Not sleeping enough? You could be increasing your risk of dementia and heart disease
How do you know if your sleep patterns are cause for concern and what, if anything, can you do to salvage them?
How have you been sleeping? Research published by Maynooth University in February revealed our sleeping habits changed significantly over successive lockdowns with the number of people in Ireland rating their sleep as poor increasing from 22% pre-pandemic restrictions to 49% during lockdowns.
Two new studies outline yet more reasons why sufficient uninterrupted slumber is essential for health.
In the first of the published papers, Dr Severine Sabia and a team from UCL and the French national research Institute Inserm tracked the health and lifestyle habits of more than 7950 Britons, all of whom self-reported their sleep patterns for about 25 years, starting when they were aged 50. In findings published in the journal , Sabia showed that people who regularly reported sleeping six hours or less on a weeknight were 30% more likely to be diagnosed with dementia than ‘normal sleepers’ (who got at least seven hours) after three decades.
“We found that short duration sleep in mid-life, assessed more than 25 years before mean age at dementia onset, is associated with dementia risk in later life,” Sabia says.
In a double blow to poor sleepers, researchers from Maastricht University Medical school then reported that longer periods of fitful or fragmented asleep – for which you can blame a crying baby, snoring partner or barking dog – led to nearly double the risk of dying from heart disease for women, compared to the general population. While the link was less evident in men, there was still an associated risk.
“Typically people will feel exhausted and tired in the morning because of their sleep fragmentation,” says Dominik Linz, an associate professor at Maastricht University who led the study.
But how do you know if your sleep patterns are cause for concern and what, if anything, can you do to salvage them?
Fitful or fragmented sleep, dubbed ‘arousal burden’ by the Maastricht researchers, is a normal part of our nightly sleep patterns. Anything from traffic noise to children, fidgeting partners to sleep apnoea and breathing problems can disrupt our sleep, although often we don’t wake long enough to register the disturbance.
It’s when it starts to impact our daily routine that problems can arise, says Motty Varghese sleep physiologist and behavioural sleep therapist at the Sleep Therapy Clinic in Dublin.
“Excessive sleep fragmentation where you wake up momentarily and return to sleep, results in poor quality sleep and prevent the progression of sleep to deeper refreshing stages of sleep,” Varghese says. “But it is not the same as waking up and staying awake for several minutes or longer which in reduced total sleep time and quantity result in a sleep debt, that can affect physical and mental health.”
In January, a team from McGill University reporting in the found that while mothers of multiple children reported more fragmented sleep than those with a single child, the number of children in a family didn’t seem to affect the father’s sleep patterns. Previous findings have found that broken sleep is linked to hardened arteries and there is a strong association between sleep apnoea and heart disease, so you should seek advice from your GP if your breathing stops and starts at night.
Fragmented sleep puts you at risk of anxiety, stress and depression. A recent study in suggested that interrupted sleep could be used as a predictor for future stress and, in a paper in the journal , Patrick Finan, a professor of psychiatry at the Johns Hopkins University School of Medicine in Baltimore, reported that several nights of interrupted sleep can lead to low levels of positive emotions, and high levels of negative mood in the morning.
Yoga or cognitive behaviour therapy can help to overcome anxiety associated with fitful sleep.
If you ruminate for an hour or more as soon as your head hits the pillow, you are not alone. Researchers from Baylor University reported that as many as 40% of people report difficulty falling asleep at least once a month. Anxiety is often an underlying cause.
“Relaxation techniques like meditation, body scan and breathing exercises, mindfulness is also helpful to calm your mind,” says Varghese.
Reducing the information load we experience before bed - not just the usual electronic but avoiding stimulating books or magazine articles which can affect some people’s ability to switch off and unwind, is also a positive step. Varghese says it can “help to put your day to bed before you go to bed by journaling early in the evening to rationalise your anxieties and engaging in relaxing activities in the evening hours”.
The Baylor study found that writing a detailed to-do list can help. Of 57 healthy young adults asked to write either about tasks that they needed to remember to complete the next few days (to-do list) or about tasks they had completed the previous few days (completed list), it was the to-do listers who fell asleep significantly faster. “Rather than journal about the day’s completed tasks or process tomorrow’s to-do list in one’s mind, our study suggests that individuals spend five minutes near bedtime thoroughly writing a to-do list,” the researchers said.
Our requirement for sleep does not diminish as we get older and is more or less fixed for life from early adulthood, even though our sleep patterns are prone to change. What changes, says Varghese, is our ability to achieve it.
“There is a decline in the stage 3 sleep and REM sleep and sleep disorders like sleep apnoea and insomnia are common among older adults,” he says. “Prioritising sleep and addressing sleep problems as we get older will help to protect the sleep.”
Some researchers have suggested the ageing process disrupts our internal body clocks so that people sleep later and wake earlier than they did in their 20s and 30s. This is partly due to deterioration in function of the suprachiasmatic nucleus (SCN), the master clock that governs our circadian rhythms. Even when over 60s do drop off, the quality of sleep is not as good as when they were younger.
Make sure you get outside every day, preferably in the morning when light is at its brightest and for at least two hours a day. Daylight is one of the most powerful cues for maintaining the SCN and a lack of exposure to daylight has been associated with sleep problems in the elderly.
A recent study, published in , found that older people who consistently reported sleeping six hours or less on an average weeknight from their 50s and 60s onwards were about 30% more likely than people who got seven hours of sleep on a regular basis to develop dementia three decades later.
A previous study involving 2,610 participants, published in February, found that dementia was double among participants who reported getting less than five hours sleep compared to those who got a regular seven to eight hours a night. The researchers from Brigham and Women’s Hospital also suggested that, among participants with an average age of 76 years, routinely taking 30 minutes or longer to fall asleep was associated with a 45% greater risk of dementia.
There is, undoubtedly, a link between sleep and brain health. Yet the links between dementia and sleep – or lack of it - are not clear cut. Dr Severine Sabia says that “we cannot confirm that not sleeping enough actually increases the risk of dementia”.
A study published in the reported the common complaints to be trouble falling asleep, frequent awakening and waking up too early. “A loss of reproductive hormones can manifest as sleep fragmentation due to hot flashes,” Varghese says. “There is also an increased prevalence of sleep apnoea among post-menopausal women, both of which can lead to raised anxiety about sleep and can result in the development of insomnia if not addressed.”
Often it is the effect hormones can have on body temperature that can lead to sleep difficulties. At night our bodies want and need to lose heat in order to sleep and our body temperature drops by around one degree as we drop off. With this in mind: don’t eat a big meal or drink alcohol too close to bedtime, don’t exercise too hard late at night which raises your body temperature, and do open windows and install a fan in your bedroom to keep things cooler. HRT, if considered appropriate by your GP, can also help to relieve severe hot flushes.
Our tendency to prefer mornings to evenings – to be a lark or an owl - or vice versa is mostly genetically determined. “If you wake up too early in the morning than you would like to it can cause “early morning awakening insomnia”,” Varghese says. “It much more common in the spring and summertime due to earlier exposure to sunlight compared to winter months.”
For larks and owls, however, waking up too early on a consistent basis is associated with depression. If early waking persists for more than four weeks and is affecting your wellbeing, it's best to see your GP who can treat the underlying cause.
A chronic lack of sleep increases the risk of obesity, diabetes and a range of other health problems, but catching up with a long lie-in at weekends is not the answer. There’s an observed link between shifts in ‘weekday’ to ‘weekend’ sleep patterns and the risk of developing metabolic problems related to obesity, diabetes and high blood pressure.
A 2019 study from the University of Colorado Boulder, published in , showed that any benefits of extra rest after a lie in are short term, and that by the middle of the next working week your body’s metabolism will be as disrupted – or more so – than if you had got up at your usual time.
The study, which allowed all participants to get three nights of eight hours sleep before some had their sleep deprived by just under five hours a night and some were allowed weekend lie-ins while others were not, also showed that the sleep deprived and lie-in groups gained just under 1.5kg in weight after 13 nights taking part in the lab-based trial. The eight-hour sleepers displayed no significant weight changes.
“Your sleep drive is determined by the length of the wake period you have before going to bed at night,” Varghese says. “A long lie-in will compromise the wake period and you can struggle to fall asleep at night. You shouldn’t compensate for late nights with lie-ins.”
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