"Every extra hour sitting down can raise your risk of type 2 diabetes by a fifth," the Daily Mirror reports. The paper reports on a study that used an accelerometer – a device that tracks movement – to look at the effects of sedentary behaviour on type 2 diabetes risk.
Researchers in the Netherlands measured the time that almost 2,500 middle-aged or older people spent sitting or lying down in one week, using an accelerometer. They found that people who had type 2 diabetes spent on average 26 minutes longer sitting or lying down, compared to people without diabetes.
From this, the researchers calculated that each additional hour of being sedentary increased the chances of a person having diabetes by 22%. It made little difference whether people sat for long periods or got up for regular breaks – the important thing was the overall amount of time spent sedentary.
Importantly, the study doesn’t tell us if people’s sedentary behaviour led to them getting diabetes, or whether people became more sedentary after getting diabetes. However, it provides more evidence that spending a lot of time physically inactive is likely to be bad for our health.
The study was carried out by researchers from Maastricht University and was funded by the European Regional Development Fund, numerous institutions from the Netherlands and by grants from three manufacturers of diabetes medication. The study was published in the peer-reviewed journal Diabetologia on an open-access basis, so it’s free to read online.
Most of the UK media’s reporting was accurate, although not all the reports made it clear the study does not prove that being sedentary causes diabetes. The Daily Telegraph did make this clear, while the Daily Mail said researchers had ruled out the possibility that diabetes made people more sedentary, which is not strictly true.
The Sun described sedentary people as "couch potatoes" who were "lazing around" – ignoring the fact that people who work at computers or drive for a living sit for much of the day.
This is a cross-sectional observational study. Researchers wanted to see if people’s activity levels were linked to whether they had type 2 diabetes, or risk factors for type 2 diabetes. Cross-sectional studies can give useful information suggesting a link between two factors – in this case, activity levels and diabetes. However, as snap-shots of information, they can’t tell us whether one causes the other, because we don’t know which factor happened first.
Researchers measured the activity levels of 2,497 people aged 40 to 75, 29% of whom had diabetes, using accelerometers. The devices were worn for eight consecutive days and measured whether they were sitting, standing or lying down, as well as speed of movement.
The researchers tested people’s glucose tolerance (a measure for diabetes) and other health measures, such as cholesterol, blood pressure and weight. After adjusting the figures to take account of known diabetes risks, they looked to see whether people’s time spent sitting or lying down was linked to their risk of having diabetes.
As well as whether people actually had diabetes, the researchers considered whether they had impaired glucose tolerance (a restricted ability to process glucose, which is often a precursor of type 2 diabetes) or metabolic syndrome. This is a collection of warning signs for diabetes, including impaired glucose tolerance, a high waist measurement, high levels of unhealthy fats in the blood and high blood pressure.
With the activity data, researchers looked at overall time spent sedentary (other than night-time sleeping), at how many "sedentary breaks" people had – for example, times when they got up and walked around or stood – and for what duration they remained sedentary at any one time.
They adjusted their figures to take account of the following confounders:
Finally, they calculated the risk of having diabetes or metabolic syndrome for each additional hour spent sedentary.
People with normal glucose tolerance spent on average 9.28 hours a day sedentary, compared to 9.38 hours for people with impaired glucose tolerance and 9.71 hours for people with diabetes.This means that people with diabetes spent on average 26 minutes longer each day being sedentary.
This equated, said the researchers, to a 22% increased risk of getting diabetes for each additional hour of time spent sedentary (odds ratio [OR] 1.22, 95% confidence interval [CI] 1.13 to 1.32). The chances of having metabolic syndrome was 39% higher (OR 1.39, 95% CI 1.27 to 1.53).
The numbers of sedentary breaks, and duration of sedentary episodes, made little difference once the researchers had adjusted their figures for confounding factors.
The researchers said this was the first time anyone had shown a link between sedentary behaviour measured by objective accelerometers, and diabetes risk, in a big group of adults. They say their results have "important implications" for public health, and that "consideration should be given to including strategies to reduce the amount of sedentary time in diabetes prevention programmes".
The researchers said their analyses of the data looking specifically at people with more severe diabetes – those taking insulin – suggest that the severity of illness is not linked to the likelihood of being sedentary, so it is more likely that inactivity causes diabetes.
This study adds to existing evidence which suggests the amount of time we spend physically inactive, either sitting or lying down, could have a poor effect on our health. It does not, however, prove that sitting for long periods causes diabetes.
The study has some strengths, including its size and the fact that activity levels were measured objectively. Activity levels in the Netherlands are likely to be similar to those in the UK, so these findings may also apply to us. However, the cross-sectional design of the study means it cannot show that sedentary behaviour is a cause of diabetes, even when taking account of the researchers’ assertion that their analysis of people with more severe diabetes makes this more likely.
Although the researchers adjusted their figures to take account of many confounding factors, they did not look at some other lifestyle aspects that could be important in developing diabetes, such as what people ate and family history of diabetes.
Study results aside, we already know that exercise and physical activity are good for cardiovascular health, so it’s not surprising that spending much of your day sitting down is likely to be a bad thing.
It can be hard to keep active if you have a job that requires you to spend a lot of time sitting down, such as being a taxi driver or working on a computer. This study gives one more potential reason to make sure you spend as much time as possible being physically active, whether that’s going to the gym, taking a walk, using the stairs instead of the lift, or just dancing around the kitchen while making dinner.
Read more about how you can incorporate a fitness regime into your day-to-day activities.