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