Most people understand that smoking causes substantial harm to lung tissue, but few realize that smoking causes more deaths from heart disease than from lung cancer. Smoking attacks the cardiovascular system on many fronts -- increasing clotting action within the blood, roughing up the lining of blood vessels and changing blood fat concentrations. Cumulatively, these actions triple the risk of cardiovascular disease among smokers.
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The Good Guys
While high levels of blood cholesterol are dangerous, a robust level of HDL cholesterol, or high density lipoprotein, is a plus for your cardiovascular system. For this reason, doctors often refer to HDL as good cholesterol. By working to remove fatty substances from your blood, HDL helps keep arteries clean and, over time, prevents blockages that can lead to stroke and heart attack. Unfortunately, smoking lowers HDL levels. Conversely, the American Heart Association reports that quitting smoking can increase HDL by up to 20 percent.
LDL Cholesterol's Damage
In contrast to HDL’s positive effects, LDL cholesterol, or low-density lipoprotein, promotes the storage of cholesterol as plaque inside arteries. Upon exposure to smoke – whether by actively smoking or breathing secondhand smoke – LDL appears to bind more effectively to artery walls. In a study conducted by Roberts and colleagues in 1996, rats that breathed cigarette smoke for only two hours showed immediate increases in carotid artery LDL. The resulting LDL promotes cellular damage to the interior blood vessel walls.
Although triglycerides may not receive as much attention as HDL and LDL cholesterol, these blood fats can greatly increase your risk of heart disease when elevated. Triglyceride levels vary throughout the day, increasing after a meal and after foods containing simple sugar and excessive carbohydrates. Because smoking raises triglycerides, the American Heart Association recommends smoking cessation as one tool -- along with dietary and other lifestyle modifications -- for keeping triglycerides in check.
Smoking Without Smoking
Mounting evidence throughout the 1990s showed that children of smokers and adults exposed to smoke in the workplace typically have lower levels of HDL cholesterol. In fact, passive smoking, or the act of breathing secondhand smoke, has been shown to pose a measurable danger to nonsmokers. California-based researchers James M. Lightwood and Stanton Glantz for the American Heart Association point to evidence showing that hospital admissions for heart attacks significantly drop after antismoking legislation is enacted throughout a municipality. In other words, you don’t have to be a smoker for cigarettes to damage your heart -- you may just have to be near one.