level, age involves membrane rigidity, mitochondria degeneration, and declined metabolism with accumulated oxidative damage, e.g., lipofuscin pigments/lipid deposit. At a molecular level, there is less synthesis of structural protein, enzyme, and ATP. Also, the cross link of sulfur atoms also interferes DNA repair.
Biological age reflects a cooperated physical, mental, and spiritual journey. Biological age can be a complicated biomarker, calculated as the distance of an individual from the mean of the chronological age cohort. A higher score than average means that biological age is older than chronological age.
Age-Related Functions and Structures
- Vision: Babies are born as hyperopia (farsight). Visual acuity usually reaches 20/20 by age 6. Infants sleeping with a light on at night before age 2 have more myopia (nearsightedness) than infants sleeping in dark.
- Presbyopia, Insulin Sensitivity decrease, Cardiovascular Diseases increase over the age of 40.
- Presbyopia is caused by weakness of ciliary muscle and loss of elasticity in the crystalline lens. Although myopia shows the symptoms of presbyopia later than others, by age 60, most everyone uses some vision aid for reading or distance. Usually, presbyopia is stabilized by age 70.
- Menopause occurs at an average age of 51. Most women do not feel hot flashes or premenopause symptoms (irritation, palpitation, depression) until their menstruation is over. This is an accelerated stage of bone density lose, which will slow down by age 60. In contrast to the dramatic seal of ovary, testosterone levels decline insidiously in men (about 1.5 percent per year after age 30) with partial reproductive power reserved to later life.
- Post menopause age: 52+. Phytoestrogen (soy, vegetables) help woman against heart disease and temporally, may bind available testosterone in the plasma.
- Retirement: 67+. As immunity declines, cancer increases in both sexes.
General Aging Factors
- Genetic/hereditary: Certain genetic regions report reaching age 90 with preserved cognition.
- Behavior; life style; self care; compensatory skills; socioeconomic status. More than 1/3 of American sleeps less than 6 hours per night. Sleep deprivation caused over 100,000 traffic accidents in 1997.
- Food and drink choices can be associated with 70 percent of disorders.
- Deviation: Although cell exhaustion can end life, people who have died of lung cancer at age 70 may have a kidney as young as age 50.
- Positive aging factors include good heart reservation; maximal breath capacity; glomerular filtration rate; glucose tolerance; body mass index; blood pressure (BP); eating healthy foods; vision acuity; sharp mental acuity; active lifestyle. Risk factors include depression; arteriosclerosis; hypertension; diabetes; stress; drug abuse; drinking of alchohol; being overweight, eating a diet high in trans fat and saturated fats (colon cancer), high Pd/Hg/Cu/AL food (cognition decline), smoking.
BMI = Body weight (kg) ÷ Weight (m), normal: 20–25, overweight >27, obesity >30. Body weight: Child (kg) ≍ Age × 2 + 7; Adult (kg) ≍ Height (cm) −105.
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