Your sleep routine is more important to your overall health than you might think. Photo / 123rf
Irregular sleep is linked to increased risks of heart attack, dementia and depression, so a routine is crucial. Here’s how to get on track.
Your mum was right when she badgered you to go to sleep at bedtime, according to the latest sleep research. In what is described as the most comprehensive study of its kind, scientists have concluded that regardless of sleep duration, failing to stick to a regular bedtime and waking time increases the risk of stroke, heart attack and heart failure by 26 per cent. It’s enough to give you nightmares.
The research involved 72,269 people and found that going to bed and waking up at different times each day was “strongly associated” with a higher risk of major adverse cardiovascular events, even if subjects regularly achieved the sweet spot of eight hours of shut-eye.
Dr Kat Lederle, a sleep specialist and therapist, explains the processes that take place during sleep are intricately timed in line with the body’s circadian rhythm.
“They take place in a certain sequence. If you shift one thing, it has a knock-on effect on the others. We know for example that sleep is important for the regulation of our hormones and if that happens at the wrong time other processes are impacted and we get what we call internal misalignment.”
Read more: What you need to know about improving your sleeping habits
Repeated and persistent fluctuations in the body’s 24-hour rhythm appear to have dire consequences for health, knocking the body’s internal clock out of kilter.
Prof Guy Leschziner, a consultant neurologist at HCA Healthcare UK’s London Bridge Hospital, explains that sleep regulates vital functions in the body and timing plays a crucial role in these.
“There are multiple functions of sleep that relate to brain and body maintenance, such as healing, development, blood pressure regulation, memory consolidation and appetite regulation,” he says. “We spend a third of our life asleep but if you’re only doing it for substantially less time, those normal mechanisms of sleep become disrupted, which has consequences to your daytime function and your health overall.”
So, what are the consequences of poor sleep?
The body’s autonomous nervous system is divided into two major networks, the sympathetic and parasympathetic nervous systems, which have opposite roles. The sympathetic system carries signals that put your body’s systems on alert, using hormones such as the stress hormone cortisol. It is most active during the day. The parasympathetic nervous network carries signals that relax those daytime systems at night. If sleep is disrupted the balance between the two systems becomes unequal and can lead to higher cortisol levels. Studies show that excess cortisol can lead to elevated blood pressure.
Lederle says: “Lack of sleep means we are awake, which will then lead to an activation of that sympathetic nervous system, which then disrupts hormone regulation.”
Sleep also allows the body to regulate leptin, a hormone that reduces appetite, and ghrelin, which increases it. When a person sleeps, leptin levels normally rise, subduing appetite. Sleep deprivation increases ghrelin levels and at the same time lowers leptin levels, making us crave high-density calorific food, which over time can lead to weight gain.
According to Leschziner, even a single night of sleep deprivation can significantly disrupt the way our body processes glucose, termed as our glucose tolerance or insulin resistance. Insulin regulates blood sugar levels because it moves glucose out of the bloodstream into cells where it provides an energy source. Diabetes is a chronic disease that occurs when the body doesn’t produce enough insulin or can’t use it properly, resulting in high blood sugar levels, or hyperglycaemia, which causes a range of serious health problems including cardiovascular disease and kidney damage.
According to Prof Eve Van Cauter, a sleep researcher and a co-author of The Impact of Sleep and Circadian Disturbances on Glucose Metabolism and Type 2 Diabetes: “Multiple studies have shown that repeated awakenings during the night, insufficient sleep, excessive sleep, and irregular sleep all promote glucose intolerance. Furthermore, if a person has prediabetes or diabetes, poor sleep will worsen the condition.”
When we sleep, the prefrontal cortex structure of the brain, the organ’s executive centre which keeps other brain areas in check, regulates activity in the amygdala, an area of the brain involved in emotions, including anxiety. When we are sleep-deprived, one of the first brain areas to be affected is the prefrontal cortex, which is less able to control the amygdala.
“Then, the amygdala is a bit like an unruly child whose parents aren’t at home,” says Lederle. “It runs around and rings the alarm bell all the time, and we get more anxious.”
This disrupted ability to regulate emotions can put poor sleepers at a higher risk of depression.
While we are still learning about the processes that take place in the brain when we sleep, it appears that memory consolidation and maintenance of good brain health are two key functions.
“We all are aware of the fact that if we haven’t slept very well, we might not function quite as well the following day as we would normally,” says Leschziner. “But there are also some associations with long-term cognitive decline as well. There is a system within the brain called the glymphatic system, which is a series of microscopic channels through which the build-up of toxins or metabolites during the day are cleansed. In deep sleep, those channels function better. If deep sleep is limited, that may have an impact on the functioning of that system and therefore allow the build-up of certain proteins within the brain.”
Lederle says: “One hypothesis is that lack of sleep can create an accumulation of waste products, including beta amyloid proteins associated with dementia.”
Just one night of sleep deprivation can lead to accumulation in the brain of the beta amyloid protein, according to a 2018 study. Researchers found signs of the protein in the hippocampus, which plays a major role in forming new memories and is one of the first areas affected by Alzheimer’s.
Sleep also allows for the deposition of memories within the brain and the regulation of synapses, which are the connections between nerve cells in the brain that are believed to transmit signals between your brain and the nervous system.
“There are multiple mechanisms by which sleep has been associated with long-term cognitive decline,” says Leschziner.
Sleep helps the body regulate blood pressure through the modulation of hormones that influence cardiovascular health.
Dr Epameinondas Fountas, of the Onassis Cardiac Surgery Centre, says: “More research is needed to clarify exactly why, but we do know that sleep influences biological processes like glucose metabolism, blood pressure, and inflammations – all of which have an impact on cardiovascular disease.”
One hypothesis is that disturbed sleep is associated with higher levels of a protein called CRP, which is a sign of inflammation, a process linked to heart and circulatory disease.
Sleep disorders have been recognised as health factors that can increase the risk of stroke. A 2018 study found sleep disorders, particularly sleep apnoea, are prevalent among people at risk of stroke. The cause of this correlation could be down to several consequences of sleep disruption including high blood pressure, plaque build-up in the arteries, inflammation and reduced blood flow to the brain.
In 2009, the Danish government compensated 38 breast cancer sufferers who had worked night shifts. The move followed research published at the end of 2007 by the World Health Organisation’s specialist cancer research unit which showed women who work through the night on a regular basis could be more likely to develop cancer.
More recently, a systematic review by the National Toxicology Program in the United States concluded there was a “high confidence” that persistent night shift work that disrupts circadian rhythms can cause breast cancer in women and may cause prostate cancer in men.
The reasons for the link are not fully understood.
Leschziner says: “The hypothesis is that if you are eating and performing other bodily functions at times that are outside your normal circadian rhythm, then that might create problems in terms of how your body deals with certain substances and certain metabolites. Sleep is important for regulating immune function and our immune system is an important part of the process of regulating the duration of pre-cancerous cells.”
Thankfully, the brain is adaptive and can counteract the effects of temporary periods of poor sleep. For example, it will prioritise the deepest stages of sleep to compensate for sleep deprivation.
“For many people, having periods of poor sleep is really not something that they should particularly worry about,” says Leschziner. “Obsession with sleep can actually drive the underlying issue.”
For a healthy sleep, Lederle advises the following:
“Find out your sleep window. When does your body want to go to bed? When does your body want to wake up? Allow your body to sleep within that window as often as you can.
“Secondly, stress, in my view, is the biggest disrupter of sleep. We can’t create a stress-free life. Stress is part of our lives, and we need it to some degree. But find ways to manage stress, handle it and recover from it. Look for ways to relax and reduce that cortisol during the day and before sleep.”
Is it possible to have a tidy divorce? Leading barrister Sharon Chandra explains how.