The relationships among individual and regional smoking, socioeconomic status, and oral and pharyngeal cancer survival: a mediation analysis

Poorer survival from oral and pharyngeal cancer (OPC) has been reported for populations of lower socioeconomic status (SES), adjusting for risk factors such as patient and clinical characteristics. Beyond these risk factors, higher rates of tobacco use may be a mediator for the observed poorer OPC survival for low SES populations. In this study, we aimed to examine the impact of the relationships among SES, individual smoking status, and living in a region with a higher smoking rate on OPC survival. We obtained Florida Cancer Data System data from 1996 to 2010 and merged the data with US Census data and Behavioral Risk Factor Surveillance System data from 1996 to 2010. We built multivariable survival models to quantify the mediational effect of individual smoking on overall and OPC-specific survival, adjusting for regional smoking, demographics, and clinical characteristics. We found that lower SES, individual smoking, and living in a region with a higher smoking rate were all strongly associated with poorer survival. We estimated that the indirect effect of individual smoking accounted for a large part (ranged from 13.3% to 30.2%) of the total effect of SES on overall and OPC-specific survival. In conclusion, individual and regional smoking are both significant and independent predictors of poor cancer survival. Higher rate of individual smoking is partially responsible for poorer cancer survival in low SES populations. Results of this study provide rationale for considering a multi-level approach that simultaneously targets both individual and contextual factors for future smoking cessation interventions.