A new study published in Diabetologia finds that the prevalence of type 2 diabetes (T2D) is elevated in people with sleep disorders and psychiatric disorders compared with the general population. The research was conducted by Nanna Lindekilde, Department of Psychology, University of Southern Denmark, Odense, Denmark, and colleagues.

Sleep disorders and psychiatric disorders are common, impair quality of life and are associated with increased mortality rates. This excess mortality is caused in part by more frequent suicides and accidents, but also by an elevated risk of developing physical conditions known to be linked to mental health problems such as cardiovascular and respiratory diseases. Diabetes is an increasingly common disease throughout the world and estimates suggest that 6% to 9% of the global general population are currently affected. Rates have been rising since 1990 onwards in a trend that is expected to continue for the next 20 years.

The authors conducted an in-depth search of four electronic databases of scientific papers and found 32 systematic reviews based on 245 unique primary studies. There were 11 categories of disorders: schizophrenia, bipolar disorder, depression, substance use disorder, anxiety disorder, eating disorder, intellectual disability, psychosis, sleep disorder, dementia, and a ‘mixed’ group that comprised different types of psychiatric disorders.

The study found that people with a sleep disorder had the highest rates of T2D with 40% of subjects having the disease while its prevalence among individuals with other psychiatric disorders was 21% (binge eating disorder), 16% (substance use disorder), 14% (anxiety disorders), 11% (bipolar disorder), and 11% (psychosis). Prevalence of T2D was lowest among people with an intellectual disability with 8% of individuals having the disease. In each case these rates are as high or higher than the 6-9% level of T2D found in the general population.

The researchers explain that sleep disorders constitute a subgroup of psychiatric disorders and have high comorbidity with several other diseases. In the review, most of the primary studies were conducted among people with additional diseases such as chronic kidney disease. “It is likely that this physical comorbidity contributes to the high T2D prevalence estimates in people with a sleep disorder. The link between T2D and sleep disorders is likely to be bidirectional with the sleep disorder raising the risk of developing diabetes, while diabetes, especially in combination with poor metabolic control, increasing the risk of developing sleep problems,” the authors say in a press release.