Rural-urban and educational gradients in head and neck cancer incidence in Finland from 1977 to 2021.

Background and purpose: Rural-urban differences in head and neck cancer (HNC) incidence remain understudied, especially in Europe. Changes over time in risk factors, such as smoking and human papillomavirus status, may be reflected in alterations of HNC incidence by subsite, educational level, and urbanity.

Material and methods: Incidence rate ratios (IRR) - adjusted for age, calendar period, educational and urbanization level, and region - and age-standardized HNC incidence per 100,000 person-years were estimated by sex, subsite, levels of education and urbanization over 5-year periods from 1977 to 2021. We estimated the average annual percent change in incidence and IRRs between levels of urbanization and education using Poisson regression.

Results: A lower incidence of oral cavity (IRR 0.82, 95% confidence interval [CI]: 0.73-0.93 for 2007-2021), oropharyngeal (0.75, 0.65-0.87), and nasopharyngeal cancer (0.43, 0.25-0.75) was noted among rural men when compared with urban men. Semi-urban men also showed lower incidences than urban men. Similarly, a lower incidence of oropharyngeal cancer (OPC) was observed among rural (IRR 0.62, 95% CI: 0.47-0.80) and semi-urban women (0.79, 0.63-0.99). Additionally, our study indicates that the rates of OPC and oral cavity cancer are increasing across all educational and urbanization levels. The rise in OPC is particularly notable since 1997-2001, especially among urban populations, in both men and women.

Interpretation: While a higher prevalence of risk factors among urban populations may explain the differences noted across the different urbanization levels, the reasons for the increasing trends across all strata remain unclear.