Aging
Aging is a progressive, predictable process in which gradual changes not caused by disease or accident occur over time. Aging affects both the body and the mind. Some age-related changes start as early as the 20s; others may not appear until people are in their 70s. Although aging is inevitable, people ageat different rates. Age-related changes eventually lead to the increased probability of death as people grow older.
Life expectancy-how long people are expected to live-has risen dramatically since 1900, when it was 47 years. Today, the average life expectancy is 76 years, an increase of about 110 days each year since 1900. Women live longer than men. People today have a much more positive attitude toward aging than earlier generations did.
The aging process involves the steady decline of organ functioning and the regulation of the body systems. Some of the age-related biological changes arepredictable. Aging and disease are related in subtle and complex ways, but aging is not the accumulation of disease. The leading causes of death among older Americans are heart disease, stroke, and cancer.
Bodily changes associated with aging generally make people more vulnerable toenvironmental conditions, to side effects of medications, and to complications of medical procedures. Changes in the regulation of the body systems increase the diversity among older people. These changes include blood pressure, temperature, fever, and body fluids. As people age, the ability of their bodies to control their blood pressure decreases, due to progressive changes in the heart and blood vessels. The body cannot regulate temperature as well, making older people more susceptible to hypothermia in cold temperatures and heatstroke in high temperatures. The body may also be less likely to start a fever to fight off an infection. The amount and composition of body fluids is reduced too. In older people, the thirst response that normally follows being deprived of water is decreased.
Aging also reduces the body's ability to resist and control infections. The skin and mucus membranes, which serve as the primary barriers to infection, may be impaired with age. Some skin conditions that impair the ability to fightinfection become common. The lining surfaces of body tissues, which also help prevent infection, may also be compromised, especially in the mouth, urethra, and vagina. Older people are also more likely than younger people to get pneumonia due to a disturbance in swallowing that makes them draw substances into the lungs instead of swallowing them. The ability to cough also decreases, making it harder for the body to get rid of organisms. The risk of infection is also increased by change in the lungs, like the collapse of the small airways and the loss of lung elasticity. Changes also occur in the gastrointestinal system that make it easier for bacteria to increase in the stomach and the intestines. These include the stomach secreting less acid, changes in theway the bowel contracts, and outpouchings called diverticular that often formin the bowel lining. Changes in the urinary tract also lower resistance to infection; these include changes to urine chemistry, decreased prostatic fluid, reduced ability of the bladder to flush, a backward flow of the bladder contents toward the kidney, and the potential blockage of urine flow by prostateenlargement or other problems. The immune system becomes less responsive aspeople age, as production of antibodies is impaired and the thymus changes.
Some of the declines in body metabolism and heart/lung function may be due todecreases in physical activity. Aging also reduces the body's ability to acquire and deliver oxygen to the tissues due to increases in the stiffness of the chest wall, impaired blood flow through the lungs, weaker heart contractions, and decreases in muscle mass. Total body metabolism declines slightly over time.
Many of the changes of aging can be seen in the way people look. People loseheight and body weight and increase body fat. By age 80, people lose approximately two inches of height, due to changes in posture, the growth of vertebrae, a forward vending of the spine, the compression of the disks between the vertebrae, increased curves in the hips and knees, and decreased joint space in the trunk, arms, and legs. Men generally gain weight until their mid-50s, when they begin to lose weight; this accelerates in the late 60s and 70s. Women gain weight until the late 60s; their weight loss after that is less than that of men. Between the age of 25 and 75, total body fat as a proportion of the body's composition doubles.
As people age, changes in skin cells cause a loss of elasticity and wrinkles.Too much exposure to the sun makes these problems worse. Skin problems include dryness, discoloration in body folds, growths, and itching; these problemsaffect about two thirds of older people. Hair turns gray and grows slower from a loss of pigment cells in the hair bulbs.
Aging brings changes in the muscles and bones. Muscle mass declines progressively after the age of 40. Hand-grip strength declines 45% by the age of 75. This, however, may be due to inactivity, nutritional deficiencies, disease, orother conditions rather than the aging process itself. Cartilage, the substance that lubricates the joints, becomes less able to adapt to repetitive stress. Common forms of arthritis begin in the 30s and progress with each decade.Joint problems, the leading cause of reduced activity among older people, are common. These include: arthritis (either sudden inflammatory or smolderinginflammatory), osteoarthritis (wear and tear arthritis), problems around thejoint,and mechanical problems with the joint. Bone loss occurs with aging, but the rate varies tremendously among people. After the age of 35, bone mineral declines. This accelerates for women after menopause and for men after theage of 60. The growth of bone slows, and it becomes thinner and more porous.Bones become more likely to collapse or break from even slight trauma. Osteoporosis is a common age-related disorder of the bones. Impairments in the muscles and bones are influenced by conditioning, nutrition, vascular and neurologic problems, and hormones.
Atrophy of the brain is usually moderate in healthy older people. From ages 30 to 70, blood flow to the brain decreases by 15 to 20 percent. At about age70, memory loss accelerates and reaction times slow down. Changes in brain structure and biochemistry do not generally affect people's ability to think and behave. What does change is the ability to retain a large amount of information over a long period of time. Neurologic conditions are common in older people and represent a major source of disability. These include cerebrovascular disorders that are caused by problems in the blood supply to the brain, degenerative disorders where a part of the brain atrophies, and other conditionslike brain tumors and seizures. Stroke, an injury to the brain caused by inadequate blood supply to the brain due to disease or obstruction of arteries in the head and neck, is a common cerebrovascular disorder. Stroke is a leading cause of death among older people.
After the age of 40, objects get fuzzy; this is the most common age-related change in vision. Called presbyopia, this is due to decreased elasticity of the lens and atrophy of the muscle that controls the lens shape. The sharpnessof vision when looking at objects that do not move decreases gradually and steadily; much of this loss can be corrected by glasses. The ability to see details in moving objects decreases faster than the ability to see details in static objects. After the age of 50, people are more susceptible to glare and night vision decreases. After the age of 60, the risk of macular degeneration,the most common reason for age-related blindness, increases. After the age of 70, the ability to see fine detail declines. The upper lid may droop or thelower lid turn inward or outward due to atrophy of tissues around the eye and loss of fat around the eye.
Changes in the structure of the ear as people age have a significant effect on hearing. The ear canal atrophies, the eardrum thickens, degenerative changes can develop in the small joints connecting the bones to the middle ear, andchanges occur in the inner ear. In the 20s, people begin to lose their ability to hear high-frequency tones. After the age of 60, they begin to lose their ability to hear low frequency tones.
After the age of 50, the sense of smell declines rapidly. By the age of 80, the sense of smell is almost half of what it was at its peak.
As people age, they tend to show disease in the heart (muscle, valves and coronary arteries), but it unclear whether there are any age-related changes without disease being present. Maximum heart rate during exercise declines 25% between the ages of 20 and 75. Coronary arteries begin to build plaque in childhood and begin clogging after the age of 50. The cells that produce heartbeats get covered with connective tissue and fat and changes occur in other parts of the heart's electrical system. Age-related declines in the heart's ability to contract include a longer contraction time, decreased response to medicines, and increased resistance to electrical stimulation; these changes do not usually result in disease. The cardiovascular system responds less efficiently to stress with age. Physical activity, nutrition, smoking, socioeconomicstatus, and other lifestyle factors contribute to heart disease in older people. Common heart conditions in older people are high blood pressure, coronaryartery disease, diseases of the heart valves, congestive heart failure, andabdominal aortic aneurysm. Blood pressure increases with aging and nearly half of all people over the age of 65 have mild high blood pressure. High bloodpressure increases the risk of heart attacks and strokes. Coronary artery disease is the progressive narrowing of the arteries that supply blood to the heart; it is the most common cause of death in people over the age of 65. Low levels of HDL, or healthy cholesterol, and high levels of LDL, or unhealthy cholesterol, contribute to the development of coronary artery disease. Coronaryartery disease can lead to heart attacks. Diseases of the heart valves, including aortic valve narrowing or leaking and mitral valve narrowing or leaking, are usually due to wear and tear in older people. Congestive heart failureoccurs when the heart cannot meet the body's demand for blood. It is common in older people. Abdominal aortic aneurysm is the widening of the major bloodvessel that leads from the heart. About two percent of people over the age of65 have aneurysm in the abdominal aorta. People with high blood pressure andartherosclerosis are at greatest risk for aortic aneurysm.
Maximum breathing capacity begins declining at the age of 20 and falls 40% byage 80. The windpipe and large airways increase as people age. Lungs becomeless elastic. As people age, they are more likely to have lung disease and progressive declines in lung function. Smoking accelerates the effects of agingand produces the greatest amount of disability. Age-related lung conditionsinclude chronic lung disease, aspiration, lung cancer, pneumonia, and tuberculosis.
There is less change in the gastrointestinal system than in other body system. The muscle contractions of the esophasgus, which affect swallowing, changes, and there is a small amount of atrophy in the lining of the small intestine. The liver decreases in size and blood flow declines. The pancreas drops a little, pancreatic ducts gradually increase in size, and the pancreas atrophies. Gastrointestinal conditions that affect older people include gastrointestinal bleeding, loss of bowel control, peptic ulcer disease, gallbladder disease, diverticulitis, appendicitis, colon and rectal cancers, and hemorrhoids and other rectal problems.
There is a 25 to 30 percent decrease in kidney mass with aging, which leads to decreased clearance of some drugs and reduction in the response to dehydration. Kidney, bladder, and urinary conditions that affect older people includeurinary tract infection, bladder cancer, kidney problems due to blood vesseldisease, problems with the way the kidneys filter, and sudden kidney failure.
Women lose the ability to reproduce after menopause, but men can reproduce even in extreme old age. In women, the rapid decline in egg production by the ovary is related to age and virtually stops after menopause, which reduces theproduction of estrogen and causes changes in the uterus and vagina. Men gradually lose the ability to reproduce since sperm cells continue to form. Although the frequency of sexual activity declines with age, it is not known how much of this is due to aging and how much is due to circumstances. Women report less sexual interest than men. Diseases common in older people, like arthritis, can have an impact on sexuality.
Cancer is the second leading cause of death among people over the age of 65 in the United States. Cancer is the malignant growth of abnormal cells in thebody. Common cancers in older people include: lung, colon, rectal, and bladder cancer. Some types of cancer, like lung and prostate cancer, are milder inolder people while others, like Hodgkin's disease and acute leukemias, are more aggressive. Also, the number of tumors resistant to chemotherapy may increase in older people.
The mind changes with aging too. Most people fear changes in their mental function more than any of the physical changes of aging. Mental function does not have to decline, however, the capacity to learn continues throughout life.As people age, they require more time than younger people to process new information and long-term memory is said to decline. Whether intelligence declines with aging is hotly debated. Dementia, memory problems that occur over a long period of time and affect many areas of cognitive functioning, affects less than 10 percent of people who are older than 65; this increases to as muchas 20 percent for people who are 85 or older.
Mental health has a major influence on how people function as they age, and even how they respond to medical illness. More than 25 percent of older peoplehave significant mental illness; among older people in institutions, this figure is more than 90 percent. Anxiety, described as unrealistic or excessiveanxiety about problems, is common. Major depression is rare in people over the age of 60, however, 10 to 15 percent of older people who are in hospitals and long-term care settings do have major depression. About five percent of people over the age of 65 in the United States have significant drinking problems.
People can influence some aspects of aging. The National Institute on Aging offers ten tips for healthy aging:
- Eat a balanced diet, which includesfive fruits and vegetables each day.
- Exercise regularly. This produces increased strength, denser bones, positive effect on fats in the blood, better handling of blood sugar, increase maximal oxygen capacity, better sleep,and an improved sense of well-being. Older people should, however, check with their doctor before staring an exercise program.
- Get check-ups on aregular basis.
- Do not smoke. Older people who do smoke should stop;it is never too late to achieve health benefits by quitting.
- Practicesafety habits at home to prevent falls and bone fractures. Wear a seatbelt in the car.
- Stay in contact with family and friends. Stay active through involvement in work, play, and community.
- Avoid too much exposureto the sun or cold weather.
- Drink alcohol only in moderation.
- Keep personal and financial records in good order. Plan for long-term housing and financial needs.
- Keep a positive attitude toward life. Do the things that bring happiness.
Other preventive health behaviors include getting a pneumonia shot and takinglow-dose aspirin therapy. Eighty percent of the people who die from pneumococcal infections, the leading cause of pneumonia, are over the age of 65. Manyexpert panels recommend that everyone over the age of 65 be vaccinated. Low-dose aspirin therapy (325 milligrams of aspirin taken every other day) is recommended for people who have two of more risk factors for coronary heart disease. These risk factors are: diabetes mellitus, a low HDL cholesterol or a high LDL cholesterol, high blood pressure, a strong family history of heart disease, and being male, severely obese, or a smoker. Some people should not take aspirin therapy; these are: people who have uncontrolled high blood pressure, severe liver disease, ulcer disease, or any other condition that increasesthe risk of bleeding. Estrogen therapy is often recommended for women who are at increased risk of osteoporosis.
Many of the ailments that are described above were once accepted as part of the normal aging process. Today, they are now being studied by researchers inbiotechnology. The results may slow the aging process during the twentieth-first century.
Researchers do not know why people age. There are many theories on how peopleage. The two main groups of theories are that aging results from either genetically programmed changes or that it occurs because of an accumulation of genetic errors due to environmental damage. Under the first group of theories,programmed cell death, which is part of human growth and development, provides a model for aging. For example, people must lose their baby teeth to make way for permanent teeth. One set of programmed cell death theories suggests that the immune system regulates aging declines, with the thymus gland acting as a biological clock. There are also many theories of aging due to errors incell functioning and environmental exposure. Under these theories, aging results from changes in the information provided by the cell nucleus during normal cell formation. Aging could result from changes in DNA, errors in the synthesis of other nuclear proteins, or alterations in the structures that modifythe way genes are expressed. No single theory fully explains the aging process, but each offers some clues.