This study was conducted in Chattogram, Bangladesh from July 2018 to December 2019. A total of 247 study sample were collected by a stratified cluster random sampling method from general attendees at Chattogram Diabetic General Hospital, Chittagong, Bangladesh. They were interviewed face-to-face by trained interviewers using written questionnaires (13). The protocol was approved by the ethical review committee of the Diabetic Association of Bangladesh (DAB). All the study steps were performed in accordance with the Helsinki Declaration. After collection, data were checked thoroughly for consistency and completeness by calling over the telephone and visiting their residents. After the exclusion of 69 participants with a family chronicle of diabetes, cardiovascular disease or stroke, 178 participants endured for this study. Moreover, we rejected 23 participants who provided missing information on dietary intake, 26 participants who did not provide blood samples, 14 participants who rendered incomplete anthropometric information and 7 participants who self-reported a history of taking medications (these medications may affect serum lipoprotein concentrations, blood pressure, and carbohydrate metabolism). Finally, 108 participants persisted for the present analysis of the associations between dietary patterns and the risk of T2D.
Dietary intakes of study participants were obtained by trained interviewers with a validated and reliable food frequency questionnaire (FFQ) used in previous studies in Bangladesh. Interviewers have averaged 6 years of data collection experience, and quality of collected data was assured through standardized training exercise and variable definitions, peer review of forms prior to submission, weekly meetings to discuss issues as they came up, and rechecking when any errors were identified during data entry. The FFQ consisted of 172 food items with standard portion sizes usually consumed by Bangladeshi participants. They were asked to recall the frequency of each food item during the previous year on a daily, weekly, monthly, and yearly basis. Each food item frequency was classified into never, less than 1 time/month, 1 to 3 times/month, 1 to 2 times/week, 3 to 4 times/week, 5 to 6 times/ week, 1 time/day, 2 times/day, and 3 times/day. Finally, data were converted into grams (g)/day or mL/d in the following analysis.
Then, 172 food items from the FFQ were aggregated into 27 food groups based on their similarity in nutrients and earlier studies to identify dietary patterns. Factor analysis (principal component) was conducted on the 27 food groups and obtained factors were rotated using orthogonal rotation so that the factors/dietary patterns were uncorrelated with each other and were easier to interpret. The eigenvalue and scree plot were applied to decide which factors remained (16). After evaluating the eigenvalues, the scree plot test, and interpretability, factors with an eigenvalues ≥2.0 were retained. Individual food items with a factor loading ≥|0.4| were considered to significantly contribute to the pattern in this study.
The labeling of dietary patterns was based on the interpretation of foods with high factor loadings for each dietary pattern. Factor scores were categorized into quartiles (Q1 represented a low intake of the food pattern; and Q4 represented a high intake of the food pattern). Two major dietary patterns were extracted: the traditional Bangladeshi dietary pattern (high in cereal, pulses, legumes, vegetables, fish and seafood, vorta/mashed vegetables, egg, street food, milk, and indigenous pitha/homemade cake) and the Western dietary pattern (high in meats, nuts, seeds and their products, processed meat, processed fish, eggs, fast foods, snacks, chocolates, ice cream, sugar-sweetened beverages, tea, and coffee).
Prior to blood pressure measurements, participants were first rested in the sitting position for five to ten minutes. Then, measurement was taken by one trained personnel with a standard mercury sphygmomanometer and the mean of three consecutive measurements was considered as the participant’s blood pressure. To evaluate fasting plasma glucose (FPG), blood samples were taken from all participants after 10-12 hours overnight fasting. Samples were allowed to clot at room temperature for 1-3 h and serum was separated by centrifugation for 15 min at 3000 rpm. Finally, FPG was measured on the day of blood collection according to a standard protocol using an auto analyzer. T2D was defined as the presence of any one of the following: (i) FPG≥7.0 mmol/L on at least two separate occasions, or an oral glucose tolerance test (OGTT) with a value≥11.1 mmol/L (15); (ii) current use of insulin or oral hypoglycemic agents; or (iii) a positive response to the question: Have you ever been diagnosed with diabetes by a doctor?