Financial interactions between physicians and the pharmaceutical industry can foster healthcare innovation and improve patient care through research collaboration.^{1, 2} However, these interactions introduce financial conflicts of interest (COIs) among physicians.^3-5 Such COIs may bias physicians’ decision-making,^6-9 though physicians do not believe so.^{1, 2, 8} Previous studies indicate that most Japanese physicians receive personal payments for speaking and consulting, excluding food and travel expenses.^10-15

Neurological disorders, particularly dementia, are receiving increasing attention from the pharmaceutical industry in Japan. The number of dementia patients is rising sharply, with 4.62 million cases reported in 2012,¹⁶ and it is predicted that more than 20% of all people aged 65 years and older will have dementia by 2030. In 2018, healthcare spending on Alzheimer's disease drugs in Japan reached approximately US$1.0 billion (JPY 1073 billion).¹⁶ Sales figures for antidementia drugs, such as memantine (Memary from Daiichi Sankyo), donepezil (Aricept from Eisai) and galantamine (Reminyl from Takeda Pharmaceutical), were $437 million, $220 million, and $160 million, respectively, in 2017. Prior research has highlighted significant financial relationships between dementia clinical guideline authors and antidementia drug manufacturers.¹⁷ However, the full extent of financial relationships between pharmaceutical companies and all neurologists in Japan has yet to be investigated. Utilizing a publicly accessible transparency database, this study investigated the extent and trends of personal payments from pharmaceutical companies to all neurologists in Japan.

This retrospective analysis used payment data publicly disclosed by major pharmaceutical companies in Japan. We included all neurologists certified by the Japanese Society of Neurology (JSN) as of February 2022. The JSN, established in 1960, is the leading professional medical society for neurologists in Japan and has been the sole credentialing body for neurologists since 1967. As of the specified date, there were 6107 board-certified neurologists recognized by the JSN.

The Japan Pharmaceutical Manufacturers Association (JPMA), representing over 70 leading pharmaceutical companies, mandates its members to disclose payments for lecturing, consulting and manuscript drafting to physicians, including recipients’ names and affiliations, on their websites, as previously explained.^{14, 15} However, per JPMA guidelines, categories such as meals, travel, accommodations and other gifts are reported in aggregate, precluding individual-level analysis.¹⁵ Therefore, our focus was on payments for lecturing, consulting and drafting services to neurologists.

We retrieved the names and affiliated hospitals of all board-certified neurologists from the JSN website. Subsequently, we collected data on personal payments made for lecturing, consulting and drafting services to these neurologists by JPMA-affiliated companies from a publicly accessible payment database covering 2016–2020 (https://yenfordocs.jp/), following methodologies used in previous studies.^{10, 12}

We calculated the mean and median payments per neurologist and the proportion of neurologists receiving payments. The concentration of payments among neurologists was assessed using the Gini index, a measure of inequality ranging from 0 (equal distribution) to 1 (all payments to one neurologist). We also analysed payment data by category and the pharmaceutical companies. Trends in the number of neurologists receiving payments and the payment amounts from 2016 to 2020 were evaluated using generalized estimating equation (GEE) models. Due to the non-normal distribution of payments, we used a log-linked GEE model with a poisson distribution for the number of neurologists receiving payments and a negative binomial GEE model for payments per neurologist.^12-15 The study period was divided into two intervals (2016–2019 and 2020) to assess the impact of the COVID-19 pandemic on payment patterns, as observed in previous studies in the United States.^18-24 For trend analysis, we adjusted for inflation, converting all payment values to their 2020 Japanese yen equivalents using the relative annual consumer price index. Given that all data used in this study were publicly available and met the definition of non-human subjects research, institutional review board approval was not required in Japan.

Of the 6107 board-certified neurologists, 3615 (59.2%) received personal payments from pharmaceutical companies between 2016 and 2020. The total amount of these payments was $45 726 920, entailing 37 337 payment transactions. For neurologists who received at least one payment, the median amount per neurologist was $2423 (interquartile range: $765–$9076), with a mean of $12 649 (standard deviation: $35 012) over the 5-year period. The Gini index, measuring payment distribution among neurologists, was 0.871, indicating that a small proportion of neurologists received the majority of these payments. Specifically, the top 1% (61 neurologists), 5% (305 neurologists) and 10% (611 neurologists) received 30.3%, 52.8% and 78.8% of all personal payments, respectively. Lecturing payments constituted 84.4% of the total payments ($38 612 931), with 58.1% of neurologists receiving at least one lecturing payment. The mean values per payment were $1243 for lecturing, $1236 for consulting and $915 for drafting services.

Of 78 pharmaceutical companies making payments to the neurologists, Daichi Sankyo made the largest amounts of personal payments totaling $6.3 million, followed by Eisai ($5.0 million), Takeda Pharmaceutical ($4.5 million), Otsuka Pharmaceutical ($3.8 million) and Kyowa Kirin ($3.2 million). The top 5 and 10 companies with the largest payment amounts were responsible for 50.2% ($22.9 million) and 74.5% ($34.1 million) of all payments over the 5 years.

The total annual payments to neurologists increased from $8.8 million in 2016 to $10.0 million in 2019 (Table 1) but decreased to $8.1 million in 2020. A similar trend was observed in the number of payments. Annually, 33.0%–36.8% of neurologists received at least one personal payment. The number of neurologists receiving payments increased significantly by 1.5% annually (95% confidence interval [95% CI]: 0.4%–2.6%, p < .001) from 2179 in 2016 to 2292 in 2019. Among those receiving payments, median annual payments per neurologist ranged from $1077 to $1356, with the median annual number of payments of 2.0. Payments per neurologist increased annually by 3.2% (95% CI: 0.9%–5.5%, p = .006) in monetary value and by 3.5% (95% CI: 2.4%–4.7%, p < .001) in the number of payments between 2016 and 2019. However, there were significant decreases of 14.3% (95% CI: −16.4% to −12.1%, p < .001) in the number of neurologists receiving payments and 21.1% (95% CI: −25.3% to −16.7%, p < .001) in payments per neurologist in 2020 compared to those in previous years.

This study provides a comprehensive analysis of the financial relationships between pharmaceutical companies and all board-certified neurologists in Japan. We demonstrated that 59.2% of these neurologists received personal payments for lecturing, consulting and writing services from 2016 to 2020, amounting to over $45.8 million. A notable finding is that a small number of neurologists received substantial payments. Additionally, there was a significant increased trend in both the amounts and the number of neurologists receiving payments during the study period. To the best of our knowledge, this is the first study to examine the full extent of financial relationships between pharmaceutical companies and neurologists in a country other than the United States.

When compared with previous research, our study offered several key insights. Ahlawat et al. reported that 51% of US neurologists received non-research payments, including meals and travel, from the healthcare industry in 2015.³ The median annual payment per neurologist in the United States was $81, with only 14.5% receiving over $500. In contrast, our study revealed that both the proportion of neurologists receiving payments and the payment amounts per neurologist in Japan are much higher than those in the United States. Moreover, the total non-research payments to all US neurologists in 2015 were $6.2 million, encompassing various payment types, including meal, travel, entertainment, consulting, honoraria, royalties and licenses and lecturing payments. In comparison, our findings show annual payments in Japan of at least $8.1–$10.0 million for only three types of personal payments. These findings indicate stronger and more widespread financial ties between neurologists and pharmaceutical companies in Japan than in the United States.

However, it is important to note that substantial and widespread financial relationships between physicians and pharmaceutical companies are not confined to neurologists in Japan. Previous studies have demonstrated varying proportions of specialists receiving personal payments: 45.3% for dermatologists,¹⁴ 52.8% for gastroenterologists,¹⁵ 62.0% for pulmonologists,¹⁰ 64.7% for haematologists,¹¹ 65.4% for infectious disease specialists,²⁵ 70.7% for rheumatologists¹³ and 70.7% for urologists.¹² Additionally, the payment amounts to neurologists are consistent with the ranges reported in these studies.^10-15

Significant increasing trends in personal payments to neurologists were observed between 2016 and 2019. The marked decrease in 2020 is likely attributable to the COVID-19 pandemic and the consequent restrictions on interactions between physicians and pharmaceutical representatives. Considering the association of such payments with clinical practices, including a preference for brand-name drugs over generic alternatives and increased healthcare costs,^{6, 7} the escalating trend in personal payments to neurologists is concerning. Future research should explore the relationship between these payments and prescribing patterns among Japanese neurologists.

This study has several limitations. There may be errors in the payment data reported by companies and recorded in the database. Furthermore, the exclusion of various payment types, such as meals, travel, royalties and gifts, due to their unavailability in Japan, likely results in a significant underestimation of the size and fraction of financial relationships between neurologists and pharmaceutical companies in Japan. Additionally, as the study only included payments from JPMA-affiliated companies, it may not capture the complete spectrum of financial interactions between neurologists and non-JPMA affiliated companies.

1 CONCLUSIONS

Despite these limitations, our study demonstrates that nearly 60% of neurologists certified by the Japanese Society of Neurology received personal payments related to lecturing, consulting and writing from pharmaceutical companies between 2016 and 2020. These payments were concentrated among a small group of neurologists and exhibited a significant increase prior to the COVID-19 pandemic. Future studies should explore the influence of these payments to neurologists on their clinical practice, health policy and research in Japan.

AUTHOR CONTRIBUTIONS

Conceptualization; methodology; resource; software; formal analysis; investigation; writing – original draft; writing – review and editing; visualization; study administration: Anju Murayama. Conceptualization; methodology; resource; software; formal analysis; investigation; writing – review and editing: Kenichi Higuchi. Conceptualization; methodology; resource; formal analysis; investigation; writing – original draft; writing – review and editing: Yuki Senoo.

CONFLICT OF INTEREST STATEMENT

The authors declared that they have no conflicts of interest for this study.

FUNDING INFORMATION

The authors declare that there were no funding sources for this study.

ETHICS STATEMENT

As this study was a retrospective analysis of publicly available data and met the definition of nonhuman subjects research, no institutional board review and approval were required. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guideline.

DECLARATION OF GENERATIVE AI IN SCIENTIFIC WRITING

During the preparation of this work, the authors used ChatGPT version 4.0 to check and correct grammatical and spelling errors. After using this tool, the authors carefully reviewed and edited the content as needed and take full responsibility for the content of the publication.