MENSTRUAL-CYCLE LENGTH PRECEDING MENOPAUSE IN RELATION TO AGE AT MENOPAUSE

Objectives: In one of the earlier hypotheses of the etiology of breast cancer (Korenman's 'oestrogen window hypothesis (1981)), it was assum ed that women with a later age at menopause have a longer period with irregular cycles preceding menopause than women with an early menopaus e. This assumption was tested in a prospective study. Methods: Subject s were 628 women, born between 1932 and 1941, who had participated in a breast cancer screening project in Utrecht, The Netherlands (the DOM -project) in 1982-1985, and who were still menstruating at that time. The women had filled out a questionnaire and a menstrual calendar ever y 2 years to determine their age at menopause prospectively. The women had not used oral contraceptives or medicines for menopausal complain ts and had reached natural menopause by 1992. The median of the mean m enstrual cycle length per woman and the median of the standard deviati on of the mean menstrual cycle length per woman were plotted against n umber of years prior to menopause in three categories of age at menopa use (44-49; 50-54; 55-59). Results: During the 9 years prior to menopa use, women with a late age at menopause have a somewhat higher mean me nstrual cycle length than women with a younger age at menopause (P = 0 .0008). Cycle length variability in the 9 years prior to menopause is not statistically significantly different between the three categories of age at menopause (P = 0.16). Conclusions: The assumption that wome n with a late age at menopause have a longer period with irregular cyc les than women with an earlier age at menopause was not corroborated b y our results. (C) 1998 Elsevier Science Ireland Ltd. All rights reser ved.