Validity of age at menarche self-reported in adulthood

Objective: To test the validity of age at menarche self-reported in adulthood and examine whether socioeconomic position, education, experience of gynaecological events and psychological symptoms influence the accuracy of recall. Design: Prospective birth cohort study. Setting: England, Scotland and Wales. Participants: 1050 women from the Medical Research Council National Survey of Health and Development, with two measures of age at menarche, one recorded in adolescence and the other self-reported at age 48 years. Results: By calculating the limits of agreement, kappa statistic and Pearson's correlation coefficients (r), we found that the validity of age at menarche self-reported in middle age compared with that recorded in adolescence was moderate (kappa = 0.35, r = 0.66, n = 1050). Validity was improved by categorising age at menarche into three groups: early, normal and late (kappa = 0.43). Agreement was influenced by educational level and having had a stillbirth or miscarriage. Conclusions: The level of validity shown in this study throws some doubt on whether it is justifiable to use age at menarche self-reported in middle age. It is likely to introduce error and bias, and researchers should be aware of these limitations and use such measures with caution.