Forecasting Stomach Cancer Burden from High Sodium Intake in Japan, 2022-2050: Scenario Analysis of Demographic...

High sodium intake is a leading dietary risk factor for stomach cancer, particularly in East Asia. In Japan, traditional dietary patterns contribute to elevated sodium consumption and a high burden of stomach cancer. This study aims to forecast disability-adjusted life years (DALYs) for stomach cancer attributable to high sodium intake in Japan from 2022 to 2050, and to assess the impact of multiple sodium reduction policy scenarios.

We conducted a longitudinal forecasting study using autoregressive integrated moving average with exogenous variables (ARIMAX) models based on Global Burden of Disease 2021 data (1990-2021). The Japanese population was stratified by sex and age groups (15-49, 50-69, and ≥70). Five future exposure scenarios were modelled: (1) reference (current trends), (2) best-case (50% reduction in sodium exposure by 2050), (3) optimal (30% reduction by 2032), (4) moderate (30% reduction by 2050), and (5) worst-case (highest exposure levels from recent years maintained). These scenarios were aligned with national and international sodium reduction targets, including the revised "Health Japan 21" (third term; 7 g/day by 2032) and the World Health Organisation (WHO) 5 g/day/30% reduction goals.

Under the reference scenario, age-standardised DALY rates are projected to decline by 31.4% (to 15.4 per 100,000) by 2050. The best-case scenario projects a 54.7% decline (to 10.1 per 100,000). Substantial demographic disparities persist: males and those aged ≥70 consistently show higher burdens. Notably, the 50-69 age group shows the greatest variation in 2050 projections across scenarios (17.1 to 73.5 per 100,000), indicating high policy sensitivity. Meanwhile, in the ≥70 group, DALY rates remain high regardless of scenario, especially among males (199.4 vs. 57.8 per 100,000 for females), reflecting cumulative lifetime exposure.

Under modelled assumptions, sustained achievement of national sodium reduction targets could meaningfully reduce future stomach cancer DALYs in Japan, with the largest absolute gains in older adults but the largest relative gains in younger and middle-aged groups. Because stomach cancer aetiology is multifactorial and the projections rest on modelled associations and a continuity-of-trend assumption, these findings support strengthened, demographically targeted sodium reduction interventions as one complementary component of a broader, multi-risk factor approach to stomach cancer prevention.