| Abstract | dc.description.abstract | Background: Our previous studies have shown that the monthly
rhythm of menarche is associated to the expectancy of holidays or vacations. If this hypothesis is
true, menarche episodes in Chile should cluster in December, the month prior to summer
vacations. Aim: To study whether the expectancy of holidays or vacations is the main
determinant of the annual rhythm of menarche. Material and methods: During 1990 and
1991, a questionnaire about the date of birth and date of menarche, was applied to girls living
in Santiago (Chile) and Medellin (Colombia), aged 8 to 18.5 years. They were requested to
register the year, month or day of menarche, only if they recalled it precisely. Results:
Discarding clerical errors, data was obtained from 3,225 Chilean and 3,435 Colombian girls.
Of these 73 and 63% of Chilean and Colombian girls recalled the day of menarche. Among
Chilean girls an excess of menarche episodes was observed in December, January and
February. The mean age per month of menarche reached its highest value of 155.6 ±15 months
in December and fell to 148 ±17 months in January (p <0.001). Among Colombian girls, mean
age per month of menarche was also higher in December and lower in January (152 ±15 and
147 ±14 months respectively, p <0.001). However a peak of 152 ±15 months was also observed in
June. Conclusions: A similar distribution of menarche episodes was observed among Chilean
and Colombian girls, with a peak in the months preceding holidays. The influence of the
photoperiod is unlikely since Medellin is located in parallel 6 and there are little variations in
daylight exposure in the different seasons. Therefore, our data supports the hypothesis that the
prospect of holidays is a determinant of menarche. | en |
