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Prevalence and Risk Factors Associated with Prehypertension and Hypertension in the Chinese She PopulationLin Y.a · Lai X.b · Chen G.b · Xu Y.b · Huang B.a · Chen Z.a · Zhu S.a · Yao J.b · Jiang Q.b · Huang H.b
aDepartment of Endocrinology, Ningde Municipal Hospital, Ningde, and bDepartment of Endocrinology, Fujian Provincial Hospital, Fujian Medical University, Fuzhou, PR China Corresponding Author
Gang Chen, MD, PhD
Department of Endocrinology, Fujian Provincial Hospital
Fujian Medical University, Box 4-704
92 Huqian Road, Fuzhou, Fujian (PR China)
Tel. +86 1350 9337 027, E-Mail email@example.com
Background: Little is known about the prevalence and cardiovascular risk factors for prehypertension and hypertension in the She ethnic minority population of Fujian province in China. Methods and Results: Between April 2009 and September 2009, 5,523 participants of She nationality aged between 20 and 80 years participated in this survey and 5,357 were eventually enrolled in analyses. The survey was carried out to assess blood pressure and cardiovascular risk factors. The prevalence of prehypertension and hypertension was 35.87 and 38.42%, respectively, in all participants. Only 26.63% of the subjects with hypertension were aware of their diagnosis. Multivariate logistic regression showed that age, gender, overweight/obesity, dyslipidemia and alcohol use were risk factors for prehypertension, and age, overweight/obesity, dyslipidemia, alcohol use, family history of hypertension and hyperuricemia were risk factors for hypertension. The clustering of 2 and ≥3 risk factors was in higher proportion for subjects with hypertension and prehypertension when compared with those with prehypertension and normotension, respectively. After adjusting for other confounding factors, multivariable logistic regression showed that the greater the number of clustering cardiovascular risk factors, the greater the odds ratios for prehypertension and hypertension are. Conclusion: Hypertension and prehypertension were common in the She population of Fujian province. Cardiovascular risk factors cluster during prehypertension and awareness of hypertension was minimal. Early lifestyle modifications could be advocated to prevent the transition from prehypertension to hypertension and cardiovascular disease.
© 2012 S. Karger AG, Basel
Hypertension is not only a major risk factor for cardiovascular disease (CVD), but also a public health challenge worldwide [1,2]. The number of adults with hypertension in 2025 is predicted to increase to a total of 1.56 billion . Meanwhile, prehypertension progresses to clinical hypertension at a rate of 19% over 4 years  and is also associated with increased risk of CVD [4,5]. Several national blood pressure surveys in the United States and other countries report that more than 30% of the general adult population has prehypertension [6,7,8]. The overall prevalence of prehypertension is 36.3%, even in disease-free adults . Lifestyle modification or medical treatment is recommended for individuals with prehypertension .
China has 56 nationalities. There are marked ethical and geographical differences in blood pressure (BP) level and the prevalence of both hypertension and prehypertension in China [11,12,13]. The She ethnic minority group is one of the minority nationalities, approximately 25% live in Ningde City of Fujian province, China. Public health resources are limited in this area. The She ethnic minority mainly works in agriculture, forestry, animal husbandry, fishing, and water industry. They have their own language and living customs which are different from the Han population. Little was known about the epidemiological data on prehypertension and hypertension in this population. Therefore, a cross-sectional investigation was conducted to assess the prevalences of prehypertension and hypertension and their related cardiovascular risk factors in the She adult population, which may be different from the Han population. Furthermore, we aimed at detecting the risk factors clustering in prehypertension and hypertension. We hope this study will provide a basis for community prevention of prehypertenion, hypertension and CVD in the She population.
Ningde City is a medium-sized city in the northeast of Fujian province in China, with a She population of 170,000, accounting for 25% of the overall She population in China. From April 2009 to September 2009, subjects of She nationality living in Ningde City, between the ages of 20–80 years after being randomly selected, were age- and gender-stratified. Participants were required to complete a questionnaire and their fasting blood samples were collected. However, some subjects did not sign the informed consent or refused to respond at the time of investigation, therefore they did not complete the questionnaire or have their BP measured and were excluded from this analysis. Finally, 5,357 participants including 2,287 males and 3,070 females were enrolled in the analysis. The study was approved by an ethical committee. All participants signed an informed consent authorized by the Diabetes Branch of the Chinese Medical Association.
An interview-based survey of hypertension was performed using a questionnaire by trained staff. The questionnaire assessed age, gender, smoking status, alcohol intake, history of diabetes, history of hypertension, history of CVD, family history of hypertension, myocardial infarction, stroke, or diabetes.
Two BP measurements were performed by well-trained doctors while the participants were in the sitting position, with a manual sphygmomanometer, after the subjects had rested for 30 min, and the mean of the two readings was used for analysis. Height and weight were recorded, and body mass index (BMI) was calculated as weight/(height2) and expressed in kg/m2. Waist circumference was taken at the level of the umbilicus with the patient in the standing position at the end of gentle expiration. Brachial-ankle pulse-wave velocity (baPWV) was measured using an automatic device (VP-2000; Colin Co., Komaki, Japan). We used the mean value of bilateral baPWV in our analyses.
After an 8- to 12-hour overnight fast, blood samples were collected followed by a 75-gram OGTT, with additional blood samples drawn at 2 h for the measurement of glucose and insulin. Blood samples were stored at –20°C until analysis. Blood glucose levels were determined by the glucose-oxidase method (Sclavo, Siena, Italy). Total cholesterol (TC), triglycerides (TG), and high-density lipoprotein-cholesterol (HDL-C) were tested by an automatic colorimetric method (Hitachi; Boehringer Mannheim, Mannheim, Germany). Low-density lipoprotein cholesterol (LDL-C) was calculated by the Friedewald-formula . Serum creatinine was measured by the Jaffé reaction method, and serum uric acid was determined by an autoanalyzer using the phosphotungstate method. The estimated glomerular filtration rate (eGFR) was calculated with the following equation: eGFR = 186 × Cr–1.154 × Age–0.203 × 0.742 (if female) .
The classification of normotension, prehypertension and hypertension was based on the classification of BP from the JNC-7 . Normotension was defined as not being on antihypertensive medication and having a systolic blood pressure (SBP) <120 mm Hg and diastolic blood pressure (DBP) <80 mm Hg. Prehypertension was defined as not being on antihypertensive medication and having a SBP of 120–139 mm Hg and/or DBP of 80–89 mm Hg. Hypertension was defined as SBP ≥140 mm Hg and/or DBP ≥90 mm Hg, and also if the individual was on antihypertensive medication. Family history of hypertension was defined as a diagnosis of hypertension in 1 parent. Awareness of hypertension was defined as self-report of any prior diagnosis of hypertension by a healthcare professional among the population defined as having hypertension. Cigarette smokers were defined as having smoked at least one cigarette per day for a year or more. Alcohol use was defined as drinking alcohol at least 12 times during the previous year. Overweight and obesity in both males and females were defined as 25 ≤ BMI <30 and BMI ≥30, respectively, according to WHO criteria . Dyslipidemia was defined as self-reported current treatment with cholesterol-lowering medication or having 1 or more of the following: TC ≥5.17 mmol/l, TG ≥1.69 mmol/l, HDL-C ≤1.03 mmol/l, or LDL-C ≥3.38 mmol/l. Hyperuricemia was defined as serum uric acid levels >420 µmol/l in males and >360 µmol/l in females. Diagnosis of diabetes was based on criteria published by the International Diabetes Federation in 2005 of fasting plasma glucose (FPG) ≥7.0 mmol/l and/or 2 h plasma glucose after glucose load (2 h PG) ≥11.1 mmol/l, or the presence of previously diagnosed diabetes treated with hypoglycemia agents. Impaired glucose regulation (IGR) was defined as 6.1 ≤ FPG <7.0 mmol/l and/or 7.8 ≤ 2 h PG <11.1 mmol/l.
All values are expressed as mean ± SD. Data for FBG and TG were skewed and log-transformed for analysis and back-transformed for presentation. Categorical variables were presented as frequencies. Prevalence rates in the overall population were calculated based on the 2000 China census data by the direct standardized method. One-way ANOVA was used to compare continuous variables among inter-groups, and Student-Newman-Keuls test was used to compare differences between two groups. Categorical data were analyzed by χ2 test. Multivariate logistic regression analyses were used to test significant risk factors of prehypertension (vs. normotension) and hypertension status (vs. normotension), with prehypertension and hypertension serving as the dichotomous outcome variables. Risk factors both significantly associated with prehypertension and hypertension included overweight/obesity, alcohol use, IGR/diabetes and dyslipidemia. The prevalences of clustering of 0, 1, 2 and ≥3 risk factors were calculated in different BP statuses. Multivariate logistic regression analyses were used to estimate the odds ratios (ORs) and 95% confidence interval (CI) of prehypertension and hypertension associated with 1, 2 and ≥3 of these clustering risk factors, adjusted for confounding factors. All data analyses were conducted using the SPSS 11.5 statistical software package. p < 0.05 was considered significant.
A total of 5,357 subjects, aged 20–79 years, were ultimately involved in the statistical analysis, including 2,287 males and 3,070 females. 1,377 individuals had a normal BP, 1,922 had prehypertension, and 2,058 had hypertension. Only 26.63% of the subjects with hypertension were aware of their diagnosis. After adjusting for age and gender, the rate of awareness of hypertension was 19.16%. The prevalence of prehypertension was 35.87% (37.82% in males and 34.43% in females, respectively), and the rate of hypertension was 38.42% (38.96% in males and 38.01% in females, respectively) in all participants. Age- and gender-standardized prevalence rates of prehypertension and hypertension in all participants were 36.38 and 29.89%, respectively. The age-standardized prevalence of prehypertension was determined to be higher in males than in females (40.64 vs. 31.92%), while the prevalence of hypertension was similar in the two groups (30.67 vs. 29.08%).
Figure 1 illustrates crude proportions of prehypertension and hypertension accounted for all participants by age in males and females. The age-specific prevalence of hypertension increased with age in both males and females. In males, the prevalence of prehypertension decreased with increasing age. However, the prevalence rate of prehypertension peaked in females at an age of 30–49 years, and then decreased with increasing age.
Table 1 shows the characteristics of the three categories of BP. Prehypertension had intermediate levels of age, waist circumference, SBP, DBP, BMI, TC, TG, LDL-C, FBG, HR, baPWV, eGFR, uric acid, serum creatinine, rates of obesity, overweight, diabetes, IGR, dyslipidemia, hyperuricemia, and these values significantly increased in parallel to BP, while HDL-C was significantly lower in hypertension as compared with the other two groups. Prehypertension had the biggest number of cigarette smokers in the three groups, and a greater rate of alcohol use was found in the prehypertension and hypertension groups. The prevalence of ‘no formal education’ increased steadily with the increased BP, while prevalence of education level in ‘≥ elementary school and < high school’ decreased with the increased BP level. The proportion of ‘> high school’ was significantly lower in prehypertension compared with the other two BP statuses. There were no inter-group differences in rate of family history of hypertension among the three groups.
The multivariable-adjusted ORs of prehypertension and hypertension associated with various risk factors are presented in table 2. Age, overweight, obesity, IGR, diabetes and dyslipidemia were significantly associated with hypertension and prehypertension. Compared to females, males were more likely to have prehypertension, while gender was not significantly associated with hypertension. Compared to subjects with an education status of no formal education, those with a higher school education were less likely to have prehypertension and hypertension. Family history of hypertension and hyperuricemia were risk factors for hypertension, but they were not a risk for prehypertension. Cigarette smoking was not significantly associated with prehypertension but was found to have a significantly negative association with hypertension.
Furthermore, we detected the risk factors both associated with prehypertension and hypertension (mentioned above) clustering in different blood statuses. These risk factors included overweight/obesity, alcohol use, IGR/diabetes and dyslipidemia. Figure 2 shows the prevalence of risk factors clustering in normotension, prehypertension and hypertension. The prevalences of clustering of 2 and ≥3 risk factors were 31.87 and 15.39% in prehypertension and 36.98 and 24.92% in hypertension, respectively. In normotension, the proportion of clustering of 2 and ≥3 risk factors were 23.44 and 6.38%, respectively. The clustering of 2 and ≥3 risk factors was in higher proportion for subjects with hypertension and prehypertension when compared with those with prehypertension and normotension (both p < 0.01), respectively.
Multivariable-adjusted ORs and 95% CI of the number of risk factors clustering for prehypertension and hypertension are shown in table 3. After adjusting for age, gender and family history of hypertension, hyperuricemia, smoking status and education status, clustering of 1, 2 and ≥3 risk factors showed an increased risk for prehypertension compared with no risk factors (OR 1.650, 2.212 and 3.737, respectively). Clustering of 1 risk factor was associated with 1.961-fold higher odds of hypertension and clustering of 2 risk factors was associated with 3.724-fold higher odds of hypertension compared with no risk factors. Subjects with clustering of ≥3 risk factors were associated with the highest OR (9.729) of hypertension.
This study focused on the She ethnic minority population with about 700,000 people in China. In this study, the crude prevalence of prehypertension was 35.87% (37.82% in males and 34.43% in females, respectively), and the crude prevalence of hypertension was 38.42% (38.96% in males and 38.01% in females, respectively) in all participants. The age- and gender-adjusted prevalence of prehypertension was 36.38% in She population adults, which was higher than the prevalence observed in Taiwanese adults (34%)  and that observed in American adults (31%) [7,18], while the prevalence of prehypertension was 44.1% in Chinese Han people in Liaoning province  and 38.39% among a Mongolian population , which were both higher than the prevalence of prehypertension in the current study. The age- and gender-adjusted rate of hypertension was 29.89%, which was significantly higher than the rate of Han people (22.45%) living the same area in Fujian province . Consistent with previous reports [7,18], we found that in She population adults the prevalence rate of prehypertension was greater in males than in females. However, the gender difference in the prevalence rate of prehypertension in She population adults was not as drastic as that seen in American adults, where 41% of males versus 23% of females were reported to have prehypertension . Our study revealed that the proportion of hypertensives increased with age in both genders and the proportion of prehypertension decreased with age in males, which was consistent with a Mongolian population . However, in the She population the prevalence rate of prehypertension peaked in females at an age of 30–49 years and then decreased with increasing age.
In this study, subjects with prehypertension had intermediate levels of waist circumference, BMI, TC, TG, LDL-C, FBG, rates of obesity, overweight, diabetes, IGR and dyslipidemia, and these values significantly increased in parallel to BP. The multiple logistic regression analysis showed that BMI, dyslipidemia, diabetes and IGR were significantly associated with both prehypertension and hypertension. However, a high education level was shown as a protective factor. We suggested that compared with people with no formal education, those of a higher education were better informed about hypertension and subsequently had a healthier lifestyle. In addition, our study found that BMI was the strongest modifiable predictor of prehypertension, which was consistent with other studies [11,19]. Aggregation of multiple risks, including obesity, elevated BP and hyperlipidemia has been shown to increase the development of coronary heart disease [21,22,23]. Our study also found that prehypertension and hypertension had a high baPWV. baPWV is a marker of arterial atherosclerosis assessment and a higher baPWV predicts an increased risk of all-cause mortality . Thus, in order to reduce the risk of CVD, losing weight and adopting a diet are necessary for subjects with prehypertension and hypertension.
In the current study, age was associated with prehypertension and hypertension, which was confirmed in other studies [11,19]. Previous studies showed that males were more likely to have hypertension [11,19], but our study found that gender was not associated with hypertension in multiple logistic regression analysis. We will continue to study this aspect as long as the reason remains unclear. Furthermore, our study and a recent report both observed that alcohol use was a predictor of prehypertension and hypertension . Therefore, to prevent prehypertension and hypertension, lifestyle modifications might be necessary for all individuals, including reducing alcohol consumption. It was demonstrated that among the She population, alcohol intake and BMI interactively influenced BP . However, our study found that smoking appeared to be a protection factor for hypertension, which was consistent with the results in a Mongolian population . Although studies have shown that current cigarette smoking is a risk factor for hypertension onset [26,27,28], other analyses suggested that individuals who smoke may lower BP compared with non-smoking individuals [29,30]. It was noted that a lower BP in smokers than non-smokers might be ascribed to the effect of smoking reducing weight . In fact, the relationship between smoking and development of hypertension is still unclear and controversial .
In the current study, uric acid level and the proportion rate of hyperuricemia increased as BP increased. Hyperuricemia was an independent risk factor for hypertension after adjusted age, gender and other risk factors, and our finding was compatible with the idea that elevated uric acid predicted the development of hypertension [33,34]. In addition, it was noted that elevated uric acid level was also associated with prehypertension [35,36,37], especially when microalbuminuria was present . However, we found a negative association between hyperuricemia and prehypertension after adjusting for other confounders. Reasons for the negative results were unknown and the association between uric acid and prehypertension should be further clarified.
The present study showed that 47.26% of adults with prehypertension had at least two of the following CVD risk factors: dyslipidemia, IGR/diabetes, alcohol use and overweight/obesity. The clustering of 2 and ≥3 risk factors was in higher proportion for subjects with hypertension and prehypertension when compared with those with prehypertension and normotension, respectively. As considered in a previous study, this might imply that prehypertension is a phase in the progression to hypertension, and thus individuals with prehypertension in the She population are at risk of hypertension and other CVDs .
Furthermore, we also found that the greater the number of clustering cardiovascular risk factors, the greater the OR for prehypertension, which indicated that prehypertension was the result of an accumulation of various risk factors. In addition, studies have shown that aggregation of multiple risk factors can increase the risk of CVD [39,40]. Also, it was investigated that hypertension and prehypertension were significantly associated with increased all-cause and cardiovascular mortality in Chinese people . Thus, with regard to prevention of hypertension and CVD, people with prehypertension should be told about the seriousness of hypertension and the importance of promoting appropriate lifestyle modifications.
The crude rate of hypertension awareness in the She population was 26.63%, whereas the rate was only 19.16% after age and gender were adjusted, which was significantly lower than that in a Chinese national survey (24%) . Previous studies in other countries have also showed a higher rate of hypertension awareness than in this study, such as in Korea (30.3%) , Iran (34%)  and the USA (68.5%) . The reasons for the poor awareness of hypertension in the She population are likely due to several factors, e.g. poor health education, difficult access to medical care or inconvenient transportation conditions. Furthermore, the low income in rural areas is a barrier for diagnosis of hypertension. Thus, increasing public awareness of hypertension using public education and health-provider strategies might be a high national health priority.
Hypertension and prehypertension were common in the She population of Fujian province. Prehypertension was associated with various risk factors and had a higher proportion of clustering of 2 and ≥3 risk factors compared with normotension. In addition, the awareness of hypertension was nominal. Therefore, early lifestyle modifications such as losing weight and increasing physical activity could be advocated to prevent the transition from prehypertension to hypertension and CVDs.
This work was supported by Grant C071002 2009Y0011 and 2010Y3012 from the Natural Science Foundation of Fujian Province, China.
The authors have no conflicts of interest to disclose.
Gang Chen, MD, PhD
Department of Endocrinology, Fujian Provincial Hospital
Fujian Medical University, Box 4-704
92 Huqian Road, Fuzhou, Fujian (PR China)
Tel. +86 1350 9337 027, E-Mail firstname.lastname@example.org
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