The study included 3,639 postmenopausal women taken from the prospective Rotterdam Study. Women self-reported age at natural menopause. The researchers categorized women’s menopause as premature (<40 years), early (40-44 years), normal (45-55 years) and late (>55 years).
With a median follow-up of almost 10 years, the researchers identified 348 women with incident type 2 diabetes. Women with premature natural menopause had a hazard ratio of 3.7 for type 2 diabetes (95% CI, 1.8-7.5). This decreased with increasing age at menopause. Women with early menopause had a hazard ratio of 2.4 (95% CI, 1.3-4.3) and women with normal menopause had a hazard ratio of 1.60 (95% CI, 1.0-2.8).
The risk of having diabetes reduced by 4% per 1 year older at menopause (HR=0.96; 95% CI, 0.94-0.98).
The researchers adjusted for factors including body mass index, glycemic traits, metabolic factors, C-reactive protein, endogenous sex hormone levels or shared genetic factors; none of which affected the association between age of onset of menopause and type 2 diabetes. According to Asllanaj, this suggests that early menopause can be an independent marker for having type 2 diabetes later in life.
“This was a surprise to us since previous work from our research group have shown that higher endogenous estradiol levels, as well as low levels of other sex hormones such as sex hormone binding globulin and dehydroepiandrosterone in postmenopausal women are linked to an increased risk of type 2 diabetes,” Asllanaj said. “However, in our study the levels of these sex hormones were measured further from menopause, and not at time of menopause onset. Therefore, future studies should look whether levels of these hormones assessed during the menopause transition can explain the results we found.”
Based on these results, Asllanaj said that menopause may be a critical period to evaluate women’s risk for type 2 diabetes as it may be an appropriate time to introduce interventions to reduce this risk.