Some Notes on Aging 343 



of diabetes mellitus. This disease is not limited to the classic confines of its 

 relationship to carbohydrate and intermediary metabolism: serious disturbances 

 of lipid metabolism may also occur, linked with enhanced tendency for vascular 

 changes; the term of pregnancy is frequently lengthened in diabetic mothers 

 retinal changes may occur in diabetics, and the disease in general may be 

 associated with somewhat early changes related to aging. There seems to be 

 no reason to suspect that diabetes is a more complicated disease fundamentally 

 than loss of islet-cell function or absence of insulin; but it does seem that the 

 results of this functional deficiency can produce several different conditions 

 that may even interact to compound the pathologic impact of the basic 

 deficiency. 



Another example of general disease being associated with a specific disease 

 is observed in the follow-up of cancer patients. In cancer of the rectum, death 

 from intercurrent disease may be just as likely as death from recurrence of 

 the mahgnancy. There is also general evidence, from comparisons of mortality 

 from disease in nineteen western countries, that high incidence of any one kind 

 of disease is associated with high incidence of other diseases (la). Some factors 

 affecting adult health and life expectancy might be expected to be common 

 to several kinds of overt disease; other factors influencing health may have 

 a limited efiTect upon a single system. For example, in overweight individuals 

 the increased risk of death is attributed to increased incidence of arterio- 

 sclerosis and hypertensive disease, while the tendency toward cancer is not 

 significantly changed from the average of the population. In radiation exposure, 

 all major diseases may be enhanced. Leukemia, however, may be increased 

 by a factor of 10, while other degenerative diseases are elevated less than 

 twice. It is quite possible that some kinds of disease are less likely to occur 

 following radiation exposure, even though the general trend is toward more 

 severe and earlier degenerative disease following significant radiation exposure. 

 Similarly, smoking generally enhances degenerative disease by a factor of 

 2 while lung cancer is increased tenfold. These observations point to the 

 interrelationships in etiologic factors in disease, and the possibility that causative 

 factors in development of degenerative disease may have interactions that 

 accelerate the appearance and consequences of disease change. 



Vascular Disease 



GoFMAN and associates (3) have been able to show that the change in the 

 wall of the artery in arteriosclerosis is essentially a linear thickening throughout 

 aging. Thus, the shift toward occlusive change results from narrowing of a 

 cylindrical tube by a progressive thickening of the mass, reducing the radius 

 of the lumen. The function describing the reduction of blood flow in the 

 artery involves the cross-sectional area of the artery, which is proportional 

 to the square of the radius of the artery. Since blood flow in the artery is 

 related to cross-sectional area, blood flow changes in arteriosclerosis are 

 not proportional to time lived but rather vary as a power function of time. 

 The fact that elasticity of the artery may fall off" sharply as sclerotic thickening 

 occurs probably accelerates the process. Thus, from several points of view, 

 vascular change is not likely to produce a linear accumulation of disturbance 

 with time lived, even though the basic feature of the disease is reasonably 



