Confirmación de la expectativa vacación-estudio como factor principal del ritmo anual de incidencia y edad de menarquia

Abstract

Expectancy of vacation as a determining factor of the annual rhythm of menarche (Rev Méd Chile 2006; 134: 606-12).

The monthly rhythm of incidence and age at menarche: thirty five years of research: The circa-vacation-study expectancy rhythm of incidence and age at menarche

“…In Mar until Jun lower means of menarche age should be observed (menarche refractory to study delay); the monthly mean should increase from Jun to Dec (the delayed menarche during the Stu-months) as the Vac-months approach. This pattern was seen in Santiago (temperate zone S Hemisphere), Medellín (equatorial zone, N. Hemisphere) and Riberão Preto (Brazil, temperate zone, S. Hemisphere) and published previously (Valenzuela 2004(Valenzuela , 2006. The present study intends to test formally the hypothesis of the infl uence of Stu-months and Vac-month on the age at menarche.…”

“…By assuming that the study regime decreases the MI and delays menarche of susceptible girls, we proposed a hypothesis on the monthly rhythm of the age at menarche (Valenzuela, 2006). The hypothesis proposed that the last month(s) of the long vacation period (with a high MI) and the following Stu-months (with a low MI) should present the lowest means of the age at menarche.…”

“…As pointed out in the Introduction, our studies showed that it was not properly the fi esta period or holidays, but rather the expectancy of fi esta or holidays is the factor that increases the MI. It was evident that the environment or circumstances related to the expectancy of fi esta (relaxation or reward) or non-fi esta (stress or unwanted situation) could impress strongly the neuro-psycho-endocrine system, so as to change the age of circa-vital events such as menarche (Valenzuela et al, 1999;Valenzuela, 2004Valenzuela, , 2006. I think that the expectancy of the event, and not necessarily the event itself was the cause of the rhythm, because of the left-biased bell shaped distribution of menarche around the event.…”

“…I think that the expectancy of the event, and not necessarily the event itself was the cause of the rhythm, because of the left-biased bell shaped distribution of menarche around the event. This precluded a recruitment distribution where menarche increases its incidence in the previous days (or weeks or months) of the event (Vac-months) and decreases drastically after the event (Valenzuela et al, 1999;Valenzuela, 2004Valenzuela, , 2006. We have called the factor of the rhythm fi esta as a preliminary approach.…”

“…To refute seasonality our method assumed: 1) the consistent antithetical expectancies that should necessarily be found between Northern and Southern Hemispheres; 2) the marked diff erences in climatic conditions between equatorial, tropical, temperate, Arctic and Antarctic and polar earth zones; 3) the similarities of MI that should be found in months of the same season; 4) the marked or antithetical diff erences that should Biol Res 46: 21-26, 2013 be found in MI of months belonging to antithetical seasons (summer and winter) and the similarities that should be found in months of diff erent seasons with similar climatic conditions (autumn and spring); 5) the similarity of the rhythm that should be found in regions with the same latitude, altitude and geographical conditions. With all these expected situations we refuted conclusively the seasonality of the circa-annual rhythm of MI; for example: 1) marked rhythms were found in samples from tropical or equatorial zones where the rhythm was not expected (Chennai in India and Medellín in Colombia); 2) in all the examined samples strong diff erences were found among months of the same season or with the same photoperiod and temperature; it was frequent to fi nd a peak of MI followed by a trough of MI in contiguous months (Valenzuela et al, 1996a(Valenzuela et al, , 1996b(Valenzuela et al, , 1999Valenzuela 2004, Valenzuela 2006; 3) samples from contiguous regions belonging to diff erent countries show diff erent MI rhythms. One of the most striking diff erences in the menarche incidence (MI), between Hemispheres was found in Feb, with a peak in Santiago (summer) and a trough in Europe (winter, Valenzuela et al 1991Valenzuela et al , 1993Valenzuela et al , 1996aValenzuela et al , 1996b.…”