Med. J. Cairo Univ., Vol. 80, No. 1, June: 391-396, 2012 www.medicaljournalofcairouniversity.com Correlation between Waist Circumference (WC), Body Mass Index (BMI) and Cardiometabolic Risk Factors in Egyptians EBTISSAM ZAKARIA, M.D.; MARY N. RIZK, M.D. and NASHWA S. GHANEM, M.D. The Department of Internal Medicine, Faculty of Medicine, Cairo University Abstract Introduction: Central obesity, a prominent feature of metabolic syndrome and obesity contributes to premature mortality from all causes of death. Obesity is not included in standard multivariable risk assessments because of major imperfections in its measurement. BMI performs poorly as a predictor of death except in very large population cohorts. More recently, assessing central obesity by measuring WC is supported by data that suggest superior prediction of CVD. WC is strongly correlated with risk for DM and CVD. Evidence suggests that anthropometric measurements as BMI, WC, or waist/hip ratio (WHR) assess metabolic risk better than measurements of percentage of body fat using dual-energy X-ray absorptiometry. The International Day for Evaluation of Abdominal obesity (IDEA) suggested that routine measurement of WC in addition to BMI is a useful clinical marker for CVD risk assessment even in patients with normal weight. Purpose: We aimed at comparing WC to BMI in correlating with the risk factors of metabolic syndrome and hence the development of the metabolic syndrome itself. We also aimed at identifying the mean cut off for WC among Egyptians. Material: This is a cross-sectional survey of 300 Egyptians, 241 males (54.3±10.2 years) and 59 females (52.6±9.91 years). Methods: A special questionnaire for personal data and clinical examination was used. We used International Diabetic Federation (IDF) guidelines for definitions of metabolic syndrome to compare Egyptian data with those of International ones. Anthropometric assessment was made using standardized equipment. Laboratory investigations (FBS, Cholesterol, LDL, HDL, and TG) were performed. Statistical analysis using SPSS version 17 was done. Results: Mean WC in this Egyptian sample of people is (higher for women 87.3±15.1cm) and lower for men (84±11.5cm) than IDF data. WC negatively correlated to HDL, and positively correlated to TG, FBS, SBP and age. Conversely, BMI positively only correlated to FBS. Conclusions: WC better correlates to metabolic syndrome parameters when compared to BMI. WC may also serve as a better anthropometric surrogate of visceral adipose tissue; Correspondence to: Dr. Nashwa S. Ghanem, The Department of Internal Medicine, Faculty of Medicine, Cairo University hence we recommend its inclusion in standard clinical examination. Key Words: Metabolic syndrome Obesity Waist circumference Cardiovascular disease Body Mass Index. Introduction THE current obesity epidemic poses a global concern because of its related health problems. Obesity increases the risk for diabetes mellitus (DM), hypertension, coronary heart disease, dyslipidemia, certain cancers, and obstructive sleep apnea, among other comorbidities [1]. The term "metabolic syndrome" has been used by various organizations to represent different entities. Some, such as the World Health Organization (WHO), have used this term to indicate a state of insulin resistance with dysmetabolism secondary to the former condition [2,3]. The International Diabetes Federation (IDF) in (2005) has come up with a convenient definition [4]. For a person to be diagnosed with metabolic syndrome he or she must have: Central obesity (defined as waist circumference >94cm for man and >80cm for women of European origin. Plus any two of the following four factors: Raised TG levels: >150mg/dL (1.7mmol/L), or specific treatment for this specific abnormality. Reduced HDL cholesterol: <40mg/dl (1.0mmol/L) in males and <50mg/dl (1.3mmol/L) in females, or specific treatment for this lipid abnormalities. Raised blood pressure: Systolic BP >130 and/or diastolic >85mm Hg, or treatment of previously diagnosed hypertension. Raised fasting plasma glucose (FPG) >100mg/dL (5.6mmol/L), or previously diagnosed type 2 diabetes. Later on the IDF and AHA/NHLBI representatives held discussions to attempt to resolve the 391
392 Correlation between Waist Circumference (WC), Body Mass Index (BMI) remaining differences between definitions of metabolic syndrome and produced the international consensus definition of metabolic syndrome in 2009 with WC cut off point use Population and country-specific definitions [5]. In south Asian countries (Chinese, Malay and Asian-Indian populations), the IDF defined the central obesity as waist circumference of >90cm for men and >80cm for women [6]. Other populations, e.g. Middle Eastern population (e.g. Egypt) have not had their standard central obesity cut offs identified. It is now well understood that obesity, in particular abdominal adiposity, is associated with increased risk of CVD and diabetes mellitus. As Yusuf et al., [7] demonstrated, obesity as one of the nine easily evaluated, modifiable risk factors (abnormal lipids, smoking, hypertension, diabetes, abdominal obesity, consumption of fruits, vegetables, alcohol and physical activity), that account for more than 90% of Acute myocardial infarction (AMI) risk. However which obesity indicator is better predictor of metabolic risk? Evidence suggests that anthropometric measurements like (BMI, WC, WHR) assess metabolic risk better than measurements of percentage of body fat using dual-energy X-ray absorptiometry [8]. The International Day for Evaluation of Abdominal obesity (IDEA), a cross-sectional, study of more than 168,000 primary care patients, suggested that routine measurement of WC in addition to BMI is a useful clinical marker for CVD risk assessment even in patients with normal weight [9]. (WC) is widely advocated as a marker of health risk and is a key diagnostic criterion for metabolic syndrome (MS). It is adovacted that waist circumference (WC) may predict increased risk of morbidity [10] and mortality [11] beyond that explained by BMI alone [12]. An expert panel, organized by the National Heart, Lung, and Blood Institute (NHLBI), has recommended that WC be measured as part of the initial assessment and be used to monitor the efficacy of weight-loss therapy in overweight and obese patients who have a BMI <35kg/m 2 [13]. Objectives: Compare between WC and BMI in correlating with the risk factors of metabolic syndrome and hence the development of the metabolic syndrome itself. In addition, we aimed at identifying an average Egyptian cut off point for waist circum- ference among 300 Egyptian randomly chosen patients in our referral center at Kasr Al-Ainy hospital, internal medicine outpatient clinics. Subjects and Methods This is a cross-sectional study done in Internal Medicine and Cardiology Outpatient Clinics in Kasr Al-Ainy hospital during the period march 2009 - September 2009. The first 300 patients in the outpatient clinics were randomly recruited with ages (52.6±9.91 years), 241 males and 59 females. Informed consent was obtained from patients participated in the study. Inclusion criteria: Any two of the following four factors: - Raised TG levels: 150mg/dl (1.7mmol/L), or specific treatment for this specific abnormality. - Reduced HDL cholesterol: <40mg/dl (1.0mmol/ L) in males and <50mg/dl (1.3mmol/l) in females. - Raised blood pressure: Systolic BP 130 or diastolic 85mm Hg, or currently on treatment for hypertension. - Raised fasting plasma glucose (FPG) >100mg/dl (5.6-7.0mmol/L). Exclusion criteria: - Subjects who are pregnant. - Subjects with hernia. - Subjects with ascites. For all subjects the following was done: Personal history (name, sex, age, occupation, smoking, alcohol intake). Past history (angina, vascular disease, cardiovascular intervention) and other diseases (DM, HTN, Dyslipidemia, Stroke, Others). Complete clinical examination, laboratory investigation (FBS, Cholesterol, LDL, HDL, TG). Anthropometric assessment was then made using standardized equipment. Body weight was measured with minimal clothing (for which no correction was made) using Seca scale and approximated to the nearest 0.01kg. Height was measured without shoes using a Holtain portable anthropometer and approximated to the nearest 0.1cm. Waist circumference was taken at the end of normal expiration, midway between the inferior margin of the ribs and the superior border of the iliac crest using a flexible non stretchable plastic tape and approximated to the nearest 0.1cm [14]. Statistical analysis: Result was analysed using SPSS software, version 17. Distribution and fre-
Ebtissam Zakaria, et al. 393 quencies of independent variables were examined. Correlations analyses were done by pearson s correlation coefficient. All data are expressed as mean values ± SD (standard deviation). Results Women were more frequently younger in age and have higher BMI & W.C but lower HDL than men; conversely, men presented with older age, and had higher TG, SBP, DBP & FPG & HDL than women. W.C is higher for women in our study (87.3± 15.1cm) but lower for men (84±11.5 cm) than IDF guidelines. On applying IDF classification (cut-off pint) to our study group, we observe that 92% of our study sample have elevated W.C (90cm for men & 80cm for women), 71% have SBP 130 mmhg, 81% have DBP 85mm Hg, 68% have FPG 100mg/dl, 62% have TG >150mg/dl & 52% only have HDL 40 <mg/dl. Correlation of W.C & BMI with age show that increase age is associated with increase in W.C. but not with increased BMI. Correlation of W.C & BMI with TG show that increase WC is associated with increase in TG, whereas increase in TG is not associated with increase in BMI. Correlation of W.C & BMI with HDL show that increase HDL is associated with decrease in W.C., whereas no association was found between HDL & BMI. Correlation of W.C & BMI with FBS show that increase W.C & BMI is associated with increase in FBS. Correlation of W.C & BMI with SBP show that increase W.C is associated with increase in SBP as well as diastolic blood pressure, whereas increase in BMI is not associated with elevation of either systolic or diastolic blood pressure. Table (1): Anthropometric, clinical & laboratory characteristics of subjects by sex. Females Males Age (yrs) 52.6±9.91 54.3±10.2 BMI (Kg/m 2 ) 37.889±5.028 29.7±3.2 W.C (cm) 87.3±15.1 84±11.5 TG (mg/dl) 120±35.5 128.4±34.82 HDL (mg/dl) 40.53±5.5 43±4.6 SBP (mmhg) 125.33±18.75 138.2±17.5 DBP (mmhg) 77.6±10.33 83±10 FPG (mg/dl) 137.47±29.93 143±27.2 *Results are presented as mean ± standard deviation. 130.0000 120.0000 110.0000 100.0000 Observed Linear W.C 90.0000 60.000 90.000 120.000 150.000 180.000 45.0000 40.0000 35.0000 30.0000 Observed Linear TG Fig. (1): Scatter plots and regression line for correlation between W.C and TG show that increase WC is associated with increase TG ( r=0.710). BMI 25.0000 60.000 90.000 120.000 150.000 180.000 TG Fig. (2): Scatter plots and regression line for correlation between BMI and TG (r= 0.031). Scatter plot graphs & correlation of BMI with TG show that increase in BMI is not associated with increase in TG. Table (2): Correlation between W.C & other variables. WC Age TG HDL SBP DBP FBS WC Pearson 1.588.710.396.410.217.188 Correlation Table (3): Correlation between BMI & other variables. BMI Age TG HDL SBP DBP FBS BMI Pearson 1.283.031.038.236.555.231 Correlation Discussion There is strong ongoing controversy regarding which obesity marker is more predictive of metabolic syndrome. Whether obesity markers such as waist hip ratio (WHR), Waist circumference (WC), and Neck circumference (NC) [15,16], might actually
394 Correlation between Waist Circumference (WC), Body Mass Index (BMI) be more predictive regarding metabolic syndrome than BMI, remains an open debate that we tried to solve in this study. In this study the International Diabetic Federation (IDF) guidelines 2005 was used as it is one of the most convenient, widely used, definitions of metabolic syndrome at time of study design to compare Egyptian cut points with those of international ones. This study aimed at comparing between WC and BMI in correlating with the risk factors of metabolic syndrome and hence the development of the metabolic syndrome itself. In addition, it aimed at identifying an average Egyptian cut off for waist circumference among 300 Egyptian randomly chosen patients in our referral center of Kasr Al-Ainy Hospital, Internal Medicine Outpatient Clinic. We found that most of our subjects were men 80% & 20% were women. Most of subjects were in their forties and fifties. Hence, we anticipated that the prevalence of metabolic syndrome is high. This was close to the age of subjects in a study done in Switzerland where the mean age was 51 for women and 53 for men [17]. In our study, women had a higher BMI & W.C but lower HDL than men; conversely, men presented with older age & had higher TG, SBP, DBP, FPG & HDL than women. BMI for women and men is more in this study (37.889±5.028 & 29.7±3.2Kg/m 2 ) than in the Swiss study (25±4.8 & 26.5±3.9Kg/m 2 ) for women and men respectively. This is due to the high prevalence of obesity in Egypt [18]. TG level was lower for women and men in this study (120±35.5 & 128.4±34.82mg/dl) respectively than in a study done in Iran (138 & 149mg/dl) for women and men respectively [18]. HDL is lower for women in this study (40.53±5.5mg/dl) but nearly equal for men comparing to previous study in Iran (50.12±12.06 & 42.79±11.93mg/dl). Little information is available on physical activity, but this could also be attributed to the lack of physical activity among Egyptian women more than Egyptian men. SBP measurement is higher in our study among both women and men (125.33±18.75 & 138.2± 17.5mm/Hg respectively than in Iranian study (121.43±20.59 & 125±16.76mm/Hg), on the other hand, DBP measurements are not so different between our study (77.6±10.33 & 83±10) for wom- en and men respectively, and Iranian study (78±10.32 & 79.49±8.55). A possibility of high salt intake in the Egyptian population could be anticipated as a reason for these differences but warrant further study. FPG measurements are higher in women and men in this study (137.47±29.93 & 143±27.2mg/dl) respectively than the study done in Iran (100mg/dl for women and men). The prevalence of diabetes in Egypt is estimated at 5%-8% and this level is increasing over time. In fact, it is announced that Egypt will be one of the top ten countries in diabetes prevalence, by year 2030 [3]. The prevalence of diabetes mellitus and of hypertension in Egypt parallel that of obesity, and both are very high. A large proportion of the population is quite sedentary, particularly in the cities [18]. We observed-according to IDF-that 92% of our study sample have elevated W.C (90cm for men & 80cm for women), 71% have SBP 130 mmhg, 81% have DBP 85mm Hg, 68% have FPG 100mg/dl, 62% have TG >150mg/dl & 52% have HDL 40<mg/dl. We have found that the mean WC in Egyptian sample of people is 87.3cm for women and 84cm for men compared to IDF guidelines which are 80cm for women and 90cm for men (which is higher for women and lower for men in Egyptian population). This would provide a different cutoff to be taken into consideration among the Egyptian population. Using Pearson correlation coefficient, our study showed that waist circumference was positively correlated with a variety of metabolic syndrome risk factors, in contrast to Body Mass Index which was not. Namely, WC negatively correlated to HDL, and positively to TG, FBG, SBP and age. On the other hand, BMI had only positive correlation to FBG and HDL. Hence, WC would be a better prognostic criterion for metabolic syndrome parameters when compared to BMI. It can also serve as a better anthropometric surrogate of visceral adipose tissue, with a better predicting capacity of mortality and morbidity of metabolic syndrome than BMI. This was supported by the work done by De Koning et al., 2007 [19] as well as Yusuf et al., 2005 [10]. The role of abdominal (visceral) obesity and the underlying molecular and cellular mechanisms central to this association have been the subject of intensive research in recent time. Metabolic syndrome is associated with a pro-inflammatory state,
Ebtissam Zakaria, et al. 395 and the role of visceral obesity leads to alteration of the normal physiological balance of adipokines, insulin resistance, endothelial dysfunction and a pro-atherogenic state. In association with this, the presence of conventional cardiovascular risk factors such as hypertension, dyslipidaemia and smoking results in a significantly elevated cardiovascular and metabolic (cardiometabolic) risk. Better understanding of the molecular mechanisms central to this association has lead to the development of potential therapeutic agents [6]. Our sample is representative of a large single referral institution. We need to expand the sampling and incorporate other health institutions to reach better cut off points. Nevertheless, it represents a red flag of warning against the ever increasing consequences of our sedentary lifestyle especially among Egyptian females. Conclusions and Recommendations: Obesity epidemic is directly linked to cardiovascular risk, and is now considered as a major, independent risk factor for atherosclerosis. Obesity should be considered as a disease requiring treatment and more importantly prevention in the general population. WC reflects the magnitude of the abdominal fat tissue, including subcutaneous and visceral adipose tissue. Although it is a simple and crude measurement, it has been shown to confer an increased risk for DM, CVD, and mortality, independent of BMI. It is now clear that different ethnic groups should be assessed according to their race-specific cutoffs to improve risk evaluation. We have attempted to identify preliminary Egyptian cutoff standards for WC, so further study is needed to specify ethnic-specific WC values. National standards for waist circumference are needed to study trends, and the likely medical and psychological costs of, obesity in Egyptian people. 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