The number of both outpatient claims and prescribed drugs decreased from fiscal year 2018 to fiscal year 2021, especially in fiscal year 2020. A study reported a substantial decrease in the number of visiting outpatients and outpatient prescriptions, particularly in May 2020 compared to May 2019 [9]. In our study, while the number of claims temporarily decreased from 2019 to 2020, the number of prescribed antihypertensive drug tablets showed a consistent upward trend. This trend remained consistent for both national averages and regional categories. Additionally, the prescribing trends for ARBs and ACEIs did not change significantly during the COVID-19 pandemic. This may be supported by the observation that the prescribing trends for antihypertensive drugs were similar across regions. Consequently, it appears that the increase in BP observed in 2020 was not attributable to antihypertensive drugs, but rather might be influenced by factors such as medication adherence and mental stress. The length of prescription coverage used in patients with chronic conditions increased throughout the COVID-19 pandemic period in Japan [9]. This may have negatively impacted medication adherence although few studies assessed medication adherence during the pandemic in Japan. Regarding mental stress, depression and anxiety disorders has been reported to increase during the COVID-19 pandemic in most countries [10].

A study reporting a decreasing trend in ARBs prescription rates after the COVID-19 pandemic [5] used the Medical Data Vision (MDV) database, which includes the DPC hospitals as survey data. This survey highlighted declining ARBs prescription rates even before 2019, a trend inconsistent with our current findings. Since the DPC system in Japan primarily serves acute-care hospitals, the previous report was limited to antihypertensive prescription trends among patients with relatively severe diseases [5, 6]. Another study reported that most of Japanese hypertensive patients prefer visiting primary clinics rather than acute-care hospitals [11]. Our study, based on the NDB Open Data, encompassing nationwide claims, showed no decrease in the number of prescribed ARBs and ACEIs tablets post-COVID-19 pandemic. This implies potential differences in antihypertensive drug prescription trends between data from DPC hospitals and those from primary clinics. Several scientific societies have issued statements calling for ARBs and ACEIs should be continued in COVID-19 patients because the benefits outweigh the risks [4]. In our current study, the results did not show decrease in the number of prescribed ARBs and ACEIs tablets post-COVID-19 pandemic. This result shows that ARBs and ACEIs prescriptions could have been adequately maintained throughout the COVID-19 pandemic in Japan. Although one report indicated the positive association between loop prescription and COVID-19 risk, it is thought that the use of loop diuretics only reflects the existence of impaired conditions such as heart failure or renal damage [12].

Significant regional differences were observed in the number of prescribed antihypertensive drugs per capita. The findings indicate that antihypertensive prescriptions in the Hokkaido/Tohoku region are substantially higher than the national average. This discrepancy may be attributed to regional variations in the aging population, the prevalence of hypertensive patients, and differences in criteria for reviewing medical claims by insurers. Notably, this result could not be precisely adjusted for age, which limits our ability to conduct a detailed causal analysis.

In our study, the number of prescribed tablets for antihypertensive drugs showed annual increases throughout the COVID-19 pandemic period. This is thought to be mainly due to the aging of the population. As for other factors, improved awareness of the importance of hypertension treatment may have influenced the increase in antihypertensive prescriptions [13, 14].

This study has some potential limitations. First, the NDB Open Data only provided information on the number of tablets prescribed in each fiscal year and did not include data on the number of patients with hypertension who received prescriptions of antihypertensive drugs. Second, the NDB Open Data offered data solely on the 100 most prescribed drug products within each therapeutic category. Consequently, this study could not include the number of prescriptions that were not prescribed in the top 100, potentially leading to an underestimation of the total number of antihypertensive drug tablets prescribed in each fiscal year. Individual data are needed for detailed tests of change and analyses of the drivers of prescribing change.