Page 6 Complete Your CE Test Online - Click Here Unfortunately, even if there are studies, most research does not examine causality; many widely-publicized studies are strictly observational. If a study is only researching correlations, it might report, for instance, that weight loss is correlated with cancer, or with death. This would certainly sound familiar to nurses, because most people lose weight when they have cancer or another serious illness. However, this is statistically termed confounding. Incredulously, some study reports confuse things like this, in this case implying that poor nutrition was the cause of the illness and death. Illness caused the weight loss and not the other way around. Although this may seem like a silly example, non- medical writers often do not understand such obvious issues as reverse causality or confounding. And even statisticians do not always know about basic anatomical processes, e.g. cachexia of chronic disease. Cancer risk factors and carcinogens Cancer risk factors include exposure to chemicals or other substances, as well as certain behaviors. They include things people cannot control, like age and family history. Other risks can be controlled. Likewise, some carcinogens can be avoided, but others cannot. Limiting exposure to avoidable risk factors may lower the risk of developing certain cancers [176]. Lifestyle, diet, and exercise Obesity People who are obese may have an increased risk of several types of cancer, including cancers of the breast (in women who have been through menopause), colon, rectum, endometrium, esophagus, kidney, pancreas, and gallbladder [180]. Conversely, eating a healthy diet, being physically active, and maintaining a healthy weight may help reduce risk of some cancers [115]. These healthy behaviors also help to lessen the risk of some other illnesses, such as heart disease, Type-II diabetes, and high blood pressure (see section “Cancer Prevention”). Tobacco Decades of research have consistently established a strong causal link between tobacco use and cancers. Smoking is associated with one out of every three cancer deaths (32%), and four out of every five lung cancer deaths (80%) [14]. Cardiovascular disease, heart attacks, strokes, COPD, ectopic pregnancy, erectile dysfunction, and gingivitis are other health risks that are elevated for tobacco users [27]. Cigarette smoking: According to the National Cancer Institute (NCI), cigarette smoking is strongly correlated with the following cancers or cancer sites [70, 156, 233]: ● ● Lung. ● ● Oral cavity. ● ● Pharynx. ● ● Larynx. ● ● Esophagus. ● ● Bladder. ● ● Kidney. ● ● Pancreas. ● ● Stomach. ● ● Cervix. ● ● Acute myelogenous leukemia. The NCI notes that the body of evidence confirming these links is substantial. Further support is demonstrated by the lung cancer death rates in the U.S., which have mirrored smoking patterns [148]. The risks of lung cancer due to smoking are dose-dependent and increase markedly by the number of years smoked; cancer and other health risks also increase with number of cigarettes smoked per day [174]. Some of the risk increase relates to the smoker’s age: in the general population (which includes both smokers and nonsmokers) the average probability of a man developing lung cancer goes from one in 608 from to age 49, to one in 16 when the man is 70 or older [14]. Current smokers, on average, have about 20 times the risk of lung cancer compared to nonsmokers [174]. It is easy to see that young smokers who just started smoking are at much less immediate risk than someone who is older and has smoked 30 years. Daily smoking means constant exposure to harmful chemicals. Of the more than 7,000 chemicals in tobacco smoke, at least 250 are known to be harmful, including hydrogen cyanide, carbon monoxide, and ammonia. Among the 250 known harmful chemicals in tobacco smoke, at least 69 are considered carcinogens. These cancer-causing chemicals include the following [275, 277, 288]: ● ● Acetaldehyde. ● ● Aromatic amines. ● ● Arsenic. ● ● Benzene. ● ● Benzo[α]pyrene. ● ● Beryllium (a toxic metal). ● ● 1,3–Butadiene (a hazardous gas). ● ● Cadmium (a toxic metal). ● ● Chromium (a metallic element). ● ● Cumene. ● ● Ethylene oxide. ● ● Formaldehyde. ● ● Nickel (a metallic element). ● ● Polonium-210 (a radioactive chemical element). ● ● Polycyclic aromatic hydrocarbons (PAHs). ● ● Tobacco-specific nitrosamines (TSNAs). ● ● Vinyl chloride. Because smoking is the kind of exposure that is fairly easy to measure, this extensive body of evidence has led to the estimation that cigarette smoking causes 30% of all cancer deaths in the U.S. [14]. Smoking avoidance and smoking cessation result in decreased incidence and mortality from cancer [174]. According to the American Cancer Society, smoking shortens the lives of men and women by an average of 12 and 11 years, respectively [27]. Most practicing health professionals know that illness and disability associated with smoking usually begins long before death. Although quitting smoking at younger ages preserves life and health better, quitting can prolong life at almost any age, even after a lung cancer diagnosis [238]. Studies have shown that continued tobacco use after cancer diagnosis is linked to worse outcomes, such as decreased survival and cancer recurrence. In addition, smoking increases the risk of surgical complications and other co-morbidities that can increase deaths from other causes in people with cancer [298]. Secondhand smoke: Solid evidence indicates that exposure to secondhand smoke causes lung cancer as well as other health risks. The U.S. Environmental Protection Agency, the U.S. National Toxicology Program, the U.S. Surgeon General, and the International Agency for Research on Cancer have all classified secondhand smoke as a known human carcinogen. Approximately 3,000 lung cancer deaths occur each year among adult nonsmokers in the U.S. as a result of exposure to secondhand smoke [192]. Compared with nonsmokers who are not exposed to secondhand smoke, nonsmokers exposed to secondhand smoke have approximately a 20% increased risk of lung cancer. Note that this is relative risk, so it is 20% above the average lung cancer risk in unexposed nonsmokers, not a 20% absolute risk [174]. Evidence-based practice: Drug treatments, including nicotine replacement therapies (e.g. gum, patch, spray, lozenge, and inhaler), selected antidepressant therapies (e.g. bupropion), and nicotinic receptor agonist therapy (varenicline), result in better smoking cessation rates than placebo [156]. Cancer risks from alternative tobacco products As cigarette smoking decreases, tobacco companies and other commercial interests are coming up with alternative tobacco products, such as [66,117]: ● ● Hookahs, also called water pipes, which are used to smoke special tobacco that comes in different flavors, such as fruits, mint, chocolate, coconut, licorice, and cappuccino.