Table 2.

Risk factors and preventive factors for NPC.

Risk factorDirection of associationa
Well-confirmed risk factors
 Older age (up to ∼60 years in high-incidence areas)↑↑
 Male sex
 Cantonese ethnic background↑↑
 Tobacco smoke
 Chinese-style salted fish (in early life)
 Epstein–Barr virus infection (positive IgA serology)↑↑
 First-degree family history of NPC↑↑
 Certain HLA-A and HLA-B alleles↑/↓
Possible risk factors, based on substantial data
 Indoor air pollution
 Other preserved foods
 Fresh fruits and vegetables
 Epstein–Barr virus sequence variation↑↑
 Chronic respiratory tract infection/inflammation
 Occupational wood dust
 Other types of occupational dust or smoke
 Certain HLA-D alleles↑/↓
Inconsistent findings
 Outdoor air pollution↑/–
 Occupational formaldehyde↑/–
 Traditional herbal medicines↑/↓/–
  • Abbreviations: HLA, human leukocyte antigen; IgA, immunoglobulin A; NPC, nasopharyngeal carcinoma.

  • aArrows indicate the approximate magnitude of the relationship, although the magnitude can vary substantially depending on the intensity, duration, and other characteristics of exposure.

  • ↑: slight to moderate increase in risk.

  • ↑↑: moderate to large increase in risk.

  • ↓: slight to moderate decrease in risk.

  • ↓↓: moderate to large decrease in risk.

  • ↑/↓: slight to moderate increase or decrease in risk, depending on genotype or exposure type.

  • –: no change in risk.