Introduction
Biologically, aging entails the process of growing old, which involves biological changes in the body systems, organs, and body parts of an organism. Aging has both positive and negative aspects simply because it covers numerous aspects of one’s life including physical, psychological, and social changes, which vary and differ greatly from the activities of the young age. In human beings, physical changes in aging may include a reduction in body growth and muscle wasting while psychological changes imply mental changes, response and reaction time changes coupled with emotional changes. Some attributes of aging lead to reduced responses to stimulus while other dimensions of aging cause an increase in knowledge of events and circumstances due to wisdom gained over time.
Aging and nervous system
Aging affects many body systems including the nervous system whereby, as aging sets in, there is a correspondent decrease in the rate of protein production in the body. The reduced protein synthesis affects among others, the production, and secretion of the neurotransmitters, which on the other hand slow down or reduce the reaction time following a stimulus (Kahn, & Rowe 1987, p.144). This reduces the functions of the target cells and organs hence ineffective delayed responses occur in many aging people. According to Bowling, “In aging, there is an increase in synaptic delay and a 5-10% decrease in the speed of nerve conduction, causing reflexes to slow” (2005, p.23). This synaptic delay results from the reduced production and secretion of the neurotransmitters and the less functioning synaptic knob, which retarded physiological reactions in the body. The body adapts to the low secretion of the neurotransmitters by slowing the response time to allow enough time for enough neurotransmitter production to carry out an effective response or reflex.
Aging in addition affects the brain as the central nervous system and causes mental impairments such as memory loss and alertness. According to Bowling, “there is weight of the brain decline with age due to brain shrinkage caused by loss of brain cortical neuron” (2005, p. 24). The loss of brain weight results from the decrease in the number of nerve cells due to aging and the nerve cells have less dendrite at their ends. These aspects affect the normal functions of the brain as a center for nervous coordination and therefore lead to malfunctioning of the nervous system in elderly people.
Increased activity of the nervous cells over a long period as aging continues, results in some of the nerve cells losing their myelin sheath or coating and therefore, the speed of nerve impulse transmission in a nerve cell reduces significantly making the elderly less responsive to stimulus especially with sight, sound and taste (Willis 1996, p. 112). Wearing out of the myelin coat of the nerve cell exposes the nerve axon and diminishes the ability of the nerve cell to transmit impulses leading to conditions such as impaired sound perception by the eardrum, reduced light sensation by the cornea, and low taste sensation by the taste buds in the tongue.
Effects of aging on the nervous system lead to a reduction in the velocity of signal transmission due to varied effects on the nerve cells or on the neurotransmitter secretion. With reduced production of the neurotransmitter, synaptic function slows down consequently slowing the rate of signal transmission through the nerve and therefore delayed response to a stimulus. Furthermore, deformation of some nerve cells because of aging such as loss of myelin sheath and decreased receptors on the surfaces of nerve cells and organs such as cornea, eardrum, and taste bud can lead to visual impairment, deafness or complete lack of taste sensation in elderly people
Hormone production and aging
Hormonal secretions in the body can decrease, increase, or remain unchanged during the course of aging but this trend differs from person to person depending on sex. Numerous body systems depend on hormonal secretions for their functioning and therefore, hormones form a major component of control of body systems (Minaker 2007, p. 221). Aging results in changes in manner and mechanism of the body systems control with some target organs becoming less sensitive to their hormones or low production of enough hormones to cause the control. Reduction in metabolic rate with aging leads to reduction in the secretion of thyroid hormones resulting in a reduction in body mass of many aging people (Manker 2007, p. 224). With the low production of thyroid hormone, metabolic rate decreases gradually from the age of 30 years onwards.
The parathyroid gland reduces the secretion of the parathyroid hormones with advance in age causing weakness of bones as calcium accumulation gradually declines. This phenomenon can cause osteoporosis in the elderly hence leading to impaired mobility or pain (Knopman 2007, p.442) implying that elderly people require calcium and phosphorus supplements to avoid osteoporosis. In addition, aldosterone and cortisol secretion by the adrenal gland reduces with age whereby the reduction of these hormones leads to a reduction in blood pressure. Electrolytes balance in the kidneys, controlled by the aldosterone hormone ensures the stability of blood pressure and therefore age poses the risk of low blood pressure.
Sexual hormones variation changes with age depending on the sex of the person with a slight decrease in the secretion of testosterone in males while on the other hand, females experience reduced levels of estradiol and estrogens especially after menopause (Knopman 2007, p.444). In women, prolactin hormones diminish drastically while in males there is a slight reduction of the testosterone hormone and therefore, the reproductive hormones of males remain slightly unchanged even in old age. This implies that, after menopause females remain sexually inactive while on the contrary, males remain sexually active.
Aging and drug pharmacokinetics
Aging not only involves hormonal and nervous system effects, but also entails pharmacological and surgical intervention effects. These effects propagate the initiation of responses to therapeutic interventions applied to the aged in cases of illness. According to Dugdale, “…aging has a dramatic effect on the response to pharmacological, surgical and rehabilitative interventions with altered response to drugs” (2009, p.452). Alteration in response to drugs may lead to low efficacy of drugs prescribed to the aged and this can lead to an increase in mortality rates for the elderly out of adverse drug reactions. As old age becomes a risk factor to disease due to the decreasing immunity, medication becomes inevitable to the old and therefore, this can increase exponentially the mortality rate of the aged from drug-related reactions.
Although adverse drug reactions pose a threat to the lives of the elderly, little is done on clinical trials of pharmacological effects of the drugs on the elderly. According to McLean, & Le-Couteur, “It is estimated that adverse drug reactions are the fourth to the sixth greatest cause of death and about 5% of the hospital admissions are related to the management of people suffering from drug reaction related toxicity” (2000, p.664). These estimates represent a significant number of death risks accruing from the unreported prevalence of occurrence of adverse drug reactions in elderly people. In most cases, adverse drug reactions in the elderly are associated with altered drug pharmacokinetics and the usage of more than two drugs at a time (Polypharmacy), which causes drug-drug reactions; therefore, this association of drug reaction to polypharmacy and altered pharmacokinetics reduces the quest for clinical trials on the effect of aging on the adverse drug reactions.
None severity of adverse drug reactions in the elderly makes them less likely to notice and report and therefore, little or no documentation about adverse drug reactions in the aged. This allows the use of clinical trials data obtained from the younger generation because there is little about the elderly although they continue suffering from adverse drug reactions. In addition, adverse drug reactions in the elderly occur with specific types or classes of drugs and are not dependent on polypharmacy nor on altered pharmacokinetics (Dugdale 2009, p.454). This trend, therefore, calls for replacement of these drugs evoking reaction in elderly instead of undertaking clinical trials to collect enough data and information on the effects of age on drug reactions and therefore as a result, elderly representation in clinical trials remains minimal.
Conclusion
Age affects most of the body systems ranging from the nervous system, hormonal systems, and pharmacological activity and reactions of the body among other effects. Each aspect of the biological system affected by aging results in varied outcomes with some leading to physical impairment; for instance, loss of vision while others lead to drug-reaction-related disorders. There are pharmacological changes about aging even though there is minimal information and data from clinical trials calls for dosage manipulation especially in elderly medication.
Reference list
Bowling, A., (2005). Ageing well. New York: Open University press.
Dugdale, D., 2009. General medicine. Washington: Washington university press.
Kahn, R., & Rowe, W., 1987. Human ageing. Usual aging science journal, 237(48), pp.144-145.
Knopman, S., 2007. Alzheimer’s disease and other dementias. Philadelphia: Saunders
McLean, A., & Le-Couteur, M., 2000. Aging biology and Geriatric clinical pharmacology, Australia: University of Sydney press.
Minaker, K., 2007. Common clinical sequel of aging. Baltimore: University of Maryland Press.
Willis, S., 1996. Adult development and aging. New York: HarperCollins College Publishers.