Real world patterns of dyslipidemia care before and after a national fee revision in Japan: A nationwide study using a 30 million patient claims database

Dyslipidemia is a key risk factor for cardiovascular disease, and its prevalence continues to rise with population aging in Japan. A 2024 change to the fee categories in Japan's insurance system aimed to encourage a more holistic approach and better patient involvement in developing treatment plans; however, the real-world impact of these changes on patient outcomes remains unclear. Using a nationwide claims database, we sought to: (1) describe the achievement of low-density lipoprotein cholesterol goals and major adverse cardiovascular events among patients with dyslipidemia; (2) compare lipid control and outcomes under the previous disease-specific management fee with those under the new lifestyle disease management fee, and (3) identify patient groups that may benefit from additional lifestyle-based interventions. We conducted a retrospective cohort study among adults aged ≥ 18 years with dyslipidemia (International Classification of Diseases, Tenth Revision code E78) and at least one lipid measurement. In total, 590,000 patients contributed 23,600,010 outpatient visits. Ourpatient visits were the unit of observation for lipid and fee-category analyses; cardiovascular outcomes and patient-years were analyzed at the patient level. The primary outcome was low-density lipoprotein cholesterol goal attainment; secondary outcomes were changes in lipid parameters, major adverse cardiovascular events, and all-cause mortality. Low-density lipoprotein cholesterol goals were attained at 58.3% of outpatient visits under the previous fee and 58.5% under the new fee, and less often in secondary than in primary prevention, despite high statin use and frequent combination therapy with ezetimibe or fibrate. Lipid levels were broadly similar across fee periods. Cardiovascular event rates were also similar, but post-revision patient-years were limited to approximately 6 months (58,500 vs. 1,542,800 patient-years); therefore, this comparison is exploratory and cannot exclude an effect of the new fee structure. Longer follow-up and complementary designs are needed to evaluate the causal impact of the new fee on outcomes.