THE importance of sleep duration and quality are well established, but bedtimes and wake-up times can also have an impact on health and wellbeing. It is a factor that scientists around the world are keenly interested in, as they step up their research to determine the effects — both positive and negative — of an early or late bedtime.
Some have even gone so far as to draw parallels between bedtime and IQ, creativity and even income levels. Indeed, those who go to bed late are more likely to have lower incomes, according to researchers in Finland.
Increased risk of diabetes
A study published in the Annals of Internal Medicine recently rekindled the bedtime debate. Research conducted by Brigham and Women’s Hospital researchers suggests that the evening chronotype, which corresponds to going to bed late and waking up late, is associated with a less healthy lifestyle and an increased risk of diabetes.
To come to this conclusion, the scientists analysed data from 63,676 nurses, collected between 2009 and 2017, integrating numerous parameters such as chronotype, diet, body mass index, tobacco and alcohol use, physical activity, and diabetes history.
They then compared the data with diabetes follow-up data from selfassessments and medical records.
They found that people considered to be night owls and late risers were more likely to develop type 2 diabetes, with an increased risk of 72 per cent before other lifestyle factors were taken into account, and 19 per cent after these parameters were taken into consideration.
The researchers also observed a greater propensity to consume alcohol, and in greater quantities, to eat unhealthy food, to smoke, and to sleep less, among night owls.
“When we controlled for unhealthy lifestyle behaviours, the strong association between chronotype and diabetes risk was reduced but still remained, which means that lifestyle factors explain a notable proportion of this association,” the study first author said.
Go to bed between 10 and 11pm to preserve heart health
What is the ideal bedtime to reduce the risk of heart disease? This is the question that a team of British researchers attempted to answer, with a study published in 2021 in the European Heart Journal – Digital Health. “The body has a 24-hour internal clock, called circadian rhythm, that helps regulate physical and mental functioning.
While we cannot conclude causation from our study, the results suggest that early or late bedtimes may be more likely to disrupt the body clock, with adverse consequences for cardiovascular health,” said study co-author Dr David Plans of the University of Exeter.
Here, it is not a question of going to bed early or late to preserve heart health, but of going to bed within a specific time window. After analysing data from more than 88,000 people aged 43 to 79, recruited between 2006 and 2010 (with sleep and wake schedules tracked via accelerometer and cardiovascular monitoring), the researchers suggested that the optimum bedtime should be between 10pm and 10:59pm to reduce the risk of developing cardiovascular disease.
They noted that the risk was 25 per cent higher when night owls fell asleep at midnight or later, and 24 per cent higher when those with earlier bedtimes fell asleep before 10pm.
Late evenings linked to repetitive negative thoughts
Bedtime could also impact mental health, or at least be associated with elevated levels of stress and anxiety, according to 2014 research from scientists at Binghamton University, United States.
At the end of their research, the scientists concluded that people who slept less and went to bed later often experienced more repetitive negative thoughts than others. “Making sure that sleep is obtained during the right time of day may be an inexpensive and easily disseminable intervention for individuals who are bothered by intrusive thoughts,” the study’s lead authors said in a news release.
“If further findings support the relation between sleep timing and repetitive negative thinking, this could one day lead to a new avenue for treatment of individuals with internalising disorders.”
It should be noted that there is no direct cause-and-effect relationship between bedtime and anxiety levels, as the latter may well lead people to fall asleep later and influence sleep quality. However, paying attention to bedtimes could potentially play a role in the treatment of certain disorders. – ETXDailyUp
