12 Reasons to Really Quit Smoking

We'll spare you the lecture. (Seriously, though. Stamp out that butt and flush the pack, already.) Tobacco use, namely cigarette smoking, is the chief cause of preventable death in the United States. Left unbridled, smoking could kill more than a billion people this century, according to the World Health Organization. That equals the number who would die if a Titanic sank every 24 minutes for the next 100 years, as former U.S. Surgeon General C. Everett Koop so starkly put it at a March press conference.

Video: Smoking Cessation

Still, it may be harder than ever to quit: Three quarters of today's smokers trying to shed the habit are heavily hooked on nicotine, up 32 percent from almost two decades ago, according to research presented at the American College of Chest Physicians' annual meeting in October. So quitting, for most, is not merely a matter of willpower. Nonetheless, the reasons to do so keep amassing—and they're not all about heart disease, lung cancer, or respiratory problems. Here's a few downsides you might not have considered.

1. It fogs the mind. Smoking may cloud the mind, according to accumulating research. A June study in the Archives of Internal Medicine found that smoking in middle age is linked to memory problems and to a slide in reasoning abilities, though these risks appeared lessened for those who'd long quit; this is important, the authors wrote, because other research has shown that people with mild cognitive impairment in midlife develop dementia at an accelerated rate. Their report piggybacks on several focused on the older set: A 2007 analysis of 19 prior studies concluded that elderly smokers face a heightened risk of dementia and cognitive decline, compared with lifelong nonsmokers. And in 2004, researchers reported in Ne urology that smoking appeared to hasten cognitive decline in dementia-free elderly smokers, bringing it on several times faster than in their nonsmoking peers.

2. It may bring on diabetes. As if we need any more risk factors for diabetes, an analysis published in the Journal of the American Medical Association last year found that across 25 prior studies, current smokers have a 44 percent greater chance of developing type 2 diabetes than nonsmokers do, and the risk was strongest for those with the heaviest habit, who clocked 20 or more cigarettes per day. In an accompanying editorial, researchers made a striking estimation: That some 12 percent of all type 2 diabetes cases nationwide might be attributable to smoking.

3. It invites infections. In October, the federal Advisory Committee on Immunization Practices made its first ever recommendation that all smokers ages 19 to 64 be added to a short list of candidates for the pneumococcal vaccine. That's because there are very strong data showing that the risk of infection by pneumonia-causing bacteria is substantially greater for smokers than for nonsmokers, says Pekka Nuorti, a medical epidemiologist at the Centers for Disease Control and Prevention. Exactly why is unclear, though there's evidence that smoking may damage the respiratory system's protective mucous membranes, making it easier for infectious organisms to latch on and cause disease, says Nuorti. Other research suggests that smoking may interfere with immunity, compromising people's ability to fight infections, he adds.