ch3 aging tb

One of the more popular cellular theories of aging comes from a discovery made by Leonard Hayflick in 1996

He discovered that cells grown in laboratory petri dishes divide only a finite number of times before they die. This is known as the Hayflick limit. Furthermore, Hayflick found that the number of divisions a cell is able to make depends on the age of the cell.

There is evidence to suggest that the limit placed on cell division is due to the

shortening of telomeres, which are the end tips of chromosomes. According to Lin and colleagues (2012), telomeres play an important role in aging by regulating the cell’s response to stress and damage to DNA molecules. It also has been shown that telomere shortening and dysfunction are associated with age-related diseases including cardiovascular disease, Type 2 diabetes mellitus, and cancer

Examples of error theories of aging include

the wear and tear theory (Weismann, 1882) and the free radical theory of aging

caloric restriction (CR)

The idea that reducing calories, without malnutrition, can extend life is not a new idea. In 1935, McCay and colleagues published the first paper showing that a 25 to 30 percent reduction in caloric intake, without malnutrition, extends the average and maximum lifespans in rats. This classic study with rats was followed by numerous CR studies with a variety of species including fish, monkeys, dogs, hamsters, flies, primates, humans, as well as yeast (Chung et al., 2013). Interestingly, CR not only extends the life of the species that have been studied, but has also been shown to lower the risk of developing cancer, diabetes, and cardiovascular diseases in these various species. CR is the only established anti-aging paradigm to serve as the gold standard in research studies that assess aging interventions. CR has become a priority research focus of the National Institute on Aging (NIA) in the United States

NIA study found that calorie restriction modified risk factors for

age-related diseases and influenced indicators associated with longer lifespan such as blood pressure, cholesterol, and insulin resistance

The Okinawans of Japan are a group of people who are of particular interest to CR researchers as they were known to have

among the longest life expectancy in the world.

This increased longevity is believed to be the result of the Okinawans’ diet, which traditionally was low in

fat and sugar, had fewer calories, was rich in antioxidants and seafood, and was high in legumes and soy. However, by the 1960s, population-wide CR among the Okinawans was over and generations thereafter have had a higher BMI across all age groups, as well as more cardiovascular risk factors and more metabolic syndrome as compared to other Japanese. Despite the fact that very little scientific evidence shows that CR extends life and reduces the likelihood of developing chronic illness in humans, there are a number of people practicing CR.

Primary aging

is defined as the gradual and inevitable process of bodily deterioration that takes place throughout life. It is argued that this accumulation of biochemical damage leads to changes such as impaired vision and hearing, slowed movements, decreased resistance to infections, and a reduced ability to adapt to stress.

Secondary aging

on the other hand, is believed to be the result of disease and poor health practices such as not exercising, smoking, and an unhealthy diet. Unlike primary aging, secondary aging is believed to be preventable either through lifestyle choice or modern medicine.

The epidermis is

the outer layer of the skin. It is made up of mostly flat, scale-like cells called squamous cells.

Under the squamous cells are round cells called

basal cells. 

The deepest part of the epidermis also contains

melanocytes. Melanocytes produce melanin, which gives skin its colour.

Another main layer of the skin is the dermis. This inner layer of skin, which lies below the epidermis, contains

blood and lymph vessels, hair follicles, and glands. These glands produce sweat, which helps regulate body temperature, and sebum, an oily substance that helps keep the skin from drying out. Sweat and sebum reach the skin’s surface through tiny openings called pores.

The hypodermis (subcutaneous layer) lies between the

dermis and underlying tissues and organs. It consists of mostly adipose tissue and is the storage site of most body fat.

Aging of the skin, also known as cutaneous aging, is the result of both

intrinsic and extrinsic aging.

Intrinsic aging takes place over

years and occurs irrespective of extrinsic factors, is defined as the gradual irreversible changes in structure and function of an organism that occur due to the passage of time

Extrinsic aging

on the other hand, is due to external factors such as exercise, diet, exposure to sunlight, and smoking.

With intrinsic aging, the skin becomes pale, thinner, and more fragile. Fine wrinkles and exaggerated expression lines are apparent, and the skin becomes dry and less elastic. These changes are due to

reductions in the amount of collagen produced, diminished functioning of the sweat and oil glands, reductions in the amount of elastin that is produced, and reductions in the formation of glycosaminoglycan (polysaccharides) that exist naturally in the dermis of the skin as natural moisture factors. Of interest, of all the wrinkles that occur with age, few are due to this intrinsic aging process.

Intrinsic aging of the skin, although universal, is significantly different among different populations, with

Caucasians having an earlier onset and greater skin wrinkling and sagging than other skin types. There also are gender differences in intrinsic aging of the skin. For example, skin becomes less elastic with age, with changes in elasticity more pronounced in older women than older men.

Skin thickness

decreases with age, with this decrease thought to be due to reduction in collagen with age. This decrease is faster in older women than older men due primarily to estrogen deficiency during and after menopause. In addition, the post-menopausal use of estrogen increases collagen content, dermal thickness, and elasticity, and decreases the likelihood of senile dry skin.

The use of estrogen and/or progesterone (e.g., hormone replacement therapy [HRT]) may increase the risk of

breast cancer and cardiovascular events.

Both the North American Menopause Society and the American College of Obstetrics and Gynecology agree that use of menopausal hormone therapy (MHT) should be

individualized and not discontinued solely based upon patient age. Both organizations suggest that extended use of MHT (beyond age 60 or even 65 years) may be reasonable when the clinician and patient agree that the benefits of symptom relief outweigh the risks.

For women who choose extended use of MHT (more than five years or beyond age 60 years)

restarting estrogen at the lowest dose possible and making plans for a future attempt to stop the estrogen is recommended

One of the best ways to minimize wrinkles and reduce the other changes to your skin described above is to protect your skin against both

UVA and UVB rays. Protection against UVA and UVB rays also helps to minimize the risk of skin cancer. Skin cancer is currently the most common type of cancer—it also is one of the most preventable types of cancer Use sunscreen that has (SPF) of 15 or higher. Limiting exposure to UV from the sun or from artificial sources such as sunlamps and tanning beds, also can reduce the risk of developing skin cancer.

baby-boomer cohort is the first generation with expectations of leisure time, good health, and an increased desire for

preservation of a youthful appearance.

Cleopatra’s most famous beauty secret was

bathing in milk and honey.

Preoccupation with one’s appearance extends across the lifespan, the onset of middle age is associated with an increase in this preoccupation because of

negative stereotypes and myths associated with aging. This obsession with a youthful appearance, as well as factors such as self-esteem, perceptions of body, and life satisfaction, has resulted in a proliferation of and demand for surgical and non-surgical cosmetic procedures that are designed to reverse the aging process .

Cosmetic surgery is concerned with

the “maintenance, restoration, or enhancement of an individual’s physical appearance through surgical and medical techniques”

With age, we lose

muscle mass, our mucous membranes thin and become drier, and we lose fine coordination.

These changes occur in the larynx as well as the vocal cords, resulting in

presbyphonia, a term used to describe the changes associated with the aging voice. These changes include a higher pitch voice in men and a lower pitch voice in women, reductions in volume and projection (a “thin” voice), tremor or shakiness in the voice, difficulty in being heard in noisy situations, and, for those who sing, reduced vocal endurance

Greying of the hair is due to

a reduction in melanocytes. These cells, which produce melanin, are located in the lower region of hair follicles.

Androgenetic alopecia

(commonly known as male pattern baldness) is the most common form of hair loss in men, affecting 30–50 percent of men by age 50 (Cranwell & Sinclair, 2000). In women, the role of androgens in female pattern baldness is less clear

Results from an older study indicate that androgenetic alopecia can be

stressful for both men and women, but substantially more stressful for women

Despite the availability of medications for androgenetic alopecia

(e.g., finasteride [Propecia] and minoxidil [Rogaine] and hair transplants, none works well. For individuals who are not bothered by hair thinning, simple assurance that this is a benign disorder is all that is required.

Vision declines with age. The pupil become smaller and less responsive to

variations in light, the lens begins to lose elasticity and thickens and yellows, and the muscles that control both pupil size and the reaction to light lose strength

The decreased ability of the pupil to adjust to varying light conditions also results in a gradual loss in

dark adaptation, which makes it more difficult to adapt from darkness to bright light (or vice versa). Changes in dark adaptation with age make it more difficult to read a menu in dimly lit restaurants or in finding your seat in a dark movie theatre

The loss of elasticity in the lens results in

difficulties in accommodation.

With normal aging, this loss of elasticity results in a condition called

presbyopia. Presbyopia, which typically becomes noticeable in individuals beginning around age 40, is part of the natural aging process. As such, presbyopia is not a disease and cannot be prevented.

Symptoms of presbyopia include

difficulty reading small print, needing to hold material at arm’s length to properly focus on it, eyestrain or headaches after reading or doing close work, and a need for brighter lighting when reading or doing close work.

Presbyopia is easily corrected through

wearing of prescription glasses (e.g., reading glasses, bifocals, or progressive lenses) or contact lenses. More recently, corneal implants are being used to correct presbyopia. These implants, which are placed in the middle layer of the cornea, result in improvements in near and intermediate vision without a significant loss of distance vision, contrast sensitivity, or stereopsis (depth perception).

The yellowing of the lens with age affects colour perception

It results in dulling of colours and difficulties differentiating between colours and between colour shades (e.g., blue, green, and violet). It also can create difficulties in determining where an object ends and its background begins.

Three common age-associated diseases are

macular degeneration, cataracts, and glaucoma.

Two types of Age-related macular degeneration

wet and dry.

Wet AMD

which accounts for two-thirds of all AMD, occurs when abnormal blood vessels start to grow under the macula behind the retina. Often, these new blood vessels are very fragile and leak blood and fluid, which causes the macula to bulge or lift from its normal place in the back of the eye. Damage to the macula often occurs rapidly and is severe. In the early stages, thermal laser surgery may prevent severe damage for some individuals.

Dry AMD

which accounts for the remaining one-third of all AMD, is the result of thinning of the macula. The degree of vision loss with dry AMD depends on the location and amount of thinning of the lining of the retina. Currently, there are no treatments or cures for dry AMD.

A cataract

is an opacification (clouding) of the crystalline lens of the eye, which blocks light from reaching the retina of the eye. Cataracts are a leading cause of vision loss and the most common cause of reversible blindness in the world

Cataracts may be due to a variety of causes

some are congenital, a few occur during the early years of life, but as noted above, age is the most common risk factor. Surgery can be done to improve vision for those with cataracts. With cataract surgery, historically, the cloudy lens was removed and replaced with an artificial lens. This provided clear vision to patients but did not correct their refractive error, resulting in their need to continue wearing spectacles or contact lenses after surgery.

A diet rich in Vitamins C and E and consumption of foods containing carotenoids has been found to reduce the risk of

cataracts in older individuals

Glaucoma

a group of diseases characterized by increased intraocular pressure, also is more common with age. The normal fluid pressure inside the eye (intraocular pressure) increases, which can result in damage to the optic nerve leading to blindness.

The most common type of glaucoma is

primary open-angle glaucoma.

Early detection and treatment are important for the prevention of damage to the optic nerve and vision loss. There are a number of common tests for glaucoma. One of those tests (tonometry) involves

measuring the pressure in the eye by delivering a small puff of air. There are a number of medications available to treat glaucoma

Hearing loss occurs when there is a problem with, or damage to

one or more parts of the ear or the nerve pathways in the brain involved in hearing

There are two main types of hearing loss

conductive hearing loss and sensorineural hearing loss.

Conductive hearing loss

is caused by abnormalities or damage to the outer (pinna) or middle ear (e.g., eardrum or ossicles).

Sensorineural hearing loss

typically results from permanent damage to the inner ear (cochlea) or the auditory nerve. The cumulative effects of repeated exposure to daily traffic sounds or construction work, noisy offices, equipment that produces noise, and loud music can cause sensorineural hearing loss. Ninety percent of hearing loss is sensorineural, with this type of hearing loss caused by impaired functioning of the cochlear hair cells.

Potential causes of sensorineural hearing loss include

congenital (present at birth) or acquired (exposure to loud sounds or presbycusis).

Presbycusis is

a progressive and irreversible sensorineural hearing loss resulting from degeneration of the cochlea or associated structures of the inner ear or auditory nerves. It is most marked at higher frequencies, occurs gradually, most often occurs in both ears, and affects each ear equally. It is also one of the most common chronic conditions in older adults, with one in three adults 65 years of age and older having this type of hearing loss

men were more likely than women to have hearing loss

63 percent versus 46 percent—as were older adults compared with those aged 40 to 59 years.

What causes presbycusis?

long-term repeated exposure to noise resulting in gradual, irreversible damage to the sensory cells and other structures, which in turn leads to permanent hearing loss. In the current population of older adults, this may be the result of working with noisy machinery. However, for the baby boomer cohort (and in younger cohorts as well), regular and/or prolonged exposure to noise as a result of listening to loud music (on their iPhones, for example) is a risk factor, with this type of exposure more harmful to the cochlea than the natural process of aging

There is a link between a gene (the glutamate metabotropic receptor 7 [GRM7] gene) that produces a key protein in the inner ear and impairments in pure-tone thresholds and

difficulties in speech perception in older individuals

Genetics and environment interact, linking presbycusis to

other neurodegenerative risk factors such as medical conditions (cardiovascular diseases diabetes, hypertension, obesity, renal failure) and lifestyle factors (smoking and diet).

One of the defining characteristics of presbycusis is a gradual loss of the ability to hear high-frequency sounds (over 2 KHz). For example, the consonants

s, z, t, f, and g are high-frequency, high-pitched sounds that are “soft.” Conversely, vowels (e.g., a, e, i, o, and u) are low-frequency, low-pitched, “loud” sounds.

The majority of speech information is carried by

the consonant sounds. These differences affect an older person’s ability to understand what is being said.

Individuals with presbycusis will be able to hear when someone is speaking (from being able to hear the louder, low-frequency vowels) but will not be able to

understand what is said due to the loss of consonant information.

Individuals with normal hearing performed much better on tests of

cognitive functioning than individuals with hearing loss

Research indicated that those individuals with hearing loss had a higher probability of

developing dementia, with the probability increasing as the severity of hearing loss increased

It is important to make decisions about an individual’s functional ability based on

performance and not on the date of birth on their birth certificate.

Helen Keller often is credited with noting that

“blindness cuts us off from things, but deafness cuts us off from people”

Presbycusis negatively impacts a person’s

ability to communicate with others (Davis et al., 2016). It also is not surprising, then, that studies have found that hearing loss in older adults can lead to depression, isolation, social withdrawal, and reductions in overall quality of life

Strategies that you can use when conversing with an older individual with hearing loss

facing the person and maintaining eye contact (or positioning yourself at eye level) as facial expressions and body language are important sources of information in communication. Speaking at a normal rate in a clear voice also is helpful. It is important that you not shout, as shouting not only distorts your words but also can be demeaning. If the individual has difficulty understanding what is said, rephrase rather than repeating the same words over and over again. Reducing the background noise (turning off the television or turning down the radio) when conversing with an older individual can be helpful.

Hearing loss can be minimized by

the use of hearing aids

Hearing aids was associated with improvements in

physical, emotional, mental, and social well-being. Of interest, these benefits were more noticeable to family members and friends than to the actual users themselves

24 percent of Canadians aged 70 to 79 wear

a hearing aid or aids.

Prior to the introduction of digital hearing aids in 1996, modern hearing aids were of the

analogue type

Analogue hearing aids

sound is converted to an electric signal and amplified.

Compared to the older analogue hearing aids, not only do the newer digital hearing aids have

improved sound quality, they also are smaller in size, are more comfortable to wear, and have reductions in the amount of feedback. Some can sync up wirelessly with Bluetooth to a smart phone, enabling the individual to hear calls through the hearing aid. There are even accessories that allow the individual to stream audio from an MP3 player, laptop, or TV right to the hearing aid! Most advanced hearing aids today connect to secondary devices such as remote controls and hearing microphones, and many offer rechargeable options. One feature that is especially valuable to hearing aid users is the ability to set multiple programs to specify settings for unique environments (e.g., restaurants, movie theatres, or airports). And, some of the new devices have geographic coordinate information (geotagging) that automatically adjusts when the user arrives at a location such as their workplace or their family physician's office

the newer hearing aids can be expensive ranging from $995 to $4000 per ear, with the cost of the hearing aids borne by

the individual

To increase awareness of and tackle the stigma associated with hearing loss in older adults

the International Federation of Aging has released a formal Statement of Intent indicating that aging and hearing care sectors join forces to raise awareness of the association between hearing and healthy aging, and the importance of improving access to hearing care for older adults

Our taste receptors are located in small oval structures called

taste buds, which are situated mainly on the tongue, as well as in the mouth and throat. When the chemicals in food activate the taste receptors, signals are sent to processing regions in the brain and decoded, and we perceive the taste of food

A common misconception is that the taste receptors that respond to different tastes are located

in separate regions of the tongue (e.g., taste receptors for sweet on the tip of the tongue, taste receptors for bitter on the back of the tongue, etc.).

Taste receptors in humans are

scattered throughout the tongue.

Another misconception about taste is the belief that there are

four distinct tastes sweet, salty, bitter, and sour.

A fifth taste, umami, has been identified, with this taste described as

rounded, rich, and savoury (Lindemann et al., 2002).

There is a growing body of evidence for the existence of a sixth taste

fat. Although it has yet to be confirmed, its existence is particularly important given the increasing prevalence of overweight and obesity. In the last three decades in Canada alone, the prevalence of obesity has increased

In general, the majority of the studies show a decline in ____ with age

taste sensitivity

Diseases or conditions such as upper respiratory and middle ear infections; radiation therapy for cancers of the head and neck; head injuries; and surgeries to the ear, nose, and throat, common drugs such as antibiotics and antihistamines, and poor oral hygiene and dental problems also can contribute to

taste disorders in older adults

The sense of smell depends on sensory receptors that are located in

the olfactory epithelium lining the roof, superior conchae, and septum of the nasal cavity.

Doty and Kamath (2014) reported that decreased olfactory function is present in

over half of individuals between the ages of 65 and 80 years, and in over three quarters of those over the age of 80.

Age-related decline in the sense of smell is associated with an increased risk of

developing dementia

A study found a reduction in the sense of smell was a good predictor of

death

In this study, older individuals who had lost their sense of smell (anosmia) had

three times the odds of death as those with a normal sense of smell (normosmic).

The belief is that the olfactory system is an early indicator of overall physiological declines and, as such, the decline in smell serves as

the “canary in the coal mine.”

Loss of taste and smell with age can result in older individuals losing an interest in

food, which in turn can lead to malnutrition

Canadians consume about 3400 mg of sodium each day? This is more than double the amount that we need! There now is ample evidence that too much sodium is associated with

high blood pressure, which is a major risk factor for stroke, heart disease, and kidney disease, with excessive sodium intake linked to an increased risk of osteoporosis

Somatosensory function refers to

the detection, discrimination, and recognition of touch sensation and proprioception

Tactile thresholds and thresholds for pain and temperature

increase significantly with age

A reduced sensitivity to pain can result in

older adults not knowing how severe an injury is after burning themselves or after falling down the stairs because they do not perceive the pain.

techniques that older individuals can use to minimize the risk of injury due to changes in touch with age include

adjusting the water temperature on the water heater to reduce the risk of burns, regular inspection of the skin for signs of a pressure sore or injury, and frequent monitoring of the thermostat in the home to prevent overheating or becoming too chilled.

Cardiovascular disease (CVD)

is an umbrella term used to describe many diseases of the cardiovascular system, including diseases of the heart (e.g., arteriosclerosis, coronary artery disease, valvular heart disease, heart failure) as well as diseases throughout the body (e.g., peripheral vascular disease

what is a Stroke

the result of an interruption of blood flow to the brain or rupture of blood vessels in the brain, also is classified as a disease of the cardiovascular system. Heart disease is the second leading cause of death after cancer, and a leading cause of hospitalization in Canada