**3. Age and gender**

The incidence of nasopharyngeal carcinoma increases two to three times more frequently in men than in women [27]. Male predominance in the population is a common trait among NPC patients. Male dominance in the incidence of NPC can be partly explained by biological or gender differences or different lifestyles in the prevalence of some environmental risk factors, such as smoking and hazardous occupational exposure [28].

The nasopharyngeal carcinoma incidence in most low-risk groups is consistent with increasing age [29]. On the other hand, in the 50 to 59 age group, the incidence of NPC increases because these groups are more susceptible, and then decreases [30], which is related to the exposure of these groups to carcinogens in the early life stages [31].

It can take several decades for nasopharyngeal carcinoma to develop malignant cells. After that, the signs appear. Therefore, the outcome of carcinogens exposure in early life will have a sizeable effect on the development of this cancer [28].
