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(Hypertension. 2007;50:e65.)
© 2007 American Heart Association, Inc.

Letters to the Editor

Interstudy Variability in the Ambulatory Arterial Stiffness Index

Dirk G. Dechering; Ahmet Adiyaman; Marijke van der Steen; Theo Thien

Nijmegen Medical Centre, Radboud University, Nijmegen, The Netherlands

To the Editor:

In 2006, Li et al¹ proposed the ambulatory arterial stiffness index (AASI) as a novel marker for arterial stiffness. AASI is derived from the linear relationship between systolic blood pressure and diastolic blood pressure observed using 24-hour ambulatory blood pressure monitoring.

The literature published on this topic shows some large differences in the mean AASI between studies. In our opinion, these differences cannot be fully accounted for by differences in methodology and patient characteristics. The Table shows a review of important issues of methodology and determinants of AASI from 4 original articles. In summary, an increase of AASI was relatively consistently found in women, in subjects with higher age, lower body height, increasing pulse pressure, hypertension, diabetes, and past cardiovascular disease.

View this table: [in this window] [in a new window]   Important Determinants of AASI in 4 Articles Published on AASI Along With Our Unpublished Study Data

Close observation of the studies by Dolan et al² and Hansen et al³ reveals a mean AASI of 0.15 U higher in the Danish cohort from the cohort of Hansen et al compared with the Irish cohort from Dolan et al. Looking at the baseline characteristics of these 2 studies, we find several factors that would rather suggest a comparatively lower mean AASI in the Danish study population (relatively fewer women, lower pulse pressure, less hypertensive subjects, and subjects with diabetes). With regard to study design, we noticed no noteworthy differences except for the ratio of night:day blood pressure readings.

Schillaci et al⁴ showed in the May 2007 issue that a nocturnal nondipping pattern tended to significantly flatten the slope of diastolic blood pressure on systolic blood pressure, thereby increasing AASI. The mean AASI in this Italian cohort was as low as 0.31. We hypothesized that the unusual high percentage of night measurements in this Italian study may have added to this low value. In a preliminary analysis of our study data (1325 hypertensive subjects referred to our center for ambulatory blood pressure monitoring), we found the ratio of night:day blood pressure readings to significantly influence AASI, with relatively more readings at night tending to decrease AASI (r=–0.10; P=0.001). Thus, nighttime dipping and ambulatory blood pressure monitoring protocols are probably 2 factors contributing to the discrepancies between the mean AASI in the reviewed articles.

In conclusion, important differences in mean AASI are present in the reviewed literature. Future research is necessary to identify possible confounders and, resting on our and future findings, standardization has to be established for AASI determination to draw unequivocal conclusions.

	Acknowledgments

 
Source of Funding

The Nederlandse Hartstichting (Dr E Dekker student grant), Den Haag, The Netherlands, supported the fellowship of A.A. in Leuven.

Disclosures

None.

	References

Top References

 
1. Li Y, Wang JG, Dolan E, Gao PJ, Guo HF, Nawrot T, Stanton AV, Zhu DL, O’Brien E, Staessen JA. Ambulatory arterial stiffness index derived from 24-hour ambulatory blood pressure monitoring. Hypertension. 2006; 47: 359–364.[Abstract/Free Full Text]

2. Dolan E, Thijs L, Li Y, Atkins N, McCormack P, McClory S, O’Brien E, Staessen JA, Stanton AV. Ambulatory arterial stiffness index as a predictor of cardiovascular mortality in the Dublin Outcome Study. Hypertension. 2006; 47: 365–370.[Abstract/Free Full Text]

3. Hansen TW, Staessen JA, Torp-Pedersen C, Rasmussen S, Li Y, Dolan E, Thijs L, Wang JG, O’Brien E, Ibsen H, Jeppesen J. Ambulatory arterial stiffness index predicts stroke in a general population. J Hypertens. 2006; 24: 2247–2253.[Medline] [Order article via Infotrieve]

4. Schillaci G, Parati G, Pirro M, Pucci G, Mannarino MR, Sperandini L, Mannarino E. Ambulatory arterial stiffness index is not a specific marker of reduced arterial compliance. Hypertension. 2007; 49: 1–6.[Free Full Text]

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				G. Schillaci, G. Pucci, M. Pirro, and G. Parati Response to Interstudy Variability of Ambulatory Arterial Stiffness Index Hypertension, September 1, 2007; 50(3): e66 - e66. [Full Text] [PDF]

This Article Extract Full Text (PDF) All Versions of this Article: 50/3/e65    most recent HYPERTENSIONAHA.107.096065v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Dechering, D. G. Articles by Thien, T. Search for Related Content PubMed PubMed Citation Articles by Dechering, D. G. Articles by Thien, T. Pubmed/NCBI databases Medline Plus Health Information High Blood Pressure Related Collections Other hypertension