Incidence of nasopharyngeal carcinoma and milk consumption : a worldwide ecological analysis

Abstract

Background: Nasopharyngeal carcinoma (NPC) is a common malignancy in South Asia and North Africa. In recent years, NPC incidence is dramatically decreasing which cannot be explained by the current etiological factors. Moreover, milk consumption is promising as factor to be investigated and showed declining trend in worldwide. To our knowledge, there are no population level studies to examine the association between NPC and milk & dairy products consumption.

Objective: The objective of this study was to investigate the relationship between NPC incidence and per capita consumption of milk at the population level.

Methods: These were two types of ecological studies (cross-sectional and longitudinal ecological study). NPC incidence data were collected from Cancer Incidence in Five Continents Vol. IX (1998-2002) and several population-based cancer registries. Data of per capita consumption of milk & dairy were obtained from Food Agriculture Organization (FAO).

Results: In cross-sectional ecological study, age-standardized incidence rate (ASIR) of NPC is negatively associated with per capita consumption of milk & dairy products in 48 countries/ regions from 1961 to 2009. Moreover, in one-way sensitivity analysis, the result was consistent with the above. In longitudinal ecological study from around 1980 to 2009, ASIR of NPC (both genders) was negatively correlated with milk consumption per capita in Hong Kong and Singapore. The ASIR of NPC (both genders) was decreased with per capita consumption of milk from around 40 to 140 kg/capita/year in Hong Kong and Singapore. Further, such negative associations were found statistically significantly between NPC and milk consumption in Hong Kong after adjusting for HDI.

Conclusion: Our study provided information on the protective association between NPC and milk & dairy products. Our ecological study shows that higher per capita consumption of milk & dairy products is associated with a lower risk of NPC development. However, our finding need to future confirm since there are major limitations on data and methods. Further research is needed for confirmation of the link between milk consumption and NPC.