MEDizzy - The systemic effects of the aging cluster into four domains:

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General Considerations in Clinical Medicine 1

The systemic effects of the aging cluster into four domains: body composition, the discrepancy between energy demand and utilization, homeostatic dysregulation, and neurodegeneration. All of the following statements regarding these effects are true EXCEPT:

ExplanationThe systemic effects of aging are multidimensional and contribute overall to the concept of frailty. Frailty is defined as a physiologic syndrome characterized by diminished reserve and decreased resistance to stressors. Frailty increases an individual’s vulnerability to adverse outcomes and death. The four recognized domains are body composition, the discrepancy between energy demand and utilization, homeostatic dysregulation, and neurodegeneration. Body composition changes are marked by a progressive loss of lean muscle mass following the third decade of life. The loss of muscle mass is greater in fast-twitch than in slow-twitch fibers and is associated with a loss in muscle strength. The reason behind the loss is unknown, but some research suggests this is due to the loss of motor neurons. Coincident with the loss of muscle mass is an increase of fat mass that begins in middle age. However, late in life, fat mass begins to decrease again (option A). This mirrors changes in weight, which tends to increase until about 65 to 70 years in men and somewhat later in women before declining later in life. Waist circumference does increase throughout the life span, indicating ongoing fat deposition in the viscera. The effects of aging on the balance between energy demand and utilization are reflected by decreases in maximal oxygen consumption (option C) as well as progressive decreases in the resting metabolic rate (RMR). Although the RMR does decline with aging, one should have caution in the setting of acute illness when the RMR may rise substantially. The high RMR in the setting of acute illness is associated with higher mortality. Homeostasis is generally measured by evaluating signaling pathways that involve hormones, inflammatory mediators, and antioxidants. Testosterone and estrogens decrease with aging, whereas inflammatory cytokines, including C-reactive protein and interleukin-6 (option B), rise. In addition, there is also evidence of oxidative stress and the production of reactive oxygen species with aging. Neurodegeneration begins to become more evident after the age of 60 and is more apparent is some areas of the brain than others. The lateral prefrontal cortex and hippocampus (option D) are most likely to show evidence of atrophy in individuals with mild cognitive impairment, whereas the primary visual cortex is relatively preserved. In addition, functional imaging studies may show impaired coordination between brain areas responsible for higher-order functioning with more difuse activation rather than the highly localized activity that is seen in younger individuals.