Maintaining a normal daily rhythm while being active during the day and sleeping at night can have more benefits than you might expect

    Abdulaziz Sobh

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    A new study found that it is related to improvements in mood and cognitive functioning, as well as a lower likelihood of developing major depression and bipolar disorder. The study, published on Tuesday in the journal The Lancet Psychiatry, analyzed interruptions in circadian rhythms, or daily sleep and wake cycles, of more than 91,000 adults in the United Kingdom. He measured these interruptions using a device called an accelerometer that is worn on the wrist and measures daily activity levels. The participants were taken from the Biobank of the United Kingdom, a large cohort of more than half a million adults in the United Kingdom from 37 to 73 years. The researchers found that people with more disturbances of the circadian rhythm, defined as an increased nocturnal activity, decreased activity during the day or both, were significantly more likely to present symptoms compatible with bipolar disorder or major depression. They were also more likely to have decreased the feeling of well-being and reduced cognitive functioning, according to a computer-generated reaction time test. For all participants, activity levels were measured over a seven-day period in 2013 or 2014, and mental health indicators such as mood and cognitive functioning were measured using an online mental health questionnaire that participants completed in 2016 or 2017. "It is widely known that a good night's sleep is a good thing for well-being and health, and that's not a big surprise," said Dr. Daniel Smith, professor of psychiatry at the University of Glasgow and lead author of the study. "But I think the least known and what comes out of this work is that not only is it important to sleep well, but having a regular rhythm of being active in the light of day and inactive in the dark over time is important for well-being mental " The findings were found to be consistent even when controlled by a number of influencing factors, such as age, sex, lifestyle, education, and body mass index, according to Smith. "I think one of the most surprising things we found was the consistency in the direction of our association in everything we consider in terms of mental health," Smith said. The daily circadian rhythm is controlled by a collection of neurons in an area of the brain called the hypothalamus. The hypothalamus helps regulate a series of important behavioral and physiological functions, such as body temperature, eating and drinking habits, emotional well-being, and sleep, according to the National Institute of General Medical Sciences. The findings are consistent with research that indicates a link between sleep interruptions and mood disorders. A 2009 study, for example, showed that men who worked night shifts for four years or more were more likely to have anxiety and depression than those who worked during the day. However, the new study is the first to use objective measures of daily activity and is among the largest of its kind, according to Aiden Doherty, a senior researcher at the University of Oxford, who was not involved in the research. "This study is the first large-scale investigation of the circadian rhythm association objectively measured with various mental health, well-being, personality and cognitive outcomes, with an unprecedented sample size of more than 90,000 participants," Doherty wrote in an email. "Previous studies have been very small (in a few hundred people) or dependent on self-report measures (ask people what they think they do) ... However, this study used objective device-based measures in more than 90,000 participants, and then linked this information to the standard measures of mood disorders, subjective well-being and cognitive function, "he added. The findings have important consequences for public health, particularly for those who live in urban areas, where circadian rhythms are often altered due to artificial light, according to Smith. "By 2030, two-thirds of the world's population will live in cities, and we know that living in an urban environment can be quite toxic to your circadian system because of all the artificial light to which you are exposed," Smith said. "Then we should think of ways to help people tune into their natural rhythms of activity and sleep more effectively, hopefully, that will protect many people from mood disorders." For those who struggle to maintain a constant circadian rhythm, certain strategies, such as avoiding technology at night, have proven to be an important part of good sleep hygiene. "It's not very important to use your phone late at night and have a regular pattern of sleep," Smith said. "But equally important is a pattern of being exposed to the sun and daylight in the morning and doing activity in the morning or at noon so you can sleep properly." Based on the observational nature of the study, the researchers could not show causality, which means that it is not clear whether sleep disturbances caused mental health problems or vice versa. "It's a cross-sectional study, so we can not say anything about cause and effect or what came first, mood disorder or circadian disruption," said Kristen Knutson, associate professor of neurology at Northwestern Feinberg School of Medicine. , that is not involved in the study. "And they are likely to affect each other in a circular way," he added. The researchers also looked exclusively at adults between 37 and 73 years of age, which means that the results may not apply to younger individuals whose circadian rhythms are known to be different from those of older adults, according to Smith. "The circadian system changes throughout life - if you have children, you know that very young children tend to be nocturnal," Smith said. "My suspicion is that we could see even more pronounced effects in younger samples, but that has not been done yet, as far as I know." But the study adds more credibility to the idea that sleep hygiene, including maintaining a consistent pattern of sleep and wake cycles, can be an important component of good mental health, according to Smith. "It's an exciting time for this type of research because it's starting to have some applications in the real world," Smith said. "And from my point of view as a psychiatrist, I think it's probably little recognized in psychiatry how important healthy circadian function is, but it's an area that we're trying to develop."