The rise in blood pressure (BP) is a crucial risk factor for life-threatening diseases and should be assessed in individuals in their early life stages. Adachi and colleagues investigated the secular trend of BP from 2003 to 2023 among Keio University students [1]. As supplemental information, the university is one of the most prestigious private universities in Japan, and there are students with various orientations, e.g., being good at studying, sports, and extracurricular activities. The diverse characteristics would support the external validity of the population to a certain extent, though only university students were included in the study. Data were extracted from health check-ups among all undergraduate students every 5 years (mean age per survey, 20.1–20.5 years old) because BP measurements were not entirely performed during the COVID-19 pandemic (2020–2022). This simplified approach inevitably results in avoiding duplicate measurements per student, since undergraduate course consists of 4-year grades and few students repeat a grade twice. The key finding is that BPs remained generally stable in the survey years 2003, 2008, 2013, and 2018. Meanwhile, average systolic BP in women and men rose to 3.1 mmHg and 2.5 mmHg, respectively, from 2018 to 2023. In contrast, the prevalence of hypertension, as those with BP  ≥ 140/  ≥ 90 mmHg, decreased in the same period, from 0.9% to 0.3% in women and 7.3% to 3.7% in men. Based on the fixed-point observation data of >100,000 university students in total, the authors urge caution regarding student BP and long-term BP trends following the end of the COVID-19 pandemic.

The prevalence of hypertension in university student age is not high, although it varies according to reports. Based on the same Keio University annual health check-up data of 2015–2017 [1], Kawabe and colleagues reported that 0.2–0.4% of women and 3.2–3.7% of men were classified as having hypertension [2]. It should be emphasized that out-of-office BP measurements can further identify while-coat hypertension [3]. In 2003 and 2004, Ejima and colleagues reported that among 24,866 university students in northern Japan who attended annual health check-ups (22.7% women; age <30 years), only nine men (<0.04%) were diagnosed as sustained hypertension after the assessment at three office occasions and self-measured home BP measurements [4]. By adding home BP measurements for 48 students with office BP ≥ 140/ ≥ 90 mmHg, the prevalence of white-coat hypertension was ≈4 times higher than that of sustained hypertension. However, the same research group later stated that students with white-coat hypertension and sustained hypertension have similar characteristics, though limited data were obtained at health check-ups, and long-term follow-up is recommended after all [5]. The majority of students with hypertension by office measurement would be classified as white-coat hypertension, and assessment of out-of-office BP is essential for the precision diagnosis and management of hypertension [3]. In addition, sex differences cannot be ignored in these age groups neither, as also found in the Keio University students [1, 2].

According to Japanese statistics, BP among Japanese adults has decreased since at least 1961, except for diastolic BP among men aged 30–59 years [6]. Such a long-term reduction trend was also reported in the Japanese Hisayama population [7]. Since the steady popularization of antihypertensive drug therapy has greatly contributed to BP reduction, it is unsurprising that before the COVID-19 pandemic, there were no notable changes among university students who usually did not take antihypertensive medication [1]. Whereas, in the recent publication by the same Keio study group, BP in Japanese junior and senior high school students (mean age, 15 years old), average systolic BP decreased in boys while diastolic BP increased in girls in the same before-pandemic period [8]. However, these changes were only ≤3.0 mmHg in girls and ≤1.1 mmHg in boys. The population of these adolescents consisted of seven schools of the same group located in the Tokyo area [8]. Thus, the diversity would be less than the University studies, where university students come from nationwide Japan [1, 2, 4, 5], weakening the external validity of the results [8]. Zhang and colleagues published conflicting findings among national databases in Eastern China regarding the trend of BP changes among children aged 7–18 years old from 2012 to 2022 [9]; they found a decline in the prevalence of elevated BP according to two databases, while an increasing trend in elevated BP was found in another database. The gap in BP trends among studies and age ranges cannot be overlooked for refining our strategy for diagnosing and treating hypertension.

A systematic drift of measurement values of BP is a crucial issue when interpreting the population study results [10]. For instance, stroke mortality can be reduced by 5.8% in women and 8.9% in men when the average BP level among Japanese decreases by 4 mmHg [6]. However, a systematic error between two different BP measurement devices can be more than 4 mmHg even when both devices have passed the up-to-date edition of the clinical validation protocol [10]. Though caution about the fundamental drift by automated oscillometric BP devices compared with mercury devices was raised [11], automated devices or electronically generated pressure column (quasi-mercury) devices [6] have replaced mercury sphygmomanometers in national surveillances to comply with the Minamata Convention on Mercury [10]. Kim and colleagues recently reported that among 278 volunteers enrolled in the Korean national survey in which BPs were measured under strict conditions, the average BP differences between those measured by automated device and quasi-mercury device were 2.6 (SD, 6.2) mmHg for systolic BP and 5.1 (5.6) mmHg for diastolic BP [12]. In the two long-term Keio University studies [1, 8], BPs had been measured by an automated Colin BP-103i II monitoring device in common. Although the device is not listed as a recommended device on websites by scientific authorities such as STRIDE-BP [13], the device was certified and marketed, and has been widely used in clinical practice in Japan. The continuous application of the same device model and stable condition, i.e., BPs were measured by a trained nurse in a relaxed and sitting position in the Keio studies [1, 8], enabled the assessment of the long-term changes in BP levels and prevalence of hypertension. Nevertheless, we have to admit that absolute BP values captured by automated BP monitors are not fully guaranteed; thus, validation of BP measurement devices by independent third parties are demanded [3, 10]. Furthermore, the BP measurement conditions, particularly the rest status before the measurement, significantly impact the values. Because the COVID-19 pandemic influenced psychological conditions among university students [14], it might bring out the discrepancy result between BP trends and the prevalence of hypertension in the Keio students [1].

The study design by Adachi and colleagues [1] is classified as a repeated cross-sectional survey [15], namely a tracking survey (the word is preferably used in a marketing research field), in which researchers periodically collect data from the same population but from different participants. Although this design allows us to constantly monitor situations and changes in health conditions, a causal relationship and contributors to the changes are usually difficult to identify. They [1] estimated that the BP rise in 2023 was due to the impact of the COVID-19 pandemic on the students It would be a reasonable assumption, and recent studies from different countries provided supportive findings [16, 17]. Such BP rise was also found in an early pandemic phase based on self-measured home BP [18]. Compulsory lifestyle changes, psychological stress, and limited access to medical care during the pandemic may have influenced BP [19]. However, as the authors [1] stated, reasons for pandemic-associated BP rise are at least multifactorial, and this phenomenon might be explained by currently unidentified factors. In this respect, the current findings are valuable also for future research.

BP rise and hypertension in students as a lifetime risk factor should be detected in an early phase of their lives [20]. Like the Keio University students [1, 2], Japanese university students usually measure BP annually at school health check-ups based on governmental promotion regarding school healthcare. Although this system cannot be direct evidence that the Japanese have one of the longest life expectancies in the world, the assessment of BP from the student period would likely be useful. Furthermore, accurate BP measurement is the foundation of all subsequent decisions in individuals and populations [3]. We should pay more attention to BP measurement in the general population, including students.