Characteristics of population
In this study, 342 (male 171, female 171) precursor cases and 342 (male 169, female 173) control population were investigated, average age in the case group was 62.4±10.7 years old, and average age in the control group was 61.7±10.7 years old. Among these investigated people, they are all Han races, so racial analysis was no further conducted again. The difference of age and sex between case group and control group were not significant (tage=0.894, page=0.372; x2sex=0.119, psex=0.730 ). Total number of nuclear family members investigated was 8814 (4454 in case group, 4360 in control group), and the average nuclear family member was 12.88 (case group is 13.02; control group is 12.74).
Among 4104 investigated population in the elder member of a family (include father, mother, grandpa, grandma, maternal grandpa and maternal grandma), there were 839 relatives were definitely diagnosed with hypertension. The prevalence of hypertension was 20.44% in the elder relatives of this investigation. Among 3265 non-hypertensive relatives, there may also be some patients with potential or recessive hypertension who have not been clearly diagnosed. There is no reverse effect on the results of this study, so no further discussion will be conducted.
Family history
There were 2055 hypertensive patient has been clearly diagnosed in the hospital among this investigated population in this study, the average prevalence was 23.32%. The prevalence rate of hypertension of first-degree relatives was 33.99%; prevalence rate of second- degree relatives was 17.60%; prevalence rate of third-degree relatives was 13.51%. This result showed that the order of hypertension prevalence rate was as follows: first-degree relatives > second- degree relatives > third-degree relatives.
All prevalence rates of hypertension of case group relatives were significantly higher than that of control group relatives. The result showed a phenomenon of familial aggregation in the distribution of hypertension. See tab1.
Among these family members and relatives in case and control group, there were 575 hypertension in parent population, the prevalence was 42.03%; 549 in sibling population, the prevalence was 39.96%; 100 in offspring population, the average prevalence was 11.64%; 291 in paternal siblings population ( brother and sister of father), the prevalence was 18.27%; 255 in maternal siblings population ( brother and sister of mother), the prevalence was 16.89%; 46 in paternal cousin population, the prevalence was 13.11%; 239 in maternal cousin population, the prevalence was 13.59%. The difference of hypertension prevalence in three degree relative populations between case group and control group were significant. See table 1.
Among 4104 investigated population in the elder member of 684 families (include father, mother, grandpa, grandma, maternal grandpa and maternal grandma), there were 575 hypertension cases in parent population (include father and mother), the prevalence of parent was 42.03%; and 89 hypertension cases in grandparent population (include grandpa and grandma), the prevalence of grandparent was 6.51%; and 69 hypertension cases in maternal grandparent population (include maternal grandpa and maternal grandma), the prevalence of maternal grandparent was 5.04%. Because most of the grandparents and maternal grandparents have been died before this investigation, a large number of hypertension cases may be omitted because of unknown or not diagnosed in the retrospective investigation, resulting in the low prevalence of these two groups of population. See table 2.
Table 1: The hypertension prevalence rate (%) of relatives in case and control group
|
control group
|
|
case group
|
|
|
|
|
|
total
|
disease
|
prevalence
|
|
total
|
disease
|
prevalence
|
|
x2
|
p
|
|
first-degree relatives
|
|
|
|
|
|
|
|
|
|
|
parent
|
684
|
228
|
33.33%
|
|
684
|
347
|
50.73%
|
|
14.853
|
<0.001
|
siblings
|
704
|
217
|
30.82%
|
|
670
|
332
|
49.55%
|
|
21.557
|
<0.001
|
offspring
|
440
|
33
|
7.50%
|
|
419
|
67
|
15.99%
|
|
11.899
|
0.001
|
|
1828
|
478
|
26.96%
|
|
1773
|
746
|
42.07%
|
|
48.167
|
<0.001
|
second- degree relatives
|
|
|
|
|
|
|
|
|
paternal siblings
|
791
|
123
|
15.55%
|
|
802
|
168
|
20.95%
|
|
5.375
|
0.020
|
|
maternal siblings
|
740
|
107
|
14.46%
|
|
770
|
148
|
19.22%
|
|
4.339
|
0.037
|
|
|
1531
|
230
|
15.02%
|
|
1572
|
316
|
20.10%
|
|
9.635
|
0.002
|
|
third-degree relatives
|
|
|
|
|
|
|
|
|
|
|
paternal cousin
|
176
|
14
|
7.95%
|
|
175
|
32
|
18.29%
|
|
6.330
|
0.012
|
|
maternal cousin
|
825
|
97
|
11.76%
|
|
934
|
142
|
15.20%
|
|
3.897
|
0.046
|
|
|
1001
|
111
|
11.09%
|
|
1109
|
174
|
15.69%
|
|
7.282
|
0.007
|
|
Total
|
4360
|
819
|
18.78%
|
|
4454
|
1236
|
27.75%
|
|
83.649
|
<0.001
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Note: “total” was the number of people investigated, “disease” was number of hypertension, “prevalence “=”disease / total *100%; x2 and p value were calculated by x2 test.
Table 2: The hypertension prevalence rate (%) of elder member in case and control group
|
Control group
|
|
Case group
|
x2
|
p
|
|
No
|
Yes
|
%
|
|
No
|
Yes
|
%
|
|
father
|
222
|
120
|
35.08
|
|
170
|
172
|
50.32
|
16.158
|
<0.001
|
mother
|
234
|
108
|
31.48
|
|
167
|
175
|
51.29
|
27.057
|
<0.001
|
grandpa
|
323
|
19
|
5.57
|
|
311
|
31
|
9.03
|
3.107
|
0.078
|
grandma
|
323
|
19
|
5.57
|
|
322
|
20
|
5.81
|
0.027
|
0.869
|
maternal grandpa
|
331
|
11
|
3.28
|
|
324
|
18
|
5.16
|
1.764
|
0.184
|
maternal grandma
|
324
|
18
|
5.25
|
|
320
|
22
|
6.45
|
0.426
|
0.514
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Note: “No” was number of non-hypertension, “Yes” was number of hypertension, x2 and p value were calculated by x2 test.
FH affects onset age of hypertension
If one or more relatives of the first-degree relatives (include father, mother, grandpa, grandma, maternal grandpa and maternal grandma) have been definitely diagnosed with hypertension, family history (FH) is called positive, otherwise is called negative. Among 342 cases in the case group, the result showed that the average onset age in population with positive FH is 48.74 (48.74±11.16) years old, and the average onset age in population with negative FH is 54.38 (54.38±9.87) years old. The difference about two FH groups showed statistically significant (t=4.589, P<0.001). Among the first-degree relatives, the efficacy on the age of onset of hypertension in offspring is different for different relatives. See table3.
Table 3 showed that either parents or grandparents or maternal grandparents in the first-degree relatives could affect the onset age of hypertension of children, it's just that the level of effect was different. Grandpa and grandma are particularly influential among the first-degree relatives. The average onset age of children with grandpa or grandma positive was respectively 39.55 (39.55±11.95) or 39.88 (39.88±11.90) years old; and the average onset age of children with grandpa or grandma negative was respectively 51.07 (51.07±10.59) or 51.08 (51.08±10.60) years old. The difference about two groups showed statistically significant (see table3). The results suggest that the onset age of hypertension of children with grandpa or grandma positive was about 11 years earlier likely than that of children grandpa or grandma negative.
Table 3: The average onset age of hypertension in case group with different family history
|
Hypertension
|
N
|
Onset age (y)
|
t
|
p
|
mean
|
SD
|
father
|
Yes
|
167
|
48.42
|
11.16
|
3.194
|
0.002
|
|
No
|
175
|
51.90
|
10.81
|
mother
|
Yes
|
166
|
49.16
|
11.12
|
1.832
|
0.068
|
|
No
|
176
|
51.17
|
11.04
|
grandpa
|
Yes
|
26
|
39.55
|
11.95
|
5.768
|
<0.001
|
|
No
|
316
|
51.07
|
10.59
|
grandma
|
Yes
|
27
|
39.88
|
11.90
|
5.682
|
<0.001
|
|
No
|
315
|
51.08
|
10.60
|
maternal grandpa
|
Yes
|
15
|
43.67
|
9.77
|
2.883
|
0.010
|
|
No
|
327
|
50.50
|
11.09
|
maternal grandma
|
Yes
|
18
|
43.64
|
10.21
|
3.086
|
0.005
|
|
No
|
324
|
50.57
|
11.06
|
Note: “N” was the number of people, “mean” and “SD” were the mean and standard deviation of onset age, t and p value were calculated by t test.