Poor or disrupted sleep has long been associated with a variety of negative health outcomes, from obesity and heart disease to dementia and depression. But there is an ongoing debate amongst researchers over the causal direction of these associations.
Does insomnia play a direct role in causing these conditions, or is poor sleep simply a symptom of these diseases? For example, are insomniacs more likely to eat unhealthy food at odd hours, leading them to display higher rates of obesity and diabetes?
“We know from past research that there’s a link between sleep and a person’s risk of type 2 diabetes, but it hasn’t been clear which comes first, bad sleep or higher blood sugars, or if other factors are at play,” said Faye Riley, from Diabetes UK.
This new study, published in the journal Diabetes Care and funded by Diabetes UK, set out to unpack the association between insomnia and high blood sugar levels using an analytic method known as Mendelian randomization. The technique allows for novel insights into causal relationships using observational data.
The focus of the research was on how blood sugar levels were influenced by five different sleep measures: insomnia (as defined by a difficulty getting to sleep or staying asleep), overall sleep duration, level of daytime sleepiness, nap frequency and chronotype (night owls versus early morning larks). Using data from the UK Biobank the researchers looked at more than 300,000 adults.
Interestingly, the researchers found only one clear connection between sleep traits and high blood sugar levels, and that was in the insomnia group. Those reporting frequent insomnia symptoms were linked with high blood sugar levels, and using Mendelian randomization the researchers concluded insomnia was playing a causal role in the hyperglycemia.
James Liu, corresponding author on the study, said these findings indicate directly treating insomnia could have a significant therapeutic impact on blood sugar levels and diabetes. The estimates in the study suggest interventions targeting insomnia could have as large an impact on diabetes as something like weight loss.
“We estimated that an effective insomnia treatment could result in more glucose lowering than an equivalent intervention, which reduces body weight by 14 kg (30.8 lb) in a person of average height,” said Liu. “This means around 27,300 UK adults, aged between 40- and 70-years-old, with frequent insomnia symptoms would be free from having diabetes if their insomnia was treated.”
According to the researchers, these findings call for a randomized clinical trial to explicitly measure the impact of insomnia treatments on diabetes. This is the only way to robustly validate these new findings.
Further study is also needed to understand exactly how insomnia could be causing increased blood sugar levels. The researchers hypothesize a number of potential mechanisms that could be playing a role mediating the link between high blood sugar and insomnia.
“They could include mediation by depression, anxiety, bipolar disorders, or alterations of sleep physiology, with the genetic correlations between insomnia and depression-related traits being stronger than those seen with other sleep-related traits,” the researchers write in the study. “Several hormones that sleep disturbance may influence (e.g., evening cortisol, nighttime growth hormone, ghrelin), together with possible influences on brain glucose utilization, alterations in the sympatho-vagal balance, and proinflammatory processes, may also be relevant.”
Riley is cautious to note these findings do not mean fixing insomnia will be a cure-all for diabetes. She stresses diabetes is a condition influenced by a variety of genetic and lifestyle factors but the new study does indicate treating insomnia could be a helpful part of a broader set of interventions to treat patients with diabetes.
“… it’s important to remember that type 2 diabetes is a complex condition, with multiple risk factors,” said Riley. “Eating a healthy balanced diet, being active, along with getting enough sleep, are all essential components of good health for everyone – including those at risk of, or living with, type 2 diabetes.”
The new study was published in the journal Diabetes Care.
Source: University of Bristol