Physiological Changes of Aging
Agerasia, or healthy and vigorous old age, is not a very familiar term. This may be due to the fact that old age has not been traditionally revered by our society and many depict aging as anything but a healthy and vigorous stage of life. Although disease and impaired function are not an inevitable consequence of the aging process, there are certain systemic and oral physiological changes that are a factual part of growing older.
Systemic
Illness and aging are not always related. However, due to a reduction in cells and a decreased metabolism, the aging body tends to work less efficiently. As a result, homeostasis, immunity, and the ability to withstand stress become impaired.
The skin is one of the most noticeable areas indicative of aging. Lines appear in the face, particularly around the eyes, nose, and mouth. This is due to subcutaneous fat loss, dermal thinning, decreasing collagen and elastin, and a 50% decline in cell replacement. Inevitably, with the reduction of cell replacement in the skin, the person may be more prone to infection since wounds may heal more slowly. Another aging characteristic is that the skin takes on an almost transparent appearance as it loses elasticity. Brown spots appear in areas exposed to the sun due to localized melanocyte proliferation. However, overall melanocyte production decreases in the aging process. Body temperature also becomes difficult to regulate as a result of the decrease in size, number, and function of sweat glands and the loss of subcutaneous fat.6,7
Hair, nails, vision, and hearing are also targets of the aging process. Hair loses its pigmentation and takes on a gray or white appearance and often becomes thinner. The nails exhibit more brittleness, longitudinal ridges, and may have malformations. Aesthetic changes occur in the eye area. The eyes rest deeper in the sockets, eyelids lose their elasticity, the cornea flattens, the pigmentation of the iris becomes irregular or fades, and fatty deposits may form under a thinning yellow conjunctiva. Due to the size reduction of the pupil, the older adult needs about three times as much light as a younger person to see objects clearly. Therefore, night vision and depth perception are weakened. Color vision, especially to hues of blue to green, is also affected due to weakening in cones in the retina. Cataracts (an opacity of the lens) are common in persons aged 65 and older. Possible etiologies include diabetes, retinal detachment, glaucoma, chemical changes in lens proteins, etc. Changes also emerge in the older adult’s hearing. The extent of hearing loss varies with each individual. Before a person reaches young-old status around the age of 60, they may experience difficulty hearing high-pitched sounds, especially the consonants s,z,t,f, and g.6-8
The progression of age also causes some changes to occur in the respiratory, cardiovascular, gastrointestinal, renal, neurological, musculoskeletal, immune, and endocrine systems. There is a decrease in pulmonary function due to respiratory muscle degeneration and a reduction in ventilatory capacity. The lungs exhibit more rigidity, and the size of the alveoli declines. Respiratory fluids decrease by 30%; therefore the risk for pulmonary infection and mucous plugs increases.6,9,10
The size of the heart may become slightly smaller, thereby losing its contractile strength and efficiency. It has been reported that cardiac output at rest in an individual of 70 years old decreases by as much as 30 to 35%.6 Stress also can have a deleterious effect on the older person’s heart, and it may take the heart rate longer to regulate following exercise.6,11
There is a reduction in the mucosal elasticity and secretions of the gastrointestinal system. This, in addition to medications, can contribute to a loss of appetite and constipation. Additionally, there is less efficient metabolism and detoxification of drugs by the liver.6,12
Other age-related changes occur in the renal system. Overall, kidney function may diminish starting as early as age 40. The size of the kidney and bladder decrease, and there is an impaired renal clearance of drugs. There is also reduction in the ability for the renal system to respond to sodium uptake. Typically, there is an increase in residual urine, frequency, and nocturia in the older adult.6
Nerve transmission slows down in the older adult person; therefore the reaction time to external stimuli is slower and there is an increase in the pain threshold. The older adult may need to rest more during the day, since sleep patterns become more irregular and frequent awakenings occur.6
Changes observed in the musculoskeletal, immune, and endocrine systems are characterized by a decrease in height, bone mass, muscle mass, and collagen formation. Less elasticity in the joints and supporting structures tend to be evident. Walking may prove difficult for some older adults. In order to compensate, the person may walk by taking shorter steps and stand with legs spread for balance.6
As age increases, so does the incidence of autoimmune disease. The body’s ability to recognize host cells and detect and destroy antigens and mutant cells becomes difficult. Susceptibility to infection increases since there is a decreased antibody response. The absorption of vitamin B12 may decline resulting in reduced erythrocyte mass and a decrease in hemoglobin and hematocrit.6,13
Lastly, age progression affects the endocrine system. Most notably, there is a diminished ability for the body to tolerate stress. This is evident in the production of glucose. In response to stress, the blood glucose level rises and regulation is impaired, increasing the risk of diabetes.6,9
Oral
Myths related to changes in the oral cavity associated with aging are no longer as widely accepted as they were 10 to 20 years ago. For instance, the myth that most older adults will lose their teeth was a common misconception about age progression. As mentioned previously, a greater percentage of the older adult population are retaining their natural teeth, thereby reducing the need for complete or partial prostheses. Another myth that still exists to some degree is that dry mouth is a normal consequence of growing old. In healthy adults, changes in salivary composition and flow are minimal to nonexistent. Dry mouth is usually disease or medication-induced.
Specific alterations in the oral soft and hard tissues can occur later in life. Oral soft tissues exhibit some of the same changes as the skin. There is a loss of elasticity and the tissues tend to become thinner and less vascular. The lips can be dry, and the oral mucosa and tongue may appear smooth and shiny due to their thinner nature and the existence of nutritional deficiencies. The capillaries are more fragile; therefore petechiae on the mucosa occur more frequently. Evidence of hyperkeratosis may be evident from broken teeth, restorations, ill-fitting dentures, or tobacco use. Often the tongue becomes fissured and sublingual varicosities may present that appear as deep, red, or bluish nodular dilated vessels on either side of the midline on the ventral surface of the tongue and the floor of the mouth.14
The older adult commonly displays gingival recession. However, this may be the result of prior disease, insufficient attached gingiva, or malpositioned teeth. An increase in the thickness in cementum can also be observed. Color changes in the teeth may arise from the long-term intake of food with coloring agents or from prolonged tobacco use. Occlusal or incisal attrition may be derived from long-term dietary habits, occupational factors, or bruxism. Teeth that display attrition may be more brittle and prone to chipping.15
