Adequate sleep duration and sleep quality is essential for every aspect of health and well-being, including cognitive and physiological functions.^1,2 Further, evidence suggests that reduced sleep duration, poor sleep quality and circadian misalignment may have adverse effects on the diurnal rhythm of insulin sensitivity due to several underlying and interconnected mechanisms.^1,2

Recent reports have found that between 33% to 45% of Australian adults experience inadequate sleep duration or poor sleep health. ² Further, the Sleep Health Foundations' National Survey has reported a decline in sleep quantity for Australian adults over the past decade, from 7.4 hours to 7 hours, with 12% of Australian adults reporting a sleep duration of less than 5.5 hours.² This reduction in sleep health may be due to a modern lifestyle characterised by demanding workloads and increased usage of technology before bedtime, causing reductions in optimal sleep and disruptions in the sleep-wake cycle (Figure 1).¹

Over the last decade, this decline in sleep health has occurred in parallel with increasing prevalence of type 2 diabetes (T2DM).¹ Further, research suggests that sleep restriction and sleep fragmentation may be significant lifestyle risk factors for T2DM that are comparable to traditional risk factors such as obesity, poor diet and reduced physical activity (Figure 2).¹

Effects of sleep manipulation on markers of insulin sensitivity

In a systematic review and meta-analysis by Sondrup et al.¹ researchers investigated the impact of sleep restriction, slow wave sleep (SWS) suppression, rapid eye movement sleep disturbance, sleep fragmentation, and circadian misalignment on markers of insulin sensitivity.

Sleep restriction and insulin sensitivity

The review highlighted reduced sleep duration had detrimental effects on whole-body, peripheral and hepatic insulin sensitivity, with some studies showing that only one night of sleep restriction is enough to have an acute negative effect on insulin sensitivity.

There are several underlying mechanisms in which sleep restriction is thought to negatively affect insulin sensitivity, which are primarily driven by endocrine system disruption and changes in the insulin signalling pathway.

Sleep restriction causes a physiological stress, evident from increased cortisol concentrations, and activation of the hypothalamic-pituitary-adrenal (HPA) axis. The stressed state following sleep restriction could also activate the sympathetic nervous system, resulting in increased levels of catecholamines and growth hormone, leading to increased lipolysis, subsequently up-regulating levels of non-esterified fatty acids and free fatty acids, decreasing the hepatic insulin sensitivity and peripheral glucose uptake.

Glucose uptake may be further compromised by the down-regulation of protein kinase B in the insulin-signalling pathway, indicating that sleep restriction may have detrimental effects on a cellular level.

Sleep quality and insulin sensitivity

The proportion of the sleep stages, especially SWS suppression, appears to be essential for metabolic function, with SWS suppression being linked to impaired β-cell function.

In addition, SWS suppression could also reduce certain brain waves including hippocampal sharp wave-ripples, which are present in the non-REM sleep stages and regulate peripheral glucose metabolism, negatively impacting metabolic function.

Circadian misalignment and insulin sensitivity

Circadian misalignment, which can be caused by inverting the daily rhythm by 12 hours, has been reported to decrease glucose tolerance and insulin sensitivity by increasing postprandial glucose and late phase postprandial insulin levels. Therefore, long term misalignment of the sleep-wake rhythm may impair glucose tolerance and insulin sensitivity, partly explaining the increased risk of T2DM in shift workers.

Influencing sleep quality to promote metabolic health

The results of the studies reviewed in this systematic review and meta-analysis indicate that healthy metabolic function is in part dependent on the duration, quality, and timing of sleep, and that neglecting sleep can have detrimental effects on markers of insulin sensitivity.

Therefore, in patients presenting with pre-diabetes or abnormalities in insulin markers, part of a holistic treatment plan should include appropriate herbal and nutritional treatments along with lifestyle changes to help improve all aspects of sleep quality including, sleep restriction, SWS suppression, rapid eye movement sleep disturbance, sleep fragmentation, and circadian misalignment.

References

1. Sondrup N, Termannsen AD, Eriksen JN et al. Effects of sleep manipulation on markers of insulin sensitivity: A systematic review and meta-analysis of randomized controlled trials. Sleep Med Rev. 2022 Feb 1;62:101594.  doi: 10.1016/j.smrv.2022.101594.
2. Meaklim H, Jackson ML, Bartlett D et al. Sleep education for healthcare providers: Addressing deficient sleep in Australia and New Zealand. Sleep Health. 2020 Oct;6(5):636-650. doi: 10.1016/j.sleh.2020.01.012.
3. Adapted from Salehinejad MA, Azarkolah A, Ghanavati E et al. Circadian disturbances, sleep difficulties and the COVID-19 pandemic. Sleep Med. 2022 Mar;91:246-252.  doi: 10.1016/j.sleep.2021.07.011
4. Reutrakul S, Van Cauter E. Sleep influences on obesity, insulin resistance, and risk of type 2 diabetes. Metabolism. 2018 Jul;84:56-66. doi: 10.1016/j.metabol.2018.02.010.

The information contained within is intended to be used as an educational tool and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.