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Behavioral Factors Affecting Health
and the number of years since cessation. Smoking cessation reduces respiratory symptoms and respiratory infections. Smokers who quit have better pulmonary function than continuing smokers.177 For persons without overt COPD, pulmonary function improves about 5% within a few months of quitting. Cigarette smoking accelerates the age-related decline in lung function; with abstinence, the rate of decline returns to that of never smokers. With sustained abstinence, the risk of developing COPD and the COPD mortality rate are lower than they are in continuing smokers,16 but do not return to the level found in nonsmokers, probably because smoking has resulted in irreversible injury to the airways and parenchyma.1 For example, in the U.S. Veterans Study, the mortality ratio for current smokers was about 12, and was reduced to 10 among ex-smokers 10 years after cessation. After more than 20 years of abstinence, the mortality rate was still twice that of nonsmokers.178 Smokers with destructive lung changes can often stabilize after cessation but do not regain lost lung function.175 Smokers have more respiratory symptoms than do nonsmokers. The frequency of respiratory symptoms in children and adolescents is greater in current smokers than nonsmokers or former smokers.179 The 2004 Surgeon General’s report concluded that smoking was a cause of wheezing in children and adolescents, that there was insufficient evidence to determine whether there was a causal relationship between active smoking and physician-diagnosed asthma in children and adolescents, and that the evidence was suggestive but not sufficient to infer a causal relationship between active smoking and a poorer prognosis for children and adolescents with asthma.1 The 2004 Surgeon General’s report concluded that there is a causal relationship between active smoking and chronic respiratory symptoms (chronic cough, phlegm, wheezing, and dyspnea) among adults.1 These symptoms have a dose-response relationship with the number of cigarettes smoked per day, and they decrease with cessation. Smoking contributes to these symptoms by decreasing tracheal mucous velocity, increasing mucous secretion, causing chronic airway inflammation, increasing epithelial permeability, and damaging parenchymal cells.16 The Surgeon General also concluded that there was inadequate evidence to determine whether there was a causal relationship between active smoking and asthma in adults, that the evidence was suggestive but not sufficient to infer a causal relationship between active smoking and increased nonspecific bronchial hyperresponsiveness, and that active smoking was a cause of poor asthma control.1
Gastrointestinal Disease Cigarette smoking is associated with symptomatic gastroesophageal reflux disease. Compared with nonsmokers, smokers have reduced lower esophageal sphincter pressure and reduced salivary function, which contribute to a longer acid clearance time.180 Up to 100% of duodenal ulcers and 70–90% of gastric ulcers are associated with H. pylori infection.181 The remaining ulcers are linked to the use of nonsteroidal anti-inflammatory drugs.182,183 Smokers of both sexes have a high prevalence of peptic ulcer disease, with a clear dose-response relationship.1,56 The ACS CPS-I found that the relative risk of mortality for peptic ulcer among men was 3.1 for current smokers and 1.5 for former smokers compared with lifetime nonsmokers.12 Duodenal ulcers heal more slowly among smokers than nonsmokers, even with therapy. Both gastric and duodenal ulcers are also more likely to recur among smokers. Smoking cessation is associated with fewer duodenal ulcers, improved short-term healing of gastric ulcers, and reduced recurrence of gastric ulcers.16 Likely mechanisms by which smoking promotes peptic ulcer disease include the potential for tobacco smoke or nicotine to increase maximal gastric acid output and duodenogastric reflux, and to decrease alkaline pancreatic secretion and prostaglandin synthesis.1 Bicarbonate secretion from the pancreas is reduced immediately after smoking, leading to a decrease in duodenal bulb pH.184 The pH level appears to be the most important determinant for the development of gastric metaplasia in the duodenum, which allows colonization by
H. pylori.185 Four studies controlling for H. pylori infection have shown an association between smoking and ulcer.1 The 2004 Surgeon General’s report concluded that smoking causes ulcers in persons who are H. pylori-positive and that the evidence was suggestive but not sufficient to infer a causal relationship between smoking and the risk of peptic ulcer complications.1
Diseases of the Mouth Epidemiological studies from several countries have shown that cigarette smokers have more periodontal disease than do nonsmokers, and the 2004 Surgeon General’s report concluded that smoking causes periodontitis.1,186,187 A recent study concluded that more than 50% of the cases of adult periodontitis in the United States are attributable to cigarette smoking.188 A strong association has been noted between both the duration of smoking and the number of cigarettes smoked per day and the level of periodontal disease.1,188,189 Data from two cohort studies suggest that cigar and pipe smokers also have significantly greater periodontal disease and bone loss than nonsmokers.190,191 Moderate-to-severe periodontal disease occurred in 8% of nonsmokers, 13% of pipe smokers, and 16% of cigar and cigarette smokers.192 Risk decreases with sustained cessation.1 The likely mechanism for smoking-related periodontal disease is reduction in immune response, possibly making the smoker more susceptible to bacterial infection. Smoking also impairs the regeneration and repair of periodontal tissue. The 2004 Surgeon General’s report also concluded that the evidence was not adequate to determine causality between smoking and coronal dental caries, and that the evidence was suggestive but not sufficient to infer a causal relationship between smoking and root-surface caries.1 Chewing tobacco has also been implicated in the development of root-surface caries, and to a lesser extent, coronal caries.193 Leukoplakia or gum recession occurs in 44–79% of smokeless tobacco users133,194 and can occur even among young people.179,195 Gum recession commonly occurs in the area of the mouth adjacent to where the smokeless tobacco is held. Among adult users of smokeless tobacco or snuff, the risk of oral disease has been well documented, and changes in the hard and soft tissues of the mouth, discoloration of teeth, decreased ability to taste and smell, and oral pain have been reported.196–198 One study of smokeless tobacco users in a high school population reported that 49% of these teenaged users (averaging 1.7 years of smokeless tobacco use) had soft tissue lesions, periodontal inflammation, or both, or erosion of dental hard tissues.199
Other Diseases The 2004 Surgeon General’s report reported several other causal relationships between smoking and disease. The report concluded that smoking causes diminished health status that could manifest as increased absenteeism from work and increased use of medical care, adverse surgical outcomes related to wound healing and respiratory complications, low bone density in postmenopausal women (the evidence was suggestive but not sufficient to infer causality in men), and hip fracture.56 It was noted that smoking is one of the major causes of fracture in older persons that can be prevented. The report also concluded that smoking causes nuclear cataracts.1 The 2004 Surgeon General’s report concluded that the following relationships between smoking and disease were suggestive but not sufficient to infer causality: erectile dysfunction, exudative (neovascular) age-related macular degeneration, atrophic age-related macular degeneration, and the opthalmopathy associated with Graves’ disease.1 A recent cohort study reported that smoking is a risk factor for cognitive decline from ages 11 to 64, after adjusting for childhood IQ, level of education, occupational status, and other factors.200 Current smoking is also associated with mental illness. In 2003, among those aged 18 or older who had serious mental illness in the past year, 44% were past month cigarette smokers.201