Physical Fitness and Activity Levels in association to Glucose Metabolism after Gestational Diabetes – a follow-up study
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Introduction: Gestational diabetes mellitus (GDM) is defined as the discovery or onset of glucose intolerance during pregnancy and is a disease with escalating incidence amongst pregnant women worldwide. After GDM, there is a life-long increased risk of impaired glucose tolerance or type 2 diabetes. This risk can be reduced with lifestyle changes such as exercise, and pharmacological therapy. There are currently few studies on how exercise habits and bodily fitness affect glucose metabolism in this group of women, but these studies show promising results for the opportunity of good health after GDM diagnosis. Aim: The main aim of this study is to evaluate how self-reported physical activity levels as well as strength- and aerobic fitness associates to glucose metabolism in women with previous GDM. The long-term goal is to improve preventative strategies for individuals with or at risk of developing type 2 diabetes mellitus. Methods: The study design is retrospective cross-sectional. Participants consisted of women diagnosed with GDM in the Gothenburg region between 2005-2009 (n=542). They attended two follow-ups at 5 years (5y, n=237) and 10 years (10y, n=127) where they underwent an oral glucose tolerance test (OGTT), answered exercise habits questionnaires, and performed strength- and aerobic tests at 10y. The women were divided into three groups: normal glucose tolerance (NGT), impaired glucose tolerance (IGT) and type 2 diabetes mellitus (T2DM) for each follow-up. Most data were non-normally distributed. Statistical methods consisted of Mann-Whitney U-test for comparisons between two groups, and Kruskal-Wallis test for 3 or more groups, Pearson’s chi-squared and Fishers Exact test for comparing categorical data and Spearman correlations. Students independent t-test for two-group comparisons of normal-distributed data. Results: There were no significant differences in self-reported exercise habits between glucose tolerance groups at both follow-ups, but all women generally reported less weekly mean volume of exercise compared to what is currently recommended by the World Health Organization (WHO). Self-reported resistance training and combined endurance/resistance-training had a significant correlation to lower HbA1c, glucose- and insulin-levels at 5y and 10y. Higher maximal isometric strength and higher VO₂-max was also significantly associated to better glucose metabolism. The women with NGT were significantly physically fitter compared to the women with T2DM. Conclusions: Women with previous GDM generally report exercising less than what is currently recommended by the WHO. Resistance- and combined endurance/resistance training is the exercise form most associated with better glucose metabolism. Having a stronger and fitter body is also associated to a healthier glucose metabolism.