Regional variation in outpatient dysphagia rehabilitation claims in community settings: a nationwide ecological analysis of medical and dental services using open claims data in Japan

Japan is experiencing an unprecedented demographic shift toward a ‘super-aged’ society, and aspiration pneumonia prevention has become a critical public health priority. Although dysphagia rehabilitation is essential to maintain oral intake in older adults, regional patterns of its billed provision across Japan remain unclear. We aimed to investigate nationwide patterns of billed outpatient dysphagia rehabilitation (feeding function therapy) provided by the medical and dental sectors using the National Database of Health Insurance Claims (NDB) Open Data and explore its ecological association with dental home-visit claims. This ecological cross-sectional study analyzed fiscal year 2023 NDB Open Data and public population statistics. Outpatient claims for feeding function therapy (medical, H004; dental, H001) and dental home-visit claims were divided by the population aged ≥ 65 years for each of the 47 prefectures (claims per 100,000 population aged ≥ 65 years; crude rates that are not age-standardized). Regional variation was evaluated using the coefficient of variation and maximum-to-minimum ratio of the prefectural rates. The association between dental dysphagia rehabilitation claims and dental home-visit claims was assessed using Pearson's and Spearman’s correlation coefficients. Nationally, outpatient claims per 100,000 population aged ≥ 65 years were 1,011.1 for dental and 127.5 for medical feeding function therapy, and dental claims accounted for 88.8% of the combined outpatient H004/H001 claims. The unweighted means of the 47 prefectural rates were 647.9 (dental) and 121.4 (medical). Dental claims varied considerably across regions (coefficient of variation = 1.00; maximum-to-minimum ratio = 151.4). Dental dysphagia rehabilitation claims showed a moderate positive correlation with dental home-visit claims (Pearson r = 0.58, 95% confidence interval: 0.35–0.74, p < 0.001; Spearman ρ = 0.53, p < 0.001). Medical and dental claims were not correlated across prefectures (Pearson r = 0.00, p = 0.98). Among outpatient feeding function therapy claims in fiscal year 2023, the dental sector accounted for most claims, which showed a moderate association with dental home-visit claims at the prefectural level. Billed activity varied markedly across prefectures, but because claims reflect service use rather than need, these differences cannot be interpreted as inequity in access. These descriptive findings warrant further evaluation with patient-level data of whether strengthening dental home-visit services and medical–dental collaboration would improve dysphagia rehabilitation within community-based care.