You know smoking causes lung cancer, emphysema, and heart disease, but you're still lighting up. To help you get on the wagon this new year, we've compiled a list of little known ways your life can go up in smoke if you don't kick the habit.

From an increased risk of blindness to a faster decline in mental function, here are 10 compelling -- and often surprising -- reasons to stick to your resolution in 2005. And so you don't have to go it alone, we've also put together a step-by-step guide on how to use WebMD Resources to get started. No butts about it!

Alzheimer's Disease: Smoking Speeds Up Mental Decline

In the elderly years, the rate of mental decline is up to five times faster in smokers than in nonsmokers, according to a study of 9,200 men and women over age 65.

Participants took standardized tests used to detect mental impairment when they entered the study and again two years later. Higher rates of mental decline were found in men and women -- and in persons with or without a family history of dementia or Alzheimer's disease, the researchers reported in the March issue of the journal Neurology.

Smoking likely puts into effect a vicious cycle of artery damage, clotting and increased risk of stroke, causing mental decline, writes researcher A. Ott, MD, a medical microbiologist with Erasmus University Medical Centre in the Netherlands.

The bottom line: The study provides substantial evidence that chronic tobacco use is harmful to the brain and speeds up onset of Alzheimer's disease, Ott says.

Lupus: Smoking Raises Risk of Autoimmune Disease

Smoking cigarettes raises the risk of developing lupus -- but quitting cuts that risk, an analysis of nine studies shows.

Systemic lupus erythematosus -- known as lupus -- is a chronic autoimmune disease that can cause inflammation, pain, and tissue damage throughout the body. Although some people with lupus have mild symptoms, it can become quite severe.

For the analysis, Harvard researchers reviewed studies that examined the relationship between cigarette smoking and lupus. Among current smokers, there was "a small but significant increased risk" for the development of lupus, they report. Former smokers did not have this increased risk, according to the study, which appeared in the March issue of Arthritis & Rheumatism.

SIDS: Maternal Smoking Doubles Risk

Smoking increases the risk of sudden infant death syndrome, or SIDS, a European analysis shows.

The researchers compared 745 SIDS cases with more than 2,400 live babies for comparison and concluded that just under half of all deaths were attributable to infants sleeping on their stomachs or sides. Roughly 16% of SIDS deaths were linked to bed sharing, but for unknown reasons, bed sharing was particularly risky when the mother smoked. The risk was very small when mothers did not smoke during pregnancy, the researchers say.

Maternal smoking alone was associated with a doubling in SIDS risk. The risk was 17 times greater, however, for babies who bed shared and had mothers who smoked. The findings are reported in the Jan. 17 issue of The Lancet.

"The safest thing to do is to put the baby to bed on his back with no bedcovers in the same room with parents who don't smoke," London School of Hygiene and Tropical Medicine epidemiologist Robert G. Carpenter, PhD, tells WebMD.

Colic: Smoking Makes Babies Irritable, Too

Exposure to tobacco smoke may increase babies' risk of colic, according to a review of more than 30 studies on the topic.

Colic often starts a few weeks after birth, peaking at about 5 to 8 weeks of age. It usually goes away by 4 months of age. Babies' symptoms include irritability, inconsolable crying, red face, clenched fists, drawn-up legs, and screaming.

Colic affects an estimated 5%-28% of babies born in Western countries. Its causes have been attributed to everything from exposure to cow's milk proteins to feeding difficulties to maternal depression or anxiety.

Tobacco smoke appears to raise levels of a gut hormone called motilin in the blood and intestines. Motilin increases the contractions of the stomach and intestines, increasing the movement of food through the gut. "Higher-than-average motilin levels are linked to elevated risks of infantile colic," the researchers write in the October issue of the journal Pediatrics.

An Increased Risk of Impotence

Guys concerned about their performance in the bedroom should stop lighting up, suggests a study that linked smoking to a man's ability to get an erection. The study of nearly 5,000 Chinese men showed that men who smoked more than a pack a day were 60% more likely to suffer erectile dysfunction, compared with men who never smoked cigarettes.

Overall, 15% of past and present smokers had experienced erectile dysfunction, more commonly known as impotence. Among men who had never smoked, 12% had erection problems, according to the study, presented last year at the American Heart Association's annual Conference on Cardiovascular Disease Epidemiology and Prevention in Miami.

Blindness: Smoking Raises Risk of Age-Related Macular Degeneration

Smokers are four times more likely to become blind because of age-related macular degeneration than those who have never smoked. But quitting can lower that risk, other research shows.

Age-related macular degeneration is a severe and progressive condition that results in loss of central vision. It results in blindness because of the inability to use the part of the retina that allows for 'straight-ahead' activities such as reading, sewing, and even driving a vehicle. While all the risk factors are not fully understood, research has pointed to smoking as one major and modifiable cause.

"More than a quarter of all cases of age-related macular degeneration with blindness or visual impairment are attributable to current or past exposure to smoking," Simon P. Kelly, MD, an ophthalmic surgeon with Bolton Hospitals in the U.K, wrote in the March 4, 2004 issue of the BMJ. He came to his conclusion after reviewing three studies involving 12,470 patients.

But other studies show that former smokers have an only slightly increased risk of age-related macular degeneration, compared with never smokers, he writes.

Rheumatoid Arthritis: Genetically Vulnerable Smokers Increase Their Risk Even More

People whose genes make them more susceptible to developing rheumatoid arthritis are even more likely to get the disease if they smoke, say Swedish researchers.

In fact, certain genetically vulnerable smokers can be nearly 16 times more likely to develop the disease than nonsmokers without the same genetic profile, according to the study in the October issue of the journal Arthritis & Rheumatism.

Swedish researchers asked participants about their smoking habits and screened their blood for a gene-encoding protein sequence called the shared epitope (SE), which is the major genetic risk factor currently linked to rheumatoid arthritis. Compared with people who had never smoked and lacked SE genes, current smokers with SE genes were 7.5 times more likely to have rheumatoid arthritis.

Smokers with double SE genes were almost 16 times more likely to have rheumatoid arthritis, while smokers without SE genes were only 2.4 times more likely to be affected.

Snoring: Even Living With a Smoker Raises Risk

Smoking - or living with a smoker -- can cause snoring, according to a study of more than 15,000 men and women.

Habitual snoring, defined as loud and disturbing snoring at least three nights per week, affected 24% of smokers, 20% of ex-smokers, and almost 14% of people who had never smoked. The more people smoked, the more frequently they snored, the researchers reported in the October issue of the American Journal of Respiratory and Critical Care Medicine.

Even nonsmokers were more likely to snore if they were exposed to secondhand smoke in their homes. Almost 20% of these nonsmokers snored, compared with nearly 13% who had never been exposed to secondhand smoke at home.

Acid Reflux: Heavy Smoking Linked to Heartburn

People who smoke for more than 20 years are 70% more likely to have acid reflux disease than nonsmokers, researchers reported in the November issue of the journal Gut.

Roughly one in five people suffer from heartburn or acid reflux, known medically as gastroesophageal reflux disease or GERD.

The researchers based their findings on two major public health surveys conducted in Norway in the 1980s and 1990s. Just more than 3,100 people who complained of having heartburn and 40,000 people without reflux symptoms answered questions about lifestyle factors including diet, exercise, alcohol consumption, and tobacco use.

Breast Cancer: Active Smoking Plays Bigger Role Than Thought

Other research out in 2004 shows that active smoking may play a much larger role in increasing breast cancer risk than previously thought.

In the study, published in the Jan. 7 issue of the Journal of the National Cancer Institute, researchers looked at breast cancer risk among 116,544 women in the California Teachers Study who reported their smoking status. Between 1996 and 2000, 2,000 of the women developed breast cancer.

The prevalence of breast cancer among current smokers was 30% higher than the women who had never smoked -- regardless of whether the nonsmokers had been exposed to secondhand or passive smoke.

Those at greatest risk: Women who started smoking before age 20, who began smoking at least five years before their first full-term pregnancy, and who had smoked for longer periods of time or smoked 20 or more cigarettes per day.

So get going and check out the WebMD Resources for quitting this destructive cycle.

And There's More ...

If those top 10 reasons weren't enough to motivate you to quit smoking, keep this in mind:

• Smoking is linked to certain colon cancers.
• Smoking may increase the risk of depression in young people,
• Some studies have linked smoking to thyroid disease.

If you're finally convinced you should quit, you can start right now with these WebMD resources: