Objective   To analyze the relationship between soil selenium content and liver cancer mortality in 156 districts/counties covered by a vital registration system in China and to provide references for the application of trace selenium in the prevention and treatment of liver cancer.

  Methods   We collected following data for the 156 districts/counties: population sampling survey in 2012, liver cancer mortality and hepatitis B/C incidence in 2012, disease behavioral risk factor survey in 2010, socio-economic development and healthcare resources in 2013, and interpolatedly estimated soil selenium content based on sampling survey data published in 1994. Dimension reduction process was performed for socio-economic development and healthcare resource indicators with factor analysis. Generalized additive model was adopted to analyze the relationship between soil selenium content and liver cancer mortality. SAS for Windows 9.4 was employed and the significant level was set to be 0.05 in data statistics.

  Results   There was a nonlinear relationship between soil selenium content and liver cancer mortality. Two common factors were derived in dimension reduction for indicators of socio-economic development and healthcare resources, representing economic development and health resource, and the cumulative contribution rate of the two common factors was 91.24%. The results of generalized additive model analysis revealed a significant difference between the complete model of liver cancer mortality and the model without soil selenium content as a non-parametric variable (P < 0.001). The non-parametric smooth component effect graph demonstrated an analogous ‘N’ shape correlation between soil selenium content and the non-parametric smooth component of liver cancer mortality.

  Conclusion   Higher soil selenium content may correlate with increased risk of liver cancer mortality but moderate to upper soil selenium content may associate with low liver cancer mortality. The results should be concerned when conducting selenium supplementation-related liver cancer prevention.