Sitting comfortably? Not after reading this…

It’s unlikely anyone would be surprised to be told that being physically active is important to ensure they remain in good health. And for most of us, we could probably do a little bit more to be active within our day-to-day routine (including simple activities like walking more or choosing to take the stairs). If you do meet the suggested targets for physical activity (from WHO: “Adults aged 18-64 should do at least 150 minutes of moderate-intensity physical activity throughout the week, or do at least 75 minutes of vigorous-intensity physical activity throughout the week, or an equivalent combination of moderate- and vigorous-intensity activity”), you’d be forgiven for thinking that’s enough. But is it? Just this week, we saw headlines warning of the dangers of sitting for long periods of time. The Daily Mail led with: “Sitting’s bad for the heart… and the gym WON’T help: Each hour sat down increases levels of deposits in the arteries by 14%”, and the Independent was a more cautious, but no less striking, “Each hour of sitting increases chance of heart disease by 14%”.

What did the media say?

Both outlets reported recent research from the Medical College of Wisconsin, led by Dr Jacquelyn Kulinski. Information on the time spent sitting was obtained from 2,031 adults, aged 50 years old on average. It was reported that the participants sat (at work or at home watching TV for example) from 2 hours per day, up to 12 hours.  The Mail reported that “for every hour spent sitting, the levels of artery deposits increased by 14 per cent.” So, sitting for longer appeared to be associated with more “deposits in blood vessels that act as signal for heart disease”, according to the Independent. We need to be careful with reporting increases as percentages though. The figure of an increase in deposits of 14% for every extra hour sitting could (and probably will) be easily misinterpreted as suggesting a 100% increase could result from just over 7 hours of sitting. To interpret the 14% figure, we need to know the baseline levels. Say for example, level of deposits was measured on a scale of 0-100 (0 being absolutely no deposits). Let’s say the people sitting two hours a day had a score of 5. Those sitting for 3 hours would have 14% more than that, or a score of 5.7. Those sitting 4 hours would have a score of 6.4, etc. In that context, it’s really interesting to see how the levels of deposits might increase in a very step-wise nature with sitting time (a dose response relationship), but it also shows what the percentage increases actually look like in the units of the measured variable. That’s just an example, as we don’t have the data in this research (more on that below). But if you want more on interpreting similar figures, take a look at our How to “Research the Headlines” post looking at risk.

Many people might not be surprised to read that such a link exists, but what’s perhaps more discouraging is the thought that getting more exercise might not be the answer. The Mail suggests “before you put your trainers on to make up for a day at your desk, experts warn going to the gym won’t help either.” What are we to do?

Luckily the lead author is quoted in both articles with some advice, suggesting: “Reducing the amount of time you sit by even an hour or two a day could have a significant and positive impact on your future cardiovascular health… The lesson here is that it’s really important to try and move as much as possible in your daily life, for example, take a walk during lunch, pace while talking on the phone, take the stairs instead of the elevator and use a pedometer to track your daily steps.”

What did the research actually say?

At this stage, I can’t say. The findings were reported at a major international conference, the American College of Cardiology, but haven’t yet been published. That’s not uncommon. Researchers often take their latest findings to meetings to present to their peers. It can generate useful feedback to help develop new ideas, or give different ways of thinking about the data as the analyses are finalised. By not being available in a peer-reviewed publication, however, the findings presented can’t be looked at in detail by those not present in that auditorium. It means the findings are preliminary (though possibly completely accurate), and while they will likely to be published soon, until that time we need to be cautious in our interpretation of them.

For the current research, we don’t have details of the study design. If it only had data at one point in time, it might be those sitting longer had poorer health that led them to sit longer. Both causal interpretations are valid unless the researchers were able to somehow discount one (or there may well be a dynamic feedback). Ideally, we’d need data following people over time to see that sitting for longer results in poorer outcomes. We’d need to see what the measure of the artery deposits was, and how that relates to actual cardiovascular events. I know I’d also want to get a better sense of how both physical activity and inactivity (the latter would include sitting time) might be independent predictors of health. The idea that long periods of sitting might cancel out any exercise is a potentially damaging message if it demotivates individuals from getting a bit more active.

The bottom line.

The dangers to our health from long periods of sitting may be one of the next big public health messages. This won’t be the last you hear about this. If your job means you sit for long periods of time, that doesn’t mean you should give up on trying to get more exercise, as the Daily Mail headline almost alludes to. Indeed, Dr Kulinski suggests “It’s clear that exercise is important to reduce your cardiovascular risk and improve your fitness level.” While the results need to be seen and scrutinised properly, there’s probably no harm in thinking about how we could all break up the length of time we spent sitting.

If you were sitting comfortably to begin with, I won’t apologise for making you squirm in your chair. I may very well be saving your life. You’re welcome.