2. Ageing process and physiological changes

#### 2.1. Changes in nervous system

According to World Population Prospects (1950–2050), the proportion of elderly in developing countries is rising more rapidly, in comparison with developed ones [2]. The report published by the US Department of Health and Human Services shows that more developed nations have had decades to adjust to this change in age structure (Figures 1 and 2). As we see in Figure 1, it has taken more than a century for France's population aged 65 or older to rise from 7 to 14%, whereas many developing countries are growing rapidly in number and percentage

Figure 1. Speed of population ageing in developed countries. Source: U.S. Census Bureau [3]; Kinsella & Gist [4].

Figure 2. Speed of population ageing in developing countries. Source: U.S. Census Bureau [3]; Kinsella & Gist [4].

of older individuals [2].

4 Gerontology

Ageing is associated with many neurological disorders, as the capacity of the brain to transmit signals and communicate reduces. Loss of brain function is the biggest fear among elderly which includes loss of the very persona from dementia (usually Alzheimer's disease). Multiple other neurodegenerative conditions like Parkinson's disease or the sudden devastation of a stroke are also increasingly common with age [8].

Alzheimer's and Parkinson's diseases are the progressive neurodegenerative diseases associated with ageing [9]. Alzheimer's is characterised by progressive cognitive deterioration along with a change in behaviour and a decline in activities of daily living. Alzheimer's is the most common type of pre-senile and senile dementia. This disease causes nerve cell death and tissue loss throughout the brain, affecting nearly all its functions. The cortex in the brain shrivels up and this damages the areas involved in thinking, planning and remembering. The shrinkage in a nerve cell is especially severe in the hippocampus (an area of the cortex that plays a key role in the formation of new memories) as well as the ventricles (fluid-filled spaces within the brain) also grow larger. Alzheimer's disease causes an overall misbalance among the elderly by causing memory loss, changes in personality and behaviour-like depression, apathy, social withdrawal, mood swings, distrust in others, irritability and aggressiveness [10, 11].

Nearly, 33 million Indians have neurological disorders, and these occur twice as often in rural areas [12]. According to the World Health Organisation (WHO) [13], nearly 5% of men and 6% of women aged 60 years or above are affected with Alzheimer's-type dementia worldwide. In India, the total prevalence of dementia per 1000 elderly is 33.6%, of which vascular dementia constitutes approximately 39% and Alzheimer's disease constitutes approximately 54% [14].

Stroke is another common cause of mortality worldwide [13]. However, in India, the prevalence rate of stroke among elderly is reported to be very low compared to Western countries [15–17].

#### 2.2. Cognition

A mild decline in the overall accuracy is observed with the beginning of the 60s that progresses slowly, but sustained attention is good in healthy older adults. Cognitive function declines and impairments are frequently observed among the elderly. Normally, these changes occur as outcomes of distal or proximal life events, where distal events are early life experiences such as cultural, physical and social conditions that influence functioning and cognitive development [17].

salivary glands get affected, and the volume and quality of saliva diminish. All changes combine to make eating less interesting [32]. Studies show that the physiological decline in the density of the taste acuity and papillae results in a decline of gustatory function [33]. In fact, studies done on taste dysfunction show that ageing-associated changes in the density of taste acuity may affect taste function differently in different regions of the tongue [34]. Taste perception declines during the normal ageing process. A study done on the healthy elderly shows that after about 70 years of age, taste threshold begins to increase resulting in dysgeusia [34]. Chewing problems associated with loss of teeth and use of dentures also interfere with

Ageing Process and Physiological Changes http://dx.doi.org/10.5772/intechopen.76249 7

As we get older, our olfactory function declines [35]. Hyposmia (reduced ability to smell and to detect odours) is also observed with normal ageing [36]. The sense of smell reduces with an increase in age, and this affects the ability to discriminate between smells. A decreased sense of smell can lead to significant impairment of the quality of life, including taste disturbance and

It has been reported that more than 75% of people over the age of 80 years have evidence of major olfactory impairment. Many long-term studies show the evidence of a decline in olfaction considerably after the seventh decade [37]. Another study found that 62.5% of 80–97-yearolds had olfactory impairments [38]. However, it is widely accepted that taste disorders are far less prevalent than olfactory losses with age [38]. Ageing also causes atrophy of olfactory bulb neurons. Central processing is altered, resulting in a decreased perception and less interest in

As we age, our sense of touch often declines due to skin changes and reduced blood circulation to touch receptors or to the brain and spinal cord. Minor dietary deficiencies such as the deficiency of thiamine may also be a cause of changes [40]. The sense of touch also includes awareness of vibrations and pain. The skin, muscles, tendons, joints and internal organs have

A decline in the sense of touch affects simple motor skills, hand grip strength and balance. Studies have shown that muscle spindle (sensory receptors within the muscle that primarily detects changes in the length of this muscle) and mechanoreceptor (a sense organ or a cell that responds to mechanical stimuli such as touch or sound) functions decline with ageing, further

Normal ageing is characterised by a decrease in bone and muscle mass and an increase in adiposity [43, 44]. A decline in muscle mass and a reduction in muscle strength lead to risk of

loss of pleasure from eating with resulting changes in weight and digestion [36].

taste sensation and cause reduction in saliva production [32].

receptors that detect touch, temperature or pain [41].

3. Changes in musculoskeletal system

interfering with balance [42].

2.4.4. Smell

food [39].

2.4.5. Touch

Cognition decline results from proximal factors (multiple serial cognitive processes) including processing speed, size of working memory, inhibition of extraneous environmental stimuli and sensory losses. This is a threat to the quality of life of those affected individuals and their caregivers [18].

Impaired cognition among elderly is associated with an increased risk of injuries to self or others, the decline in functional activities of daily living and an increased risk of mortality [19–21]. Mild cognitive impairment is increasingly being recognised as a transitional state between normal ageing and dementia [22, 23].

#### 2.3. Memory, learning and intelligence

According to various studies [24–26], the effect of normal ageing on memory may result from the subtly changing environment within the brain. The brain's volume peaks at the early 20s and it declines gradually for rest of the life. In the 40s, the cortex starts to shrink and people start noticing the subtle changes in their ability to remember or to do more than one task at a time. Other key areas like neurons shrink or undergo atrophy and a large reduction in the extensiveness of connections among neurons (dendritic loss) is also noticed. During normal ageing, blood flow in the brain decreases and gets less efficient at recruiting different areas into operations. The whole group of changes taking place in the brain with ageing decreases the efficiency of cell-to-cell communication, which declines the ability to retrieve and learn [27]. It also affects the intelligence, especially fluid intelligence (problem-solving with a novel material requiring complex relations) declines rapidly after adolescence. Perceptual motor skills (timed tasks) decline with age [28].

#### 2.4. Special senses

#### 2.4.1. Vision

Ageing includes a decline in accommodation (presbyopia), glare tolerance, adaptation, lowcontrast activity, attentional visual fields and colour discrimination. Changes occur in central processing and in the components of the eye. These numerous changes affect reading, balancing and driving [29].

#### 2.4.2. Hearing

Ageing causes conductive and sensory hearing losses (presbycusis); the loss is primarily high tones, making consonants in speech difficult to discriminate [30].

#### 2.4.3. Taste acuity

Losing sense of taste is a common problem among adults [31]. Taste acuity does not diminish but salt detection declines. Perception of sweet is unchanged and bitter is exaggerated. The salivary glands get affected, and the volume and quality of saliva diminish. All changes combine to make eating less interesting [32]. Studies show that the physiological decline in the density of the taste acuity and papillae results in a decline of gustatory function [33]. In fact, studies done on taste dysfunction show that ageing-associated changes in the density of taste acuity may affect taste function differently in different regions of the tongue [34]. Taste perception declines during the normal ageing process. A study done on the healthy elderly shows that after about 70 years of age, taste threshold begins to increase resulting in dysgeusia [34]. Chewing problems associated with loss of teeth and use of dentures also interfere with taste sensation and cause reduction in saliva production [32].

#### 2.4.4. Smell

impairments are frequently observed among the elderly. Normally, these changes occur as outcomes of distal or proximal life events, where distal events are early life experiences such as cultural, physical and social conditions that influence functioning and cognitive develop-

Cognition decline results from proximal factors (multiple serial cognitive processes) including processing speed, size of working memory, inhibition of extraneous environmental stimuli and sensory losses. This is a threat to the quality of life of those affected individuals and their

Impaired cognition among elderly is associated with an increased risk of injuries to self or others, the decline in functional activities of daily living and an increased risk of mortality [19–21]. Mild cognitive impairment is increasingly being recognised as a transitional state between normal

According to various studies [24–26], the effect of normal ageing on memory may result from the subtly changing environment within the brain. The brain's volume peaks at the early 20s and it declines gradually for rest of the life. In the 40s, the cortex starts to shrink and people start noticing the subtle changes in their ability to remember or to do more than one task at a time. Other key areas like neurons shrink or undergo atrophy and a large reduction in the extensiveness of connections among neurons (dendritic loss) is also noticed. During normal ageing, blood flow in the brain decreases and gets less efficient at recruiting different areas into operations. The whole group of changes taking place in the brain with ageing decreases the efficiency of cell-to-cell communication, which declines the ability to retrieve and learn [27]. It also affects the intelligence, especially fluid intelligence (problem-solving with a novel material requiring complex relations) declines rapidly after adolescence. Perceptual motor skills (timed tasks) decline with age [28].

Ageing includes a decline in accommodation (presbyopia), glare tolerance, adaptation, lowcontrast activity, attentional visual fields and colour discrimination. Changes occur in central processing and in the components of the eye. These numerous changes affect reading,

Ageing causes conductive and sensory hearing losses (presbycusis); the loss is primarily high

Losing sense of taste is a common problem among adults [31]. Taste acuity does not diminish but salt detection declines. Perception of sweet is unchanged and bitter is exaggerated. The

tones, making consonants in speech difficult to discriminate [30].

ment [17].

6 Gerontology

caregivers [18].

2.4. Special senses

balancing and driving [29].

2.4.1. Vision

2.4.2. Hearing

2.4.3. Taste acuity

ageing and dementia [22, 23].

2.3. Memory, learning and intelligence

As we get older, our olfactory function declines [35]. Hyposmia (reduced ability to smell and to detect odours) is also observed with normal ageing [36]. The sense of smell reduces with an increase in age, and this affects the ability to discriminate between smells. A decreased sense of smell can lead to significant impairment of the quality of life, including taste disturbance and loss of pleasure from eating with resulting changes in weight and digestion [36].

It has been reported that more than 75% of people over the age of 80 years have evidence of major olfactory impairment. Many long-term studies show the evidence of a decline in olfaction considerably after the seventh decade [37]. Another study found that 62.5% of 80–97-yearolds had olfactory impairments [38]. However, it is widely accepted that taste disorders are far less prevalent than olfactory losses with age [38]. Ageing also causes atrophy of olfactory bulb neurons. Central processing is altered, resulting in a decreased perception and less interest in food [39].

#### 2.4.5. Touch

As we age, our sense of touch often declines due to skin changes and reduced blood circulation to touch receptors or to the brain and spinal cord. Minor dietary deficiencies such as the deficiency of thiamine may also be a cause of changes [40]. The sense of touch also includes awareness of vibrations and pain. The skin, muscles, tendons, joints and internal organs have receptors that detect touch, temperature or pain [41].

A decline in the sense of touch affects simple motor skills, hand grip strength and balance. Studies have shown that muscle spindle (sensory receptors within the muscle that primarily detects changes in the length of this muscle) and mechanoreceptor (a sense organ or a cell that responds to mechanical stimuli such as touch or sound) functions decline with ageing, further interfering with balance [42].

## 3. Changes in musculoskeletal system

Normal ageing is characterised by a decrease in bone and muscle mass and an increase in adiposity [43, 44]. A decline in muscle mass and a reduction in muscle strength lead to risk of fractures, frailty, reduction in the quality of life and loss of independence [45]. These changes in musculoskeletal system reflect the ageing process as well as consequences of a reduced physical activity. The muscle wasting in frail older persons is termed 'sarcopaenia'. This disorder leads to a higher incidence of falls and fractures and a functional decline. Functional sarcopaenia or agerelated musculoskeletal changes affect 7% of elderly above the age of 70 years, and the rate of deterioration increases with time, affecting over 20% of the elderly by the age of 80 [46]. Strength declines at 1.5% per year, and this accelerates to as much as 3% per year after 60 years of age [47]. These rates were considered high in sedentary individuals and twice as high in men as compared with those in women [48]. However, studies show that on an average, men have larger amounts of muscle mass and a shorter survival than women. This makes sarcopaenia potentially a greater public health concern among women than among men [48].

diabetes, affect the remodelling of tissues as the rate or volume of nutritional delivery for the regeneration of cells is compromised. It is very important to control the pathological processes to optimise healing and repairing the potential of the musculoskeletal system. Essential vitamins like vitamin D and vitamin C play major roles in the functional growth of muscles and bones. Lack of certain minerals like calcium, phosphorus and chromium can be the result of age-related digestive issues. As such, it results in imbalance in the production of certain hormones like calcitonin and parathyroid that regulate the serum concentration of vitamins and minerals (due to tumours that are highly prevalent in elderly) or it causes a decreased absorption from the gut. Age-related deterioration of muscular strength and balance control mechanisms has been associated with a reduced performance on functional tasks [51–53]. Comparing the isometric strength levels of the same muscle group, the loss of strength begins sooner among women than among men. It is reported that women are weaker than men in the absolute strength of various muscle groups in all stages of life. Various studies state that women have a longer life span, so the prevalence of disability among women is also more compared with men and it is

Ageing Process and Physiological Changes http://dx.doi.org/10.5772/intechopen.76249 9

The human body is made up of fat, lean tissue (muscles and organs), bones and water. After the age of 40, people start losing their lean tissue. Body organs like liver, kidneys and other organs start losing some of their cells. This decline in muscle mass is associated with weakness,

The tendency to become shorter occurs among the different gender groups and in all races. Height loss is associated with ageing changes in the bones, muscles and joints. Studies show that people typically lose almost one-half inch (about 1 cm) every 10 years after age 40 [59]. Height loss is even more rapid after age 70. These changes can be prevented by following a

Changes in the total body weight vary for men and woman, as men often gain weight until about age 55 and then begin to lose weight later in life. This may be related to a drop in the male sex hormone testosterone. Women usually gain weight until age 67–69 and then begin to lose weight. Weight loss later in life occurs partly because fat replaces lean muscle tissue and fat weighs less than muscle [60]. Studies have also shown that older people may have almost one-third more fat compared to when they were younger. Fat tissue builds up towards the

Today, as standards of living continue to rise, weight gain is posing a growing threat to the health of inhabitants from countries all over the world. Obesity is a chronic disease, prevalent in both developed and developing countries, and it is affecting all age groups. Indeed, it is now so common

healthy diet, staying physically active and preventing and treating bone loss [60, 61].

centre of the body, including around the internal organs [60, 62, 63].

marked with advancing age [54–56].

disability and morbidity [57, 58].

5. Obesity in elderly: prevalence

4. Body composition changes in old age

Skeletal muscle strength (force-generating capacity) also gets reduced with ageing [45, 46] depending upon genetic, dietary and, environmental factors as well as lifestyle choices. This reduction in muscle strength causes problems in physical mobility and activity of daily living. The total amount of muscle fibres is decreased due to a depressed productive capacity of cells to produce protein. There is a decrease in the size of muscle cells, fibres and tissues along with the total loss of muscle power, muscle bulk and muscle strength of all major muscle groups like deltoids, biceps, triceps, hamstrings, gastrocnemius (calf muscle), and so on. Wear and tear or wasting of the protective cartilage of joints occurs. The cartilage normally acts as a shock absorber and a gliding agent that prevents the friction injuries of the bone. There are stiffening and fibrosis of connective tissue elements that reduce the range of motion and affect the movements by making them less efficient. As part of the normal cell division process, telomere shortening occurs. DNA is more exposed to chemicals, toxins and waste products produced in the body. This whole process increases the vulnerability of cells.

With ageing, toxins and chemicals build up within the body and tissues. As a whole, this damages the integrity of muscle cells. Physical activity also decreases with age, due to a change in lifestyle. Somehow, the physiological changes of the muscles are aggravated by age-related neurological changes [49]. Most of the muscular activities become less efficient and less responsive with ageing as a result of a decrease in the nervous activity and nerve conduction.

A study was done by Williams et al. [50], who evaluated the muscle samples from both elderly and young adults and suggested that limb muscles are 25–35% shorter and less responsive in elderly healthy individuals when compared to young adults. In addition, the overall fat content of muscles was also higher in elderly population, suggesting transformation in the normal remodelling with age. Age-related musculoskeletal changes are much more prominent in fast-twitch muscle fibres as compared to slow-twitch muscle fibres. With ageing, the total water content of the tissue decreases and loss of hydration also adds to the inelasticity and stiffness. Alterations in the basal metabolic rate and slowing metabolism (as part of the physiological ageing process) result in muscle changes. This leads to the replacement of proteins with fatty tissue (that makes muscle less efficient).

Hormonal disorders can affect the metabolism of bones as well as muscles. Research suggests that menopause in women marks the aggravation in the deterioration of musculoskeletal changes due to lack of oestrogen that is required for the remodelling of bones and soft tissues. Certain systemic conditions like vascular disorders or metabolic disorders, in the case of diabetes, affect the remodelling of tissues as the rate or volume of nutritional delivery for the regeneration of cells is compromised. It is very important to control the pathological processes to optimise healing and repairing the potential of the musculoskeletal system. Essential vitamins like vitamin D and vitamin C play major roles in the functional growth of muscles and bones. Lack of certain minerals like calcium, phosphorus and chromium can be the result of age-related digestive issues. As such, it results in imbalance in the production of certain hormones like calcitonin and parathyroid that regulate the serum concentration of vitamins and minerals (due to tumours that are highly prevalent in elderly) or it causes a decreased absorption from the gut.

Age-related deterioration of muscular strength and balance control mechanisms has been associated with a reduced performance on functional tasks [51–53]. Comparing the isometric strength levels of the same muscle group, the loss of strength begins sooner among women than among men. It is reported that women are weaker than men in the absolute strength of various muscle groups in all stages of life. Various studies state that women have a longer life span, so the prevalence of disability among women is also more compared with men and it is marked with advancing age [54–56].
