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ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XV, Issue VI, June 2026
Carotid Artery Diameter and Blood Pressure: A Weak and Sex-Dependent
Association in a Normotensive Nigerian Population
Selekeowei Peter Kespi Kpuduwei, MD, PhD, FWACS
Department of Surgery, Federal Medical Centre Yenagoa, Bayelsa State, Nigeria
DOI:
https://doi.org/10.51583/IJLTEMAS.2026.150600051
Received: 17 June 2026; Accepted: 22 June 2026; Published: 04 July 2026
ABSTRACT
Background: The relationship between systemic arterial blood pressure (BP) and carotid artery diameter is often
derived from hypertensive cohorts. This study explores this relationship in a normotensive Nigerian population
to understand vascular physiology in the absence of pathology.
Methods: We analyzed data from 104 healthy adults. Carotid artery diameters were measured via
ultrasonography. Pearson's correlation and ANOVA were used to assess relationships with systolic blood
pressure, diastolic blood pressure and their mean arterial pressures (MAP).
Results: Mean age of the cohort was 28 years. In the overall cohort, correlations between BP and carotid
diameter were largely absent or weak. A sex-stratified analysis revealed a distinct pattern: in females, there were
significant positive correlations between MAP and the right ECA (r=0.453, p=0.003) and left ECA (r=0.335,
p=0.030). No significant correlations were observed in males at all. No correlations existed between the larger
common and internal carotid arteries with blood pressure parameters
Conclusion: The relationship between arterial blood pressure and carotid artery diameter in healthy,
normotensive individuals is weak and exhibits sexual dimorphism, being evident only in females. This suggests
that the strong correlations reported in literature are likely a feature of pathological hypertensive remodeling
rather than normal physiology. The female-specific association warrants further investigation.
Keywords: Blood pressure, Carotid artery diameter, Normotensive, Correlation, Healthy Nigerian population.
INTRODUCTION
Systemic blood pressure is a fundamental determining factor of arterial wall stress and a key driver of vascular
remodeling. The US Center of Disease Control (CDC) defines hypertension “as systolic blood pressure (SBP)
of ≥130 mm Hg or diastolic pressure (DBP) of ≥80 mm Hg” and also noted an increasing number of the condition
among its young adult population.
1
However, the definition of hypertension in Nigeria remains the same as that
of the World Health organisation (WHO), which is “persistent elevated systolic blood pressure of ≥140 mm Hg
or diastolic pressure of ≥90 mm Hg measured twice” or in the condition of taking antihypertensives or has been
previously diagnosed by a physician.
2,3
Lawal reports a prevalence of 9.2 to 70.3% of hypertension in Nigeria
and awareness rate between 12 to 93.2%,
4
which makes it a public health emergency with all of its attributes
becoming a science to study. It is estimated that 1 in 3 adult Nigerians are pre-hypertensive with (SBP ≥130 mm
Hg or DBP of ≥80 mm Hg).
5
Hypertension is implicated in cardiovascular, renovascular and cerebrovascular
diseases as a significant risk factor for morbidity and mortality. Chronic elevations of system blood pressure
evoke series of mechanobiological responses from arteries as a result of phenotypic changes often by the primary
cells of the wall. These are said to be differential gene expression driving remodeling in the arteries.
1
This
vascular remodeling that occurs in hypertension result from structural changes in the so called vascular smooth
muscle cells (VSMCs) supported by other primary cells like the endothelial cells, fibroblasts and resident
macrophages.
1,6
In hypertension, increased distending pressure leads to structural adaptations, including an
increase in arterial diameter to normalize wall stress
7,8
. By Poiseuille’s law, lumen diameter is more significant
in vessel resistance to blood flow than vessel length and viscosity because vessel resistance is inversely
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proportional to radius of its lumen to the fourth power (r
4
). Hence, forces that act to either reduce or increase the
radius of a vessel (that is to say its lumen diameter) say by 50% cause significant impact on vessel resistance by
16-fold.
6
Since it has been recognized that vessel resistance is a key driver and biomarker of established
hypertension,
9
the relation that exists in its absence or pre-hypertensive states needs to be studied among healthy
people. Interestingly, the vascular remodeling is not a one-way traffic: it can be hypotrophic, hypertrophic or
eutrophic. Moreso, it can also be inward remodeling (reduction of lumen diameter) or outward remodeling
(increase in lumen diameter). Wherefore, “inward remodeling” is reported as the commonest in hypertensive
states that leads (under passive conditions) to reduction of lumen diameter while “outward remodeling” is
commoner among those on antihypertensives and conditions of increased flow.
6
Consequently, positive
correlations between carotid diameter and blood pressure are consistently reported in studies involving
hypertensive patients, which remains the basis for the presumptions.
10,11
From the above, one would presume a
differential increase in luminal diameter of all critical arteries like the carotid, coronary and renal arteries in
normotensive individuals in the same population where hypertensive individuals have luminal diameter
reduction as highlighted in previous studies.
However, the nature of this relationship in healthy, normotensive individuals, where such compensatory
remodeling is presumed absent, is less clear. Establishing this baseline is crucial for interpreting vascular changes
in early disease. Unfortunately, there is paucity of studies on association between carotid artery luminal diameter
and blood pressure among normotensive individuals in Nigeria despite establishing reference values and sexual
dimorphism in previous studies.
12,13
This study aims to characterize the relationship between arterial blood
pressure and carotid artery diameter in a cohort of normotensive adults in Nigeria.
METHODS
Study Design and Participants: This cross-sectional study involved 104 healthy Nigerian adult volunteers
between 18 and 65 years with no history of hypertension in 2020. With no ethnic or occupation restriction they
were randomly selected following Helsinki guidelines. Study received ethical approval of the University of Port
Harcourt with number UPH/CEREMAD/REC/MM71/003 and all participants were enrolled after an informed
consent form was signed. Resting brachial blood pressure was measured using an electronic sphygmomanometer
(“KD-595”), confirmed manually. Both systolic and diastolic blood pressures were measured from which Mean
Arterial Pressure (MAP) was calculated.
Carotid Ultrasound: Using an EcoMed version VERTU-3-portable machine with linear transducer and
frequency of 7.0 MHz, standardized B-mode ultrasound was performed to measure the end-diastolic lumen
diameters of the common carotid artery (CCA), internal carotid artery (ICA), and external carotid artery (ECA)
with participants in supine position and head slightly tilted to assess the carotid groove. ALARA safety principle
was followed. Each scan was performed by a certified consultant radiologist with 10 years’ experience.
Statistical Analysis: Data analysis was done using IBM SPSS version 23. The relationship between carotid
diameters and BP parameters was assessed with Pearson's correlation coefficient. Analysis of Variance
(ANOVA) was used to compare diameters across MAP categories (Optimal, Normal, High-Normal). Analyses
were conducted for the total sample and stratified by sex.
RESULTS
The mean age was 28 years and there were 62 males and 42 females. Luminal diameters were CCA 4.5-7.6 mm,
ICA 4.4-7.5 mm and ECA 3.0-6.7 mm. For the total cohort, no significant correlations were found between any
BP parameter and the diameters of the CCA or ICA. In sex-stratified analysis, a divergent pattern emerged. Table
1a shows that in males, no significant correlations were observed.
In females (table 1b), however, significant positive correlations were found between MAP and the diameter of
the right ECA (r=0.453, p=0.003) and left ECA (r=0.335, p=0.030). While male values remain unchanged (table
2a), ANOVA and post hoc in females (tables 2b & 2c) confirmed that right ECA diameter differed significantly
across MAP categories (F=3.72, p=0.03). No significant differences were found for the CCA or ICA in either
sex when categorized by MAP.
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Table 1a: Relationship between carotid artery size and blood pressure parameters in male participants
Parameters
Correlation
Right diameter
Left diameter
CCA
ICA
CCA
ICA
ECA
Systolic BP
r
0.098
0.384**
0.021
0.168
0.039
p-value
0.451
0.002
0.870
0.193
0.762
Diastolic BP
r
0.112
0.199
-0.083
0.019
-0.010
p-value
0.388
0.121
0.523
0.884
0.939
MAP
r
0.116
0.297*
-0.046
0.084
0.010
p-value
0.370
0.019
0.725
0.514
0.937
** = Correlation is significant at the 0.01 level (2-tailed), * = Correlation is significant at the 0.05 level (2-tailed),
r = Pearson correlation.
Table 1b: Relationship between carotid artery size and other measured parameters in female subjects
Parameters
Correlation
Right diameter
Left diameter
CCA
ICA
ECA
CCA
ICA
ECA
Systolic BP
r
0.233
0.255
0.436**
-0.185
0.187
.353
*
p-value
0.138
0.103
0.004
0.240
0.236
0.022
Diastolic BP
r
0.083
0.263
0.360*
-0.130
0.149
0.242
p-value
0.601
0.092
0.019
0.411
0.345
0.122
MAP
r
0.172
0.298
0.453**
-0.178
0.191
0.335*
p-value
0.275
0.055
0.003
0.260
0.226
0.030
** = Correlation is significant at the 0.01 level (2-tailed), * = Correlation is significant at the 0.05 level (2-tailed),
r = Pearson correlation.
Table 2a: ANOVA comparing carotid artery diameter according to MAP in male subjects
Carotid
artery
diameter
(cm)
MAP
N
Descriptive statistics
ANOVA
Min
Max
Mean
SD
df
F-value
p-value
Right
CCA
Optimal
49
0.46
0.81
0.61
0.09
3
1.89
0.14
Normal
6
0.56
0.83
0.68
0.10
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High
Normal
4
0.55
0.69
0.63
0.06
ICA
Optimal
49
0.35
0.81
0.59
0.09
3
0.78
0.51
Normal
6
0.52
0.77
0.64
0.11
High
Normal
4
0.59
0.67
0.64
0.04
ECA
Optimal
49
0.31
0.61
0.48
0.07
3
2.43
0.07
Normal
6
0.40
0.71
0.55
0.10
High
Normal
4
0.52
0.56
0.55
0.02
Left
CCA
Optimal
49
0.43
0.77
0.60
0.08
3
0.53
0.67
Normal
6
0.42
0.74
0.58
0.13
High
Normal
4
0.52
0.64
0.58
0.06
lCA
Optimal
49
0.39
0.73
0.60
0.08
3
0.35
0.79
Normal
6
0.55
0.71
0.62
0.06
High
Normal
4
0.55
0.63
0.60
0.04
ECA
Optimal
49
-0.43
0.71
0.46
0.16
3
0.43
0.73
Normal
6
0.43
0.65
0.53
0.08
High
Normal
4
0.47
0.51
0.49
0.02
* = significant, CCA = Common Carotid Artery, ICA = Internal Carotid Artery, ECA = External Carotid Artery,
MAP = Mean Arterial Pressure
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Table 2b: ANOVA comparing carotid artery diameter according to MAP in female subjects
Carotid artery
diameter (cm)
MAP
N
Descriptive statistics
ANOVA
Min
Max
Mean
SD
df
F-value
p-value
Right
CCA
Optimal
28
0.43
0.76
0.60
0.07
2
2.10
0.14
Normal
10
0.46
0.70
0.60
0.07
High
Normal
4
0.55
0.77
0.68
0.10
ICA
Optimal
28
0.27
0.79
0.59
0.10
2
1.70
0.20
Normal
10
0.51
0.79
0.65
0.08
High
Normal
4
0.47
0.79
0.63
0.14
ECA
Optimal
28
0.33
0.58
0.49
0.07
2
3.72
0.03*
Normal
10
0.43
0.79
0.55
0.10
High
Normal
4
0.42
0.69
0.58
0.12
Left
CCA
Optimal
28
0.47
0.70
0.59
0.06
2
0.61
0.55
Normal
10
0.50
0.68
0.57
0.06
High
Normal
4
0.54
0.68
0.59
0.06
ICA
Optimal
28
0.43
0.75
0.59
0.07
2
1.79
0.18
Normal
10
0.50
0.81
0.64
0.09
High
Normal
4
0.57
0.75
0.63
0.08
ECA
Optimal
28
0.26
0.59
0.47
0.06
2
5.31
0.01*
Normal
10
0.41
0.64
0.52
0.08
High
Normal
4
0.53
0.66
0.58
0.06
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Table 2c: Post hoc multiple comparison test of carotid artery diameter in female subjects
Carotid artery
diameter (cm)
MAP (I)
MAP (J)
95% C.I
M.D (I-J)
S.E of
M.D
p-value
Lower
Upper
Left
ECA
Optimal
Normal
-0.11
0.01
-0.05
0.02
0.15
High
Normal
-0.19
-0.02
-0.11
0.04
0.01*
Normal
High
Normal
-0.15
0.04
-0.06
0.04
0.32
* = significant, C.I = Confidence Interval, M.D = Mean Difference, S.E = Standard Error of Mean Difference.
Figure 1: A scatterplot of right diameter of the external carotid artery and bulb against mean arterial
pressure in female subjects.
DISCUSSION
The primary finding of this study is the weak and sexually dimorphic nature of the arterial blood pressure-carotid
diameter relationship in health. The carotid artery pressure – carotid artery diameter relationship has been noted
to be almost linear one in previous studies among patients.
14
However, among our participants the correlation is
a not similar (figures 1). Even though among the females, there was significance, it was weak (tables 1b & 2b).
We see mostly in literature, the correlation of increased carotid artery diameter or intima-media thickness with
cardiovascular and neurovascular diseases (hypertension, atherosclerosis, aortic regurgitation, stoke, etc) in
patients in comparison to control (normal) subjects without those risk factors.
15
However, little is said in the
same publications about correlation of the parameters BP, pulse to the diameter and wall thickness in normal
healthy subjects. This is one aspect this index study has helped to reveal. Lanne et al had written that the pressure
and diameter relationship of arterial wall is curvilinear and appears to be biphasic, having an inflection at 90-
rtECAdiam = 0.0046x + 0.1084
R² = 0.2049
rtBulbdiam = 0.0046x + 0.367
R² = 0.1172
0
0.2
0.4
0.6
0.8
1
1.2
0 20 40 60 80 100 120
rtEcCA and bulb diameter (cm)
Mean arterial pressure
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110 mm Hg, above which the vessel is stiffer and less compliant. This is because during small arterial wall
distensions (by normal pressure), elastin bears the load, while during large distensions (higher pressure) both
elastin and collagen bear the load.
16
It was also highlighted that, the nonlinear curves drawn from the dependence
of these indexes on blood pressure makes it difficult for general application, which was demonstrated by
Bonyhay et al.
17
The general lack of a strong, consistent correlation in this normotensive cohort supports the
hypothesis that the significant associations reported in other studies are a consequence of persistent, pathological
hypertensive stimulus leading to structural remodeling.
7,8
The isolated correlation found in the ECA of females
is intriguing and without a clear physiological explanation in the literature. It may reflect sex-specific differences
in vascular reactivity, hormonal influences on the muscular ECA versus the elastic CCA/ICA,
18–20
or simply be
an occurrence by chance in this exploratory analysis. The fact that our cohort was young population (mean age
28 years) and normotensive means that age-related stiffening and hypertensive remodeling were minimized,
providing a clearer window into normal vascular physiology.
16
LIMITATION
The study did not compare the relationship of blood pressure with carotid luminal diameters between
normotensive and hypertensive individuals in the same population at the same time. In addition, there was no
follow up to identify changes.
CONCLUSION
In a healthy Nigerian population, blood pressure is not a major determinant of carotid artery diameter, and any
association appears to be weak and specific to the external carotid artery in females. This underscores that the
carotid diameter-BP relationship observed in patient populations is an acquired phenomenon. Understanding this
baseline is vital for distinguishing early pathological change from normal anatomical variation.
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