Independent relationship between 24-hour blood pressure and carotid intima-media thickness
Date
2013
Authors
Metsing, Lebogang Stanley
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Introduction: The changing socio-economic landscape in Africa has brought with it
unique health challenges previously uncommon in people of African ancestry. Noncommunicable
diseases such as coronary artery disease and stroke have emerged as
pressing public health concern highlighting the need to find more on-target diagnostic
tools as well as therapeutic interventions. Although ambulatory blood pressure (AMBP)
has in many studies conducted in the western world proved to be an independent
predictor of carotid intima-media thickness (C-IMT), such results cannot outright be
imputed to people of African ancestry living in Africa. That is because people of African
ancestry living in Africa are not only of a different ethnicity but are still in the early
phases of an epidemiological transition while people in the western countries who are
mostly Caucasians, are believed to be in the middle to late phases of an epidemiological
transition.
Methods: The relationship between the intima-media thickness of the common carotid
artery (SonoCalcTM IMT version 3.4) and AMBP (Space labs model 90207) was
determined in 320 randomly selected participants of African descent living in an urban
developing community in South Africa. Relationships were determined after adjustment
for (clinic blood pressure) BPc, age, gender, alcohol and tobacco use, the presence or
absence of diabetes mellitus or inappropriate blood glucose control measured by glycated
hemoglobin (ghb), antihypertensive therapy and menopausal status.
III
Results: Mean age for the study population was 43.7± 16.0 years. Both BPc and AMBP
parameters were strongly associated with C-IMT (p<0.001) in univariate analysis. In
multivariate analysis with BPc. and AMBP entered into separate models and after
adjusting for cofounders, BPc. and AMBP maintained significant associations with CIMT.
[BPc (partial r=0.0648, p< 0.1612), systolic blood pressure 24 (SBP24) (partial r=
0.236, p< 0.001), systolic blood pressure day (SBPd) (partial r= 0.302, p<0.05), systolic
blood pressure night (SBPn) (partial r= 0.0983, p<0.05)]. When adjustments were made
with BPc. and SBP24 entered into the same model, BPc lost its association with C-IMT,
[SBP24 (partial r=0.236, p<0.001) SBPd (partial r=0.149, p<0.05), SBPn (partial
r=0.172, p<0.05)]. Importantly the relationship between SBP24 and C-IMT persisted
independent of body mass index (BMI), BPc and age. SBP24 had the highest significant
association with C-IMT.
Conclusion: SBP24 independently predicts C-IMT even in a model that includes
conventional systolic blood pressure (SBPc) leading to the conclusion that AMBP is a
more effective tool at diagnosing C-IMT alterations while BPcdoes not have an
independent relationship C-IMT.
Description
Dissertation submitted to the Faculty of Health Sciences, University of Witwatersrand in
fulfillment of the Master of Science in Medicine in the School of Physiology