Results:

A total of 133,353 women were included in this analysis. The percentage of women who reported sleeping difficulty (having difficulty falling or staying asleep all or most of the time) was 5.9% in NHS and 4.8% in NHSII. Sleeping difficulty was associated with a higher body mass index (BMI), less physical activity, lower dietary quality score, shorter sleep duration, more frequent snoring, more common use of minor tranquilizers, more frequent excessive daytime sleepiness, higher likelihood of shift work, and higher prevalence of hypertension and depression symptoms. A total of 6,407 incident cases of type 2 diabetes were identified during up to 10 years of follow-up. Risk for type 2 diabetes was hazard ratio [HR], 1.45 (95% confidence interval [CI], 1.33-1.58) for women with sleeping difficulty compared to women without sleeping difficulty after adjustment for lifestyle factors at baseline. After further adjustment for hypertension, depression, and BMI, this association between sleep difficulty and type 2 diabetes was somewhat attenuated, but remained significant (HR, 1.22; 95% CI, 1.12-1.34). Women who reported all four sleep conditions (sleeping difficulty, frequent snoring, sleep duration ≤6 hours, and sleep apnea in NHS or rotating shift work in NHSII) had more than a fourfold increased likelihood of type 2 diabetes (HR, 4.17; 95% CI, 2.93-5.91).