Fewer than six hours or more than 10 hours of sleep, and poor quality of sleep are associated with a greater risk for diabetes, according to research being presented Thursday at ENDO 2023, the Endocrine Society’s annual meeting in Chicago, Ill.

Poor sleep quantity and quality, and its impact on the risk for diabetes or obesity has been previously studied. However, this study sought to explore the longitudinal effects.

“Most previous studies did not examine changes in various glycometabolic parameters, like over 14 years. The pattern of changes in various glycemic parameters may provide clues to the mechanism underlying the association between sleep duration and incident diabetes mellitus,” said Wonjin Kim,  M.D., Ph.D., of CHA Gangnam Medical Center and associate professor at CHA University School of Medicine in Seoul, South Korea.

Kim and colleagues collected data from 8,816 of 10,030 healthy participants of the ongoing Korean Genome and Epidemiology Study (KoGES)-Ansung and Ansan Cohort Study. They identified diabetes cases and sleep duration and quality. Sleep duration was categorized into four groups: <6, 6-7, 8-9, or 9 hours per day. Sleep quality was measured among those with a sleep duration of <10 hours per day.

During the 14-year follow-up period, 18% (1630/8816) were diagnosed with diabetes. The researchers observed a U-shaped relationship between sleep duration and incident diabetes, with the greatest risk when sleep duration was ≥10 hours per day. During the study, this group also showed decreased insulin glycogenic index, which is a marker of insulin secretory function. The risk for incident diabetes increased among study participants who slept <10 hours per day when their Epworth Sleepiness Scale (ESS) score was >10.

“Even if sleep duration is less than 10 hours, the likelihood of developing diabetes is greater when quality of sleep decreases,” Kim said.