We carried out a health survey in urban Mwanza, the second largest city in Tanzania located on the shore of Lake Victoria. Participants were 97 men aged 20 to 50 years who were informed of the purpose and procedures about the study and signed an informed consent form. The study included a BP survey, anthropometrical measurements, blood and 24U collection and a lifestyle questionnaire. This study was approved by the Ethics Committees of Mukogawa Women’s University and Weill Bugando University College of Health.
All measurements and blood sampling were performed by an experienced physician and a nurse at a local community healthcare centre or hospital. Body weight and height were measured with subjects standing and wearing light clothes. From these results, body mass index (BMI; weight (kg) / height (m)2) was calculated. Waist circumference (WC) was measured using a flexible steel measuring tape. Blood pressures and pulse rates were measured after a 5- to 10-minute rest using an automatic digital BP measurement system (Omron Digital HEM-907, Tokyo, Japan). The mean of 3 readings was used in this analysis.
Blood samples were taken after at least 10 hours of fasting. Blood analyses including serum total cholesterol (TC), HDL-C, TG, FBG, haemoglobin A1c (HbA1c), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were assessed at SRL Inc. (Tokyo, Japan). Enzymatic methods for TC, HDL-C, TG and FBG, a latex agglutination method for HbA1c and a gas chromatographic method for EPA and DHA were performed. Non-HDL-C was calculated by subtracting HDL-C from TC. The atherosclerosis index (AI) was calculated as non-HDL-C / HDL-C.
24U was collected using an aliquot cup (Izumi Seisakusho, Osaka, Japan) and various markers of diets were analyzed, including creatinine, Na, K and Tau. Na and K were determined by electrode methods and creatinine was analyzed by enzymatic method. Tau was assessed using high performance liquid chromatography. Sodium-potassium ratio (Na/K) was calculated by the measured values and the amounts of daily excretion for Tau and sodium chloride (NaCl) were also calculated by the 24U volume. Success or failure in 24U collection was judged from the diagnostic criteria based on calculated values of the daily creatinine excretion in 24U. The results of those who failed to complete 24U collection were excluded from the analyses.
We used International Diabetes Federation (IDF) criteria to define the MS risks: WC ≥ 94 cm, BP ≥ 130/85 mmHg, FBG levels ≥ 100 mg/dl (5.6 mmol/l), TG levels ≥ 150 mg/dl (1.7 mmol/l) and HDL-C levels < 40 mg/dl (1.0 mmol/l) in men. Since the criteria was set to be lower than other criteria such as in the WHO or the National Cholesterol Education Program-Adult Treatment Panel ⊠ definitions, we could detect people having MS risks at an earlier stage.
Intake frequency was assessed using a food frequency questionnaire about 135 food items. For each, eating frequency was assessed and categorized into 9 levels; never in a month, 1 to 3 times per month, once per week, 2 to 4 times per week, 5 to 6 times per week, once per day, 2 to 3 times per day, 4 to 5 times per day and 6 or more times per day. For simplification in some cases for analyses, they were divided into 4 groups; less than once per month, 2 to 4 times per week, 5 to 6 times per week and more than once per day. Furthermore, information regarding employment, education, alcohol intake, smoking, medical history and physical activity were recorded.
Differences between young adults and the middle-aged were investigated using the Student’s t test. Prevalence rates of MS risk factors were compared using a chi-square test. Relationships between two parameters were assessed by a calculation of Pearson’s correlation coefficients. To compare characteristics among the three groups classified by the excretion levels of Tau in 24U, analyses of one-way variance was used. All statistical analyses were undertaken using the SPSS for windows package version 15 (SPSS Inc, Chicago, IL). Results are presented as means ± standard deviations. A P value of 0.05 was set as the level of significance.