Study design and participants
An epidemiological, cross-sectional comparative, facility-based study was conducted between January 2018 and December 2019 in Khartoum State, the capital of Sudan. Various orthopaedic outpatient clinics were visited for the selection of the study sample. Postmenopausal women whose last menses were at least a year ago were eligible. In addition, women with no previous history of hepatic, renal, thyroid dysfunction, heart disease, diabetes, hypertension, hormonal replacement therapy, lowering lipid drugs, and/or medications that could alter bone metabolism or lipid profile were recruited.
Diagnostic criteria for osteoporosis and osteopenia
Dual-energy X-ray absorptiometry (DEXA) was used to measure bone mineral density (BMD) in g/cm2) in the proximal femur and lumbar spine using Hologic Inc. ASY00409 X-Ray Controller for Hologic Discovery Bone Densitometry. According to the symptoms, signs, and bone mineral density T-score, women were diagnosed by an Orthopaedic. Osteopenia was diagnosed with T-score of >-2.5 and ˂-1, whereas osteoporosis with a T score of ≤-2.5 based on the World Health Organization (WHO) diagnostic classification[17]. In the current study, women's results were presented based on having a normal T-score, osteopenia, or osteoporosis.
Data collection
Anthropometric measurements:
Weight was measured twice following published protocols. The OMRON - Body Fat Scale (BF508l, China) was used after being calibrated. Women were asked to remove heavy clothes, shoes and accessories and readings were taken to the nearest 0.1g. A portable stadiometer (SECA-213 model, Germany) was used after calibration to measure height twice, and women were asked to remove their shoes. Quetelet Body Mass Index (BMI) was calculated using standard formulas (weight in kilogram ÷ height in meters square). The WHO classification was used to define BMI as follows: underweight (<18.5 kg/m2), normal (18.5- 24.9 kg/m2), overweight (25.0- 29.9 kg/m2), obese (≥30 kg/m2) [18].
Waist circumference (WC) was measured twice using a non-stretchable measuring tape. Women fasted for 8 hours. Measurements were made at the approximate midpoint between the lower margin of the last palpable rib and the top of the iliac crest. Readings were taken from the right side of the body. The cutoff values associated with increased CVD risks in women were set at >88 cm [19].
Blood sampling and biochemical measurements
After a minimum of 8 hours of overnight fasting, peripheral blood (5mL) was drawn in plain containers. The lipid profile (total cholesterol, triglyceride, LDL-C, and HDL-C) was assayed in serum samples on the Roche/Hitachi Cobas c311 system (Roche Diagnostics GmbH, Germany). The precision and accuracy of the techniques used in this study were checked each time, and each batch was analyzed by including commercially prepared control sera. Serum cholesterol was classified as: normal <200 mg/dL, borderline 200-239 mg/dL, and high ≥240 mg/dL; triglycerides: normal <150 mg/dL, borderline high 150-199 mg/dL, and high ≥200 mg/dL; LDL-C: normal level <130, borderline high 130-159 mg/dL, high 160-189 mg/dL, and very high >189mg/dL; HDL-C: optimal ≥60mg/dL, borderline low 59-41 mg/dL, and low ≤40 mg/dL [24]. The Atherogenic Index of Plasma (AIP) was calculated as the logarithmical transformed ratio of molar concentrations of TG to HDL-C [20]. The AIP was classified as: low CVD risk <0.1, medium risk 0.1-0.24, and high risk >0.24 [20].
Furthermore, the number of CVD risk factors among women were independently calculated based on their BMI (>25kg/m2), serum cholesterol (>200 mg/dL), triglycerides (>150mg/dL), LDL-C (>130mg/dL), and HDL<40mg/dL.
Quality assurance
Data collectors attended three training sessions. These sessions included how to take anthropometric measurements, collect blood samples, and analyze blood samples.
Ethical considerations
Ethical approval was obtained from the Deanship of Scientific Research at the Sudan University of Science and Technology (NO: DSR-IEC-03-08). All the procedures used in this study met the current revision of the Helsinki Declaration. The study protocol was explained to women who provided a signed consent before the start of the study. It is important to note that the enrollment in the study was voluntary, and no incentives were provided to women.
Statistical analysis
Data were coded, and statistical analysis was performed with Social Package of Statistical Science (SPSS) version 26.0 (SPSS Inc., Chicago, IL, USA). The Kolmogorov–Smirnov test was used for testing the normality of continuous data (age, waist circumferences, BMI, total cholesterol and triglycerides, LDL-C, HDL-C levels). Continuous variables with normal distribution were presented as Mean (SD), whereas continuous variables with skewed distribution were presented as Median with Interquartile Ranges. The Analysis of Variance (ANOVA) test was used to determine the differences between the three groups of women. Spearman correlation was used to find the association between variables. The Multiple Linear Regression model was also used to determine the most significant risk factors which affected the T-score values. The significance level was set at ≤0.05.