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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 31, No 6, November/December 2020
AFRICA
299
including IS and HS, in hypertensive populations, as well as the
association between the combination of UA and total cholesterol
(TC), triglyceride (TG), low-density lipoprotein cholesterol
(LDL-C) and homocysteine (Hcy) levels and stroke risk.
Methods
We recruited 4 710 consecutive hypertensive patients from the
hypertension management information system of 60 community
health service centres (CHSCs) in Nanshan District, Shenzhen,
from April 2010 to September 2011. Eight sub-districts were
selected in Nanshan district, and then six to eight communities
were selected from each sub-district using a simple random
procedure according to a sequence of computer-generated
random numbers.
Written informed consent was obtained from all participants.
The study was approved by the ethics committee of the
collaborating hospitals and Nanshan Center for Chronic Disease
Control.
All the hypertensive patients were diagnosed in one of
the collaborating hospitals, according to at least three blood
pressure tests at different times, and registered in the electronic
information system of CHSC. There were 307 stroke patients
among the 4 710 hypertensive patients.
The following information was collected through in-person,
standardised questionnaire interviews: age, gender, smoking,
alcohol use, leisure and occupational physical activities, detailed
history of hypertension and medications used, and family
history of IS. Height and weight were measured using standard
methods, with participants wearing light clothing and no shoes.
Body mass index (BMI) was calculated as weight (kg)/height
squared (m
2
).
Both leisure and occupational physical activity levels were
assessed as in a previous study.
20
Drinking categories were
determined according to the content of National Institute on
Alcohol Abuse and Alcoholism (NIAAA).
21
Blood samples were collected from each participant after
overnight fasting and centrifuged for 15 minutes at room
temperature at 3 000 rpm. Biochemical measurements included
fasting glucose, TC, TG, LDL-C, UA, Hcy and creatinine (Cr)
levels. TC, TG, LDL-C and glucose levels were measured using
enzymatic methods, UA was determined quantitatively with
uricase, Cr was detected by the Jaffe method, and Hcy was
measured with a circulating enzymatic method. All of these
indicators were tested on an automatic biochemical analyser
(HITACH 7080). We calculated estimated glomerular filtration
rate (eGFR) according to the formula: eGFR (ml/min per 1.73
m
2
)
=
175
×
plasma creatinine
-1.234
×
age
-0.179
×
0.79 (if female).
22
Normal values for the serological markers were as follows:
TC
≥
5.18 mmol/l; TG
≥
1.7 mmol/l; LDL-C
≥
3.37 mmol/l; HU
>
360
μ
mol/l in females; HU
>
416
μ
mol/l in males; and Hcy
>
15 mmol/l.
23-25
Participants were divided into four groups by
quartiles (Q1– Q4) of serum UA level:
≤
274, 274–332, 332–396
and
>
396
μ
mol/l.
Systolic blood pressure (SBP) and diastolic blood
pressure (DBP) were measured using a standard mercury
sphygmomanometer on the right arm of seated participants
after five minutes of rest. Hypertension was defined as SBP
≥
140
mmHg and/or DBP
≥
90 mmHg or current use of medication to
control blood pressure.
26
We included cerebral infarction, embolism and small-vessel
disease as indicative of IS, and intracerebral haemorrhagic or
subarachnoid haemorrhagic stroke as an event of HS. The stroke
subtypes (ischaemic, intracerebral haemorrhagic and subarachnoid
haemorrhagic) were independently adjudicated retrospectively
by two neurologists using a standardised manner based on
clinical assessment and neuro-imaging (computed tomography
or magnetic resonance imaging). IS and HS diagnoses were also
validated through the Stroke Registration system in Shenzhen.
Statistical analysis
Qualitative data are presented as frequency (%) and were
analysed using the chi-squared test. Quantitative data are
presented as mean [standard deviation (SD)] and were analysed
by t-test, or as median [interquartile range (IQR)] and if not
normally distributed, were analysed by non-parametric tests.
The association between UA level and stroke was estimated
by logistic regression model, with the lowest quartile of UA and
normo-uricaemia as the reference. Corresponding odds ratios
(ORs) and 95% confidence intervals (CIs) were calculated in
the crude model (M0), multivariable model 1 (M1) adjusted
for age and gender, and multivariable model 2 (M2) adjusted
for age, gender, BMI, TG, TC, LDL-C, Cr, glucose, Hcy, heart
ratio, SBP, DBP, drinking, smoking, sport, heart failure, kidney
disease, hypertensive retinopathy, diabetes, family history of
stroke and hypertension years.
We selected four serological indicators (TG, TC, LDL-C,
Hcy), based on their effect on UA level and stroke,
27-29
in
combination with UA level to estimate their associations with
stroke risk. The normal values of all four serological markers
were used as reference. Statistical analyses were performed with
the SAS 9.1 (SAS Inst, Inc, Cary, NC, USA). The forest plot was
conducted by R 3.1. All tests were two-sided with a statistical
significance level of
<
0.05.
Table 1. Demographic and clinical characteristics of the participants
Variables
Stroke
Total
(
n
=
4710)
No (
n
=
4403) Yes (
n
=
307)
p
-value
Age
57.68
±
11.72 62.57
±
11.16
<
0.0001 58.00
±
11.75
TG
2.06
±
1.58 1.87
±
1.49 0.0449 2.04
±
1.58
TC
5.18
±
1.01 5.07
±
1.07 0.0639 5.17
±
1.02
LDL-C
3.16
±
0.79 3.01
±
0.85 0.0011 3.15
±
0.80
BMI
24.81
±
3.03 24.44
±
3.20 0.0422 24.78
±
3.05
SBP
134.39
±
14.99 134.20
±
14.18 0.8233 134.38
±
14.94
DBP
83.17
±
10.38 82.21
±
9.03 0.0760 83.10
±
10.30
Heart rate
75.26
±
7.66 75.03
±
7.84 0.6152 75.24
±
7.67
Cr
81.90
±
18.47 81.85
±
23.92 0.9673 81.90
±
18.87
Glucose
5.93
±
1.28 5.78
±
1.55 0.1202 5.92
±
1.30
Hcy
14.80
±
9.81 17.36
±
14.26 0.0022 14.97
±
10.18
UA
339.16
±
94.76 354.66
±
97.65 0.0057 340.17
±
95.02
Hypertension years
<
0.0001
<
2
891 (18.92)
37 (0.79)
928 (19.70)
2
+
1288 (27.35)
53 (1.13)
1341 (28.47)
5
+
1037 (22.02)
81 (1.72)
1118 (23.74)
>
10
1187 (25.20)
136 (2.89)
1323 (28.09)
eGFR
87.66
±
27.88 87.87
±
21.56 0.8408 87.68
±
27.51
SBP, systolic blood pressure; DBP, diastolic blood pressure; TC, total cholester-
ol; UA, uric acid; LDL-C, low-density lipoprotein cholesterol; TG, triglycerides;
Hcy, homocysteine; BMI, body mass index; Cr, creatinine; eGFR, estimated
glomerular filtration rate.