Association between sleeping difficulty and type 2 diabetes in women

Li Y, Gao X, Winkelman JW, et al.
Diabetologia 2016; published online ahead of print 2 February 2016

Background

Inadequate or fragmented sleep in healthy young adults has been associated with impaired glucose regulation [1, 2]. Sleep disturbance negatively affects metabolism and has been associated with type 2 diabetes (T2DM) risk factors, such as obesity [3], hypertension [4] and depression [5], as well as with increased risk T2DM itself [6-7]. However it is not clear whether the observed associations are independent of health behaviours, other cardiovascular risk factors or other sleep disorders.
In this study, the association between sleeping difficulty and the risk of developing T2DM was examined, based on the extracted data from two independent cohorts of US women: the Nurses’ Health Study (NHS) [8] and NHSII [9]. Sleeping difficulty was defined as having difficulty initiating or maintaining sleep most of the time or all the time.
Data from 133,353 women were analysed with a follow-up of 10 years. Furthermore, the combined effect between sleeping difficulty and short sleep duration, frequent snoring, sleep apnoea and rotating shift work were assessed, and the extent to which the effects of sleeping difficulty on T2DM  are mediated through BMI, hypertension and depression was quantified.

Main results

• At baseline, 5.9% in NHS and 4.8% in NHSII of women reported sleeping difficulty.
• Women with sleeping difficulty had an increased risk of T2DM compared with women without sleeping difficulty, independent of a variety of risk factors. The multivariate-adjusted HR for T2DM comparing women with and without sleeping difficulty was:

• 1.45 (95% CI: 1.33 - 1.58) after adjustment for lifestyle factors at baseline,
• 1.22 (95% CI: 1.12 - 1.34) after further adjustment for hypertension, depression and BMI

• A significant interaction was observed between sleeping difficulty and shift work for risk of T2DM
(P for multiplicative interaction = 0.08, P for additive interaction= 0.04)
   The multivariate-adjusted HRs

• of shift work only was 1.27 (95% CI: 1.14 - 1.42),
• of sleeping difficulty only was 1.40 (95% CI: 1.23 - 1.59)
• of both conditions was 2.30 (95% CI: 1.78 - 2.96)

   as compared with women without sleeping difficulty and never shift work
• Women who reported all four sleep conditions (sleeping difficulty, frequent snoring, sleep duration ≤6 h and sleep apnoea in NHS or rotating shift work in NHSII) had more than a fourfold increased likelihood of T2DM (HR 4.17, 95% CI: 2.93 - 5.91)

Conclusion

In 2 large independent cohorts of females, sleeping difficulty, defined as having difficulty initiating or maintaining sleep most of the time or all the time, was significantly associated with T2DM. While this finding can be partially explained by associations with hypertension, BMI and depression symptoms, it was very powerful when combined with other sleep disorders. These findings support the need to manage sleep disturbance in the context of T2DM prevention.

Find this article online at Diabetologia

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