Validity and reproducibility of self-reported age at menopause in women participating in the DOM-project.

To study validity and reproducibility of self reported age at menopause. Subjects were 1003 and 4892 Dutch women respectively aged 58-73, who participated in a population-based breast cancer screening project. The median time since menopause was 7 years for the validity study. The time span between the two questionnaires in the reproducibility study was 7-9 years. Of the women with a natural menopause, 70% recalled their age at menopause correctly to within one year. For women with a surgical menopause this percentage was 80%. The validity decreased with increasing number of years since menopause. Reproducibility to within one year was 71% for women with a natural menopause and 79% for women with a surgical menopause; 95% of the women were consistent in reporting whether they had had a natural or a surgical menopause. As a consequence of this misclassification, the effect of age at menopause may be underestimated in studies relating self reported age at menopause to disease occurrence or mortality.