We read with great interest the article titled “Association of nighttime very short-term blood pressure variability determined by pulse transit time with adverse prognosis in patients with heart failure” by Sato et al., which explores the prognostic implications of nighttime very short-term blood pressure variability (BPV) in heart failure (HF) patients (Fig. 1) [1]. This is a relevant and timely contribution to cardiovascular research, particularly in highlighting an innovative approach using pulse transit time (PTT) to evaluate BPV. However, we have identified several aspects of the study that warrant further clarification and discussion, particularly concerning the methodology, statistical robustness, and the broader implications of the findings.

Fig. 1
figure 1

Association of nighttime very short-term blood pressure variability determined by pulse transit time with adverse prognosis in patients with heart failure

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Firstly, the authors employed multivariable Cox proportional hazards models to examine the association between BPV and clinical outcomes. While this approach is appropriate, the selection of covariates in the models lacks sufficient justification, particularly in Model 3, where variables such as heart rate, blood pressure, and apnea-hypopnea index were included. The omission of other potential confounders, such as the duration and adjustment of antihypertensive therapy during the follow-up period, may have introduced bias. Furthermore, the study does not discuss whether the proportional hazards assumption was validated, nor does it include sensitivity analyses to test the robustness of the results [2, 3]. These omissions raise questions about the reliability of the reported hazard ratios, especially given that the effect sizes for systolic and diastolic BPV (e.g., HR 1.199 and 1.101, respectively) are modest and may have limited clinical significance in guiding patient management.

Additionally, the study’s focus on nighttime BPV, while novel, presents a narrow view of BP dynamics in HF patients. The exclusion of daytime or 24-h BP variability limits the comprehensiveness of the findings and raises concerns about whether nighttime BPV alone can fully capture the prognostic significance of BP variability in HF [4, 5]. This limitation is compounded by the exclusive use of PTT-based measurements, which, although non-invasive, require further validation against standard methods such as intra-arterial monitoring [6]. Without data on measurement accuracy or error margins, it remains unclear whether PTT is sufficiently reliable to assess very short-term BPV in clinical practice.

Finally, the generalizability of the study’s findings warrants careful consideration. The patient population was recruited from a single center in Japan, and the unique characteristics of this cohort, including higher salt sensitivity and specific cardiovascular risk profiles, may not be representative of other populations [7]. Moreover, the relatively small sample size and low event rates, particularly for cardiac deaths (n = 24), limit the statistical power to detect meaningful subgroup differences or explore additional stratifications [8]. These factors, along with the lack of longitudinal data on changes in treatment regimens, underscore the need for cautious interpretation and further research to validate the applicability of the findings across diverse clinical settings.

In summary, while this study provides valuable insights into the prognostic role of nighttime very short-term BPV in HF patients, addressing the above issues would significantly enhance the robustness and clinical applicability of the conclusions. We hope the authors will consider these points to further strengthen this important line of research.