No, questi dati sono stati desunti da pazienti che soffrivano di un disordine maniacale per cui si contavano i capelli che perdevano giorno dopo giorno.
sono stati portati in un convegno ed è stato documentato lo schema che questi stessi soggetti hanno tracciato sul libro che ho citato sopra.
In 2012, a 39-year-old long-haired male presented at the Center for Dermatology and Hair #65532;Diseases Professor Trüeb with early androgenetic alopecia. He had counted his hairs shed in the course of hair washing every 3 days from the years 1996–2011 and plotted their mean value against the month of the year (Fig. 3.14b). There was a striking congruence with the graphic formerly demonstrated for women by Kunz et al., which proves that men are subject to the same seasonal changes of hair growth and shedding as women. The difference is that the hair shedding is less noticeable in men, who commonly wear their hair shorter. Moreover, men usually have a lesser sensitivity than women for the condition of their hair. Nevertheless, this fluctuation may also reflect in subsequent clinical images taken of patients (Fig. 3.14c, d).
The cyclical activities of the hair follicle are the mechanism by which mammals change their coat of hair to meet the exigencies of growth, sea- sonal changes in the ambient environment, and, perhaps, normal wear and tear. It seems likely that environmental factors, such as the photoperiod, mediate through the optic pathway and the neuroendocrine system coat phenotype and function to match environmental changes. The fact that human hair follicles, just as those of other mammals, undergo cyclical activity and are influenced by hormones implies that human hair is not unaffected by these phenomena.
From an evolutionary point of view, the maintenance of the low winter level of hair shedding and the postponement of hair fall until the end of summer might, perhaps, be postulated as having a selective advantage with respect to isolation of the head against the cold in winter and protection of the scalp against the midday sun in summer, respectively.
The existence of seasonal fluctuations in hair growth and shedding may complicate the assessment of pharmacologic effects when treating hair loss:
Awareness of these fluctuations is prerequisite to providing the correct cause and prognosis to the patient, ensuring patient compliance with therapy.
Ultimately, seasonal fluctuations of hair growth and shedding may have potentially seri- ous implications for investigations with new hair growth-promoting agents: Depending on the stage of periodicity in growth and shedding of hair for a particular subject, the heterogenicity of included subjects may be enough to distort the clinical efficacy results and the perceived benefit of an investigational agent. In the active stage of seasonal telogen effluvium, the involved hair fol- licles would probably fail to respond to the thera- peutic agent, which may cause a false-negative result. In the recovery stage, the increased amounts of spontaneously regrowing hair might be interpreted falsely as a positive result.
(pag. 112-114 Male Alopecia Trueb, Won So Lee, Ed. Springer 2014)