Fifty-year trends and future projections of nasopharyngeal carcinoma incidence in Sihui City, southern China: an age-period-cohort analysis (1971–2020)

The long-term trend of nasopharyngeal carcinoma (NPC) in traditional high-prevalence areas of Southern China remains poorly characterized. This study aimed to delineate the 50-year incidence trends (1971–2020) and project future rates up to 2040 in Sihui, a well-known endemic region, providing evidence for targeted prevention strategies. Data of NPC were collected from local Cancer Registry and Statistics for 1971 to 2020 in Sihui. Age-standardized incidence rates (ASIRs) of NPC were calculated using the world standard population. Joinpoint regression analysis was performed to quantify the temporal trend of NPC incidence. An age-period-cohort (APC) model based on Poisson regression was applied to evaluate the independent effects of age, period, and birth cohort on NPC incidence risk on the observed incidence trends.Furthermore, age–period–cohort models implemented in the NORDPRED package were used to project NPC incidence from 2021 to 2040. The overall ASIRs of NPC in Sihui over the 50-year period were 31.19 per 100,000 person-years for males and 13.26 per 100,000 person-years for females. Male NPC incidence exhibited a continuous and gradual downward trend throughout the study period. In contrast, female incidence remained stable in the early period and decreased obviously from 2009 to 2020. The relative risk (RR) of NPC increased with advancing age, reaching a peak in the 50–59-year age group and declining thereafter. The period effect on NPC incidence was relatively flat across both gender. Analysis of the cohort effect revealed a progressive reduction in NPC risk among successive birth cohorts for both male and female. Future projection indicate that the incidence of NPC will further decrease to 14.52 and 4.65 per 100,000 for male and female, respectively, by the period 2036–2040. In the traditional endemic region of China, we found that the incidence of NPC remained relatively stable before 2010, but decreased significantly thereafter, and this trend is expected to continue over the next 20 years. The possible reason is presumed to be the reduced exposure to environmental risk factors resulting from economic development.