1. Women that experienced gestational diabetes during pregnancy were significantly less likely to develop type II diabetes mellitus if they engaged in increased levels of total physical activity each week.
2. In the same cohort of women who had experienced gestational diabetes, greater amounts of sedentary activities like watching television were associated with increased BMI and a greater risk of developing type II diabetes mellitus.
Evidence Rating Level: 2 (Good)
Study Rundown: Women who experience gestational diabetes mellitus (GDM) during pregnancy are at a substantially increased risk of developing type 2 diabetes mellitus (T2DM) later in life. As diabetes has rapidly become a worldwide epidemic, the identification of modifiable risk factors for T2DM could be used to help prevent the disease in at-risk populations. This study analyzed prospective data from the Nurse’s Health Study II (NHS II) to examine the role of physical and sedentary activities on the likelihood of progressing from GDM to T2DM.
This study found that women previously diagnosed with GDM who met the minimum level of weekly physical activity as recommended by a US federal guideline were 45% less likely to progress to T2DM than women who did not meet the recommendation. Further, every 5 metabolic equivalent hours (MET-h) increase in weekly physical activity was associated with a 9% decrease in the risk of progressing to T2DM. Additionally, the study found that increased amounts of sedentary activities like watching television were linked with higher BMI and a greater likelihood of progressing to T2DM. Though this study may be limited by the potential for screening bias and residual confounding, it used prospective data to link the levels of physical and sedentary activity to the risk of progressing from GDM to T2DM.
In-Depth [prospective cohort]: This study followed 4554 women from the NHS II study who were diagnosed with GDM to determine how levels of physical and sedentary activities affected progressing to T2DM. Overall, 635 women progressed to T2DM during 59,287 years of follow up. Those women who met the recommended minimum level of weekly physical activity (>7.5 MET-h: equivalent to 75 minutes of vigorous-intensity physical activity) had a relative risk of progressing to T2DM of 0.55 compared with those women who did not meet the recommendation (p < 0.001, 95% CI: 0.46-0.66). Additionally, each 5 MET-h increase in physical activity was associated with a 9% lower risk of developing T2DM (RR: 0.91, 95% CI: 0.88-0.94).
Though a dose-response relationship was found between the average amount of television watched per week and the likelihood of progressing to T2DM, this association was no longer significant after adjusting for BMI. Furthermore, it was found that after being diagnosed with GDM, women who increased their level of physical fitness (>7.5 MET-h/wk increase, T2DM RR: 0.53, 95% CI: 0.38-0.75) and/or decreased their duration of television viewing (> 1 hour/wk decrease, T2DM RR: 0.72, 95% CI: 054-0.96) decreased their likelihood of developing T2DM, showing that the effects were dynamic and not just correlated with baseline levels of physical and sedentary activity.
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