Chronic telogen effluvium is due to a reduction in the variance of anagen duration

Background/Objectives: Chronic telogen effluvium and diffuse cyclical hair loss in women are well-described clinical entities characterized by chronic and fluctuating increases in hair shedding without loss of hair volume. We sought to investigate the follicular dynamics of chronic telogen effluvium and diffuse cyclical hair loss using a previously validated computer simulation known as the follicular automaton. Methods: Using our model, we were able to simulate reductions in both the mean and variance of anagen duration and thus investigate their consequences with respect to both hair volume and hair shedding. Results: We showed that reducing the mean anagen duration results in a loss of hair volume without prominent fluctuations in hair fall: findings that reproduced the key features in androgenetic alopecia. In contrast, a reduction in the variance of anagen duration generated follicular dynamics that accurately reproduced the known key features of chronic telogen effluvium and diffuse cyclical hair loss: acute exacerbations, periodicity and only minimal reductions in long-term hair volume. Conclusions: We provide evidence that suggests chronic telogen effluvium may be secondary to a reduction in the variance of anagen and suggest this pathological state represents a new functional type of recurrent hair shedding.