One
hour of physical activity per day could offset health risk of 8 hours of
sitting
THE LANCET
A new study of over 1 million people finds that doing at least
one hour of physical activity per day, such as brisk walking or cycling for
pleasure, may eliminate the increased risk of death associated with sitting for
8h a day.
Physical inactivity is linked to an increased risk of heart
disease, diabetes and some cancers and is associated with more than 5 million
deaths per year [1] and, as the first global economic analysis of physical
inactivity shows, costs the world economy over US$67.5 billion per year in
health care costs and lost productivity.
The findings come from a new four-paper Series published today in The Lancet and launched in London ahead of the Summer Olympic Games. The authors of the Series warn there has been too little progress in tackling the global pandemic of physical inactivity since the 2012 Olympics, with a quarter of adults worldwide still failing to meet current recommendations on physical activity.
Sitting time, physical activity and risk of death
Researchers analysed data from over 1 million people from 16
studies. The research team wanted to see how many hours of daily physical
activity would be required to eliminate the association between prolonged
sitting time and increased risk of death. Examples of physical activity were
brisk walking at 5.6 km/h or cycling for pleasure at 16 km/h.
The researchers classified individuals into four equally sized
groups according to how active they were - less than 5 mins a day for the least
active, up to 60-75 mins a day for the most active [2].
People who sat for 8 hours a day but were physically active had
a much lower risk of death compared to people who sat for fewer hours a day,
but were not physically active. This suggests that physical
activity is particularly important, no matter how many hours a day are spent
sitting.
In fact, the increased risk of death associated with sitting for 8 hours
a day was eliminated for people who did a minimum of 1 hour physical activity
per day. The greatest risk of death was for people who sat for long periods of
time and were inactive.
WHO guidelines recommend that adults should do at least 150 mins
of physical activity per week [3], which is much lower than the 60-75 mins per
day identified in this analysis. The study also warns of the progress that
remains to be made in increasing levels of physical activity since only about
25% of people in the analysis did an hour or more physical activity per day.
"There has been a lot of concern about the health risks
associated with today's more sedentary lifestyles," says lead author
Professor Ulf Ekelund, the Norwegian School of Sports Sciences, Norway and the
University of Cambridge, UK "Our message is a positive one: it is possible
to reduce - or even eliminate - these risks if we are active enough, even
without having to take up sports or go to the gym."
He adds: "For many people who commute to work and have office-based
jobs, there is no way to escape sitting for prolonged periods of time. For
these people in particular, we cannot stress enough the importance of getting
exercise, whether it's getting out for a walk at lunchtime, going for a run in
the morning or cycling to work. An hour of physical activity per day is the
ideal, but if this is unmanageable, then at least doing some exercise each day
can help reduce the risk." [4]
The research team also looked at time spent watching TV per day
- a specific type of sedentary behaviour - in a subgroup of approximately half
a million people. They found similar results: sitting watching TV for over 3h
per day was associated with an increased risk of death in all activity groups,
except the most active.
The authors stress that the association is likely not because of a causal link between watching TV and an increased risk of death, but simply that watching TV is a specific type of sedentary behaviour. The increased risk of death associated with sitting watching TV for many hours a day was slightly greater than the increased risk of death associated with total sitting time.
The authors say that this could be due to a number of factors - for instance, long hours watching TV may be a marker of a more unhealthy lifestyle in general including being less likely to take exercise. Also, because people usually watch TV in the evenings after dinner which might affect their metabolism, or because people may be more likely to snack while watching TV.
The authors stress that the association is likely not because of a causal link between watching TV and an increased risk of death, but simply that watching TV is a specific type of sedentary behaviour. The increased risk of death associated with sitting watching TV for many hours a day was slightly greater than the increased risk of death associated with total sitting time.
The authors say that this could be due to a number of factors - for instance, long hours watching TV may be a marker of a more unhealthy lifestyle in general including being less likely to take exercise. Also, because people usually watch TV in the evenings after dinner which might affect their metabolism, or because people may be more likely to snack while watching TV.
The authors warn that the study mainly included data from people
aged over 45 years old from the USA, Western Europe and Australia, so may not
apply to other populations.
Economic burden of physical inactivity
In the first study to estimate the global economic burden of
physical inactivity, researchers estimated the total cost of physical
inactivity to be at least INT$67.5 billion in 2013 [5] - equivalent to what
US$67.5 billion could buy in the United States in 2013, or the total Gross
Domestic Product of Costa Rica in the same year.
In the USA alone, the economic burden of physical inactivity in 2013 was US$27.8 billion, compared to R$3.3 billion in Brazil, £1.7 billion in the UK and AUS$805 million in Australia.
In the USA alone, the economic burden of physical inactivity in 2013 was US$27.8 billion, compared to R$3.3 billion in Brazil, £1.7 billion in the UK and AUS$805 million in Australia.
The study found that high-income countries bear a much larger
proportion of the economic burden associated with physical inactivity (80.8% of
health-care costs in high income countries and 60.4% of indirect costs),
whereas low-income and middle-income countries have a larger proportion of the
disease burden (75.0% of the global burden of disease for physical inactivity
is borne by low and middle income countries).
"The current economic cost of physical inactivity is borne
mainly by high income countries. However, as low and middle income countries
develop, and if the current trajectory of inactivity continues, so too will the
economic burden in low and middle income countries who are currently poorly
equipped to deal with chronic diseases linked to physical inactivity,"
says lead author Dr Melody Ding, University of Sydney, NSW, Australia.
"Our study makes the economic case for a global response to promote physical activity to tackle diseases such as diabetes, heart disease and some cancers, with the aim of reducing health inequalities." [4]
"Our study makes the economic case for a global response to promote physical activity to tackle diseases such as diabetes, heart disease and some cancers, with the aim of reducing health inequalities." [4]
The authors note that the study only included costs for the five
major diseases associated with physical inactivity (coronary heart disease,
stroke, type 2 diabetes, breast cancer, and colon cancer), therefore the cost
calculations are based on conservative estimates, and the true cost may be even
higher.
Progress since the 2012 Olympic Games
Although there has been progress in developing national
policies, the authors found these were too often not being put into practice.
In 2010, 75% of countries reported having a physical activity policy but only
44% reported it being operational. In 2015, over 90% had a policy and 71%
reported it being operational.
But there has been little progress in increasing levels of physical activity with 23% of the global adult population and 80% of school-going adolescents failing to meet the WHO recommendation of 150 minutes of moderate-intensity exercise per week in 2015.
But there has been little progress in increasing levels of physical activity with 23% of the global adult population and 80% of school-going adolescents failing to meet the WHO recommendation of 150 minutes of moderate-intensity exercise per week in 2015.
"In the past four years, more countries have been
monitoring progress in physical activity, but evidence of any improvements is
scarce. We know that physical inactivity is linked to diseases including heart
disease, diabetes and some cancers, and new evidence also shows that 300000
cases of dementia could be avoided annually if all people were physically
active. The global pandemic of physical inactivity remains, and the global
response has been far too slow" says lead author Professor Jim Sallis,
University of California San Diego, San Diego, CA, USA [4].
Smarter approaches to physical activity
Increasing levels of physical activity will require
collaboration between schools, urban planning, transport, sports and recreation
and the environmental sectors, and greater efforts should be made to actively
monitor physical activity as a risk factor in clinical practice.
The authors point to several successful examples such as the Bus Rapid Transit (BRT) System introduced in Curitiba (Brazil), Bogota (Colombia) and Cambridge (UK) which puts stops further apart than traditional bus stops to encourage walking; or the Coordinated Approach to Child Health (CATCH) in the USA which promotes a healthy school environment including physical activity, food, nutrition and sun protection.
The authors point to several successful examples such as the Bus Rapid Transit (BRT) System introduced in Curitiba (Brazil), Bogota (Colombia) and Cambridge (UK) which puts stops further apart than traditional bus stops to encourage walking; or the Coordinated Approach to Child Health (CATCH) in the USA which promotes a healthy school environment including physical activity, food, nutrition and sun protection.
"Large-scale problems require large-scale solutions, and we
need commitment from governments, as well as international organisations to
tackle the global public health challenge of physical inactivity. Science and
practice are providing important evidence, but now is the time for
action," says Professor Rodrigo Reis, Washington University in St Louis,
St Louis, MO, USA [4].
Writing in a linked Comment, Dr Pam Das, Senior Executive Editor
and Dr Richard Horton, Editor-in-chief of The Lancet say:
"The world needs to get serious about physical activity. And that means
money--for capacity in public health departments to undertake adequate
surveillance, cross sector partnerships, interventions, policy monitoring, and
research, especially the cost-effectiveness of interventions. There is
extensive evidence about the need for action to improve physical activity, what
actions are most promising, and who needs to be involved. But capacity and
funding remains insufficient because physical activity is not taken seriously
enough to rise to the top of the funding priorities."
NOTES
[1] Findings come from The Lancet Physical
Activity Series 2012 http://www.thelancet.com/series/physical-activity
[2] Physical activity was expressed in metabolic equivalent of
task (MET)-hours per week. The four quartiles were 2·5 MET-h per week
(equivalent to about 5 min of moderate intensity activity per day), 16 MET-h
per week (25-35 min per day) and 30 MET-h per week (50-65 min per day), and
35·5 MET-h per week (60-75 min per day).
[4] Quotes direct from authors and cannot be found in the text
of the Articles
[5] Estimates are provided in International Dollars (INT$) which
corresponds to the cost adjusted for purchasing power in the USA in 2013. It is
widely used in economics to compare costs in different countries over time.
Table 1 provides costs for 142 countries in INT$.