1.5 Age and Sex Differences in the Association of Brachial and Central Blood Pressure Variability with Arterial Stiffness
Authors: Yu Shikai , Connolly Kathleen , Kulkarni Spoorthy , Selvarajah Viknesh , Woodcock-Smith Jean , Wilkinson Ian , McEniery Carmel 
Published: February 2020

Abstract
Background
Both blood pressure variability (BPV) and arterial stiffness (AS) are significantly influenced by age and sex. However, whether the association between BPV and AS differs with age and sex remains unclear. We examined age and sex differences in the association between brachial and central BPV and AS in a cohort of healthy individuals, covering a wide age-span.

Methods
24-hour brachial and central blood pressures (Mobil-O-Graph) and aortic pulse wave velocity (aPWV) (SphygmoCor) were measured in 957 healthy individuals (age range: 18–88 yrs; mean age: 46 ± 18 yrs; 45% males). BPV was calculated as standard deviations of 24-hour (time-weighted, 24wSD), daytime (dSD) and night-time systolic blood pressures. Correlation analyses were performed, separately, in groups stratified by age (≤40, 41–60, and >60 yrs) and sex.

Results
aPWV significantly correlated to brachial and central 24wSD and dSD (p ≤ 0.02 for all) in both males and females, but females showed significantly stronger correlations of aPWV to brachial 24wSD (correlation coefficient [r]: 0.31 vs. 0.11, p = 0.001) and dSD (r: 0.32 vs. 0.12, p = 0.001) and to central 24wSD (r: 0.34 vs. 0.20, p = 0.02) and dSD (r: 0.34 vs. 0.21, p = 0.03), compared to males (Table 1). After stratification by age and sex, in both males and females, significant correlations between aPWV and BPV indices were observed in middle-aged and older adults, but not in younger adults (Tables 2 and 3).

Conclusion
Correlation between BPV and AS differs with age and sex. BPV relates to AS in middle-aged and older adults and more strongly relates to AS in females.
Table 1
Correlation between SBP variability and aortic pulse wave velocity in males and females

SBP variability
Males (n = 431)
Females (n = 526)
p*

r
p
r
p

Brachial

24 h time-weighted SD
0.11
0.02
0.31
<0.0001
0.001

Day SD
0.12
0.01
0.32
<0.0001
0.001

Night SD
0.01
0.81
0.16
0.0002
0.02

Central

24 h time-weighted SD
0.20
<0.0001
0.34
<0.0001
0.02

Day SD
0.21
<0.0001
0.34
<0.0001
0.03

Night SD
0.08
0.08
0.18
<0.0001
0.12

*p-value derived from Z-test; SD, standard deviation; r, correlation coefficient.

Table 2
Correlation between SBP variability and aortic pulse wave velocity in younger, middle-aged and older males

SBP variability/
Younger adults Age ≤ 40 yrs/ N = 208/
Middle-aged adults 40 < Age ≤ 60/ N = 104/
Older adults Age > 60 yrs/ N = 119/

r/
p/
r/
p/
r/
p/

Brachial

24 h time-weighted SD
0.06
0.42
0.20
0.04
0.23
0.01

Day SD
0.09
0.17
0.20
0.04
0.22
0.01

Night SD
−0.04
0.58
0.20
0.04
0.08
0.38

Central

24 h time-weighted SD
0.12
0.09
0.26
0.008
0.23
0.01

Day SD
0.15
0.03
0.27
0.006
0.26
0.005

Night SD
0.01
0.93
0.20
0.04
0.08
0.41

SD, standard deviation; r, correlation coefficient.

Table 3
Correlation between SBP variability and aortic pulse wave velocity in younger, middle-aged and older females

SBP variability
Younger adults Age ≤ 40 yrs N = 214
Middle-aged adults 40 < Age ≤ 60 N = 157
Older adults Age > 60 yrs N = 155

r
p
r
p
r
p

Brachial

24 h time-weighted SD
0.08
0.26
0.12
0.14
0.25
0.002

Day SD
0.12
0.09
0.14
0.08
0.21
0.008

Night SD
0.03
0.62
0.07
0.37
0.22
0.006

Central

24 h time-weighted SD
0.11
0.12
0.20
0.01
0.24
0.003

Day SD
0.13
0.05
0.20
0.01
0.19
0.02

Night SD
0.07
0.31
0.10
0.22
0.21
0.008

SD, standard deviation; r, correlation coefficient.