Study Examines Link Between Insomnia and Diabetes Risk

Researchers who examine modifiable causes of diabetes might benefit from focusing their resources on psychiatric distress rather than insomnia, according to a recent study.

Although previous research has shown that symptoms of insomnia are linked with type 2 diabetes, insomnia symptoms are also correlated with a variety of covariates that could confound or mediate associations. To better assess whether insomnia symptoms cause type 2 diabetes, Michael J. Green, MRC, SCO, and colleagues, examined data from a 20-year, prospective cohort study in the West of Scotland. The 996 study participants were followed starting at age 36 and did not have diabetes at that time.

The study included data from 4 follow-up visits. The last visit evaluated diabetes via self-report, blood test (HbA1c ≥ 6.5% or 48 mmol/mol), and whether the individual was taking diabetic medication.

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Traditional regression and marginal structural models were used to estimate the effects of insomnia on incidence of type 2 diabetes, and adjustments were made for time-dependent confounding such as smoking, diet, physical inactivity, obesity, heavy drinking, and psychiatric distress. Adjustments were also made for gender and baseline occupational status.

Results using traditional logistic regression indicated that risk of developing type 2 diabetes would increase with more years of experiencing insomnia. However, time-varying factors may confound the association, so the researchers also used marginal structural models to overcome potential bias. These models showed “considerable attenuation in the association,” the researchers stated. They added that “The attenuated association under those methods least likely to introduce bias, suggests that associations between insomnia symptoms and type 2 diabetes are largely confounded by other factors.”

Because research resources are valuable and randomized controlled trials are an expensive undertaking, the study’s authors suggest directing research efforts at potentially modifiable causes of type 2 diabetes other than insomnia. “Psychiatric distress might be a good candidate for further investigation since it appeared to be the strongest potential confounder of the association between insomnia and type 2 diabetes incidence,” they said.

“Indeed, in this regard, treatment for insomnia may still have some value as this can help reduce psychiatric distress, and the strongest evidence here of insomnia being causally related to type 2 diabetes was when concurrent measures of psychiatric distress were viewed as mediators, rather than confounders,” the researchers concluded.

—Lauren LeBano

Reference

Green MJ, Espie CA, Popham F, Robertson T, Benzeval M. Insomnia symptoms as a cause of type 2 diabetes incidence: a 20 year cohort study. BMC Psychiatry. Published March 16, 2017. doi:10.1186/s12888-017-1268-1264.