In a 9-year study, type 2 diabetics who regularly suffered from sleep problems had an 87% higher risk of death compared to people without diabetes or sleep problems.
Many diabetics suffer from sleep disturbances mediated by disease-associated problems such as nocturia, restless legs syndrome, nocturnal hypoglycaemia, peripheral neuropathy and sleep-disordered breathing. These sequelae can result in fragmented sleep and poor quality of life.1
A recent prospective, population-based study published in the Journal of Sleep Research investigated whether there is an association between mortality and sleep problems.2 Data from 487.7 thousand adults from the UK Biobank were analysed.
Many diabetics regularly suffer from sleep disorders, which is associated with increased all-cause mortality.
Participants were asked about sleep disturbance on or off and followed up for 9 years. Among those who also had diabetes, 24% reported rarely or never having sleep disturbances, about half responded "sometimes" (48%) and 28% responded "often/usually".
Even without the presence of diabetes, frequent sleep disturbances were associated with a 31% increased risk of mortality (from any cause), and the association was robust to adjustment for other factors. Among diabetics, the association was clear: diabetes alone was associated with a 67% increased risk, and diabetes and frequent sleep disturbances together were associated with an 87% increased risk.
"To our knowledge, this is the first study to examine the effect of the combination of insomnia and diabetes on mortality risk," the authors write. There is already much evidence in the opposite direction: numerous epidemiological studies have described an association between insufficient sleep duration or quality and the risk of obesity, insulin resistance and type 2 diabetes.3,4
Experimental sleep restriction has been shown to result in changes in appetite-regulating hormones and increased feelings of hunger.3 Fragmented sleep has also been shown to be associated with impaired regulation of glucose metabolism. This is already evident in healthy individuals.5 In both observational and Mendelian randomisation studies, insomnia emerged as a risk factor for type 2 diabetes.6 Sleep duration and quality were even predictors of poorer HbA1c in several studies.3,4
Non-communicable diseases (NCDs), such as diabetes, are partly responsible for the stagnation in life expectancy improvements. It is estimated that mortality rates due to these NCDs will increase by about 54% between 2016 and 2040, with a doubling of deaths expected specifically due to type 2 diabetes.7
"Given that NCDs are the leading causes of death and rates of premature mortality are not declining as targeted, it is important to gain a better understanding of the underlying causes of NCD-associated mortality," write the authors of the current Biobank study. If chronic poor sleep can impair glycaemic control in diabetic patients, then this could be a mechanism for the increased mortality in patients suffering from both disorders.
Sleep extension and sleep quality improvement should be tested as an intervention to reduce obesity and the risk of diabetes, and optimise glycaemic control in patients with type 2 diabetes.
References:
1. Surani, S., Brito, V., Surani, A. & Ghamande, S. Effect of diabetes mellitus on sleep quality. World J Diabetes 6, 868–873 (2015).
2. Schantz, M. von, Ong, J. C. & Knutson, K. L. Associations between sleep disturbances, diabetes and mortality in the UK Biobank cohort: A prospective population-based study. Journal of Sleep Research n/a, e13392.
3. Reutrakul, S. & Cauter, E. V. Sleep influences on obesity, insulin resistance, and risk of type 2 diabetes. Metabolism - Clinical and Experimental 84, 56–66 (2018).
4. Knutson, K. L., Ryden, A. M., Mander, B. A. & Van Cauter, E. Role of sleep duration and quality in the risk and severity of type 2 diabetes mellitus. Arch Intern Med 166, 1768–1774 (2006).
5. Stamatakis, K. A. & Punjabi, N. M. Effects of sleep fragmentation on glucose metabolism in normal subjects. Chest 137, 95–101 (2010).
6. Yuan, S. & Larsson, S. C. An atlas on risk factors for type 2 diabetes: a wide-angled Mendelian randomisation study. Diabetologia 63, 2359–2371 (2020).
7. Foreman, K. J. et al. Forecasting life expectancy, years of life lost, and all-cause and cause-specific mortality for 250 causes of death: reference and alternative scenarios for 2016-40 for 195 countries and territories. Lancet 392, 2052–2090 (2018).