Sitting comfortably? Well try not to stay that way for too long — doing so could seriously damage your health.
Many of us spend nine hours a day or more sitting and that’s not just at work — according to new figures more than a third of people spend longer sitting at the weekend than they do toiling at their desks, with leisure time often now dominated by screen time, whether that’s slouched in front of the TV or surfing the net on a computer.
It’s a habit that’s not just bad news for backs, it increases the risk of serious disease, even premature death. Indeed, a study published today suggests long periods spent sitting contributed to 70,000 deaths in 2016 in the UK, and for the first time has put a figure on its cost to the NHS — £700 million a year.
Sitting seems to have an independent impact, affecting the way our hormones behave, how our metabolism works and our brain functions — it may even kick-start inflammation in the body (file image)
And these figures are conservative, report the researchers from Queen’s University Belfast and Ulster University in the Journal of Epidemiology & Community Health. They concluded that measures should be taken to reduce sedentary behaviour with the aim of improving population health and reducing the financial burden on the health service.
The danger isn’t simply that spending large periods of time doing nothing means you’re more likely to become obese (which in itself increases the risk of many diseases).
Sitting seems to have an independent impact, affecting the way our hormones behave, how our metabolism works and our brain functions — it may even kick-start inflammation in the body.
The number of health conditions associated with prolonged periods of sitting makes for uncomfortable reading: cardiovascular disease, type 2 diabetes, certain forms of cancer such as lung cancer and premature death from all causes.
It also affects the brain, with studies showing that it can impact on mood, cognition, memory as well as raising the risk of dementia.
Even gym regulars may not be protected, suggests research — if they then spend the rest of their day sitting.
Sitting seems to have such a negative impact on our health that some have dubbed it the new smoking. ‘I don’t think that’s overblowing it,’ says Dr Carolyn Grieg, a reader in musculoskeletal ageing and health at the University of Birmingham.
‘There are few things that have an impact on so many different elements of our wellbeing.’
And Dr Mike Brannan, national lead for physical activity at Public Health England says: ‘Even if you are physically active, sitting for long periods of time damages your health and greatly increases your risks of a broad range of health conditions.’
IT TAMPERS WITH YOUR HORMONES
So why is sitting such bad news? One area under investigation is how periods of inactivity change the way hormones such as insulin behave. Insulin helps keep blood sugar levels within the normal range by ‘mopping’ up excess sugar in cells.
Preliminary research in animals has found that prolonged sitting reduces the activity of some of the enzymes responsible for this kind of clear up, leaving more fats and sugar circulating in the blood, explains Dr Stacy Clemes, a reader in active living and public health at Loughborough University.
‘So if you sit for long periods, research shows that your body’s response to insulin, after eating, becomes less effective. This can raise the risk of type 2 diabetes.’
While she adds that this research hasn’t been replicated yet in humans, ‘what has been shown in a lot of studies is that if you regularly break up your sitting time that seems to be beneficial for blood glucose control especially’.
When it comes to heart disease there may be many factors — not least that sitting seems to lead to raised cholesterol, adds Martin Cowie, a consultant cardiologist at the Royal Brompton Hospital and a professor of cardiology at Imperial College London. ‘Muscles become deconditioned and not so good at utilising cholesterol as they would normally be leading to more circulating in the blood,’ he says.
Furthermore, he says inactivity reduces the ratio of beneficial HDL cholesterol to harmful LDL cholesterol. HDL can slow or even reduce furring of the arteries.
Multiple studies, in an attempt to work out why sitting is so bad for us, have started to look at what it does to levels of inflammatory markers. Inflammation is the body’s response to injury; it prompts the release of chemicals that induce inflammation as part of the healing process.
Preliminary research in animals has found that prolonged sitting reduces the activity of some of the enzymes responsible for this kind of clear up, leaving more fats and sugar circulating in the blood, explains Dr Stacy Clemes, a reader in active living and public health at Loughborough University (file image)
This is fine if you have a cut on your finger but chronic inflammation in a blood vessel, for example, could actually be harmful. Indeed low-level chronic inflammation is now linked to several diseases, including type 2 diabetes, heart disease and possibly depression.
One study, which monitored activity levels in 558 GP patients across Leicestershire by giving them movement sensors, found that those who moved the least, and spent the most time sitting, had the highest levels of chemicals such as interleukin and leptin, which are associated with inflammation.
As for its effect on the brain, people who sit for long periods have reduced thickness in the medial temporal lobe, the part that plays a key role in the formation of new memories and spatial awareness, according to a study published in the journal PLoS One last year.
In the study, 35 people aged 45 to 75 were given MRI brain scans and asked to record their sitting times for a week — the MRI was then repeated at the end of the week.
Those sitting longest had the thinnest medial temporal lobes. The researchers said why was unclear but commented: ‘Sedentary behaviour appears to have direct neurobiological effects’.
The very fact that sedentary behaviour affects the cardiovascular system and impacts on blood sugar levels will also impact on the brain — as will the fact that it triggers inflammation. It’s thought that it may even reduce the turnover of new brain cells.
GYM USERS CAN’T BE COMPLACENT
You might assume that the ill-effects of sitting are largely restricted to those with a couch-potato lifestyle — but the evidence suggests even those who meet the recommended levels of exercise can’t hold back the ill-effects that prolonged sitting brings.
In other words, you can’t undo the damage done by a day sitting in the office by popping to the gym on the way home.
A 2017 U.S. study, for example, involving 8,000 adults, published in the Annals of Internal Medicine, found that prolonged periods of sitting increased the risk of premature death irrespective of other factors such as the amount of exercise they did.
And a study published last year in the journal JNCI Cancer Spectrum found that two hours spent sitting watching TV a day was associated with a 70 per cent increased risk of colorectal cancer, independent of weight and whether or not the study participants did any form of exercise.
In other words the exercise (while it will have other benefits) cannot cancel out the bad effects of sitting for too long. ‘I used to think, “I’m fine, I may sit down for work but I do lots of exercise”, then evidence starts to come out that there seems to be some kind of independent link to sitting and it has got stronger and stronger,’ says Dr Clemes.
Indeed to cancel out the negative impact of sitting for eight hours a day you need to do mopre than 60 to 75 minutes’ moderate intense activity a day, well over the 150 minutes’ moderate exercise (such as brisk walking) per week that the current guidelines recommend for those aged 19 to 64, according to a 2016 study in The Lancet.
So is it the new smoking, as it’s sometimes described? Some in the scientific community feel the smoking analogy is unhelpful.
A paper last year in the American Journal of Public Health pointed out that while excessive sitting (which they defined as being more than eight hours a day) raises the risk of chronic diseases and premature death by 10 to 20 per cent, smoking increases the risk of premature death by 180 per cent. Yet many more people sit for hours, especially office workers, than smoke, so arguably the problem affects millions more.
Indeed, when you look at some of the risks associated with excess sitting, if they were relating to a food item or a drink it’s unlikely it would be on sale to the under-18s and would almost certainly be subject to punitive taxes.
The authors of last year’s study in JNCI Cancer Spectrum said that while it wasn’t clear how prolonged sitting was linked to colorectal cancer, they speculated that it may explain why rates of this cancer are rising among the under-50s — who are more sedentary today than in the past.
Scientists such as Dr Grieg are now trying to discover exactly why sitting is so bad — and at what point putting your feet up and having a bit of a rest tips into the danger zone and starts to have a negative impact. ‘Working out exactly what sitting does to us on a physiological level and trying to generate the data will mean we can make specific recommendations about sitting,’ she says.
At the moment, the expert view is unequivocal. ‘People should sit less and move more,’ says Dr Brannan. Yet the official guidance is vague.
The Health and Safety Executive advises office workers to have five to ten-minute screen breaks each hour.
However, a 2011 report entitled Start Active Stay Active issued by the four chief medical officers in the UK advised only that ‘all adults should minimise the amount of time spent being sedentary (sitting) for extended periods’. But what an extended period is wasn’t made clear. ‘At the moment, we can’t say so many hours is too much — but the evidence is getting stronger for regularly breaking up sitting — and after every 30 minutes stand up and move around,’ says Dr Clemes.
But to do that people need to become more aware of how long they are spending sitting — at the moment they tend to wildly underestimate this.
YOU SIT LONGER THAN YOU THINK
Research involving state-of-the-art motion sensors found that people spend around two-and-a-half hours more time sitting a day than they think they do, says Sebastien Chastin, a professor of health behaviour dynamics at Glasgow Caledonian University, who has conducted several studies analysing sitting habits.
‘I’ve found that people commonly spend over ten hours a day sitting — and what was stunning is how widespread that is — all sorts of people, all sorts of ages do this.
‘Even when I looked at my own data my reaction was “wow” — I’m 37 and do physical activity most days of my life — I thought I spent six or seven hours seated, in fact I spend ten.’ And the older you get, the more time you tend to sit.
‘It is not unusual for elderly people to sit uninterrupted for four hours a day,’ says Dr Grieg.
So what is the answer? Some experts say that almost as important as vigorous exercise is encouraging people to undertake more light intensity physical activity — in other words moving a bit more, whether at home or at work, to cut back on the amount of time spent sitting.
‘Over the years, the time spent engaged in sport has not changed that much, but what has changed is the amount of time we do light activity,’ says Professor Chastin.
‘Mechanisation at work, gadgets for housework, more screen time, more inactive transportation, more time spent in education, different types of work means that we have less light incidental activity in our lives.
‘It’s crept up on us and we have not seen it.’
Guidance issued by Public Health England in 2014 acknowledged that ‘reducing inactivity could prevent up to 40 per cent of many long-term conditions’.
However while there are pages about how to get more exercise, sitting is addressed in a few sentences expressing that: ‘while a growing body of evidence points to the risks of sedentary behaviour, we don’t yet know what exact level of harm is incurred. However, we should avoid being sedentary for extended periods.’
But, there are signs that the message about the need to move more is being heard.
At Loughborough University, where Dr Clemes works, they have taken measures to build more activity into everyday life.
‘So we have shared bins and printers in the corridor rather than by our desks so we have to get up and walk to them,’ she says.
‘We also have a meeting room with standing desks.’
SHOULD YOU GET A STANDING DESK?
Sit/stand desks, that allow people to vary their day between sitting and standing, have gained much attention. On the face of it these might seem a great idea but it’s not that straightforward.
‘Sit/stand desks are great at reducing sitting time at work, but there is a tendency to sit more at home,’ says Dr Clemes.
‘We found when measuring office workers sitting and standing time during and outside of working hours before and after they’d been given a sit/stand desk, they reduced their overall sitting time at work after three months by 20 per cent, but increased their sitting time at home after work by 8 per cent.
‘While we saw an increase in sitting at home, office workers still experienced an overall reduction in total daily sitting time, which is very positive.’
And, as with everything it’s possible to have too much of a good thing — even standing.
‘The research says it [a sit/stand desk] just shifts the load,’ says Ashley James, an occupational health physiotherapist in Liverpool. ‘If you use a standing desk you find lower back pain reduces but leg, calf and ankle pain can increase. The best way to use the desk is with variation.’ In other words, regularly changing between sitting and standing.
However he thinks it is key to neither sit nor stand for too long.
‘It’s important to say that not all sitting is bad — in fact there is good evidence in blue-collar workers that sitting for a certain amount of time a day reduces the risk of injury. It’s doing too much of any one thing that it the issue.’
Ashley James believes going for ten-minute walks every hour can be just as good — and much cheaper than standing desks.
And Dr Clemes has just finished a pilot four-and-a-half-month study in eight primary schools — four of which were given six standing desks for children to use — and found they made a marked difference.
‘Teachers reported the standing desks improved the children’s concentration and improved behaviour,’ says Dr Clemes. ‘But the biggest promising effect was the improvement it had on reading scores.’
More of the children using the sit/stand desks met their expected level of reading than those in the class who were not.
‘We know from studies that children who sit a lot are likely to become adults who sit a lot and our thinking is if we can get in early and change their mindset these children will be less likely to be so sedentary,’ she says.
But what about for people at home?
‘We probably do need more public health messages to get across that sitting for long periods is unhealthy and we need to break up sitting,’ says Dr Clemes. ‘I also think we have to be careful not to discriminate against people who may not be physically able — there are things that people can do to get more movement involving their upper body.’
She is starting a lab-based study to see if using arm resistance bands (large elastic bands that can help give muscles a workout by providing resistance to pull against) have a beneficial effect on older, more sedentary patients.
This follows research published in 2017 in the journal Diabetes, Obesity and Metabolism which found that blood sugar levels in obese patients who used an arm crank for five minutes every 30 minutes dropped by 57 per cent after meals compared with those who were inactive.
Indeed, while sit/stand desks and new office designs may help some, one concern is that the impact of sedentary behaviour may have the biggest effect on the most frail — for example the elderly and hospital patients. Yet those are often the people who sit the most.
‘We know that, after 48 hours of bed rest, people are already losing muscle and bone health — our bodies are made to move,’ says Professor Chastin.
‘So in a geriatric ward, why are we keeping people sitting for so long? I know people are afraid of falling, but we need to get patients out of bed and moving more.’
Hospitals are reducing the time patients spend in bed — ‘pyjama paralysis’ — as figures show doubling the amount of time spent moving can reduce the time a patient needs to spend in hospital.
But Professor Chastin says while the science is developing, the overall message is quite clear: ‘It doesn’t matter where you are, how old you are or what you are, the important thing is to move.’