Comprehensive assessment of metabolic syndrome among rural Bangladeshi women

Metabolic syndrome (MS) is described as a cluster of abnormalities that confers an increased risk of developing atherosclerotic cardiovascular diseases (CVD) and also type 2 diabetes mellitus (T2DM). In fact, MS is now considered as a global epidemic [1], with current estimates about 20-30% of the adult population worldwide is affected [2]. Of interest to the current study is the fact that the prevalence of these disorders (MS and CVD) among South Asians [3], a community that represents one-fifth of the global population [4], is on the rise. This development imposes a significant health burden to the subcontinent that has limited resources. The exact cause of this health trend is currently not clear. Nonetheless, several factors are believed to be potential etiological factors in the development of MS, including increased urbanization, economic growth, irregular meal times, and lifestyle change and adoption of western diet [5]. Unfortunately, millions of people in South Asia are facing a double health burden [2] i.e., the impact of poverty-related diseases (associated with infections and nutrition) is being exacerbated by the increasing load of chronic non-communicable diseases [6]. To date there has been very few studies conducted on rural women in Bangladesh. Because of our earlier preliminary data on this population were alarming, we decided to undertake a more detailed study to investigate the metabolic syndrome in rural Bangladeshi population, who are mostly poor and physically active. We found a higher prevalence of diabetes among Bangladeshi women, surprisingly, even in those living in rural regions [7].

The purpose of the present study was; therefore, to evaluate the prevalence of MS, identify the set of signature risk factors of MS and CVD that are unique to South Asia. Further we will examine the correlation of MS and CVD to the socio-economic and environmental conditions, particularly in Bangladesh rural women.

The present study is, to date, one of the largest community-based and comprehensive MS surveys done on rural Bangladeshi women. A total of 1,535 females aged between 15 and 85 years were included for analysis in the present study (mean ± SE age of 40.50 ± 0.35 years). Women aged 35 to 54 represented about half of the participants; whereas elderly women aged 65 and above represented only 5.15% (Figure 1A). The age-wise distribution of subjects were 13.49% (< 25 years), 19.74% (25-34 years), 24.69% (35-44 years), 25.08% (45-54 years), 11.86% (55-64 years) and 5.15% (65 years+) (Figure 1A).

The present study reports the first comprehensive MS epidemiological study that evaluated 1535 women of different age groups from rural Bangladesh. Based on three different criteria, the prevalence of MS was found to be 25.60% (NCEP ATP III), 36.68% (modified NCEP ATP III), and 19.80% (IDF criteria), respectively. We found a prevalence of MS that was highly age-dependent, i.e., there was an approximate four-fold increase in prevalence between age group 25-34 years to age group 55-64 years.

The prevalence of the MS in rural Bangladeshi women (36.68%), as revealed here, is similar to that reported in rural women of India (36.4%) using the NCEP ATP III criteria with ethnic specific cut off value for waist circumference [14]. Prevalence of MS was higher (36.68% vs. 25.60%) when ethnicity specific cut-offs for waist circumference were applied. Several population studies have reported an increase in the prevalence of the MS with age, regardless of definition [15‐34], with some noting a peak in the seventh decade and then a decline in both sexes [15, 22, 26, 34] or only in men [16, 17, 21, 25, 29, 33]. In the present study, the prevalence of MS increased with age but a slight decline as noted after the age of 65 years, consistent with findings reported in India [35]. The prevalence of MS was the lowest in the age group below 25 years (2.90%), while it progressively increased with age, plateauing between 55 to 64 years (43.96%). These findings indicate that aging may be a risk factor for MS for Bangladeshi rural women.

In the present study, based on the original NCEP ATP III criteria, low serum HDL levels was found to be the most common risk factor of MS, .i.e., it was observed in 85% of the target population. It is important to note that mean HDL levels were also found to be lower than the normal range even in the non-metabolic group (Non-MS vs. MS; 42.48 ± 1.05, 37.03 ± 1.47). When WC cut-offs specific for Asians were used as baseline for analysis, low HDL again emerged as the most common risk factor of MS followed by elevated plasma glucose level and hypertension. This observation in the pattern of profile MS in the present study is consistent with reports of previous studies performed in India [21, 36]. These Indian studies actually demonstrate a significantly higher prevalence of low HDL cholesterol in Indian women (90.2%) as compared to US women (39.3%). In the present study, a consistently high prevalence (> 80-90%) of low HDL was observed across generations, i.e., from young to old. This observation in our target population is critical considering that epidemiological studies have established a strong inverse association between HDL concentrations with increased risk of coronary artery disease. For every mg/dl decrease in HDL, the risk for CAD increases by 2-3% [37]. However, the causality of this relationship is hard to prove [38].

Low HDL can be either monogenic or purely environmental or, in most cases is multifactorial/polygenic in origin [39]. HDL levels are under considerable genetic control with heritability estimates of up to 80% [40]. Besides, the high prevalence of low HDLC even in many individuals without obesity and hypertriglycemia, suggests an ethnic predisposition to this type of dyslipidemia. Reports of disproportionately high prevalence of low HDLC in South and Middle East Asia have been accumulating recently [41]. Gupta et al. suggested that this could be due to a high prevalence of hypoalphalipoproteinemia in the Indian population and needs to be confirmed in larger prospective studies [21]. Prevalence of high TG and low HDL-C might contribute to the high prevalence rate of MS in this study population. Metabolism and the genes associated with HDL and TG are reported, at least in part, to be linked to each other [42]. Further analysis is needed to explore the influence of life style, food pattern or physical activity of Bangladeshi rural women on such type of dyslipidemia.

The prevalence of many of the components of MS has been found to be increased over age in the present study. The prevalence of elevated fasting blood glucose and hypertension increased with age in rural Bangladeshi women. The overall prevalence of hypertension in this target population was 29.43%. This hypertensive rate is higher than previously reported, i.e., prevalence of 18.2% [43]. The higher prevalence of elevated BP in our subjects may be attributed to their higher intake of saturated fat and high calorie foods. Prevalence of high blood level of TG increased, peaking between 55 to 64 years. However, in the case of HDL level there was no age-specific prevalence. These patterns in prevalence, as revealed by the present study, were similar to those in a cross-sectional population survey in urban Asian Indian adults reported by [44]. Consistent to other reports [35], we also found an age-dependent increase in the prevalence of elevated fasting plasma glucose level. Thus from the present findings, we state that age might be a strong risk factor for the high prevalence of many of the components of MS in Bangladeshi rural women although the most common prevalent component (low level of HDL) did not shown any age-specific distribution pattern.

In the present study, elevated waist circumference is the least frequent component of MS in rural Bangladeshi women based on the ATP III criteria. The average waist circumference in this population was found to be 74.80 cm, which is consistent with another study of rural Bangladeshi women which reported a waist circumference of 68 cm [43]. Based on these findings, we speculate that many Bangladeshis women are metabolically obese but physically non-obese. In the present study, even when we re-evaluated our data using the modified Asian waist circumference cut-off, we still found that 18.05% of our participants did not have central obesity, even though they still had MS. Another point noteworthy is that both urban males and females had significantly higher WC and WHR (waist hip ratio) compared with their rural counter-parts, according to an Indian study by Das. This means that urban dwellers have a significantly higher central adiposity compared with rural dwellers [14]. We do not know whether there is a similar pattern in Bangladesh. We currently have an ongoing study assessing the profile of MS in Bangladeshi urban female population.

In our study, MS was significantly more prevalent among upper SES compared to lower SES which indicates SES as an emerging risk factor of MS in developing countries like Bangladesh and this finding is consistent with a study by Deepa et al., the prevalence of MS among persons belonging to middle income group was significantly higher compared to those from lower income group (18.7% vs. 6.5%) [45]. But it should be noted that the percentage of upper SES people were few in the present study population.

Few studies have demonstrated not only increased prevalence of diabetes but also other cardio metabolic risk factors including glucose intolerance and insulin resistance [46], central obesity, abnormal triglyceride and HDL among offspring of diabetic parents [47]. In our study, those with history of diabetes in either or both parents had significantly increased risk of having metabolic syndrome and other cardio metabolic risk factors including central obesity, abnormal triglyceride and HDL. Also, those whose both parents were diabetic were significantly more at risk than if only one of their parents had diabetes, thus showing evidence for genetic predisposition for developing metabolic syndrome and cardio metabolic risk factors. Similar result has been observed in a study done in 321 adolescent Indians [48]. In that study, the study subjects whose both parents had diabetes had significantly more prevalence of cardio metabolic risk factors as compared to those whose parents did not have diabetes. Thus genetic factors may play a potential role for MS development in Bangladeshi population.

The present report complements earlier MS reports performed in Bangladesh [7, 49]. The study by Rahim was also conducted in a rural community, but in the outskirts of Dhaka city. The criteria they used to assess the prevalence of MS were modified ATP vs. IDF vs. WHO and their findings based on these criteria were 25.1% vs. 15.7 vs. 9.2%, respectively. The figures obtained in their study were lower compared to the present study. Discrepancies in such studies are a common. For instance, the prevalence of MS in different parts of India varied from 11% to 41% [5, 36, 50]. The underlying causes for the observed differences between studies within the same region and country may be attributed to various factors, including the type of criteria employed (EGIR, ATP III and IDF), target age groups and variation in the pattern or sets of risk factors of MS. Bhopal's findings that a large proportion (65%) of women in Bangladesh had low HDL cholesterol level, are consistent with those of the present study [51].

In the present study, as we determined the prevalence of metabolic syndrome in Bangladeshi rural women, so we have difficulty in including the parameter work type (desk work type or physical work type) to our multivariate logistic regression analysis model. In current investigation, 45 (3.03% of total study participants) subjects were categorized to desk work and the most of the subjects fell into physical work categories (1345, 93.27% of total study participants) and some missing cases (55 subjects, 3.7% of total subjects). More intensive investigation is warranted in future in this respect. Through a cross sectional study design it is not possible to make a concrete interpretation at this regard.

The present manuscript shows MS is an important public health problem in Bangladesh although very few studies have been done on it. The high prevalence of MS may also have serious implications for health care costs in rural Bangladesh. Thus, studies designed to examine the direct medical costs associated with MS are urgently needed.

Several steps can be taken to reduce the prevalence of potential CVD risk factors in this population. A potential initiative for dietary modifications and enhanced physical activity may have implications to reduce this public health burden [52‐54]. While proper management of the individual risk factors and abnormalities of MS can reduce morbidity and mortality, a more integrated strategy will provide a better outcome. Implementation of the strategies cited here will require a community outreach. Thus, education and training of health care providers is critical. It is important to ensure that health care providers have the knowledge and skills necessary to not only treat MS patients but organized an effective MS prevention program to the community.

In conclusion, the present study reveals a high prevalence of MS in rural Bangladeshi women, with low serum HDL levels as the most common risk factor. These findings should prove useful in the formulation of health policies and prevention programs.