July 03, 2018
Past use of oral contraceptives increases the prevalence of insulin resistance and diabetes among postmenopausal women, shows the first study of its kind from South Korea.
Sung-Woo Kim, MD, from Daegu Catholic University Hospital, South Korea, presented results of the cross-sectional study here at the American Diabetes Association (ADA) 78th Scientific Sessions.
"The present study showed a definite association between the past use of oral contraceptives and an increased prevalence of diabetes in postmenopausal women, especially in those who used them for longer than 6 months," Kim said in an interview with Medscape Medical News.
But he added that even in nondiabetic women, "use of oral contraceptives was significantly associated with higher fasting insulin and insulin resistance."
Session moderator Julie Bower, PhD, associate professor of epidemiology at Ohio State University, Columbus, asked Kim about the timing of the development of diabetes with respect to oral contraceptive use.
"Previous studies in younger women did not find an association between oral contraceptive use and development of diabetes. Do you think that this association is something only seen later in life?" she asked.
Kim responded, "These postmenopausal women had been on oral contraceptives for longer than in the prior studies which looked at current use," and it can take many years to develop diabetes due to insulin resistance, "so long-term observation is needed."
Another possible explanation is that this cohort "took older versions of the contraceptives," he suggested.
First Study to Look at Postmenopausal Diabetes
Kim explained that estrogen is an important regulator of glucose homeostasis.
And he acknowledged that two prior large-scale, prospective studies in relatively young (premenopausal) women had evaluated the effect of current use of oral contraceptives on the incidence of diabetes but found no association, although he noted that in these studies, the follow-up periods were limited.
Data for the cross-sectional retrospective study were drawn from the large, population-based, nationwide Korea National Health and Nutrition Examination Survey (KHANES) from 2007 to 2012.
Information on duration of oral contraceptive use, age at menopause and at diabetes diagnosis, use of hormone replacement therapy, hypertension, hyperlipidemia, smoking status, alcohol use, and physical activity were collected.
The study included 6554 postmenopausal women in their mid-60s. Of these, 849 had diabetes and had used oral contraceptives for longer than 6 months, while 409 had diabetes but had used the pill for less than 6 months.
In addition, fasting glucose and insulin levels were available for 3338 of the nondiabetic postmenopausal women, so the association between insulin resistance and prior contraceptive use was also examined.
Diabetes Risk Almost 35% Higher if Pill Used for >6 Months
Of women who had used oral contraceptives for longer than 6 months, 19.4% had diabetes. The percentage dropped to 14.4% for those who used oral contraceptives for less than 6 months, compared with 14.3% in the reference group of women who had never taken the pill, reported Kim.
This meant the prevalence of diabetes was around 35% higher, even after adjusting for multiple confounding factors in the postmenopausal participants who had taken the pill for longer than 6 months, compared with those who had never taken oral contraceptives (odds ratio, 1.34; P < .01).
In terms of diabetes risk associated with duration of oral contraceptive use, the odds ratio for each 1-month's use was 1.005 (P < .01).
"The prevalence of diabetes showed an increasing trend of 0.5% per 1 month of oral contraceptive use," Kim reported.
"These results suggest that prolonged use of oral contraceptives at childbearing age may be a potential risk factor for developing diabetes after menopause," he asserted.
Taking oral contraceptives for longer than 6 months also led to a significant increase in fasting insulin levels and insulin resistance (the latter assessed using the homeostatic model of insulin resistance) in nondiabetic participants, compared with those who had never used the contraceptive pill.
Bower concluded by saying, "We do know that exposures that occur earlier in life can influence health outcomes many years later, but there is lots that can happen along the way that can complicate things."
Next steps should include "examining these and other data more closely to determine whether this increased risk is due to the oral contraceptives themselves, or other diabetes risk factors that may also be associated with, or a result of oral contraceptive use," she added.
Kim acknowledged that the study had several limitations and added that "further investigation is necessary to clarify the long-term effect of oral contraceptives on the risk of diabetes in later life."
Neither Dr Kim nor Dr Bower have disclosed any relevant financial relationships.