Comprehensive quality of life outcomes of Japanese traditional medicine (Kampo medicine) for functional somatic symptoms: a retrospective observational study

Background Functional somatic symptoms (FSS) are characterized by persistent somatic symptoms without identifiable organic abnormalities that lead to decreased quality of life (QOL). Japanese traditional medicine (Kampo medicine) is widely used to treat FSS; however, its generational benefits remain unclear. This study evaluated Kampo medicine treatment in patients with FSS, with a sub-analysis stratified by generation. Methods This retrospective observational study included adult patients with FSS who visited our outpatient department between July 2020 and March 2023. Comprehensive QOL was evaluated at baseline and 6 months using the EuroQol 5-dimension 5-level (EQ-5D-5L) utility value, the EuroQol Visual Analog Scale (EQ VAS), and the 12-item Short-Form Health Survey (SF-12) three-component summary (Physical [PCS], Mental [MCS], and Role/Social [RCS]). Changes were compared with the established minimal clinically important difference (MCID) thresholds (EQ-5D-5L, 0.05; EQ VAS, 5; SF-12,3). Additionally, patients were stratified into working-age (< 65 years) and older (≥ 65 years) groups for analysis. Statistical significance for QOL scores was set at p < 0.01 after Bonferroni correction. Results Of the 79 included patients, 58 were of working age group and 21 were of older groups, respectively. For the overall population, the EQ-5D-5L utility value and EQ VAS scores improved significantly from baseline to 6 months (both p < 0.001, respectively), and the median changes exceeded the MCID thresholds (0.058 and 7, respectively). The SF-12 showed significant improvements in PCS (Δmedian 3.2, p = 0.001) and MCS (Δmedian 2.8, p = 0.002), though MCS did not reach the MCID threshold. Subgroup analysis revealed distinct generational patterns: the working-age group showed significant and clinically meaningful improvements in EQ VAS score (Δmedian 6, p < 0.001) and PCS (Δmedian 3.9, p = 0.0011). Conversely, the older group demonstrated a significant and clinically meaningful improvement in MCS (Δmedian 4.4, p = 0.002), whereas no significant changes were observed in EQ-5D-5L measures or PCS. Conclusion This study suggests that Kampo treatment may improve the QOL of patients with FSS by providing comprehensive, personalized care. Integrating this approach into modern practice, while considering the patient’s life stage, could offer a potential therapeutic avenue. Trial registration Not applicable.