There is extensive information on the effect of the different drugs involved in the treatment of type 2 diabetes mellitus 2 (DM2), but little information on the kind of lifestyle to follow. Optimising this facet of lifestyle is an opportunity to improve prognosis of the disease. It is well known that exercising or avoiding smoking clearly reduce the risk of cardiovascular disease (CVD), but the effect of sleep duration is not known.
Studies in people with type 2 diabetes show that less and poorer quality sleep is associated with an increased risk of obesity, insulin resistance and poorer glycaemic control, all factors that increase cardiovascular risk. Therefore, sleep duration could be a factor that influences excess mortality in people with DM2, mortality which has been related to the sex and age of the patient at the onset of diabetes, amongst other things. However, to date, no large study has examined the role of sleep on mortality in people with type 2 diabetes.
This study from Wuhan University in China analysed data from the National Health Interview Survey conducted in the USA between 2004 and 2013, a voluntary health survey linked to the national mortality registry, in which more than 270,000 people participated, 24,212 of whom had type 2 diabetes. The survey collected information on sleep and the average number of hours slept per day, and studied the relationship with the main causes of death.
This study found that mortality in people with type 2 diabetes was higher than in the population without diabetes. In people with DM2, the highest mortality rate was clearly observed at the extremes of sleep duration. More specifically, the risk in people who slept less than 5 hours a day was 24%, and those who slept more than 10 hours a day had a risk level of 83%, much higher than those who slept 7 hours a day. This association was more pronounced in patients who were diagnosed with diabetes at an earlier age, and those with a longer history of the disease, regardless of the type of drug treatment received (pills to lower blood sugar or insulin).
This is the first large study focusing on patients with type 2 diabetes that shows that insufficient or excessive sleep duration is associated with a risk of cardiovascular mortality. Excess mortality in people with DM2 who sleep fewer hours may be related to increased sympathetic nervous system activity, which aggravates insulin resistance and consequently obesity and hypertension. For those who sleep for more hours, the problem may lie in the activation of chronic inflammatory mechanisms. Both cases are a risk factor for the development of cardiovascular diseases.
Although the work is based on self-reported questionnaires and does not analyse sleep quality, it presents for the first time a new approach to how the lifestyles of people with type 2 diabetes can influence their health and change the prognosis of their disease. It is essential for the patient to control their diabetes for a good outcome. Thus, studies such as this one indicate that guidelines on hours of sleep should be added to current lifestyle recommendations.
Author: Enric Esmatjes, endocrinologist at the Clínic Institute of Digestive and Metabolic Diseases. Hospital Clínic de Barcelona.