A lack of physical activity, or people’s failure to spend 150 minutes a week doing moderate physical activity (eg, brisk walking for 30 minutes, 5 days a week), causes around 6–10% of four major non-communicable diseases (coronary heart disease [CHD], type 2 diabetes, and breast and colon cancer) worldwide, and was responsible for around 5.3 million of the 57 million deaths globally in 2008.
The new estimates published Online First in The Lancet, indicate that physical inactivity has become a contributor to the burden of disease and shortening of life expectancy similar to tobacco smoking or obesity.
I-Min Lee from Brigham and Women’s Hospital and Harvard Medical School, Boston, USA and colleagues estimated the global impact of physical inactivity on CHD, type 2 diabetes, and breast and colon cancer by calculating population attributable fractions (PAF)—how much of these diseases could theoretically be prevented in the population if all inactive people were to become sufficiently active—by country and region.
The estimates suggest that worldwide some 6% of CHD cases are linked to physical inactivity, ranging from 3.2% in southeast Asia to 7.8% in the eastern Mediterranean region. A lack of physical activity is responsible for about 7% of type 2 diabetes cases (ranging from 3.9% to 9.6%), and 10% of breast (5.6%–14.1%) and colon cancer cases (5.7%–13.8%).
The researchers say, “Removal of physical inactivity had the largest effect on colon cancer, and the smallest on coronary heart disease, in terms of percentage reduction. However, with respect to the number of cases that can potentially be averted, coronary heart disease would have a far larger effect than would colon cancer because of its higher incidence. Although the worldwide incidence of coronary heart disease is not readily available, deaths from coronary heart disease can be viewed against colorectal cancer deaths to provide some perspective.”
For example, of the 7.25 million deaths from CHD in 2008, physical inactivity accounted for 15 000 preventable deaths in Africa, 60 000 in the Americas, 44 000 in the eastern Mediterranean region, 121 000 in Europe, 59 000 in southeast Asia, and 100 000 in the western Pacific region.
In contrast, of the 647 000 colorectal cancer deaths in 2008, 1000 deaths could have been avoided in Africa by eliminating physical inactivity, 14 000 in the Americas, 2000 in the eastern Mediterranean region, 24 000 in Europe, 4 000 in southeast Asia, and 24 000 in the western Pacific region.
Because physical inactivity is unlikely to be completely eliminated, the researchers also calculated the number of theoretically preventable deaths if inactivity decreased by 10% or 25%, translating to some 533 000 and 1.3 million deaths potentially averted worldwide every year.
What is more, say the authors, life expectancy of the world’s population would rise by around 0.68 years if physical inactivity were eliminated. This is similar to the effect of eradicating smoking or obesity.
According to Lee, “This summer, we will admire the breathtaking feats of athletes competing in the 2012 Olympic Games. Although only the smallest fraction of the population will attain these heights, the overwhelming majority of us are able to be physically active at very modest levels – e.g. 15–30 min a day of brisk walking – which bring substantial health benefits.”