Ambulatory blood pressure monitoring and mortality – Authors' reply
Authors: Alejandro de la Sierra, Natalie Staplin, Luis M Ruilope, Colin Baigent, Bryan Williams
Journal: The Lancet (2024)

We have read with interest the Correspondence concerning our Article.1Staplin N de la Sierra A Ruilope LM et al.Relationship between clinic and ambulatory blood pressure and mortality; an observational cohort study in 59 124 patients.Lancet. 2023; 401: 2041-2050Summary Full Text Full Text PDF PubMed Scopus (52) Google Scholar We thank all authors for their comments and suggestions. We agree with Shi Qi Li and colleagues, and Wei Liu and colleagues, about the possible importance of other ambulatory blood pressure monitoring parameters, such as alterations in the circadian rhythm or in blood pressure variability, and their potential additional contribution to mortality. Both issues require in-depth analyses beyond the scope of our initial publication of the principal findings. We are already working on various additional analyses examining the associations between blood pressure variability and different patterns of variation in 24-h blood pressure with mortality. These findings will be published in the near future. All four Correspondence comment on factors that could influence or explain the relationship between nocturnal blood pressure and mortality. In two of these letters, there is mention of the potential effect of sleep disorders on nocturnal blood pressure, notably, obstructive sleep apnoea. Unfortunately, the relationship between sleep disorders and blood pressure was less well recognised when the clinical data for this study were collected and thus, information on sleep patterns and obstructive sleep apnoea was not systematically collected from these patients, who were mostly attending primary care centres. Moreover, formal evaluation of sleep disorders in the very large cohort of patients involved in our study was not possible. Obstructive sleep apnoea can be associated with nocturnal hypertension and in particular, with a riser pattern.2O'Brien E Parati G Stergiou G et al.European Society of Hypertension position paper on ambulatory blood pressure monitoring.J Hypertens. 2013; 31: 1731-1768Crossref PubMed Scopus (1131) Google Scholar However, if this were the main cause of nocturnal hypertension in our study, it would imply that many millions of patients worldwide are likely to have obstructive sleep apnoea. The suggestion by Miguel A Martinez-Garcia and colleagues that obstructive sleep apnoea is likely to be the main determinant of the dominant relationship between nocturnal blood pressure and mortality is speculative; however, we acknowledge that obstructive sleep apnoea could be a factor, along with the others we suggested. These factors included the better standardisation of the nocturnal measurement, with the patient resting, supine, and immobile during blood pressure measurement, in contrast with daytime measurements, performed during daily activities.3Boggia J Li Y Thijs L et al.Prognostic accuracy of day versus night ambulatory blood pressure: a cohort study.Lancet. 2007; 370: 1219-1229Summary Full Text Full Text PDF PubMed Scopus (743) Google Scholar Another potential explanation is that nocturnal blood pressure is more likely to be elevated in conditions that predispose individuals to mortality, such as diabetes, chronic kidney disease, and ageing. Further comments related to the potential effect of sleep quality on blood pressure, especially the influence of sleep duration, as noted by Liu and colleagues. We addressed this possibility by including sleep duration as a covariate in our adjusted model. The reported hazard ratios for the associations between different blood pressure indices and mortality were essentially unchanged (changes in hazard ratio of 0·01, without affecting statistical significance) after additional adjustment for sleep duration. Finally, Wei-Min Chu and colleagues mentioned other potential confounders. We are unable to investigate the potential effect of circadian blood pressure disturbances in individuals who do shift work on mortality because night shift workers were excluded from the study. Another suggestion was that the study might have inherent bias because those intolerant to ambulatory blood pressure monitoring were excluded and might have had a different relationship between blood pressure and mortality. Chu and colleagues suggest that a randomised controlled trial might be able to mitigate this bias, but an absence of adherence to ambulatory blood pressure monitoring could still lead to bias in a trial setting, making it particularly challenging to study patients intolerant to ambulatory blood pressure monitoring. Other potential influencing factors, such as educational level, income, dietary habits, or exercise, as suggested by Chu and colleagues, were not collected in our study and thus, we were not able to adjust for them. AdlS reports lecture fees from Viatris and Sanofi. NS reports institutional grant support from Boehringer Ingelheim, Lilly, and Novo Nordisk for investigator led or designed research unrelated to this Correspondence. LMR reports consulting fees from Novartis, Bayer, Pfizer, Medtronic, ReCor, Sanofi, and Sandoz and lecture fees from Novartis, Bayer, Pfizer, Medtronic, ReCor, and Sanofi. CB reports institutional grant support from Boehringer Ingelheim for investigator designed or led research unrelated to this Correspondence. BW reports lecture fees from Daichi Sankyo, Servier, and Pfizer, and institutional grant support from Omron for investigator designed or led research unrelated to this Correspondence. Relationship between clinic and ambulatory blood pressure and mortality: an observational cohort study in 59 124 patientsAmbulatory blood pressure, particularly night-time blood pressure, was more informative about the risk of all-cause death and cardiovascular death than clinic blood pressure. Full-Text PDF Open AccessAmbulatory blood pressure monitoring and mortalityWe read with great interest the Article by Natalie Staplin and colleagues, which reports the association of ambulatory blood pressure monitoring with an increased risk of mortality in adults.1 However, we would like to highlight some key concerns. Full-Text PDF Ambulatory blood pressure monitoring and mortalityAmbulatory blood pressure measurements have shown a stronger correlation with target organ damage and cardiovascular events as compared with clinical cuff measurements. Natalie Staplin and colleagues1 conducted a substantial population-based cohort study, which conclusively showed that ambulatory blood pressure, particularly night-time blood pressure, provides more informative data on the risk of cardiovascular mortality and all-cause mortality than clinic blood pressure. Although these results are promising, there are additional aspects to be addressed. Full-Text PDF Ambulatory blood pressure monitoring and mortalityWe congratulate Natalie Staplin and colleagues on a large and well performed study.1 The authors concluded that ambulatory blood pressure was the more informative measure for all-cause and cardiovascular mortality, and suggested that night-time systolic blood pressure was most informative about risk of all-cause death and cardiovascular death. However, the results need to be further explored, since some essential factors were neglected in the analysis for health outcomes. Full-Text PDF Ambulatory blood pressure monitoring and mortalityWe read with interest the Article by Natalie Staplin and colleagues on the relationship between clinic and ambulatory blood pressure and mortality. The study provides evidence on the superiority of 24-h ambulatory over clinic blood pressure and, in particular, on the superiority of night-time, as compared with clinic and day-time blood pressure. Indeed, in this large study conducted in the general practice setting, ambulatory, and in particular, night-time systolic blood pressure, were more informative on the risk of all-cause death and cardiovascular death than clinic systolic blood pressure. Full-Text PDF