(CBS News) Sitting around may be as deadly as smoking, a new study suggests.
New research in The Lancet finds about one in 10 deaths worldwide are caused by people not getting up and engaging in physical activity such as walking 30 minutes a day for five days a week.
A team of researchers led by Dr. I-Min Lee, a professor of epidemiology at Harvard Medical School in Boston, analyzed global data on deaths in 2008 to come up with estimates on how many cases of heart disease, Type 2 diabetes, and breast and colon cancers could theoretically be prevented if all the inactive people in the world suddenly became active.
The researchers concluded people's failure to spend a minimum of 150 minutes of moderate physical activity each week led to about 6 percent of cases of coronary heart disease, about 7 percent of Type 2 diabetes cases, and 10 percent of breast and colon cancers.
That adds up to 5.3 million deaths tied to physical inactivity. Smoking, meanwhile, is responsible for about 5 million deaths worldwide.
"Removal of physical inactivity had the largest effect on colon cancer, and the smallest on coronary heart disease, in terms of percentage reduction," the researchers wrote. "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."
The researchers explained that of the 7.25 million people who died from coronary heart disease in 2008, physical activity accounted for 15,000 preventable deaths in Africa and 60,000 preventable deaths in North and South America. It also was responsible for 44,000 deaths in eastern Mediterranean region, 121,000 deaths in Europe, 59,000 deaths in Southeast Asia and 100,000 preventable deaths in the Western Pacific.
According to the study, the life expectancy of the world's population would rise by about 0.7 years if physical inactivity were eliminated, rates comparable to if the globe were able to eradicate smoking or obesity. However, the researchers realize its unlikely that inactivity will be completely eliminated, and estimated that if inactivity fell 10 percent, 533,000 more people would be alive and if rates fell 25 percent, 1.3 million deaths could potentially be avoided.
"This summer, we will admire the breathtaking feats of athletes competing in the 2012 Olympic Games," Lee said in a press release. "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."
"This is a super, super analysis," Dr. James Levine, professor of medicine at the Mayo Clinic in Rochester, Minn., who was not involved in the study, told WebMD. "We know that as soon as somebody gets out of their chair, their blood sugar improves, their blood cholesterol and triglycerides improve, and that's very consistent. Every time you get up it gets better. Every time you sit down it gets worse."
The World Health Organization estimates inactivity causes fewer deaths than the researchers found, about 3.2 million each year, reports WebMD.
A recent study in July 9 issue of BMJ Open found if people restricted their sitting time to fewer than three hours each day, they could potentially add an extra two years onto their lives. The study also found cutting television viewing to less than two hours per day could contribute to a boost in life expectancy.