Does chronological age reduce working ability?
Definitions of so-called older age often are based on a chronological age of 65 years and over, although by some authors aging is the process that starts after the 30th year of life. At the beginning occur changes in the organ functions, followed by anatomical changes as well. Some organs age faster, some slower. For example, kidneys decrease for one third, lungs do not change, liver shrinks a little, prostate increases twice. In some cross-sectional studies, muscle mass in men aged 65 is on average 12 kg less than in the so-called middle age, and in women it is approximately 5 kg less. In the heart the amount of connective tissue increases, lipofuscin is deposited in cardiac muscle, the strength of which is decreasing. In the respiratory tract the number of pathways cilia decreases, along with the alveolar surface, muscles involved in breathing change, lung elasticity is also diminished. But, in regard with the previous body capacity, "physiological aging" can be divided into three types of elderly: the "older" elderly have the highest functional capacity of 2-3 MET (MET--metabolic unit, i.e. the oxygen consumption of 3.5 ml/kg body mass in a minute), the "younger" elderly are the persons of older age having maximal functional capacity of 5-7 MET, while the "sport" elderly have the functional capacity of 9-10 MET, disregarding chronological age. The brain weight diminishes for approximately 7% compared to younger age. In temporal gyrus and area striata even 20-40% of cells are being lost, vacuolar and neuroaxonal degeneration occurs, lipofuscin is being accumulated. The brain blood flow, which is in normal conditions 50-60 ml/min/100 g of tissue, with the increase of biological age decreases to about 40 ml/min/100 g of tissue. However, this usually is not the consequence of biological age but of disease. A chronological age of 65 for the beginning of "elder hood" is a sociopolitical construct developed by social security systems and government organizations to decide an arbitrary age at which benefits should be paid. Thus, it neither a border nor do changes designating old age occurs exactly with that "age border". The changes in the organism during the so-called aging are individual. So, the functional capacity of an organism, both physical and intellectual, must be evaluated individually, having in mind biological age.
Duraković
Zijad
Z
Department of Internal Medicine, University Hospital Center "Zagreb", School of Medicine, University of Zagreb, Croatia. zdurakovic@mef.hr
Misigoj-Duraković
Marjeta
M
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism / Q000473:pathology / Q000502:physiology; D005260:Female; D005853:Geriatrics; D006801:Humans; D008297:Male; D010809:Physical Fitness