10. It may stifle sleep. Feeling groggy despite a night's slumber might be a problem for those who light up: A February study in Chest found that smokers are four times more likely to get nonrestorative sleep than those who don't smoke, and researchers deemed nicotine the likely culprit. They theorized that its stimulant properties deal smokers a double blow, making it difficult to fall asleep and also potentially sending the body into nicotine withdrawal during the night. (Half of the chemical's effect wears off within two hours.) Since inadequate shut-eye can invite health problems, consider forgoing cigarettes for the sake of your sleep.
11. It shaves years—and quality—off life. Men who have never smoked live on average 10 years longer than their peers who smoke heavily, according to an October report in the Archives of Internal Medicine. Moreover, they enjoyed a higher quality of life throughout those extra years, throwing sand in the face of the old smokers' defense that an early death is a small price to pay for a lifetime of pleasure. The study's Finnish authors drew their conclusion after scrutinizing data on more than 1,600 men tracked for nearly 30 years.
12. It's tied to lots of cancers! Not to belabor the point, but tobacco use and smoking have been linked to much more than lung cancer. In September, the CDC released a report estimating that more than 2 million cases of tobacco-related cancers were diagnosed nationwide between 1999 and 2004. Lung and bronchial cancer topped the list, naturally, but other types included stomach, pancreatic, kidney, urinary bladder, and cervical cancer. "We knew this was a big problem and a preventable problem," says Sherri Stewart, the epidemiologist at CDC who led the research. "But when you present the hard numbers, you start to see the profoundness of the problem." Her message: To protect your health, do everything you can to quit.
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