Month at mearche: a re-evaluation of the seasonal hypothesis

Valenzuela, Carlos Y; Núñez, Ernesto; Tapia, C.

doi:10.1080/03014469100001682

Cited by 14 publications

(21 citation statements)

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“…Se observa un exceso de menarquias en DIC, ENE y FEB y una depresión en los otros meses. El análisis de la incidencia ha sido ya presentado [14][15][16][17][18] . El PEDM alcanza su máximo en NOV-DIC, cae en ENE y FEB y se mantiene en esas cifras hasta JUN (149 meses) y desde allí va aumentando hasta NOV-DIC, aunque AGO tiene un PEDM superior a JUL y SEP. El ANOVA para PEDM fue muy significativo (F 11,3213 =9,99, P<<10 -6 ); entre las 66 comparaciones de pares mensuales, 16 fueron significativas con la corrección de Bonferroni.…”

Section: Resultsunclassified

“…vios [14][15][16][17] . Descartando los errores clericales y considerando niñas con edades entre 8 y 18,5 años, obtuvimos 3.225 niñas chilenas y 3.435 niñas colombianas que recordaban al menos el año de menarquia.…”

Section: A R T í C U L O D E I N V E S T I G a C I ó Nunclassified

“…II) Si la causa de REDM es el ritmo expectativa vacación(fiesta)-estudio(no fiesta) se espera un correlato entre ambos ritmos; en los meses de estudio deben tener su menarquia las niñas más tempraneras y el promedio mensual de EDM ir aumentando a medida que se acerca un período de vacación (el estudio retrasa la menarquia pero no la suprime); la expectativa de vacación, más el inicio de vacación, deben asociarse a un promedio de EDM más alto, hasta que todas las niñas retrasadas menstrúen por primera vez. En los estudios previos hubo un mínimo de incidencia de menarquia cercano al 5% en todos los países; como el promedio esperado es cercano a 1/12= 8,3% se tiene que las niñas no sujetas (insensibles) a RIMM constituyen 5/8,3 = 60%; el ritmo sería dado por el 40% de las niñas [14][15][16][17][18] . Otra interpretación puede ser que todas las niñas sean sensibles, con promedio de sensibilidad de 40%.…”

Section: A R T í C U L O D E I N V E S T I G a C I ó Nunclassified

“…Desafortunadamente, los estudios agrupan los meses en estaciones u otras categorías o utilizan clases agrupadas de niñas según menarquia temprana o tardía, con lo que es imposible un análisis no sesgado 6,[8][9][10][11] , que lleva a una circularidad epistémica 13 . Refutamos, concluyentemente, la estacionalidad climática del fotoperíodo y de la temperatura [14][15][16] . Otros estudios contribuyeron a esta refutación [7][8][9]11 .…”

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

Valenzuela

2006

Rev. méd. Chile

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Section: Resultsunclassified

Section: A R T í C U L O D E I N V E S T I G a C I ó Nunclassified

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

Valenzuela

2006

Rev. méd. Chile

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“…She suggested performing the analysis in Santiago (Chile, Southern Hemisphere) to see whether this summer peak of MI was also present. We found peaks of menarche incidence in December (Dec), January (Jan) and February (Feb) (Patri et al, 1980) and a striking relationship with the month of birth and conception (Valenzuela et al 1991(Valenzuela et al , 1993 showing non-climatic factors acting on this rhythm. By climatic factors is meant photoperiod, temperature, humidity, cloudiness and any other climatic factor.…”

Section: Introductionmentioning

confidence: 94%

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

Valenzuela¹

2013

Biol. Res.

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The hypothesis that the vacation-study-expectancy scholar regime produces most of the monthly rhythm of the age at menarche (AaM) was tested. Studies on monthly menarche incidence (MI) refuted climatic factors as a main factor in this rhythm, and indicated that the main factor of this rhythm is the succession of expectancies of study (Stu-months) or vacation (Vac-months) months within a year. Thus the hypothesis of seasonal circa-annual rhythm should be modifi ed to the circa-[vacation (fi esta)]-[study (non-fi esta)]-expectancies rhythm for the MI and age at menarche annual rhythms. In several countries Vac-months had higher MI than Stu-months. The high MI of Vac-months was followed by a large decrease when girls started their studies and a MI increase occurred as vacations approached. The hypothesis proposes that at the end of vacations and at the beginning of the study period the AaM should be lowest, and then the mean of AaM should increase because of the menarche delay of girls whose menarche was arrested by the initiation of school work. This pattern was found in four independent samples, from Chile, Colombia, USA and Brazil. The probability that this result be due to random fl uctuation of means is extraordinarily low (P<10 -8 ). I conclude that the infl uence of the expectancy of vacation and study periods on the monthly rhythm of the age at menarche is a real process that accounts for most of this rhythm.

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Monthly distribution of menarche among schoolgirls from a municipality in Southeastern Brazil

Tavares

Barbieri

Bettiol

et al. 2003

American J Hum Biol

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We studied the monthly distribution of menarche among schoolgirls from Barrinha, Brazil, a municipality of rural characteristics in the process of transition to urbanization, economically dependent on sugar cane culture and processing. The association between season of the year, month of the year, and birth month and the occurrence of menarche was evaluated. The schoolgirls who provided the date of menarche (month and year) by the recall method and who had menarche up to 36 months before the interview were selected for analysis (460 girls). The correlations between month of occurrence of menarche and month of birth and between menarche and seasons of the year were determined by the chi-square test and the mean monthly ages at menarche were compared by Student's t-test, with a significance level of 0.05. There was a correlation between month of birth and month at menarche, with a peak of occurrence of menarche in December not affected by the menstruating patterns of maturation, but no correlation between menarche and seasons of the year. The difference between mean age at menarche in December (spring-summer transition) and in June (autumn-winter transition) was not significant. Mean age at menarche during the month following school vacations was lower. We conclude that situations of stress-relaxation transition, such as end of the school year, beginning of school vacation, and, perhaps most important, the socioeconomic factor-the end of the sugar cane harvest, when rural workers receive their final payments-favor the occurrence of the peak of menarche in December.

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Month at mearche: a re-evaluation of the seasonal hypothesis

Cited by 14 publications

References 4 publications

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

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

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

Monthly distribution of menarche among schoolgirls from a municipality in Southeastern Brazil

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