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Are the effects of risk factors for timing of menopause modified by age? Results from a British birth cohort study

Mishra, Gita PhD; Hardy, Rebecca PhD; Kuh, Diana PhD

doi: 10.1097/gme.0b013e31802f3156
Articles from the Workshop on "Cross-cultural Comparisons of Midlife and Aging"

Objectives: This study investigated the influence of mother's age at menopause, early life and adult behavioral factors on the timing of menopause until age 57 years, and whether these effects vary according to the women's age at menopause.

Design: A nationally representative cohort of 1,583 British women born in March 1946 with prospective data across the life course. For factors that vary with age at menopause, analyses were stratified by age at menopause younger than 50 years or 50 years or older.

Results: Cox regression models indicated that for women with earlier menopause, those who were heaviest at 2 years had a 59% lower hazard ratio for menopause than those who were the lightest (hazard ratio [HR] = 0.41, 95% CI: 0.16-1.01), whereas this figure was 35% lower (HR = 0.65; 95% CI: 0.42-1.00) for the later menopause group. For women in the earlier group with parental divorce during childhood, the HR was 6.5 (95% CI: 2.0-21.3) times higher than that of other women. This rate decreased to 2.5 (95% CI: 1.5-4.2) for those with later menopause. In both groups, increasing mother's age at menopause was associated with decreasing HR (P < 0.0001). For all women, being breast-fed (P = 0.05), increasing cognitive ability (P = 0.009), and increasing parity (P < 0.001) delayed menopause.

Conclusions: This study found that the impact of weight at 2 years, parental divorce during childhood, and mother's age at menopause varied according to the women's age at menopause. There was further evidence that being breast-fed, higher childhood cognitive ability, and increasing parity delayed menopause. These results suggest the interaction of genetic and environmental factors in determining age at menopause.

This study finds that the early life factors of being breast-fed and having higher cognitive ability independently influence age at menopause, whereas the effects of weight at 2 years, parental divorce during childhood, and mother's age at menopause varied according to the women's age at menopause.

From the Medical Research Council National Survey of Health and Development, University College and Royal Free Medical School, London, UK.

Received September 20, 2006; revised and accepted November 15, 2006.

Funding/support: The Medical Research Council.

Financial disclosure: None reported.

Ethical approval: North Thames Multicentre Research Ethics Committee.

Address correspondence to: Gita Mishra, PhD, University College London Medical School, 1-19 Torrington Place, London WC1E 6BT, UK. E-mail: g.mishra@nshd.mrc.ac.uk.

©2007The North American Menopause Society