|Lack of Exercise as Deadly as Smoking, Study Finds|
About 5.3 million of the 57 million deaths worldwide in 2008 could be attributed to inactivity, the new report estimates, largely due to four major diseases: heart disease, Type 2 diabetes, breast cancer and colon cancer. The study finds that if physical inactivity could be reduced by just 10%, it could avert some 533,000 deaths a year; if reduced by 25%, 1.3 million deaths could be prevented. Say we got everyone off the couch and eliminated inactivity altogether: the life expectancy of the world’s population would rise by about 0.68 years (more, if you discount those who were already active), comparable to the effect of doing away with smoking or obesity.
For the study, led by I-Min Lee in the division of preventive medicine at Brigham and Women’s Hospital, scientists calculated something called a population attributable fraction (PAF), a measure of the contribution of risk factors like physical inactivity to diseases such as heart disease or diabetes, and even risk of death. The PAF told researchers how many cases of disease could theoretically be prevented if the risk factor were eliminated — that is, if all inactive people in a population were to start exercising sufficiently.
Lee and his colleagues collected data on physical inactivity and outcomes of the four major diseases — heart disease, Type 2 diabetes, breast cancer and colon cancer — as well as rates for death from all causes. They then calculated PAFs for 123 countries. Overall, the estimates suggest that lack of exercise causes about 6% of heart disease, 7% of Type 2 diabetes, and 10% of breast and colon cancers worldwide.
Exercise has long been known to can lower risk factors like high blood pressure, high blood sugar and high cholesterol, which in turn reduces the risk of heart disease and diabetes. Physical activity also keeps heart vessels healthy and inhibits the formation of atherosclerotic plaques that can cause blood clots.
As for breast cancer, exercise may protect women by reducing fat — particularly dangerous belly fat, whose metabolic activity may trigger tumor growth in breast tissue. Colon cancer may work differently: researchers believe that exercise helps keep digestion regular and prevents potentially cancer-causing waste from encouraging abnormal growths in the colon.