Table 1 Variables, descriptions and statistical treatments shown in the database of the Information System of the Cancer Hospital Registry. Brazil, 2000–2015

In-hospital morbidity rate

Related to the number of hospital admissions for oral and oropharyngeal cancers per 100,000 inhabitants in the studied period, per macroregion of Brazil. The data related to the Brazilian population necessary for the calculation were obtained from the SUS IT Department (DATASUS), which aggregates information from the Demographic Censuses, Intercensus Projections and IBGE Population Estimates. The coefficients were later standardized by gender and age group (0 to 4; 5 to 9; 10 to 14; 15 to 19; 20 to 29; 30 to 39; 40 to 49; 50 to 59; 60 to 69; 70 to 79 years and 80 years and over), by the direct method, using as a standard the distribution of the world’s population created by the World Health Organization for this purpose [19]. The standardization aims to consider and remove the effect of factors related to the population distribution that interfere with the risk of developing the disease, allowing comparisons to be made

Anatomical site (originally described in IRH/INCA as “LOCTUDET”)

The codes were grouped by anatomical region for better data presentation. Thus, for this study, the lesions were presented as: “lip” – originally classified at the IRH/INCA as C00 (lip); “tongue” – originally C01 (base of the tongue) and C02 (other parts and unspecified parts of the tongue); “other parts of the mouth” – originally C03 (gingiva), C04 (floor of the mouth), C05 (palate) and C06 (other unspecified parts of the mouth: mucosa, vestibules, retromolar area); “salivary glands” – originally C07 (parotid gland) and C08 (other major salivary glands and unspecified major salivary glands); and "oropharynx" -originally C09 (palatine tonsil) and C10 (oropharynx) [13, 20]

Macroregion

Variable organized according to the distribution of the Brazilian Institute of Geography and Statistics (IBGE, Instituto Brasileiro de Geografia e Estatística) as North, Northeast, Southeast, South and Midwest regions [21]. This variable was identified based on the hospitalized patient's place of residence, as described in the notification form

Gender

Variable categorized into female, male and no information

Skin Color

Variable categorized as white, black, yellow, brown, indigenous or without information, according to the classification of the Brazilian Institute of Geography and Statistics (IBGE)

Level of schooling

Variable categorized according to the presentation in the original database as none, incomplete elementary level, complete elementary level, high school level, higher education level or no information

Age range

Variable categorized as 20–29, 30–39, 40–49, 50–59, 60–69, 70–79 years old, 80 years old and over and “no information”, considering the sum of these age groups as the total number of cases. This classification was chosen for age group presentation, as the assessed pathology shows a relevant incidence from adulthood onwards. There was a disproportionate frequency of cases classified as 0 years old, which were considered “no information”, indicating problems with registration in the database

Alcohol consumption

Variable categorized into: never consumed, ex-consumer, consumer and not evaluated

Smoking status

Variable recategorized according to the original database into: never smoked, ex-smoker, smoker and not evaluated (the latter also included—not applicable and no information)

Macroregion

Variable organized according to the distribution of the Brazilian Institute of Geography and Statistics (IBGE, Instituto Brasileiro de Geografia e Estatística) as North, Northeast, Southeast, South and Midwest regions [21]. This variable was identified based on the hospitalized patient's place of residence, as described in the notification form

Gender

Variable categorized into female, male and no information

Skin Color

Variable categorized as white, black, yellow, brown, indigenous or without information, according to the classification of the Brazilian Institute of Geography and Statistics (IBGE)

Level of schooling

Variable categorized according to the presentation in the original database as none, incomplete elementary level, complete elementary level, high school level, higher education level or no information

Age range

Variable categorized as 20–29, 30–39, 40–49, 50–59, 60–69, 70–79 years old, 80 years old and over and “no information”, considering the sum of these age groups as the total number of cases. This classification was chosen for age group presentation, as the assessed pathology shows a relevant incidence from adulthood onwards. There was a disproportionate frequency of cases classified as 0 years old, which were considered “no information”, indicating problems with registration in the database

Alcohol consumption

Variable categorized into: never consumed, ex-consumer, consumer and not evaluated

Smoking status

Variable recategorized according to the original database into: never smoked, ex-smoker, smoker and not evaluated (the latter also included—not applicable and no information)