Highly prevalent and poorly controlled cardiovascular risk factors among Chinese elderly people living in the rural community

Abstract

Background

The epidemiological scenario of cardiovascular risk factors (CRFs) among elderly people in rural China is unclear. We seek to describe the distribution, burden and management of major CRFs among older Chinese people living in the rural community.

Methods

This cross-sectional study included 1538 participants in the Confucius Hometown Aging Project (2010–2011) of people ≥60 years of age (mean age 68.6 years; 59.1% women) who lived in a rural community nearby Qufu, Shandong, China. Data were collected through a face-to-face interview, a clinical examination and laboratory tests. We carried out descriptive analysis on the prevalence and management of major CRFs.

Results

The overall prevalence of current smoking, physical inactivity, hypertension, diabetes, high cholesterol and obesity were 13.8%, 83.7%, 76.0%, 26.6%, 42.4% and 13.1%, respectively: 82.8% and 50.4% of participants had ≥2 and ≥3, respectively, of the six CRFs. Prevalence of alcohol consumption was 18.7%. Men were more likely to smoke and consume alcohol than women, whereas women were more likely to be obese and physically inactive than men (p < 0.001). Prevalence of physical inactivity and hypertension increased with age, prevalence of alcohol intake and obesity decreased with age, and prevalence of smoking and diabetes was stable. Hypertension, diabetes and high cholesterol were treated in 60.6%, 68.1% and 41.1% of those with the disease, respectively, but only 11.3%, 13.7% and 31.7% achieved good control.

Conclusions

CRFs are highly prevalent and poorly controlled among elderly people in rural China, where men and women have different CRF profiles. Intervention programs targeting major CRFs may improve the health of older people in China.

Introduction

Cardiovascular disease (CVD) is the leading cause of death in China, and the number of annual CVD events is projected to increase by approximately 73%, driven primarily by population aging and increasing prevalence of cardiovascular risk factors (CRFs).¹ Many CRFs, such as smoking, hypertension, hypercholesterolemia, obesity, diabetes and sedentary lifestyle, are amenable to successful intervention and management thus making most cases of premature CVD preventable. Indeed, since the 1970s, the risk of CVD has declined among major industrialized countries in the world, in which approximately 45% of the decreased incidence is attributable to effective control of the major CRFs.^2,3

The prevalence of major CRFs in high-income countries has shown gradual decline in smoking, high blood pressure and total cholesterol,^4,5 coinciding with gradual increase in overweight or obesity, leisure-time physical inactivity and diabetes.^6,7 However, data on trends in prevalence of CRFs in low- and middle-income countries are sparse. In China, along with rapid urbanization and increase in people’s living standards, CRFs such as hypertension, obesity, dyslipidemia and diabetes have become increasingly common.^8–10 Indeed, the China Health and Nutrition Survey showed upward trends in the prevalence of obesity, overweight and hypertension during 1991–2009 among older Chinese people.^11,12 On the other hand, several reports have revealed low rates of medical treatment and control of these CRFs among Chinese adults.^12–14 However, such data are rarely available among elderly people living in rural China.

The rapid increase in aging population has posed tremendous challenges to the public health and health care system in China. Thus, data on prevalence and control status of CRFs among older adults are critical for policymakers to deal with the increasing challenges of population aging and the epidemiological trends of CVD. In this study, we seek to describe the distribution, burden, and medical control status of the major CRFs among older Chinese people living in the community of a rural area.

Methods

Study population

The study population included participants in the Confucius Hometown Aging Project (CHAP). Eligible participants for the CHAP included all people who were aged ≥60 years and registered in the Xing Long Zhuang community in June 2010. The community is located approximately 20 km away from Qufu (the hometown of Confucius), Shandong, China. The CHAP aimed to investigate health in aging by focusing on CRFs and atherosclerotic mechanisms in brain aging and dysfunction. A baseline survey was conducted in June 2010–July 2011. Of all eligible subjects in the community (n = 1743), 205 declined participation or lost contact or died before the examination or had missing data on demographics, leaving 1538 (88.2%) for the current analysis. Before the baseline survey, research staff for CHAP were trained by senior researchers and specialists from the Aging Research Center of Karolinska Institutet, Stockholm, Sweden.

The CHAP protocols were approved by the Ethics Committee at Jining First People’s Hospital of Jining Medical University, Shandong, China. Written informed consent was obtained from all participants, or in the case of cognitively-impaired persons from informants, usually the next-of-kin or guardians. Research within CHAP was conducted according to the principles expressed in the Declaration of Helsinki.

Data collection

Data were collected through a face-to-face interview, a clinical examination and laboratory tests by trained nurses, physicians and technicians from the local Xing Long Zhuang Coal Mine Hospital that provides routine medical and health care services to residents of the local community. Epidemiological data were collected via a questionnaire that was developed from the World Health Organization (WHO) STEPwise approach to Surveillance (STEPS) and the Study on Global Ageing and Adult Health (SAGE).^15,16 Data included demographics, cardiovascular or lifestyle-related factors (e.g. smoking, alcohol consumption and leisure activities), medical history (e.g. diabetes and hypertension) and use of medications. Height, weight and blood pressure were measured following the standard procedure.¹⁵

Body mass index (BMI) was calculated as weight (kg) divided by height (m) squared. After at least a 5 min rest, arterial blood pressure (Korotkoff phase I for systolic and phase V for diastolic pressure) was measured in the sitting position on the right arm using a mercury sphygmomanometer with the cuff maintained at the heart level. Blood pressure was measured twice on one occasion, and the mean of the two readings was used in the analysis.

After overnight fasting, peripheral blood samples were taken at the hospital. Fasting plasma glucose (FPG), total cholesterol, triglycerides, low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) were measured using an automatic Biochemical Analyzer (Olympus AU-400, Olympus Optical Co. Ltd, Tokyo, Japan) at the hospital laboratory that is licensed by the local quality and technical control authority.

Assessments of cardiovascular risk factors

Smoking status was categorized as never, former and current smoking. Alcohol consumption was assessed based on the frequency and amount of alcohol intake in a typical drinking day.¹⁷ Because very few people were heavy drinkers, alcohol consumption was dichotomized. The total metabolic equivalent (MET) in min per week were estimated according to frequency and intensity of physical activity. Leisure-time physical activity was classified into no regular, low intensity activity (<600 MET-min per week) and moderate-to-high intensity activity (≥600 MET-min per week). No regular or low intensity activities were considered as physical inactivity.¹⁸

Hypertension was defined as blood pressure ≥140/90 mm Hg or use of antihypertensive drugs. Blood pressure in the range 140–159/90–99 mm Hg was considered as stage 1, and ≥160/100 mm Hg or use of antihypertensive drugs as stage 2 hypertension.¹⁹ Diabetes was defined as FPG ≥7.0 mmol/l or current use of blood glucose-lowering agents or insulin injection, and prediabetes as FPG of 6.0–6.9 mmol/l.²⁰ We defined obesity as BMI ≥30 kg/m² and overweight as BMI of 25–29.9 kg/m². High cholesterol was defined as total cholesterol ≥6.22 mmol/l or use of hypolipidemic drugs, and dyslipidemia as total cholesterol ≥6.22 mmol/l or triglycerides ≥2.26 mmol/l or HDL-C <1.04 mmol/l or LDL-C ≥4.14 mmol/l or use of hypolipidemic drugs.²¹

Statistical analysis

We presented the prevalence of CRFs by age and gender. The burden of CRFs was assessed by counting the number of the six major CRFs, i.e. current smoking, leisure-time physical inactivity, obesity, hypertension, high cholesterol and diabetes. Alcohol consumption was not counted as a CRF because most alcohol drinkers were light-to-moderate consumers, and were not at risk for cardiovascular events. Normal distributed continuous variables were compared with the t-test, and categorical variables with the chi-square test. Triglyceride levels were log-transformed before t-test owing to skewed distribution. Among the multiple categorical factors, pair-wise chi-square tests were performed to assess the gender differences within each level. Logistic regression analysis was performed to test the trend of prevalence of CRFs with age. The IBM SPSS Statistics 19 for Windows (IBM SPSS Inc., Chicago, Illinois, USA) was used for all analyses.

Results

Table 1 shows characteristics of the study participants by gender. The mean age was 68.6 (standard deviation (SD) 4.9) years. Controlling for age, women had higher levels of systolic pressure, FPG, total cholesterol, triglycerides, HDL-C and LDL-C than men (p < 0.05), whereas men had higher prevalence of self-reported history of hypertension (p = 0.003). There was no significant gender difference in the mean of age, BMI and diastolic pressure, and in prevalence of use of hypertensive drugs, history of diabetes, use of blood glucose drugs or insulin injection, history of high cholesterol and use of hypolipidemic drugs (p > 0.05).

Table 2 presents the overall prevalence of major CRFs by gender. Men were much more likely to smoke and consume alcohol than women, whereas women were more likely to be obese and physically inactive than men (p < 0.001). In addition, men were more likely to be overweight than women (p = 0.02). There was no significant gender difference in prevalence rates of hypertension, diabetes, prediabetes, high cholesterol and dyslipidemia (p > 0.20).

Across all age groups, men were more likely to smoke and consume alcohol than women, while women were more likely to be physically inactive and obese than men (Figure 1). There was no significant gender difference in prevalence of hypertension, diabetes, high cholesterol and dyslipidemia in all age groups. The prevalence decreased with age in alcohol consumption and obesity (p for trend <0.05), increased in hypertension and physical inactivity (p for trend≤0.001), but was stable in current smoking, diabetes, high cholesterol and dyslipidemia (p for trend>0.10).

We assessed the burden of major CRFs (i.e. current smoking, physical inactivity, obesity, high cholesterol, hypertension and diabetes). Overall, 97.7% of the subjects had at least one CRF, and 82.8%, 50.4% and 20.4% had ≥2, ≥3 and ≥4 of the six major CRFs, respectively (Figure 2). The proportions having ≥2 CRFs were similar between men and women (80.8% vs 84.3%, p = 0.072).

The medical treatment of major CRFs was considered to have achieved good control for hypertension if blood pressure <140/90 mm Hg, for diabetes if FPG <7.0 mmol/l, and for high cholesterol if total cholesterol <6.22 mmol/l. Overall, 60.6% of people with hypertension were treated with antihypertensive agents, but only 11.3% achieved good control: 10.0% were aware of their hypertension but did not take any medications (Table 3). Of those with diabetes, 68.1% were treated, but only 13.7% achieved good control: 22.1% were aware of diagnosis of diabetes but did not take any medications. Of those with high cholesterol, 41.1% were treated, and only 31.7% achieved good control: one-third of those with high cholesterol were not treated. Men had higher rates of treatment and more effective control for hypertension and high cholesterol than women (p < 0.001). Finally, the proportion of undiagnosed hypertension, high cholesterol and diabetes was approximately 30%, 25% and 10%, respectively.

Discussion

This community-based study of rural older Chinese people reveals that the major CRFs are highly prevalent, but men and women have different profiles for CRFs such that men are much more likely to smoke and consume alcohol than women, whereas women are more likely to be obese and physical inactive than men. Furthermore, there is a heavy burden of CRFs among older people such that 4 in 5 and 1 in 2 have ≥2 and ≥3, respectively, of the six major CRFs. Finally, approximately 30%–60% of people with hypertension, diabetes and high cholesterol are not pharmaceutically treated, and only small proportions (∼10%–30%) of those affected people have achieved good control of these CRFs. These results underline the urgent need of implementing interventions that target the major CRFs among Chinese elderly people living in the rural area.

Consistent with previous studies of older Chinese people,²² we found that men were much more likely to smoke than women. By contrast, a population-based study of older Swedish people reported comparable smoking rates between men and women.¹⁷ Our data also showed that men are much more likely to consume alcohol than women, although the majority were light-to-moderate consumers. This is again in contrast to the Swedish report where there is no substantial gender difference in alcohol consumption.¹⁷ The distinct patterns of gender-specific prevalence of smoking and alcohol consumption among older people between China and Sweden may be due to differences in tradition, culture and tobacco and alcohol control policies. We found a higher rate of physical inactivity compared to reports from other regions of the world.²³ Thus, older people in rural China should be encouraged to participate in physical activity. Indeed, even among very old people maintaining healthy lifestyles remains critical for health aging.²⁴

We found a higher prevalence of overweight or obesity than previous reports on older Chinese people.⁹ Women were more likely to be obese than men. High prevalence of obesity and overweight may be due to excess intake of calories and lack of physical activity, whereas the higher proportion of leisure-time physical inactivity in women than in men may partly explain the gender difference in obesity. Compared to previous studies of Chinese older adults^8,9,22 we found a higher prevalence of hypertension and diabetes but a lower prevalence of prediabetes and dyslipidemia. People with prediabetes have a substantial risk to progress to diabetes and, thus, this group can be targeted for early intervention to postpone the onset of diabetes.

CRFs often occur concurrently among older people. We found that 4 in 5 older people had two or more CRFs, which was consistent with the reports from studies of middle-aged and elderly people in Asia and Europe.^25,26 Previous studies have shown that an increasing burden of CRFs is associated with an increased lifetime risk for occurrence and death of CVD.²⁷ The finding of a heavy burden of CRFs in our study population calls for action to implement interventions that target the major modifiable CRFs among older Chinese people living in the rural area.

It has been estimated that 50–75% of the decline in deaths of CVD is attributable to control of the major CRFs, especially with regard to smoking, high blood pressure and high cholesterol.^24,28 Thus, sufficient control of the major CRFs remains critical for primary and secondary prevention of cardiovascular events.^29,30 Our data showed that the major CRFs (e.g. hypertension, diabetes and high cholesterol) were poorly controlled among older Chinese people. The treatment rate of hypertension was higher in our sample than that of a previous study of older adults (60.6% vs 49.0%) but the rates of good control were comparable (11.3% vs 12.0%).¹² We found higher rates of treatment and good control for diabetes and high cholesterol compared to the results from middle-aged and elderly Chinese people.^31,32 Age may affect adherence to medical treatment because, compared to young and middle-aged people, elders are more concerned about their health and, thus, are willing to better adhere to the treatment. This is consistent with the study showing that the proportions of being treated and effectively controlled for high cholesterol increase with increasing age in high-income countries.³³ Moreover, the treatment and good control rates for high cholesterol in our sample were similar to those of Japanese elders.³³ Finally, the National FINRISK survey in Finland suggested that, compared with older men, older women were more likely to use preventive medications such as hypolipidemic and antihypertensive drugs.³⁴ By contrast, we found that men had higher proportions of treatment and effective control for hypertension and high cholesterol than women, and women were more likely to have undiagnosed hypertension and high cholesterol than men, suggesting that older women should be encouraged to seek medical examination and treatment for hypertension and high cholesterol.

Strengths of this study include the community-based design, use of standard instruments for data collection and comprehensive assessments of extensive CRFs. However, this study also has limitations. Firstly, self-reported data on some sensitive lifestyle factors (e.g. smoking and alcohol intake) may be less reliable which may generally lead to an underestimation of the true prevalence. Furthermore, we had limited power to estimate the prevalence of CRFs among the oldest people (age ≥80 years) owing to the small number in this age group.

In conclusion, this population-based study reveals that CRFs are fairly common among older Chinese people living in the rural area, where men and women have distinct profiles for CRFs. Furthermore, there is a heavy burden of CRFs as well as poor control of major CRFs such as hypertension and diabetes. These findings call for action to implement intervention programs that target major CRFs among older people living in rural China.

Acknowledgements

The authors thank all study participants for their invaluable contribution to the CHAP and all staff in the CHAP Study Group for their collaboration in data collection and management.

Funding

The CHAP was supported in part by grants from the Department of Science and Technology (2008GG00221) and Department of Health (2009-067) in Shandong, China and by the Young Scholar Grant for Strategic Research in Epidemiology at the Karolinska Institutet, Stockholm, Sweden.

Conflict of interest

None declared.

References

Author notes