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  • In this study we combine oral and

    2019-08-16

    In this study, we combine oral and oropharyngeal cancers because it is impossible to separate them owing to the limitations of data derived from annual reports. Although the incidence and mortality rates of oral and oropharyngeal cancers in China are lower than those in high-risk regions, large numbers of patients are still suffering and dying from oral and oropharyngeal cancers due to China’s large APTSTAT3-9R and the low 5-year survival rate [25]. Thus, oral and oropharyngeal cancers should be a focus of attention in China. Gender differences in oral and oropharyngeal cancers may be important. The results of this study are similar to those of the IARC which has reported that oral and oropharyngeal cancers are more prevalent in males than in females, with two thirds of oral cancer cases occurring in males worldwide [26]. Tobacco is a major risk factor for oral and oropharyngeal cancers. An estimated 301 million Chinese were current smokers in 2010, when 52.9% of males and 2.4% of females were considered to be addicted to tobacco [27]. The average number of cigarettes smoked per day was about 15 in males and ten in females. Among male smokers, 63% were 45–64 years of age, the high-risk age group for oral cancers [27]. Furthermore, it has been reported that the risk of oral and oropharyngeal cancers increases with the frequency and duration of tobacco consumption [28]. Thus, differences in smoking habits might be a reasonable explanation for the gender disparity in the incidence and mortality of oral and oropharyngeal cancers. However, the contradiction between high smoking rate and low incidence of oral and oropharyngeal cancer in China remains an elusive issue. Few studies have focused on this problem. Age is also correlated positively with the incidence and mortality rates of oral and oropharyngeal cancers. Generally, most cases occur in the fifth to eighth decades of life, probably because of prolonged exposure to tobacco, alcohol, areca nut, poor oral hygiene, and complex systemic conditions. However, an alarming trend in the incidence of oral and oropharyngeal cancers in younger people has been reported in some countries [[29], [30], [31]]. The trend appears to be continuing due to HPV infections and heavy consumption of various forms of tobacco from an early age combined with alcohol intake [32]. In addition, the change in sexual behaviors could lead to oral HPV exposure, which might lead to the increase in oral and oropharyngeal cancer incidence among those <60 years old [33]. Moreover, it has been reported that estrogen deficiency caused by the menopause or hysterectomy might contribute to the high rates of oral cancer reported among younger females [34]. The incidence rates of oral and oropharyngeal cancers were much lower in rural areas than in urban areas. This may be related to the better environment, less stress, a slower pace of life, and different dietary habits. Air pollutants are reportedly positively correlated with squamous cancer of the pharynx [35], while a diet rich in fruits and vegetables can prevent oral cancer [36,37]. However, the incidence rate began to decrease from 2009 in urban areas and increase from 2008 in rural areas. The causes might be various. On the one hand, with the popularity of cancer registries in China, increasing registries have been set up to collect the epidemiological data of rural areas which might have been missed during the earlier years. On the other hand, according to the data from National Bureau of Statistics of China, more and more rural young people have been moving to cities in recent years. The trend of a floating population might result in an increase in the proportion of elderly residents in rural areas who constitute a high-risk age group for oral cancer. In contrast, the mortality rate in rural areas was higher than that in urban areas before 2008 and decreased thereafter. The declining mortality in rural areas might be attributable to earlier diagnosis and improved treatment. With economic development in China, an increasing proportion of the rural population has access to better medical care.