Association between socioeconomic position and thyroid cancer incidence: A population-based cohort study in China.

[BACKGROUND] Thyroid cancer incidence has surged in China, which is largely driven by overdiagnosis. Based on a large multicenter cohort in China, we aimed to explore the association between socioeconomic position (SEP) and thyroid cancer diagnosis at both individual and population levels.

[METHODS] SEP was assessed using education, income, and occupation, which were synthesized into composite indicators via point-based scoring and latent class analysis (LCA). Cox models were used to estimate the hazard ratios (HRs) of SEP on the thyroid cancer risk. The relationship between regional Gross Domestic Product (GDP) per capita and age-standardized incidence rates (ASIRs) of thyroid cancer was assessed by Spearman correlation.

[RESULTS] After a median follow-up of 10 years, 508 incident cases were diagnosed among 501,916 participants. Compared to low-SEP, medium score-based SEP (HR:1.61, 95%CI: 1.26-2.06) and all high-SEP indicators were associated with increased risk, including education (2.41, 1.77-3.28), income (2.25, 1.71-2.96), occupation (1.65, 1.01-2.71), score-based SEP (2.29, 1.78-2.94), and LCA-based SEP (2.00, 1.53-2.62). Females with higher education and LCA-based SEP were associated with a higher risk of thyroid cancer. Rural residents with higher score-based SEP, LCA-based SEP, and household income had greater risk than their rural counterparts; and the opposite for urban residents with higher education. Regional GDP per capita was correlated with thyroid cancer ASIRs (r=0.66, 95%CI: 0.33-0.96).

[CONCLUSIONS] SEP is positively associated with increased risk of thyroid cancer diagnosis in China.

[IMPACT] Public health strategies targeting high-SEP populations and developed regions are crucial for reducing thyroid cancer overdiagnosis and narrowing regional disparities.