P8.154 Lack of significant decrease in total hair follicle number with advancing age

Rod Sinclair, Adam Chapman, Jill Magee

University of Melbourne Department of Dermatology, St Vincent’s Hospital

Age-related reduction in hair is seen in the axillary and pubic regions as well as the scalp.  Horizontal sectioned scalp biopsy is an ideal tool to investigate the impact of advancing age on scalp hair follicle density and morphology.  Ordinal logistic regression analysis was used to assess the relationship between total hair count and patient age at time of biopsy and to control for follicle miniaturization in 1666 horizontally sectioned midscalp biopsies from 883 women aged between 13 and 84 with hair loss. Miniaturization was assessed by calculating the ratio of terminal to vellus-like hairs (T:V) at the mid-isthmus level and considered significant if the ratio was < 4:1.  Fibrosis was documented when present.  The average number of hair follicles per biopsy is 39.6 (SD+/- 10.8). There is a highly significant negative association (p<0.0001) between age and total follicle number.  Controlling for T: V < 4:1 this association is weakened by 17%, but remains significant.  The relationship unconfounded by T: V < 4:1 shows that for every additional year of ageing, 0.077 total hair follicles (0.22%) are lost per biopsy.  When biopsies with histological evidence of fibrosis are removed from the analysis, this figure is reduced to 0.076 total hairs lost (per biopsy).    There is an inverse linear relationship between age and mean hair follicle density in women that leads to hair loss independent of androgenetic alopecia, albeit relatively small.