Prevalence of stroke and associated risk factors among middle-aged and older farmers in western China
Zhang et al. Environmental Health and Preventive Medicine
Prevalence of stroke and associated risk factors among middle-aged and older farmers in western China
Song Zhang 0 2
Zheng Liu 1
Yong-Liang Liu 0 2
Yu-Ling Wang 0 2
Tao Liu 0 2
Xiang-Bin Cui 0 2
0 Department of Medical Education, 3201 Hospital, Xi'an Jiaotong University Health Science Center , 783 Tianhan Ave, Hanzhong 723000, Shaanxi , China
1 Department of Pathology and Molecular Medicine, 3201 Hospital, Xi'an Jiaotong University Health Science Center , 783 Tianhan Ave, Hanzhong 723000, Shaanxi , China
2 Department of Medical Education, 3201 Hospital, Xi'an Jiaotong University Health Science Center , 783 Tianhan Ave, Hanzhong 723000, Shaanxi , China
Objectives: China has the world's largest population and the stroke has become the leading cause of death in recent years. The purpose of this study was to explore the associations between hypertension, family history of stroke, diabetes mellitus, obesity and stroke among middle-aged and older farmers of western China. A population-based study was conducted from June 2014 to April 2015 in Shaanxi and Sichuan provinces. Methods: Twenty thousand five hundred twenty-five Chinese middle-aged and older farmers (≥40 years) were recruited to the Qinling-Daba Mountains Region Stroke Study. A structured-questionnaire was used to collect data through face-to-face interviews. Demographic characteristics, risk factors, medical history, and other clinical characteristics were recorded for all participants. The association between hypertension, family history of stroke, diabetes mellitus, obesity and stroke were analyzed by using univariate and multivariate logistic regression analysis. Results: The stoke prevalence rate was 1380/100,000 in middle-aged and older farmers of western China. The difference in hypertension, diabetes mellitus, obesity and family history between different age groups had statistical significance (p < 0.05). The prevalence rate of hypertension and family history of stroke were higher in male population than in the female population. The difference was statistically significant (p < 0.05). Univariate logistic regression analysis demonstrated age, gender, hypertension, obesity and family history of stroke were stroke risk factors (p < 0.05). Multivariate logistic regression analysis revealed that the odds ratios of family history of stroke, obesity and hypertension were 7.177, 4.389 and 3.647 respectively. Conclusions: Family history is the strongest stroke risk factor in middle-aged and older farmers of western China.
Stroke; Risk factors; Chinese middle-aged and older farmers; Western China; Family history
In China, the stroke mortality rate is approximately 1.6
million annually, approximately 157 cases per 100,000. It
has exceeded heart disease to become the leading cause
of death . There is also a geographical difference of
stroke prevalence in China. Previous studies showed that
the stroke prevalence rate was 719 cases per 100,000
population in six China’s cities . Beijing had the
highest prevalence rate (1285 cases per 100,000 population
per year) . Interestingly, the prevalence rate was low
by 95 cases per 100,000 population in Guangxi province
(southern China) in comparison to 1249–1285 cases per
100,000 population in Harbin and Beijing cities (northern
China) [3, 4]. These studies revealed the fact that the
stroke prevalence rate varied widely among different
regions within China. In the current study, we for the first
time focused on the Chinese middle-aged and older
farmers in Shaanxi and Sichuan provinces. These two
provinces are located in the western China.
There are approximately 284 million people in western
China, including 37 million in Shaanxi province and 80
million in Sichuan province. According to the
government database of 2016, over 50% of the population was
registered as farmers. However, many of them, especially
the young people, are not engaged in agriculture after
1990 due to the urban migration. The Chinese farmers
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are a very special population who were nearly
geographically and socially immobilized in history. Today,
in the rural areas of China, most of middle-aged and
older farmers are still grouped in the village, engaged in
agriculture, and raising living organisms for food. In
the past 30 years, the diet and lifestyle of Chinese
farmers have changed remarkably as a result of China’s
fast economic and social development. The major
stroke risk factors, therefore increased substantially,
including hypertension, obesity and diabetes mellitus.
Over time, there has been a progressive increase in the
prevalence of stroke due to the influence of westernized
lifestyle, change in eating behavior and increase in the
number of older people [5, 6]. Our purpose was to
identify the stroke risk factors in middle-aged and older
farmers of western China. This stroke epidemiological
features can help us identify groups of individuals or
regions at higher risk of stroke and therefore push the
direction of stroke prevention.
Materials and methods
Study area and population
This cross-sectional study was conducted between
June 2014 and April 2015. The selection of participants
for the study was based on the database in the
National Health and Family Planning Commission.
The Health Department of Shaanxi and Sichuan
provinces contacted the farmers and sent the relevant
information to them. The farmers who would like to
attend this study have been recruited to the local
hospital for participating the study. The participants have
been informed about the research and consented to
participate. By the way, a physical medical examination
and flu vaccine have been freely provided to these
participants. A total of 24,147 Chinese farmers (from 40
to 90 year-olds) from Shaanxi and Sichuan provinces
were randomly selected for the Qinling-Daba
Mountains Region Stroke Study, part of National Stroke
Prevention and Screening Project. 20,525 farmers
participated (85%). The study population was divided into
5 age groups: 40–49, 50–59, 60–69, 70–79 and 80–89
years. Shaanxi and Sichuan provinces are located in
western China with 118.4 million people.
The epidemiologic study was conducted to evaluate
stroke and associated risk factors among adults aged
over 40 years. The selection of participants was based
on the following criteria: (1) their family has lived in
the village for at least one hundred years; (2) the people
in the village were engaged in agricultural work; (3) the
participants have lived in the village for over 20 years
in the past 30 years.
The data collection team was made up of two research
officers and four trained nurses experienced in
community data collection. Each participant underwent a
physical examination and was administered a
standardized questionnaire by a trained interviewer. The
questionnaire included data on age, sex, history of
stroke, hypertension, diabetes, and family history of
stroke. Informed consent was obtained from all
individual participants included in the study. All
procedures performed in this study involving human
participants was in accordance with the ethical
standards of the Xi’an Jiaotong University committee and
the Helsinki Declaration of 1975, as revised in 2000.
Blood pressures (BP) were measured three times at the
right brachial artery using standard mercury
Sphygmomanometers after the participant had rested for
10 min in a seated position. Hypertension was defined
as systolic BP (average of 3 readings) >140 mm Hg or
diastolic BP >90 mm Hg or the use of antihypertensive
drugs. Body mass index (BMI) was calculated as body
mass divided by the square of the body height (kg/m2).
Obesity was defined as BMI ≥30 kg/m2. Diabetes
mellitus was defined as a requirement for diabetes
medication or a repeated fasting plasma glucose level
exceeding 7.0 mmol/L or 11.1 mmol/L 2 h after eating.
Stroke was diagnosed by a neurologist in a hospital at
or above the county level based on the self-reported
history of stroke and cranial computed tomography or
magnetic resonance imaging. Nonfatal ischemic stroke,
hemorrhagic stroke, and transient ischemic attack were
all included. The family history was defined as a history
of stroke in parents, grandparents, aunts or uncles, and
first cousins. The smoking and eating habits of these
farmers have been observed.
Table 1 Demographic characteristics of the study population
Primary and less
Junior high school
Table 2 Age-specific stroke prevalence rates (per 100,000 population per year)
y years, n number, PR prevalence rates
Data were entered into a database using EpiData 3.0
software (EpiData Association Odense, Denmark). All
statistical analysis was performed using SPSS (version
18.0; SPSS, Chicago, IL). Data were presented as
percentages for categorical variables. Univariate logistic
regression analyses were used to determine whether there
were differences among the groups. The factors
showing statistically significant association with stroke in the
univariate analysis were considered for the multivariate
analysis. Multivariate logistic regression was performed
to assess associations between stroke (dependent
variable) and hypertension, family history of stroke, age,
gender and obesity. Odds ratio (OR) together with its
95% confidence interval (CI) and p values of the final
model was presented. P less than 0.05 was considered
significant, and probability values were two-sided. The
age-standardized prevalence rates were calculated by
the direct method, using the world population as a
There were 8050 males and 12,475 females with mean
age of 59.06 (40–90) years. Females accounted for
60.72% of the population (Table 1). The overall
ageadjusted stroke prevalence rate among the Chinese
middle-aged and older farmers aged 40 to 90 years was
1380/100,000 corresponding to 118.4 million people in
Shaanxi and Sichun provinces. The highest prevalence
rates in the present study were found in 70–79 age
group (2860/100,000) and the lowest in 40–49 age
group (480/100,000). Age-adjusted prevalence rates of
stroke among men were higher as rates recorded for
Table 3 Stroke risk factors associated with age groups
women (1870/100,000 compared with 1060/100,000).
The age distribution of the number of people with
stroke was illustrated in Table 2.
The difference in hypertension, diabetes mellitus,
obesity and family history of stroke among different age
groups had statistical significance (Table 3). The
difference in hypertension and family history of stroke
between male and female was significant (Table 4).
Tables 5 and 6 presented the results of univariate
and multivariate logistic regression analysis. Univariate
logistic regression analysis revealed that p value of
gender, age, hypertension, obesity and family history of
stroke was less than 0.05. Multivariate logistic
regression analysis showed that family history was the most
important stroke risk factor in Chinese middle-aged
and older farmers of western China, followed by obesity
and hypertension. Family history of stroke had an OR of
7.177 with 95% CI 5.165 to 9.973. Obesity and
hypertension had an OR of 4.389 and 3.647 with 95% CI
3.087 to 6.239 and 2.824 to 4.709, respectively.
Interestingly, the results shown that the male has a higher risk
of stroke than women.
This study is the first population-based study of the
stroke prevalence in Chinese older farmer population in
western China. Our results revealed that the stroke
prevalence rate in middle-aged and older farmers of
western China was 1380/100,000. The prevalence rate
for Chinese farmers was lower than that reported
recently by Xun Tang (1420/100,000–1690/100,000) from
Beijing Cardiovascular Disease Study . This difference
might be due to the fact that the participants were
Table 5 Risk factors associated with stroke analyzed by univariate logistic regression
Variables With Stroke Cases, n (%) Without-stroke Cases n (%)
40–49 25 (0.122) 4967 (24.20)
50–59 74 (0.36) 6282 (30.61)
60–69 92 (0.45) 5601 (27.29)
70–79 84 (0.41) 2747 (13.38)
80–89 7 (0.03) 619 (3.02)
90 0 26 (0.13)
Male 151 (0.74) 7911 (38.54)
Females 132 (0.64) 12331 (60.08)
Yes 183 (0.89) 5226 (25.46)
No 100 (0.49) 15016 (73.16)
Yes 23 (0.11) 1225 (5.97)
No 260 (1.27) 19017 (92.65)
Yes 59 (0.29) 472 (2.30)
No 224 (1.09) 19770 (96.32)
Yes 60 (0.29) 2961 (14.43)
No 223 (1.09) 17281 (84.19)
Primary and less 283(1.38) 20105(97.95)
Junior middle school 0 125(0.61)
High school or college 0 12(0.05)
Unmarried 1(0.00) 272(1.33)
Married 282(1.37) 19937(97.14)
Widowed 0 32(0.16)
Divorced 0 1(0.00)
“-” Missing value
Table 6 Stroke risk factors analyzed by using multivariate logistic regression
Family history of stroke
RC regression coefficients, SE standard error, OR odds ratio, CI confidence interval
recruited from different region. Beijing is located in the
northeast China, whereas Shaanxi and Sichuan are
located in the western China. The prevalence of stroke
was a tendency for the rates to increase gradually from
south to north and to decrease progressively from east
to west in China. According to these reports, the reason
for this related to the difference of diet, alcohol and
cigarette consumption, or prevalence of hypertension
in different China region [9, 10]. The stroke prevalence
was higher in male than in female and the hypertension
and family history was consistent with this (p < 0.01).
China now faces similar cardiovascular and stroke risk
factors as in the western nations: hypertension, obesity,
diabetes mellitus, smoking and physical inactivity.
Hypertension, obesity, diabetes mellitus and smoking
have been considered to be the four leading causes of
stroke in the Chinese population [11–14]. Among them,
hypertension remains the most important risk factor for all
types of strokes with the highest population-attributable
risk at 34.6% . China has hundreds years history of
smoking tobacco or some kind of plant leaves according to
the local customs. To our observation, most of
middleaged and older farmers in these two provinces smoked
beedi, hookah or rollies and the contents were various
including herbal fruits and tobacco. This smoking habits
appears to vary from region to region, and they are not
uniform. For example, some farmers like hookah while
some like self-made tobacco. Some farmers smoke the dry
leaf of the tree. In our search of the literature, there was no
report on the comparison of the health hazards of smoking
between these traditional tobacco and cigarette.
Furthermore, the dietary habits also vary widely among these
farmers. It depends on local traditional habits, personal
habit and personal economic status. For example, the main
foods of most farmers are rice and vegetables. However,
the main vegetables are totally different between some
counties in Shaanxi and in Sichuan since the distance
between the two counties is one thousand kilometers.
Therefore, only hypertension, obesity, diabetes and
family history of stroke have been selected to analyze.
In our study, for the first time we revealed that family
history was the strongest stroke risk factor in
middleaged and older farmers of western China. Hypertension
and obesity were the stroke risk factors followed by
family history. Interestingly, diabetes was not a stroke
risk factor in the middle-aged and older farmers of
western China. The reason for this might be due to the
fact that the older farmer has their special eating habits
based on their living conditions. According to our
observation, the main foods of the older farmer were
low-fat diet. This was consistent with the previous finding
that diabetes prevalence was much lower in farmers than
urban residents in China .
In recent years, some reports have proved that family
history was a stroke risk factor in Chinese population
[16, 17]. A study conducted in 2012 demonstrated that
family history of stroke was associated with the risk of
stroke (OR of 2.74; 95% CI, 1.76–4.26) in people
≥20 years of age . In Japan, family history of stroke
was associated with arterial stiffness in middle-aged
population (35–69 years old) . In another
casecontrol study of 195 patients (30–79 years old), family
history has been found that it was the strongest
independent risk factor for subarachnoid haemorrhage .
The high waist circumference and social isolation also
have been considered to be the risk factors of
cardiovascular [21, 22]. However, hypertension has been
recognized as the most important stroke risk factor in
Chinese population (18–74 years old) [23, 24]. The
reason for this may be related to the change of health
conditions in the Chinese population in recent years due to
obesity, unhealthy eating, and physical inactivity [25, 26].
The physiological changes such as overweight and
respiratory diseases mask the role of genetic factors in
the development of stroke. Another reason for this may
be related to the increased rates of detection of stroke.
In recent years, with the improvement in health
condition, a large number of slight stroke cases has been
identified in Chinese rural region . Moreover, our study
was for the first time to investigate the relationship
between the stroke and middle-aged and older farmers in
western China by using a detailed questionnaire survey.
Therefore, it is not surprising that many cases with a
family history have been identified.
In summary, the present study demonstrates that family
history is the strongest stroke risk factor in middle-aged
and older farmers of western China. The stroke prevalence
rate is lower in western China than northern China, but is
much higher than southern China. This information is
useful for planning and implementation of prevention
programs and represents the first step toward monitoring
the effectiveness of public health strategies to reduce the
burden of stroke among middle-aged and older farmers in
SZ participated in the design of the study and performed the statistical
analysis. ZL interpreted the data and drafted the manuscript. Y-LL and Y-LW
collected and analysed the data. TL collected the data and drafted the
manuscript. X-BC conceived of the study and participated in its design and
coordination. All authors read and approved the final manuscript.
The authors declare that they have no competing interests.
Ethics approval and consent to participate
All procedures performed in studies involving human participants were in
accordance with the ethical standards of the institutional and/or national
research committee and with the 1964 Helsinki Declaration and its later
amendments or comparable ethical standards. This article does not contain
any studies with animals performed by any of the authors.
Springer Nature remains neutral with regard to jurisdictional claims in
published maps and institutional affiliations.
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