"One jog a week is all you need to cut the risk of early death," Sky News reports.
The headline is prompted by a new review that has gathered the results from 6 large studies looking at the effect of running upon mortality in around 230,000 middle-aged adults. About 1 in 10 adults died during follow-up (which varied across studies from 5.5 to 35 years).
Any running was linked with a 27% reduced risk of dying from any cause compared with no running.
Similar risk reductions were seen for deaths from cardiovascular diseases such as heart disease, and cancer.
The findings support general understanding that physical activity is good for health. However, this does not mean that running in itself is necessary as an activity. The comparison groups may have included a varied mix of those who were sedentary and those who took other forms of activity but just did not run.
Surprisingly there was no link between how often people ran and their risk of early death. So it could be that running was just a general marker for a healthier lifestyle overall. People who regularly go for a run or jog may also have a better diet, do not smoke, and moderate their alcohol consumption. It may be a full lifestyle pattern that is reducing mortality risk.
Nevertheless, the findings support current recommendations to take regular physical activity, of at least 2.5 hours moderate intensity each week.
Where did the story come from?
This study was conducted by researchers from Victoria University, University of Sydney and University of Southern Queensland in Australia, and other institutions in Thailand, Austria and Finland. No sources of funding are reported and the authors declare no conflict of interest. The study was published in the peer-reviewed British Journal of Sports Medicine, and is freely available to access online.
The UK's media reporting of the study was accurate.
What kind of research was this?
This was a systematic review that gathered the published literature that has looked at the effect of running on risk of death overall and from specific cause, and then pooled the findings in a meta-analysis.
A systematic review is the best way of getting an overview of the available evidence on a particular research question, but the strength and quality of findings are only as good as the included studies.
Also studies looking at the effect of physical activity tend to be observational, which means it is difficult to account for all of the other health and lifestyle factors that may be influencing the relationship.
What did the research involve?
The authors searched online literature databases up to February 2019 to identify:
- prospective cohort studies (that had followed people over time)
- included generally healthy adults (not selected on the basis of disease); and
- the link between running or jogging with death from any cause, cardiovascular disease or cancer
The authors assessed study quality and extracted relevant details such as the duration of follow-up, how physical activity and mortality outcomes had been assessed, and whether the study had taken account of relevant confounding factors (like diet, smoking and alcohol use).
14 studies met inclusion criteria, which analysed different data from 6 prospective cohorts including a total 232,149 adults. The 6 cohorts were:
- the Health Survey for England and the Scottish Health Survey (combined data)
- the Aerobics Center Longitudinal Study (US)
- the National Health and Nutrition Examination Survey (US)
- the 50+Runners Association study Stanford University (US)
- the Copenhagen City Heart Study (Denmark)
- the Shanghai Men's Health Study (China)
Across studies runners made up about 10% of the sample. Participants' age at study start was variable across studies, mostly around mid-to-late 50s, but a couple of studies involved participants who were in their 40s.
Mortality outcomes were reportedly obtained from national death registries over follow-up times ranging from 5.5 to 35 years. All but 1 of the 14 studies was assessed to be of good quality.
What were the basic results?
There were 25,951 deaths across the studies (11% of the sample).
5 studies assessed the link with death from any cause. The pooled results from these studies found that any running was associated with 27% reduced risk of death during follow-up (hazard ratio [HR] 0.73, 95% confidence interval CI 0.68 to 0.79). All studies gave broadly similar results giving more confidence in the reliability of the pooled result. Further analyses by gender or other study characteristics (eg looking at the most recent data) gave similar results.
4 studies also found that running reduced risk of cancer death by 23% (HR 0.77, 95% CI 0.68 to 0.87), again with similar results between studies.
Only 3 studies looked at cardiovascular death. The pooled results found that running was associated with reduced risk (HR 0.70, 95% CI 0.49 to 0.98), though notably 2 of these 3 studies had found no effect of running. The single study that did find an effect on cardiovascular death meant that the pooled results just reached the threshold for statistical significance.
The studies did not show a clear relationship between frequency, duration or speed of running and risk of death.
How did the researchers interpret the results?
The researchers conclude: "Increased rates of participation in running, regardless of its dose, would probably lead to substantial improvements in population health and longevity. Any amount of running, even just once a week, is better than no running, but higher doses of running may not necessarily be associated with greater mortality benefits."
The findings of this review on the whole support current understanding around physical activity: that it is beneficial to health.
However, the review does not automatically mean that running in itself is necessary for better health.
Physical activity can take various forms and intensities; for example, swimming, cycling, dance, brisk walking and team sports. The main findings simply look at running vs no running, but we do not know who was in the no-running group. It could be a varied mix of people from those who do no physical activity at all to those who are active but do not run. Running was self-reported so the running category as a whole is likely to include a varied mix of frequency and intensity.
The lack of any clear relationship between increased running and reduced mortality further confuses the picture. Overall this makes it difficult to know whether running as a specific activity is beneficial and if so, how much is beneficial.
As with all observational studies, it's not possible to be sure the link is not being influenced by other health and lifestyle factors. That is, where people who run are more likely to be healthier overall, having a healthier diet, not smoking, and keep alcohol consumption in moderation.
The included studies variably accounted for these factors. Then, while the studies did not specifically recruit people with disease, some participants may have had existing health problems that prevented them from running (or possibly taking other forms of activity), and where those health factors then increased their mortality risk.
In looking only at overall, cardiovascular and cancer mortality outcomes, the review also does not explore how physical activity may benefit health and reduce disease risk across the lifespan. Again this is not restricted to running. For example weight-bearing, resistance exercises can help bone health and reduce risk of osteoporosis in older age.
The government currently recommends that adults aim to achieve 150 minutes (2.5 hours) of moderate intensity activity a week (such as brisk walking or cycling) or 75 minutes of vigorous activity (such as running).
Running is not suitable for everyone – the most important thing is staying active and reducing sedentary time.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
Sky News, 5 November 2019
The Guardian, 4 November 2019
The Daily Telegraph, 4 November 2019
Links to the science
British Journal of Sports Medicine. Published online 4 November 2019