Accelerated use of artificial intelligence-associated vocabulary in Japanese surgical journals after 2023.

PURPOSE: The increased use of artificial intelligence (AI)-based writing tools may influence academic writing styles. This study aimed to evaluate changes in writing styles in Japanese surgical journals using quantitative time-series analysis. METHODS: We analyzed articles published between 2015 and 2025 in Surgery Today and Surgical Case Reports. The writing style was quantified using predefined lexical sets for rare and common AI-related words and promotional words. The word density was calculated for each article separately. We conducted interrupted time-series analyses with 2023 as the intervention year. Observed post-2023 values were compared with the expected values based on pre-2023 trends. RESULTS: Rare-word density showed a marked post-2023 increase, with a significant change in slope (β = 1.05 per year, 95% CI: 1.01-1.10, p < 0.001). The common-word density also increased after 2023 (β = 0.48, 95% CI: 0.46-0.51; p < 0.001). Promotional word density showed a smaller but statistically significant increase in the post-2023 slope (β = 0.34, 95% CI: 0.24-0.44; p < 0.001). For all three measures, the observed post-2023 values exceeded the expected values that were extrapolated from the pre-2023 trends. CONCLUSION: Post-2023, the increase in AI-associated lexical marker use in Japanese surgical journals showed accelerated growth compared to the expected long-term trends.