The Bavi district is a rural district located in northern Vietnam, about 60 km west of the capital, Hanoi. The district has a population of about 238,000; covers 410 square kilometers; and includes lowland, highland, and mountainous areas. Agricultural production and livestock breeding are the main economic activities of Bavi residents, whose average annual income is about US $78. The study described here was conducted in 2005 within the framework of a demographic surveillance system called FilaBavi (Epidemiological Field Laboratory of Bavi). A more detailed description of the Bavi district and of FilaBavi can be found elsewhere (15). The study was conducted in accordance with WHO’s STEPwise approach to surveillance of chronic disease risk factors (STEPS). STEPS involves three primary “steps”: 1) the use of a structured questionnaire to assess study subjects’ self-reported behavioral and lifestyle risk factors for chronic diseases, 2) the measurement of subjects’ blood pressure and anthropometrical parameters, and 3) the collection and biochemical analysis of subjects’ blood samples. Because STEPS is a standardized instrument that can be applied in various settings, STEPS data can be used to compare the health status of people in different regions of a country as well as that of people in different countries (12).

In this study, we implemented step 1 and step 2 in a representative sample of 2000 adults aged 25 to 64 years (approximately 250 in each of eight groups defined by sex and 10-year age range). Twelve field workers collected the data for the study after being trained in basic interviewing techniques and standard methods of obtaining physical measurements.

The data on smoking habits were based on participants' responses to questions in the tobacco use module of the STEPS questionnaire. The questions were designed to identify both current daily smokers and current nondaily smokers. Current daily smokers were defined as those who reported smoking at least one cigarette per day, and current nondaily smokers were defined as those who reported smoking less frequently.

Participants' blood pressure was measured three times with a standard digital sphygmomanometer (Omron Healthcare, Inc, Bannockburn, Ill) while they were in a sitting position after having rested for at least 5 minutes, and we used the average of the last two readings in our analyses. We considered subjects to have hypertension if their systolic blood pressure (SBP) was at least 140 mm Hg, their diastolic blood pressure (DBP) was at least 90 mm Hg, or they were being treated for hypertension (16).

Participants' weight and height were measured while they were without shoes and wearing light clothes. Their weight was measured to the nearest 10 g with electronic scales (Seca, Hamburg, Germany), and their height was measured to the nearest 0.1 cm with portable stadiometers. We then used these height and weight measurements to calculate participants' body mass index (BMI – their weight in kilograms divided by their height in meters squared) and considered anyone with a BMI of 25 or higher to be overweight (17).

We categorized study subjects by education level and occupation on the basis of their survey responses, and we categorized them by economic status on the basis of a previous evaluation by local authorities based in part on household rice production. Each of these sociodemographic variables had three categories. The education level categories were less than secondary school (completed less than 7 years of school), secondary school (completed 7 to 9 years of school), and high school or higher (completed more than 9 years of school); the three occupation categories were farmer, government employee, and other; and the three economic status categories were low, middle, and high.

We produced both descriptive and analytical statistics using Stata 8 software (Stata Corp LP, College Station, Tex) and calculated means and proportions for variables of interest. We then used multivariate logistic regression to model the associations between our outcome variables (hypertension, smoking, overweight, and different combinations of these risk factors) and the sociodemographic factors previously described. We used 95% confidence intervals to determine whether associations were significant.

The overall 18.8% prevalence of hypertension found in this study indicates that the condition already affects a large proportion of the adult population in the Bavi district and that the prevalence has increased substantially since 2002 when a STEPS survey of the same population indicated that the prevalence was only 14.1% (18). The prevalence was also higher than the prevalence of 16.8% found in a study by the Vietnam National Heart Institute in 2001 for both urban and rural areas in some provinces in the north of Vietnam (19) and the 16.9% nationwide prevalence among people aged 25–64 reported in the 2002 Vietnam National Health Survey (20). Internationally, similar findings about high and increasing rates of hypertension have also been reported in studies of rural communities in India (4,21), China (4), and Indonesia (22).

The results of our study show that Bavi residents with hypertension were more likely to be aware of their condition in 2005 than they were in 2002 (35% vs 17%) and that they were more likely to be receiving treatment for it (20% vs 7%) (18). These higher awareness and treatment rates could be due in part to the influences of the 2002 STEPS survey, during which Bavi residents with hypertension were told about their blood pressure status and given advice or referred to the district health center for a further health check. However, the higher awareness and treatment rates did not seem to have a marked impact on the hypertension problem in Bavi, indicating the need for a more comprehensive approach to dealing with hypertension.

The high prevalence of current smoking among men that we found in Bavi (63%) was slightly higher than the 56% found in previous studies in Bavi (23,24) or the 53% found in studies of smoking prevalence in Vietnam as a whole (20,25). Smoking prevalence has also been reported to be on the rise in other Asian countries, including China (4) and Indonesia (22). The findings from this study suggest that rural Vietnam is now at the latter stage of the smoking epidemic described by WHO (26) and that if the smoking epidemic model applies, rural Vietnam can be expected to experience a substantial increase in rates of smoking-related illness and death in the coming decades (27).

The findings from this study indicate that 14% of men in Bavi had hypertension and smoked. Because people with multiple risk factors are at significantly increased risk for cardiovascular disease (28,29) and because chronic diseases have been shown to be leading causes of death in Bavi (30-32), this high rate of multiple risk factors indicates an urgent need for comprehensive and integrated interventions to reduce the prevalence of cardiovascular disease and its risk factors in Bavi.

Of particular interest are the associations we found between risk factors (hypertension, smoking, overweight, and combinations of these factors) and sociodemographic factors (sex, age, education level, occupation, and economic status).

Hypertension and smoking were each significantly more prevalent among men than among women. This finding is consistent with the results of previous studies in Vietnam (18-20,23-25). Despite the lower prevalence of hypertension and smoking rates among women, the danger that these risk factors pose for the cardiovascular health of women must not be underestimated, as hypertension and smoking have been shown to be strongly associated with coronary heart disease among women (33) as well as among men. The results of this study also confirm results from previous Vietnamese (18-20) and international studies (34) showing that age is a key predictor of hypertension.

We found that the prevalence of hypertension and the prevalence of multiple risk factors were both inversely associated with education among men, even after adjusting for other independent variables such as age and economic status. The inverse association between hypertension and education was also found in the previous local study (18) and in studies conducted in developed countries (35). In other developing countries, the pattern of the association between hypertension and education level varied; it was found to be inverse in China but direct in India (35). The rate of death from cardiovascular disease in Bavi from 1999 through 2003 was also significantly higher among less educated people (32).

In terms of occupation, women in government jobs were at significantly higher risk for hypertension than women who were farmers, possibly because of less physically active lifestyles, work pressure, and psychosocial stress. Further investigation of why these women had a relatively high prevalence of hypertension is needed.

Overall, we found hypertension to have a complex association with economic status. Among men, hypertension was highest among those categorized as being in the richest group, but among women, it was highest among those categorized as being in the poorest. The high rate of hypertension among the better-off men of Bavi may reflect their adoption of western lifestyles such as high-fat diets, less physical activity, higher alcohol consumption, and job stress. The relatively high prevalence of hypertension among poor women may reflect alternative risk factors in this setting, such as early undernutrition (35). In fact, in the past, Vietnamese people valued boys over girls and often took better care of boys. Research in Vietnam has shown that undernutrition rates were higher among girls than among boys (36).

Because this was a cross-sectional study, the results cannot be considered as more than a snapshot, and they do not allow any assessment of trends. When comparing the prevalences of chronic disease risk factors from this study with those from other studies, one must consider that other factors might contribute to any observed differences, such as differences in the age of the study subjects, in how hypertension was defined, in when the studies were conducted, in the urban versus rural characteristics of the population, or in the instruments and procedures used to measure blood pressure.

For this article, we included only data on tobacco use, blood pressure, and physical activity because these measurements have been well validated in FilaBavi. We did not assess patterns in the prevalence of other important risk factors for chronic diseases, such as alcohol consumption and physical inactivity, because of the difficulty of standardizing results (e.g., converting quantities of alcohol consumed into standard drinks, capturing farming and nonfarming components of physical activity) and of analyzing the data (especially data on alcohol consumption and physical activity).

In summary, our findings suggest that rural Vietnam is undergoing a rapid epidemiological transition characterized by an increase in the prevalence of risk factors for chronic diseases and that different sociodemographic groups in the population have moved through the course of the transition to different extents. Our findings also show that actions to reduce levels of chronic disease risk factors in rural Vietnam are clearly urgent. The area needs comprehensive and integrated interventions designed to reduce these risk factors, including both primary and secondary approaches, as well as policy-level involvements. The highest priority should be put on primary prevention, as it has been shown to be the most cost-effective approach (4,8,10,11). The aim should be to make small reductions in the prevalence of smoking and hypertension in a large proportion of the population. The interventions should address all people in society, but should focus especially on disadvantaged groups.

This was a preliminary study of risk factors for chronic diseases in a rural setting in a transitional country. Further studies over longer periods of time and deeper analyses will be required to give greater insights into the epidemiology of chronic diseases in such settings.