In women, sleeping problems are linked to an increased risk of type 2 diabetes. Researchers observed a 47% increased risk for women with 1 sleeping disorder and more than 4 times the risk for women with 4 disorders, new data published in Diabetologia indicate.
“The high prevalence of both sleeping difficulty and type 2 diabetes points to a need to further understand the link between the two conditions,” the researchers wrote. “In this study, we examined the association between sleeping difficulty, defined as having difficulty initiating or maintaining sleep most of the time or all the time and the risk of developing type 2 diabetes based on the extracted data from two independent, well-established cohorts of US women: the Nurses’ Health Study (NHS) and NHSII.”
Data from 133 353 women without diabetes, cardiovascular disease, or cancer at baseline were analyzed. Sleeping problems included sleeping difficulty, frequent snoring, sleep duration of 6 hours or less, and sleep apnea in the NHS or rotating shift work in the NHSII.
At baseline, 5.9% of women in NHS and 4.8% in NHSII reported sleeping difficulty, which was associated with a higher BMI, less exercise, worse dietary quality, 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.
During up to 10 years of follow-up, 6407 participants developed type 2 diabetes. Results indicated that women with a sleeping difficulty had a 45% (adjusted hazard ration [HR]=1.45; 95% CI, 1.33-1.58) increased risk for type 2 diabetes after adjustment for baseline lifestyle factors when compared to women without a sleeping disorder. Further adjustment for hypertension, depression, and BMI based on updated repeated measurements brought this risk down to 22% (adjusted HR=1.22; 95% CI, 1.12-1.34).
Compared with women without any sleep problems, women who reported having at least 1 of the 4 sleeping disorders had a 47% increased risk for type 2 diabetes (adjusted HR=1.47; 95% CI, 1.39-1.56). Risk was further increased for women who had 2 (adjusted HR=2.14; 95% CI, 1.99-2.31), 3 (HR=2.84; 95% CI, 2.48-3.26), and all 4 disorders (HR=4.17; 95% CI, 2.93-5.91).
In an analysis of the relatively healthy population without obesity, hypertension, or depression at baseline, which included 82 903 participants (62% of the sample), the increased risk for type 2 diabetes during up to 10 years of follow-up was 44% (adjusted HR=1.44; 95% CI, 1.23-1.74) in women with difficulty sleeping after adjustment for lifestyle factors, socioeconomic status, and baseline BMI. The risk decreased to 33% (adjusted HR=1.33; 95% CI, 1.11-1.59) after further adjustment for hypertension, depression, and updated BMI.
The researchers pointed out several limitations of their study, including the fact that sleeping difficulties were self-reported and that objective measurements of sleep onset, maintenance, duration, and quality were unavailable. They also noted that the cohort was primarily composed of white women.
However, they emphasized the strengths of the study, including the long-term follow-up and consistent findings across 2 separate cohorts, among others.
“Sleeping difficulty was significantly associated with type 2 diabetes. This association was partially explained by associations with hypertension, BMI, and depression symptoms, and was particularly strong when combined with other sleep disorders,” the researchers concluded.
“Our findings highlight the importance of good sleeping patterns and having enough sleep for preventing type 2 diabetes…The findings provide evidence to clinical physicians and public health researchers for future diabetes prevention among a high-risk population with multiple sleep disorders.”