Doctor discussing test results with his patient

Analysis of data from the Women’s Health Initiative (WHI) has found surprising evidence that not only are women with shorter reproductive spans more at risk of developing type 2 diabetes, but those with exceptionally longer spans are also more at risk.

The study looked at a cohort of 124,379 postmenopausal women, aged between 50 and 79. Questionnaires were completed by the women, collecting information covering topics such as demographic, lifestyle, health and BMI factors. The researchers worked out the reproductive length of the women by taking the age of menarche and subtracting that from the age of onset of menopause.

The women were followed for a mean of 12.2 years, and the prevalence of new diabetes cases was compared to their reproductive length. Any participants who had had a diagnosis of diabetes prior to the study were excluded from the analysis.

“The Women’s Health Initiative provides a unique setting to evaluate the associations between reproductive characteristics and diabetes because of its large size, robust characterization of reproductive histories, long duration of follow-up, and ability to prospectively ascertain type 2 diabetes,” said the Executive Director of The North American Menopause Society, JoAnn V. Pinkerton.

The researchers found that those with reproductive length of less than 30 years were at a 37 per cent higher risk of developing type 2 diabetes than those who had a more average reproductive length, around 36 to 40 years.

Previous studies have found that an early menopause increased the risk of type 2 diabetes in women, but this is the first time that it has been found that a later menopause can have a similar effect. Women who had a longer than average reproductive length were 23 per cent more at risk than those in the 36 to 40 category.

Furthermore, women who underwent the menopause earlier or later than the ages of 46 and 55 were also found to be more at risk of type 2 diabetes.

Although the menopause or reproductive length are not factors that can be controlled, it can highlight those who are at risk. It means that those women who will be at a higher risk, according to this study, can be warned to take extra to reduce other risk factors, such as weight and increase their activity levels.

“The finding that both shorter and longer reproductive durations were associated with risk of diabetes has important implications for women with early or late menopause as well as for those with BRCA gene mutations considering risk-reducing bilateral oophorectomy that would shorten their reproductive time,” said Pinkerton.

“Given the high prevalence of diabetes in postmenopausal women, those with shorter and longer reproductive periods may benefit from lifestyle counseling. Future research should focus on ways to prevent type 2 diabetes in women at risk as they age.”