PREVALENCE OF TOBACCO USE

Prevalence of cigarette smoking in the United States is now around 23% among adults and has remained around that figure for some years.⁵² Smoking prevalence has been cut in half since the first Surgeon General’s report on smoking and health in 1964, and this progress is rightly considered one of the 10 greatest public health achievements of the twentieth century.⁵⁶ The sobering aspect of this achievement is that most of those who intend to quit have probably already done so, and those who are left are the hard-core smokers, plus the 3000 new young people who start smoking each day. (It is a fair bet that few current smokers in the United States have even heard of WHO’s framework convention.) Data on smoking in the United States are presented in Box 30-1. The report is mixed, with the main concerns now centered on youth smoking and the concentration of tobacco use in lower socioeconomic groups.

Heavy marketing of ST products, principally targeted to adolescent and young adult males, has coincided with the national decline in cigarette smoking. Marketing of ST seems to have been successful; consumption of ST products in the United States almost tripled between 1972 and 1991.⁴⁹ It was estimated from a national survey that, in 1991, 5.3 million American adults (2.9% of the population) were using ST: 4.8 million men and 533,000 women.⁴⁹ This percentage had risen slightly to 3.2% of the population by 1999.⁵³

The concerns about ST’s appeal to youth seem well founded: 1995 national survey data revealed that 11.4% of high school students had used ST within the previous 30 days, 19.7% of males and 2.4% of females. ST use among whites was 14.5%, among African-Americans 2.2%, and among Hispanic students 4.4%.³¹ The 1991 national survey found that 8.2% of males ages 18-24 years were regular ST users, the highest proportion of any age-group. Even if there is some overreporting,¹⁵ presumably by individuals who wish to appear more “macho,” these figures are high. Among adults 45 years of age or older, however, ST use was more common among African-Americans than among whites.²¹ Usage of ST is highest in the South, in rural areas, and declines with increasing education.⁴⁹ Women users of ST are predominantly in the South.⁵⁹

Use of ST is extensive in the military^8,26 and is particularly heavy among Native Americans; a study conducted in seven western states found that 56% of Native Americans in the ninth and tenth grades reported that they were regular users,¹¹ as were 28.1% of sixth-graders.⁷ ST use among Native American women is substantially above the national rate for women.⁴⁴ Native Americans emerge as the ethnic group with the heaviest relative use of ST and the only one in which there is almost equivalent use among males and females.^11,61 In one study of Navajo adolescents, over 25% of ST users were found to have leukoplakia, compared to only 4% of nonusers. The duration and frequency of use were highly significant risk factors for leukoplakia.⁶¹

Prevalence of ST use is also widespread among highly visible professional baseball players; surveys carried out with major and minor league teams found that 39%-46% of players were regular users.^19,60 Another study of baseball players in 1988 found that ST users had 60 times the risk of developing leukoplakia compared with nonusers.²⁵

The remarkably high occurrence of oral cancer in India (see Chapter 23) is thought to result from the high prevalence of tobacco chewing in several forms. Because the rate of conversion of leukoplakia and other precancerous lesions to oral cancer is no higher in India than elsewhere,⁴⁵ it seems to be the high exposure to tobacco, rather than any inherent characteristics of Indian people, that leads to the high prevalence of leukoplakia, and subsequently oral cancer, in that country.

Since the pathologic effects of cigarette smoking are now extensively documented, tobacco marketing aims to foster the perception that ST is a less risky substitute for cigarettes. However, ST is far from harmless.

PATHOLOGIC EFFECTS OF SMOKELESS TOBACCO

ST is a particularly worrisome form of tobacco, because its current use by young people has the potential to increase the incidence of oral cancer in the future.⁴⁰ The American Dental Association (ADA) has firmly stated policies opposing any use of ST, and the ADA clearly rejects ST as a substitute for regular tobacco.⁵

ST is sold in several forms. The main concern is with snuff, a powdered tobacco product, which is used by placing a “dip” between the cheek and gum. Dry snuff contains high concentrations of N-nitrosamines^2,27; evidence is strong that compounds in this group are carcinogens, especially for oral cancers.^27,39 The N-nitroso compounds found in snuff are DNA-damaging agents in cancers of the aerodigestive tract.³⁵ A consensus panel of the National Institutes of Health found strong evidence that use of snuff causes oral cancers,³⁸ a conclusion for which there was ample support at the time^47,57 and subsequently.^3,17,27,29 Nicotine is absorbed from ST in amounts similar to those absorbed from cigarette smoke,⁹ which makes ST a potential risk factor for the same diseases that result from smoking. That could be why ST users face a relative risk of 2.1 for cardiovascular disease compared to nonusers. The relative risk for smokers compared to nonsmokers in the same study was 3.2.¹⁰

The continued use of snuff leads to localized tissue changes, most commonly the development of leukoplakia, which is characterized by the appearance of white, wrinkled mucosa at the site where the snuff is placed. Leukoplakia can become cancerous in 3%-5% of cases,⁴⁵ although there is also evidence that these lesions can be reversed if the ST habit is ended.^22,33 With regard to oral conditions other than precancerous soft tissue changes, no good evidence exists that ST can cause caries and periodontal diseases. Gingival recession at the site where the quid or dip is placed is common, however. It has also been found that poor oral hygiene among ST users contributes to the formation of nitrosamines in the oral cavity.