medwireNews: Women with a history of gestational diabetes have a small but significantly increased risk for long-term mortality relative to those who do not develop the condition during pregnancy, study findings indicate.
“Mortality due to CVD [cardiovascular disease] was a primary factor in this association, and it persisted regardless of the subsequent development of [type 2 diabetes],” write Yi-Xin Wang (Shanghai Jiao Tong University School of Medicine, China) and co-authors in JAMA Internal Medicine.
The study included data for 91,426 participants (mean age 34.9 years) of the Nurses’ Health Study II who reported at least one pregnancy (≥6 months) at age 18 years or older. Of these, 6.6% experienced gestational diabetes.
During more than 30 years of follow-up (2,609,753 person–years), 3973 women died, including 255 deaths from CVD and 1397 from cancer.
The researchers report that the crude mortality rate was higher for participants with a history of gestational diabetes than for those without, at 1.74 versus 1.49 per 1000 person–years. After adjustment for age, the difference between the two groups corresponded to a significant 28% increased risk for death among the women with a history of gestational diabetes.
The risk was not attenuated when Wang and team took additional potential confounders into account, and the association remained significant regardless of whether the participants subsequently developed type 2 diabetes, with adjusted hazard ratios (HRs) for death of 1.27 in the group with gestational diabetes only and 1.34 in the group with both gestational and type 2 diabetes.
Subgroup analyses revealed that the association between gestational diabetes and mortality was stronger among participants who had less healthy lifestyles, based on factors including heavy smoking (≥20 cigarettes/day: HR=1.40), overweight or obesity (BMI ≥25 kg/m2: HR=1.37), poor diet (in the bottom 60% for Alternative Healthy Eating Index score: HR=1.32), and lack of exercise (<30 minutes/day: HR=1.31).
Pregnancy factors, such as experiencing gestational diabetes in two or more pregnancies (HR=1.48) and having gestational diabetes as well as hypertensive disorders in pregnancy (HR=1.80), preterm birth (HR=2.46), or low birth weight (HR=2.11), were also associated with increased mortality risk.
Cause-specific mortality analyses showed that gestational diabetes was directly associated with a significantly increased risk for death due to CVD (HR=1.59) and a significantly decreased risk for death due to cancer (HR=0.76).
Further investigation showed that the reduced risk for cancer mortality was only present among participants who experienced both gestational diabetes and type 2 diabetes (HR=0.30) and was mediated by type 2 diabetes, suggesting “that gestational diabetes itself may not be associated with cancer mortality,” Wang et al remark.
The authors conclude that their “findings emphasize the importance for health care professionals to consider gestational diabetes as a critical factor when evaluating the later-life mortality risk of their patients.”
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