This is the first population survey using internationally standardised protocols to report the prevalence of risk factors for NCD in the Mekong Delta, Vietnam. Previous surveys on NCD have been conducted in Ha Noi and HCMC. There have been some data reported for the population of Bavi [5
], an extremely poor district of Hanoi [15
], but the findings from this study are unlikely to represent the risk profile of the population of the Mekong Delta where income is much higher and land holdings are much larger.
The first principal finding of this study was that older women in this population-based representative sample generally had an unfavourable NCD risk profile. The sex differences in SBP and TC persisted after adjustment for BMI. This has not been reported previously for Asian populations, but it mirrors reports for some Western populations that blood pressure and TC of men and women converge with advancing age [16
]. For BG, we found a statistically significant stronger cross-sectional increase with age for women that was diminished by adjustment for BMI but strengthened by additional adjustment for behavioural risk factors. This cross-sectional pattern of increasing levels of BG with age for women, and higher levels for women at older ages, appears not to have been reported previously. Factors not measured in this survey, and which may account for the elevated risk among women, were hormonal status, saturated fat consumption and salt intake.
The second principal finding was the risk profile of this predominantly rural population of Vietnam was markedly different to that reported previously for the two major cities. The prevalence of raised BG (defined as capillary whole BG of at least 6.1 mmol/L) in our sample (men: 1.0%, women: 1.1%) are lower than prevalence estimates reported for the big city convenience samples: 2.7% for men and 2.6% for women aged 20–60 in HCMC in 2004 [8
], 4.6% of men and 5.8% of women in the subset of participants aged 25–64 in another sample of HCMC population in 2001 [7
], and 5.8% of 20–74 years old residents in Ha Noi in 2005 [4
]. A possible explanation for these differences lies in the higher proportion of overweight and obesity observed in the big city surveys. The proportions of obese (BMI at least 23 kg/m2
) participants in our sample (men 23.6%, women 31.8%) were lower than that reported for the Ha Noi sample (33.7%) [4
], fewer participants in our survey (12.9%) than in the Ha Noi sample (17.5%) [4
] had abdominal obesity (waist circumference ≥ 90 cm for men or waist circumference ≥ 80 cm for women). In the HCMC sample, 18.6% of participants had BMI at least 25 kg/m2
but only 12.7% (men 11.1%, women 14.1%) of our participants exceeded this level [7
]. In the rural sample of Ha Noi from Bavi, only 3.5% of participants had BMI at least 25 kg/m2
]. Another possible explanation for the higher prevalence of raised BG in the big city samples is the lower levels of physical activity among the urban residents. There was 46.6% of men and 41.3% of women aged 25–64 in a HCMC sample in 2005 [9
] classified as having a low level of physical activity compared to 32.7% of men and 40.4% of women in our samples.
In contrast to raised BG, the proportions of participants in our sample with hypertension (27% of men and 16% of women) exceed the prevalence estimates reported for the big city surveys. Hypertension was identified among 21% of men and 10% of women in a sample of 25–64 year olds from a single commune in Ha Noi in 2007 [3
], 17.5% for the subset of 20–59 year old participants of a convenience sample from two districts of Ha Noi in 2005 [4
], and 11% for men and 9% for women aged 20–60 in HCMC [8
]. Our results are more similar to those reported for the extremely poor rural sample of Ha Noi from Bavi [5
] in 2005 (24% for men and 14% for women aged 25–64) in which the prevalence of overweight and obesity was less than a third of that found this study. Dietary sodium intake has been linked with hypertension [19
], and salt consumption may be higher in poor rural areas where it is used to add flavour to rice. No published study to date has measured dietary sodium levels in a Vietnamese population, however, and this contention remains unsupported. Alcohol has been shown to be associated with elevated blood pressure [20
]. Our prevalence estimates of alcohol consumption are the only published Vietnamese data, and, therefore, no comparisons are possible. Tobacco smoking has been associated with elevated blood pressure in another study from this region [21
]. The limited data on smoking prevalence in Vietnam show relatively minor variation through the country. In our sample, 67.8% of men and 1.1% of women were current smokers. In a HCMC sample of 20–60 year olds, 62.2% of men and 1.4% of women were current smokers in 2004 [8
] and 62.9% of men and 0.6% of women were current smokers in the Bavi sample [5
A key strength of this study was its use of a representative sample, with analysis done taking into account the complex survey design. The relatively high response proportion minimises the likelihood of selection bias, and the range and quantum of factors that were measured should be a good reflection of those factors in the Vietnamese population. The use of WHO standardised protocols, intensive training of data collection staff, pre-study testing of procedures, and the close supervision of staff during data collection, all highlight the attention that was paid to minimising avoidable sources of measurement error.
Limitations of this study need to be borne in mind. The STEPS methodology is designed to provide standardised information on key modifiable risk factors that can be measured in population-based surveys without resort to high technology instruments. It is not designed to measure total energy intake, dietary fat, dietary sodium, body fatness, or physical activity by objective methods such as accelerometry and pedometry. Information on these factors would have provided a more comprehensive picture of the relationships we studied. In addition, these cross-sectional data do not allow age-related differences in blood pressure, BG and TC to be attributed to ageing independently of cohort effects.