Smoked or chewed, firsthand or secondhand, all kinds of tobacco cause heart attacks, a huge international study finds.
The findings come from data on more than 27,000 people in 52 countries. Koon K. Teo, MB, PhD, of the University of Hamilton, Ontario, Canada, and colleagues combed through the data for evidence that tobacco use affects heart attack risk.
And they found it.
"Tobacco use is one of the most important causes of [heart attack] globally, especially in men," Teo and colleagues conclude. "All forms of tobacco use, including different types of smoking and chewing tobacco and inhalation of second-hand smoke, should be discouraged."
--People who smoke triple their risk of heart attack -- and increase that risk by 5.6% for every daily cigarette.
--Light smokers who quit have little extra risk of heart attack three to five years after quitting.
--Heavy smokers who quit see a rapid decrease in heart attack risk, but still have some extra risk even 20 years after quitting.
--Chewing tobacco more than doubles heart attack risk. Chewing and smoking ups risk more than fourfold.
--Just one to seven hours of secondhand-smoke exposure per week ups heart attack risk by 24 percent. More than 21 hours a week of secondhand smoke exposure ups heart attack risk by 62 percent.
--Switching to a water pipe won't help. It still ups the risk of heart attack.
If this makes you think that just cutting back on your smoking will help, think again. No level of tobacco use was found to be safe. This means that secondhand smoke may be even more dangerous than previously thought.
Teo and colleagues report their findings in the Aug. 19 issue of The Lancet.
In an editorial accompanying the study, Harvard researchers Sarah A. Rosner and Meir J. Stampfer, MD, DrPH, note that smoking is predicted to kill a billion people in this century.
The Teo study, they argue, "should stimulate a redoubling of our efforts to rid the planet of the scourge of smoking."
By Daniel J. DeNoon, reviewed by Louise Chang, MD
SOURCES: Teo, K.K. The Lancet, Aug. 19, 2006; vol 368: pp 647-658. Rosner, S.A. and Stampfer, M.J. The Lancet, Aug. 19, 2006; vol 368: pp 621-622.