This population-based study demonstrated a continued high prevalence of T2DM, IFG, and IGT in urbanizing rural Bangladesh consistent with previous study [10
]. Like the former study this study results also showed that the prevalence of IGT was slightly higher than that of IFG [10
]. The prevalence of IFG and T2DM were significantly higher in males but no such sex difference was observed for IGT and IFG+IGT cases. Male had higher prevalence of DM in all age groups compared with female subjects in our study. The difference in prevalence by sex widened in the older age strata. However, earlier data had shown a higher prevalence of DM among female subjects [20
]. Gender difference was not significant in India [22
], though non-significant higher prevalence of T2DM was found among women in another investigation in India [7
]. Higher prevalence of DM in women was also reported from Turkey and Pakistan [23
Studies conducted in Mauritius [25
], and Pima Indians in United States [26
] observed more IGT prevalence compared to IFG [27
]. However, studies conducted in the Netherlands [28
], Finland [29
], India [30
], and among Asian Americans [31
] did not find any difference in the prevalence of IFG and IGT.
The findings of this study showed that when FPG ≥7.0 mmol/L was used as the diagnostic criterion, the prevalence of diabetes was 6.7%, whereas it was 6.0% when the 2hPG values (≥11.1 mmol/L) were used. This finding is also consistent with previous studies in Bangladesh although they used different cut values and methods [10
]. This finding is an agreement with an Indian study where the prevalence of diabetes was 5.2% according to the FPG criteria and 4.3% according to 2hPG threshold [32
] but opposite to an Australian study [33
]. Furthermore, data showed a good agreement between the two procedures (FPG and 2hPG) for the identification of diabetic cases. Concern has been expressed that IFG might not identify the same subjects as IGT [32
]. However, the prevalence of glucose intolerance by either procedure was similar (by FPG [IFG+T2DM] was 12.0% or 2hPG [IGT+T2DM] was 12.2%). Given the higher prevalence of IFG and IGT, it can be reasonably being expected that the prevalence of diabetes will continue to increase in this population in near future.
Study found higher BMI, waist and WHR among subjects with impaired glucose regulation and it was consistence with previous two studies conducted in this population [10
]. In this study, both β-cell dysfunction (decrease insulin secretion) and insulin resistance (unusual expression) were more in diabetic as compared to normal individuals. In T2DM cases loss of insulin sensitivity was significant in both sexes which was just opposite to previous studies conducted in Bangladesh in different time point where insulin secretory defect had contributed more to the development of T2DM [34
]. Observation of this study is more consistent with those of western population where insulin resistance is thought to be the predominant defect in T2DM [36
]. Increased environmental influences like urbanization, physical inactivity, obesity and stress might be the most probable reason for this difference.
Another main issue in the present survey was the risk indicators that affected the development of DM. The present data showed that age, WHR, SBP, TC, TG and depression were variables that could predict the development of DM. In the present study, it was confirmed that the WHR, a measure indicative of central obesity, is a major risk indicator of DM which was also evident in previous studies in Bangladesh [12
]. Despite the fact that Asians have lower BMI than Western counterparts, some Asian countries have a similar or even higher prevalence of diabetes than Western countries. This finding is explained by the observation that Asian populations are more prone to abdominal obesity with increased insulin resistance compared with their Western counterparts. Therefore, central obesity is a useful marker as a risk of T2DM, especially in individuals with normal BMI values [38
The study found association of increased TC and TG with T2DM and increased TG and lower HDL with impaired glucose regulation. But these associations were contradictory to an earlier rural study [9
] though we got identical result in an urban study [35
]. These results indicate that dyslipidemia which is common in T2DM may start earlier, i.e., in prediabetic condition, even before the onset of DM. In accordance with previous studies, SBP was significant predictor of DM [20
]. Family history of DM, physical inactivity and smoking habit were not significantly associated with DM or impaired glucose regulation in this study. However, positive association was reported in a previous rural Bangladeshi study [9
]. Confounding effects of age, gender, and occupation on the activity level might be the possible explanation of non-significant association of physical inactivity with DM in this study population.
Along with the conventional risk indicator this study found significant association of depression with DM (odds ratio, 3.52; P
<0.001) and impaired glucose regulation (odds ratio, 2.44; P
<0.001) in our urbanizing rural population. Study findings are consistence with the previous findings [40
]. Along with the previous findings this study data emphasis that depressive symptoms in this culture are common, especially in those with diabetes. Psychotherapy may be necessary in addition to lifestyle changes to prevent the exponential increase in the occurrence of T2DM. In addition, a common approach including psychiatric treatment in diabetes care may be necessary to achieve improved glycaemic control in this population.
The strength of the study was that it was a population based cross-sectional study to find the prevalence of subjects with varying degrees of glucose tolerance with associated cardiometabolic risk factors in an urbanizing rural area. So far this was one of the recent studies reported from the urbanizing rural population in Bangladesh. Bias was taken care of by random sampling.
The limitation of the study was that, the prevalence among adolescents was not included. The increase prevalence in the present report is not likely to be the true prevalence of diabetes in overall urbanizing rural population of Bangladesh. The study area was selected purposively as a semi-urban, 40 km far from Dhaka and the sample size was not so large as to represent the real picture of the country burden of diabetes.
In conclusion, the higher prevalence in the present study indicates the environmental factors may encompass a strong role for the rising prevalence of diabetes in urbanizing rural population in a developing country like Bangladesh. So, from this study it can be concluded that major cardiometabolic risk factors like hypertension, dyslipidaemia, central obesity (WHR) and insulin resistance associated with depression arise before the onset of diabetes, i.e., in prediabetic condition which is also associated with diabetes and cardiovascular diseases. If the risk factors of prediabetic subjects can be diagnosed earlier, it will be easier to prevent diabetes in a resource constraint country like Bangladesh. This study further recommends a longitudinal study to demonstrate the importance of modifying risk indicator for the development of DM and reducing its prevalence in Bangladeshi population.