Extreme sleep duration may up mortality risk in individuals with T2D

Extremes of sleep duration (≤5 or ≥10 hours/day), which is a known mortality risk factor in the general population, may increase absolute mortality in adults with type 2 diabetes (T2D), a prospective study has shown.

“There is some preliminary evidence that the associations between sleep duration and mortality risk are different between people with and without diabetes,” said the researchers.

Compared with nondiabetic individuals who slept for 7 hours daily (reference duration), those with T2D who slept for ≤5 and ≥10 hours/day had higher risks of all-cause mortality (hazard ratios [HRs], 1.63 and 2.17 for ≤5 and ≥10 hours/day, respectively; p<0.001 for both). [Diabetologia 2020;doi:10.1007/s00125-020-05214-4]

In participants with T2D, those who slept for ≤5 and ≥10 hours/day had increased mortality risk vs those who slept for 7 hours daily (HRs, 1.24 and 1.83, respectively; p<0.001 for both).

“Our findings suggest that excessive or insufficient amounts of sleep may be risk factors for all-cause … mortality in people with T2D … This population may benefit from targeted sleep-related interventions to reduce the risks of adverse health outcomes,” they added.

Too much, too little sleep: both bad?

“[E]xtreme sleep duration may reflect poorer health status and reduced functioning,” said the researchers. On one hand, longer sleep duration is tied to chronic inflammatory responses, which accelerate diabetes progression and its complications, consequently increasing mortality risk, they added.

On the other, inadequate sleep in healthy adults is tied to slower glucose clearance rate and higher sympathetic nervous system activity, with the latter influencing insulin resistance and obesity. [Lancet 1999;354:1435-1439; Am J Hypertens 2001;14:103S–115S; Diabetes Obes Metab 2004;6:85-94; Hypertens Res 2012;35:4-16] “Therefore, sleep deprivation in people with T2D is likely to exacerbate complications and affect the control and management of blood glucose, which drive excess mortality risk,” they explained.

Do interventions work?

Six to 8 hours is the recommended sleep duration, be it among the general population or among individuals with T2D. [Sleep Med Rev 2017;32:28-36; Sleep Med 2011;12:215-221] “Monitoring of sleep duration may serve as a useful tool for identifying high-risk people with T2D in clinical practice for possible intervention,” said the researchers.

“However, evidence for the effectiveness of sleep interventions for improving clinical outcomes in people with T2D is complex,” the researchers noted. For instance, CPAP* – an intervention for obstructive sleep apnoea (OSA) – has been shown to improve insulin resistance and glycaemic control in individuals with T2D and OSA for 6 months; however, this benefit was not seen with shorter (3 months) CPAP use. [Am J Respir Crit Care Med 2016;194:476-485; Thorax 2007;62:969-974] “[As such,] sleep interventions as an adjunct to standard diabetes treatment may warrant further attention,” they stressed.

The study population comprised 273,029 adults who participated in the US NHIS** (n=24,212 with T2D). Participants were asked regarding the average number of sleep hours they get daily. However, the use of self-reporting without objective measurements may have influenced the findings, noted the researchers. Also, given the observational nature of the study, “the current study cannot infer causality of the sleep-mortality association among people with T2D.”

There is also insufficient data on sleep quality and other factors*** potentially responsible for poor sleep quality. “This precludes in-depth analysis in relation to sleep problems and mortality in people with T2D. Further studies in this area should concentrate on addressing such issues,” they added.