Mediation effect of healthy lifestyles on the association of socioeconomic status with mortality among US cancer survivors: a population-based cohort study

Abstract

Background: Socioeconomic inequity can lead to health disparities among cancer survivors. Although lifestyle factors are commonly considered as mediators between socioeconomic status (SES) and health, their impacts on SES-related mortality differences among cancer survivors are still unclear. This study aimed to explore the mediation effect of overall lifestyles on the relationship between SES and mortality among cancer survivors.

Methods: This study analyzed data from 2,411 cancer survivors in National Health and Nutrition Examination Survey from 2000 to 2013. Deaths were ascertained from linkage to the National Death Index with follow-up until 2019. SES was assessed by latent class analysis using family income, occupation, education and health insurance. A healthy lifestyle score was constructed based on smoking, alcohol consumption, physical activity and diet. Cox regression and mediation analyses were conducted to quantify the proportion of SES-related survival disparities explained by lifestyle factors. Finally, joint associations between SES and lifestyles on mortality risk were evaluated.

Results: During a mean follow-up of 9.0 years, 894 deaths were recorded. Compared with high SES participants, those with low SES had higher risks of all-cause mortality (HR, 2.54; 95% CI, 1.85-3.05), cancer mortality (1.92; 1.13-3.24), and non-cancer mortality (2.92; 1.96-4.33), and the proportions mediated by lifestyles were 13.5% (7.3%-23.5%), 28.7% (10.7%-57.6%), and 8.7% (3.5%-20.3%), respectively. Additionally, joint analysis revealed that individuals with low SES and unhealthy lifestyle behaviors had the highest risk of all-cause and cancer mortality.

Conclusions: Unhealthy lifestyles partially mediated socioeconomic inequity in mortality among US cancer survivors. Additionally, significant joint effects of lifestyles and SES on mortality were found. Therefore, healthy lifestyle promotion is warranted to mitigate SES-related health disparities among cancer survivors.

Keywords: NHANES; cancer survivors; healthy lifestyles; mediation analysis; socioeconomic status.