Introduction

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Who says smoking cigarettes is so bad ... well, aside from the World Health Organization, Food and Drug Administration, the Centers for Disease Control and Prevention, and every medical board and association on the face of the Earth?

But should smokers be fortunate enough to dodge all that cancer, heart disease, emphysema and the like, they will be uniquely protected — for reasons unexplained by science — against a handful of diseases and afflictions.

Call it a silver lining in their otherwise blackened lungs. Although long-term smoking is largely a ticket to early death, here are (gulp) five possible benefits from smoking. Breathe deep.

Smoking lowers risk of knee-replacement surgery

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While smokers might go broke buying a pack of cigarettes, they can at least save money by avoiding knee-replacement surgery. Surprising results from a new study have revealed that men who smoke had less risk of undergoing total joint replacement surgery than those who never smoked.

The study, from the University of Adelaide in Australia, appears in the July issue of the journal Arthritis & Rheumatism. What could be the connection? Knee-replacement surgery was more common among joggers and the obese; smokers rarely jog, and they are less likely to be morbidly obese.

After controlling for age, weight and exercise, the researchers were at a loss to explain the apparent, albeit slight protective effects of smoking for osteoporosis. It could be that the nicotine in tobacco helps prevent cartilage and joint deterioration.

Smoking lowers risk of Parkinson's disease

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Numerous studies have identified the uncanny inverse relationship between smoking and Parkinson's disease. Long-term smokers are somehow protected against Parkinson's, and it's not because smokers die of other things earlier. [10 Easy Paths to Self-Destruction]

The most recent, well-conducted study was published in a March 2010 issue of the journal Neurology. Far from determining a cause for the protective effect, these researchers found that the number of years spent smoking, more so than the number of cigarettes smoked daily, mattered more for a stronger protective effect.

Harvard researchers were among the first to provide convincing evidence that smokers were less likely to develop Parkinson's. In a study published in Neurology in March 2007, these researchers found the protective effect wanes after smokers quit. And they concluded, in their special scientific way, that they didn't have a clue as to why.

Smoking lowers risk of obesity

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Smoking — and, in particular, the nicotine in tobacco smoke — is an appetite suppressant. This has been known for centuries, dating back to indigenous cultures in America in the pre-Columbus era. Tobacco companies caught on by the 1920s and began targeting women with the lure that smoking would make them thinner.

A study published in the July 2011 issue of the journal Physiology & Behavior, in fact, is one of many stating that the inevitable weight gain upon quitting smoking is a major barrier in getting people to stop, second only to addiction.

The relationship between smoking and weight control is complex: Nicotine itself acts as both a stimulant and appetite suppressant; and the act of smoking triggers behavior modification that prompts smokers to snack less. Smoking also might make food less tasty for some smokers, further curbing appetite. As an appetite suppressant, nicotine appears to act on a part of the brain called the hypothalamus, at least in mice, as revealed in a study by Yale researchers published in the June 10, 2011, issue of the journal Science.

No respectable doctor would recommend smoking for weight control, given the toxic baggage accompanying cigarettes. This recent Yale study, however, does offer an inkling of hope for a safe diet drug to help obese people control their appetites.

Smoking lowers risk of death after some heart attacks

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Compared with non-smokers, smokers who have had heart attacks seem to have lower mortality rates and more favorable responses to two kinds of therapy to remove plaque from their arteries: fibrinolytic therapy, which is basically medication; and angioplasty, which removes the plaque by inserting balloons or stents into the arteries.

There's a catch, though. The reason why smokers have heart attacks is that smoke scars the arteries, allowing fat and plaque to build up in the first place. So, one theory as to why smokers do better than non-smokers after such therapies is that they are younger, experiencing their first heart attack approximately 10 years before the non-smoker.

A study published in an August 2005 issue of the American Heart Journal, however, states that age alone is not enough to fully explain the survival differences and that "the smoker's paradox is alive and well." No alternative theories have been put forth since.

Smoking helps the heart drug clopidogrel work better

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A study by Korean researchers in the October 2010 issue of the journal Thrombosis Research builds upon work by Harvard researchers published in 2009 that demonstrates the benefit of smoking at least 10 cigarettes a day. It seems that something in cigarette smoke activates certain proteins called cytochromes, which convert clopidogrel into a more active state.

Again, no respectable doctor is encouraging patients to start smoking to get the most out of clopidogrel. But this and the other four "benefits" of smoking reveal how tobacco — perhaps not unlike other potentially toxic plants — might contain certain chemicals of real therapeutic value.

Christopher Wanjek is the author of the books "Bad Medicine" and "Food At Work." His column, Bad Medicine, appears regularly on LiveScience.