SOME NOTES ON AGING 



Hardin B. Jones 



Division of Medical Physics and Donner Laboratory 

 University of California, Berkeley, California 



Abstract — Evidence of physiologic change with age uniformly points to a cumulative deteriora- 

 tion as age increases. Further degenerative change may occur proportionally to the amount 

 of change already acquired. As age increases, incidence of degenerative disease and death 

 increases exponentially. It is pointed out that, whatever aspect of body function is considered, 

 e.g. functional members, metabolism, cellular activity, or blood flow characteristics, a 

 relatively exponential increase in degeneration of body function occurs with increasing age 

 of the individual. It is possible that each of these separately considered systems of aging is 

 in partial equilibrium with the others, so that all general characteristics of change in functional 

 vigor with time follow a similar course. 



Increments of change in body structure and function occur as a phenomenon 

 of aging. Usually, the term 'aging' is associated with deteriorative change, 

 and as such is distinctively set off from those changes with age that are respon- 

 sible for growth and development. However, even the period of development 

 may be considered to have associated with every step some hazard that this 

 step may not be achieved fully, thus adding an increment of imperfect function 

 to the body. Such a deletion from full function, whether arising from genetic 

 inheritance, developmental processes, or accidental mishap, may count just 

 as much toward the accumulated deterioration we can manage to tolerate 

 as does the deterioration of advanced age. 



Experience of mishap accumulates throughout life. Some events, to be 

 sure, have as little residual effect upon us as the whistle of the wind, but occasion- 

 ally something of consequence occurs. As an example, it may be the crushing 

 of a finger; although we usually recover, we can remember the event because 

 of some persistent change^perhaps a scar, or a distortion of the nail, or even 

 the loss of the finger. 



Since, on the average, we live each day in a situation where there is some 

 definite but slight chance that an event of misfortune may disturb us, then the 

 longer we live under this average circumstance of risk, the more likely we are 

 to find among us individuals showing physical impairment. Inspection of 

 such a system leads to the probable conclusion that: 



Accumulated impairment = Mishap risk x Time of exposure X 

 Fraction of function lost per mishap. 



But, the risk of occurrence of an unfavorable event is subject to increase as 

 age increases, and the fraction of function lost per mishap may also increase 

 as age increases. In this system, therefore, we can expect a relatively non-lincrr 

 accumulation of average physical impairment as age increases; physical impair- 

 ment may increase as some higher power of time hved than unity. This example 



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