In a prospective cohort analysis from the Nurses’ Health Study II, women with a history of gestational diabetes mellitus had incrementally lower risks for developing type 2 diabetes for each of their modifiable risk factors, including obesity. Even women with increased genetic susceptibility to type 2 diabetes had lower risks of the disease with optimal levels of the modifiable risk factors. Five modifiable risk factors (overweight/obesity, high-quality diet, regular exercise, moderate alcohol consumption, no current smoking) were assessed in 4,275 women with a history of gestational diabetes mellitus who had repeated measurements of weight and lifestyle factors from 1991 to 2009.
Results over a median of 27.9 years of follow-up showed that 924 women developed type 2 diabetes. Those with optimal levels of all 5 factors had more than a 90% lower risk of developing type 2 diabetes compared with those with no optimal levels. Hazard ratios were 0.94, 0.61, 0.32, 0.15, and 0.08 for 1, 2, 3, 4, and 5 optimal levels of modifiable factors, respectively, a significant trend. Those with overweight/obesity had a hazard ratio of 0.40 when they had optimal control of the other 4 factors. Even with genetic susceptibility, optimal levels of 4 of the modifiable risk factors produced a hazard ratio of 0.11, and no women developed type 2 diabetes when they had optimal levels of all 5 factors.