The Effects of Aging on Hair–More Than Just Amount 482 curvature of neighboring hair fibers in an assembly.18 Therefore, an increase in hair fiber curvature with age as Nagase et al. identified for Japanese females would likely result in the appearance of frizziness with increasing age from increasing curvature and needs to be examined among Caucasian and African hair types. However, hair greasiness also affects hair fiber alignment and therefore examination of hair frizz together with curvature versus age will be required to determine the overall effect of aging on hair frizz. Aging and combing/brushing effects: Changes in hair fiber diameter with age will decrease tensile and bending resistance of hairs. We would anticipate related effects on combing ease, that is, the increase in fiber stiffness along with the diameter increase up to age ~40s for females will tend to make the hair easier to comb, while the decrease in hair density/area through the 30s will tend to make the hair comb easier. Age related effects, such as curvature and greasiness changes, will also affect combing ease at these same ages and will have to be considered. Robbins and Reich45 found increasing combing forces with increasing hair fiber curvature. In fact, the curvature effect produced a quadratic relationship with combing forces. As such, combing forces were much higher at high fiber curvatures. For Japanese hair in particular, we would expect that combing forces would increase at advanced age due to curvature increases alone. However, since other factors such as a decrease in greasiness and diameter with advancing age will also increase combing forces, but a decrease in hair density beyond age 30 will decrease combing forces, simultaneous determination of these factors is necessary to understand the total effect on combing forces with advancing age. In addition, the effects of these same variables at lower age remains an area for future investigation. Aging and hair greasiness and its effects on other hair assembly properties: It is very clear from this review of hair lipids and age that both hair lipid levels and hair lipid composition change with age. Changes occur both at puberty and between ages 45–55 and these
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The  Effects  of  Aging  on  Hair–More  Than  Just  Amount  482  curvature  of  neighboring  hair  fibers  in  an  assembly.18  Therefore,  an  increase  in  hair  fiber  curvature  with  age  as  Nagase  et  al.  identified  for  Japanese  females  would  likely  result  in  the  appearance  of  frizziness  with  increasing  age  from  increasing  curvature  and  needs  to  be  examined  among  Caucasian  and  African  hair  types.  However,  hair  greasiness  also  affects  hair  fiber  alignment  and  therefore  examination  of  hair  frizz  together  with  curvature  versus  age  will  be  required  to  determine  the  overall  effect  of  aging  on  hair  frizz.  Aging  and  combing/brushing  effects:  Changes  in  hair  fiber  diameter  with  age  will  decrease  tensile  and  bending  resistance  of  hairs.  We  would  anticipate  related  effects  on  combing  ease,  that  is,  the  increase  in  fiber  stiffness  along  with  the  diameter  increase  up  to  age  ~40s  for  females  will  tend  to  make  the  hair  easier  to  comb,  while  the  decrease  in  hair  density/area  through  the  30s  will  tend  to  make  the  hair  comb  easier.  Age  related  effects,  such  as  curvature  and  greasiness  changes,  will  also  affect  combing  ease  at  these  same  ages  and  will  have  to  be  considered.  Robbins  and  Reich45  found  increasing  combing  forces  with  increasing  hair  fiber  curvature.  In  fact,  the  curvature  effect  produced  a  quadratic  relationship  with  combing  forces.  As  such,  combing  forces  were  much  higher  at  high  fiber  curvatures.  For  Japanese  hair  in  particular,  we  would  expect  that  combing  forces  would  increase  at  advanced  age  due  to  curvature  increases  alone.  However,  since  other  factors  such  as  a  decrease  in  greasiness  and  diameter  with  advancing  age  will  also  increase  combing  forces,  but  a  decrease  in  hair  density  beyond  age  30  will  decrease  combing  forces,  simultaneous  determination  of  these  factors  is  necessary  to  understand  the  total  effect  on  combing  forces  with  advancing  age.  In  addition,  the  effects  of  these  same  variables  at  lower  age  remains  an  area  for  future  investigation.  Aging  and  hair  greasiness  and  its  effects  on  other  hair  assembly  properties:  It  is  very  clear  from  this  review  of  hair  lipids  and  age  that  both  hair  lipid  levels  and  hair  lipid  composition  change  with  age.  Changes  occur  both  at  puberty  and  between  ages  45–55  and  these  

                
        

     


                
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