Hot Topics Blog
We are well into February and we’ve had storms and floods but at least we have got rid of the worst of those dreadful dark mornings! Alongside the short days the other thing that is often fizzling out by the time we get to this stage of February are the New Year resolutions, which is a pity as for many people and ‘getting fit’ is likely to be high on the list of priorities. Indeed the YouGov stats for last year showed that exercising more was the commonest New Year resolution in Britain, with almost 50% of those surveyed saying this was their main goal. Gym memberships will have been re-instated and new trainers bought, but for some this New Year burst is either unmanageable or unsustainable. We all know physical activity improves multiple outcomes - back in 2015 the Academy of Royal Colleges published an evidence based review of exercise titled ‘The Miracle Cure’, which reviewed the plethora of proven benefits of exercise. But how much exercise is enough? I personally love running and get a huge amount of mental and physical benefit from it, but does everyone have to be doing moderate to vigorous levels of exercise to get any benefits? I’m sure we’ve all had the situation where we have discussed with patients the NHS recommended activity levels of 150 minutes of moderate intensity activity per week, and they’ve looked back at you like you’re off your rocker - How on earth am I supposed to manage that doc? So what about less intense levels of activity - does walking your 10,000 steps per day help? Or even just spending less time sitting down….
A new meta-analysis from August 2019 (BMJ 2019;366:l4570) has helped moved this debate on, giving important new data on what level of exercise intensity gives mortality benefits, and also whether sedentary behaviour plays a part. This study was important as it used objective measurements of physical activity. Historically exercise studies have used self reported levels of exercise, and as discussed in the attached editorial (BMJ 2019;366:l5051) self reports are notoriously inaccurate, often underestimating low levels of activity and overestimating more vigorous activity. With the advent of body sensor devices we can now more accurately assess physical activity levels, and this meta-analysis reviewed the data using such devices.
Using high quality studies the authors reviewed more than 36,000 middle aged and older adults (mean age ~60 years old), with a median follow-up of 5.8 years, and reviewed all-cause mortality rates based on both the intensity of activity and length of time spent active, as well as sedentary time. The results show a substantial and steep reduction in mortality as total volume of activity increases, even with light physical activity (equivalent to normal walking pace). The difference from previous studies is the effect size seen with light physical activity - this study shows substantially larger benefits for light physical activity, quite possibly due to under-reporting of lighter activity in previous self-reported studies. Importantly the study also confirms that sedentary time is directly linked to mortality - more than 9.5 hours (excluding sleep) of sedentary time/day is associated with a statistically significant increase in mortality. Whether the increased mortality with increased sedentary time is simply the flip side of those doing less physical activity, or whether sedentary time is an independent risk factor, as has been suggested, we don’t yet know.
However, the message for us in primary care, and for our patients is simple - moving more and sitting less, at any level of intensity can reap significant benefits.
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