Introduction This study examined socio-economic inequalities in survival after non-Hodgkin lymphoma, and to what extent any disparities were explained by differences in comorbidity, disease severity at the time of diagnosis, and the treatment given.

Methods Registry-based nationwide cohort study based on 5738 persons diagnosed 2000-2008 from the Danish national lymphoma database and linked for individual socioeconomic information in Statistics Denmark.

Results Long-term mortality was highest in patients with a short education as compared to those higher educated. The social difference among patient ≤80 years was increasing over time (p_interaction=0.01). Thus, in the period 2000–2004 the HR among the short educated compared with the higher educated was 1.47 (95% CI 1.34 to 1.61) and increased to HR=1.70 (95% CI 1.37 to 2.11) in 2005–2008. However, no educational differences were seen among the oldest patients of 81 years and above. The educational gradient was attenuated by including comorbidity in the models, and further slightly attenuated by including lymphoma-specific prognostic factors (stadium, elevated lactatdehydrogenase, extranodal involvement). However, the educational gradient was still significant, as was the interaction with calendar period (p_interaction=0.03). No socio-economic differences were found with respect to treatment with chemotherapy, radiation, or immunotherapy.

Conclusion Differences in survival among NHL patients with different socio-economic position are partly caused by differences in comorbidity and the severity of disease at the time of diagnosis, while no differences in treatment were found. The increasing social gradient over time may be partly explained by a more pronounced decrease in lifestyle-associated comorbidity among higher social groups in recent years.