Prevalence of Resting IADs
Resting sIADs and dIADs <10mmHg are common in the general population, but are not well characterized in young, healthy adults. To address this issue, a smaller threshold IAD of 5mmHg was examined in the present study. First-day prevalence values of resting sIADs
>5mmHg were 33.3% for sequential and 16.7% for simultaneous measurements, while dIADs
>5mmHg were found in 16.7% of participants for both sequential and simultaneous
measurements. Therefore, in this study of 18 healthy adults (16 men, 2 women) between the ages of 18 and 40 years, resting IADs of this magnitude were common. However, the majority of participants were in their early-to-mid-20s, and only 2 participants were over 30 years of age.
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Although results were unchanged when these participants were removed from the analysis (all P
> 0.05), the prevalence of IADs >5mmHg in this study should still be interpreted cautiously.
Although previous investigations of resting IADs in young, healthy adults have numerous methodological weaknesses, 2 studies have relatively few limitations, allowing for comparison of their findings with the prevalence of resting IADs >10mmHg in the present investigation.
Fotherby and colleagues,27 examining resting IADs in a sample of healthy adults between the ages of 18 and 48 years (8 men, 32 women), found simultaneous sIADs >10mmHg in only 1 out of 40 participants (~3%; measured 8 times in one visit), and no participant had a dIAD of this magnitude. In a much larger sample of 877 young, healthy Israeli Air Force recruits (806 men, 71 women; mean age 26+10 years), Grossman and colleagues29 documented sequential sIADs and dIADs >10mmHg in 111 and 77 participants (~13% and 9%, respectively; measured 2 times in one visit).
The first-day prevalence of sIADs >10mmHg in the present study (5.6% sequential and 11.1% simultaneous) fall within the range provided by these studies27, 29 and support the validity of previous data despite these earlier studies’ use of less stringent controls. Similarly, as in Fotherby and colleagues’ study,27 no dIADs >10mmHg appeared. Interestingly, however,
Grossman and colleagues29 did report a 9% incidence of dIADs >10mmHg. Thus, had the sample size in the present study increased, a similar prevalence may have been found. In any case, present findings provide supporting evidence for prevalence ranges of 3% to 13% for sIADs and 0% to 9% for dIADs >10mmHg in the general population of young, healthy adults.
Finally, as sIADs of 15 to 19mmHg and dIADs of 17 to 20mmHg have previously been found in non-CVD individuals,15 this study also sought to determine the prevalence of resting sIADs and dIADs exceeding thresholds of 15 and 20mmHg. However, no such IADs were found.
A recent meta-analysis9 demonstrated that sIADs of 10 to 20mmHg are sufficient for prescription of angiographic assessment for the presence of SS, and indicated that the specificities of sIADs
>15mmHg for PVD and CRVD were very high, meaning that when such differences are found,
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the presence of these diseases is very likely.9 Therefore, it is unsurprising that no such differences were found in a small sample of young, healthy adults.
Prevalence of Ambulatory IADs
The feasibility of a dual-arm ABPM protocol for identifying IADs in a young, healthy, adult population was also explored in this study. Indeed, sequential ABPM did identify a number of IADs, yielding prevalence values of 61.1%, 33.3%, 11.1%, and 5.6% for sIADs >5, 10, 15, and 20mmHg, respectively, on the first day. Prevalence of first-day dIADs was 22.2% and 5.6% for thresholds of 5 and 10mmHg, while no dIADs >15 or 20mmHg were found.
Only three previous investigations31, 32, 33 have examined IADs in blood pressure using ambulatory monitors. One study did not use an ABPM protocol, but compared resting readings from two different ambulatory monitors (the Del Mar Avionics Pressurometer IV, Del Mar Avionics, Irvine, California, USA, and the Spacelabs 90202, Spacelabs Inc., Redmond,
Washington, USA) to resting, auscultatory readings.31 Another used two different monitor models (the Mobil-O-Graph, I.E.M., Stolberg, Germany, and the Spacelabs 90207, Spacelabs Inc., Redmond, Washington, USA) to assess inter-model reliability.32
The other study33 was the only oneto use the same monitor model on both arms (the Tycos Quiet-Trak, Tycos-Welch-Allyn, Arden, North Carolina, USA), investigating IADs directly, for the purpose of determining which arm should be used in clinical practice for ABPM.
It found higher values (i.e., 6mmHg SBP and 3mmHg DBP) in the dominant (i.e., right) arm.33 However, this was a small-scale study using a sample of 10 hypertensive adults (6 men, 4 women) with a mean age of 45+17 years, and participants were excluded if they did not have a resting, sequential sIAD >10mmHg at baseline.33Therefore, the present study is the first to directly investigate the existence of ambulatory IADs in a young, healthy adult population, as well as the first to investigate their prevalence in any population.
Interestingly, although identification of IADs using dual-arm ABPM was possible in the present study, prevalence values were notably higher on both days than those of the
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corresponding resting, sequential sIADs and dIADs (see Table 3). Moreover, ABPM identified
“new” sIADs >5mmHg in 7 participants and >10mmHg in 6 participants who had no resting, sequential sIAD of these magnitudes, while finding “new” dIADs of these magnitudes in 3 and 1 participants, respectively. It also failed to identify sIADs and dIADs >5mmHg in 2 and 3
participants, respectively. Therefore, dual-arm ABPM appears to have over-estimated the prevalence of both sIADs and dIADs when compared to resting prevalence values. This
discrepancy between resting and ambulatory measurements may be explained by consideration of the nature of the dual-arm ABPM protocol employed in the present study. Recent activities, cuff transfer and/or participant movement during data acquisition may have alone or collectively contributed.
2.4.2 Reliability of IADs Across Testing Days