Prevalence and associated factors of metabolic syndrome among a national population-based sample of 18–108-year-olds in Iraq: results of the 2015 STEPS survey

This study aimed to assess the prevalence and associated factors of the metabolic syndrome (MetS) among 18–108-year-old persons in Iraq. Nationally representative cross-sectional data were analysed from 3703 18–108-year-old persons (32 years median age) that participated in the “2015 Iraq STEPS survey,” with complete MetS measurements. Results indicate that 39.4% of 18–108 year-olds had MetS (harmonized definition), 39.8% among women and 39.0% among men, and the mean number of MetS components was 2.4 (SD=1.4), 2.4 (SD=1.4) among women and 1.5 (SD=1.4) among men. In adjusted logistic regression analysis, aged 60–108 years (adjusted odds ratio (AOR) 6.69, 95% confidence interval (CI) 4.82–9.29), current smoking (AOR 1.38, 95% CI 1.01–1.90), past smoking (AOR 1.54, 95% CI 1.00–2.36), general overweight (AOR 4.87, 95% CI 3.07–5.63) and obesity (AOR: 8.33, 95% CI: 6.27–11.07) were associated with MetS. In adjusted linear regression analysis, aged 60–108 years (beta 1.21, 95% CI 1.06 to 1.37), male sex (beta 0.23, 95% CI 0.12 to 0.34), overweight (beta 0.77, 95% CI 0.64 to 0.90) and obesity (beta 1.27, 95% CI 1.13 to 1.40) were positively and having more than primary education (beta −0.22, 95% CI −0.34 to −0.09) was negatively associated with greater number of MetS components. Two in five participants had MetS and several associated indicators were found which could be supportive in designing intervention activities.


Background
Noncommunicable diseases (NCDs) are "estimated to account for 55% of all deaths in Iraq in 2016," which include 27% cardiovascular diseases and 4% diabetes [1]. Compared with people without metabolic syndrome (MetS), individuals with MetS have a twofold higher risk for cardiovascular disease and a fivefold higher risk for type 2 diabetes [2][3][4]. "A cluster of risk factors for cardiovascular disease and type 2 diabetes mellitus, which occur together more often than by chance alone, have become known as the metabolic syndrome." [5] "The risk factors include raised blood pressure, dyslipidemia (raised triglycerides and lowered high-density lipoprotein cholesterol), raised fasting glucose, and central obesity." [5] Globally, it is estimated that "25% of the adult population can be characterized as having MetS." [2,6] The prevalence of MetS is increasing in low-and middle-income countries with "improvement in economic situation, increasing urbanization, nutrition transition, and reduced physical activity." [7] To prevent and control MetS, it is important that national populationbased surveys are conducted periodically [8]. There is a lack of national population-based data on the prevalence and associated factors of MetS in Iraq, an upper middle-income country in the Middle East.
Factors that are associated with the prevalence of MetS include sociodemographic, health status and health risk behavior/s related variables. Sociodemographic factors associated with MetS may include, female sex [18,[19][20][21], older age [12,13,18,19,21], higher education [19], lower education [13,15], higher income [15] and urban residence [12,18,19]. Health status variables associated with MetS may include higher body mass index, general overweight or obesity [19,20] and abnormal waist-to-hip ratio [19,20]. Health risk behavior/s variables associated with MetS may include physical inactivity [20,21], low leisure-time physical activity [22], sedentary behaviour [23], combined physical inactivity and inadequate fruit and vegetable intake [24], low intake of fruits and dairy foods [25] and inadequate fruit and/or vegetable consumption [26][27][28]. In addition, frequent smoking [16], current smoking [29,30] and former smoking [31] are associated with a higher risk of MetS. Regarding alcohol use, some studies found that mild to moderate alcohol use decreased and heavy alcohol increased the risk of MetS [32,33], while other studies showed a positive association between current alcohol use and MetS [16]. The study using the Iraq STEPwise approach to noncommunicable disease risk factor surveillance (STEPS) 2015 data aimed to assess the prevalence and associated factors of MetS among 18-108 year-old persons in Iraq.

Participants and procedures
This is a secondary analysis conducted using nationally representative population-based and cross-sectional data from the "2015 Iraq STEPS survey" [34]. "STEPS focus on obtaining population-based data on the established risk factors that determine the major disease burden" [34]. "STEPS surveys collect data at three levels: Step 1-Questionnaire-based assessment includes socio-economic data, data on tobacco and alcohol use, nutritional status, and physical inactivity; Step 2includes simple physical measurements, such as height, weight, waist circumference, and blood pressure; and Step 3-includes biochemical measurements" [34]." The 2015 Iraq STEPS survey data and more detailed survey methods can be accessed; the overall response rate for STEP III was 93.5%, STEP II 98.6% and STEP I 98.8% [34,35]. Briefly, a "multistage cluster sampling was used with stratification to urban and rural areas. Primary sampling units (PSUs) (N=412) were the blocks, which consisted of 70 households or more before selection. One person from each household was randomly selected." In total, 4071 persons 18 years or older were potentially eligible in this study. However, 368 individuals were excluded from this analysis since they did not have complete MetS measurements so that 3703 participants were included in the final data analysis. Comparing participants with complete and without complete MetS measurements, there were no significant differences in terms of educational background, residence status, physical activity level, sedentary behavior/s, fruit and vegetable consumption, passive smoking, alcohol use and body weight status. However, compared to participants with complete MetS measurements, participants without complete MetS measurements were younger (p=0.018), women (p<0.001) and smokers (p=0.016).
Sample size calculation In three local studies in different institutions and hospital outpatients in Iraq [9][10][11], the average prevalence of MetS was 36%. Based on this information, the sample size was calculated with an expected MetS prevalence of 36%, acceptable margin of 5% and clusters 412; the minimum sample for each cluster is 2, the minimum sample is 824. In this study, we used all 3703 participants for the analysis.

Outcome variable: metabolic syndrome
The harmonized definition of MetS was used, including three or more of any of the following five risk factors [5]: (1) "Elevated waist circumference (waist ≥97 cm in men, ≥99 cm in women) [ Body mass index (measured <18.5 kg/m 2 underweight, 18.5-24.4 kg/m 2 normal weight, 25-29.9 kg/m 2 overweight and ≥30 kg/m 2 obesity) was measured; blood pressure (BP) measurements (average of the last two of three readings) were conducted with an electronic blood pressure monitor Spengler® ES 60. Blood samples were drawn in the morning (after 10-14 h fasting, respondents on medication for diabetes were asked to postpone taking the medication until after drawing the blood sample) and centrifuged. Levels of "fasting plasma glucose and fasting total cholesterol and lipid profile were determined using the enzymatic method (glucose oxidase for fasting blood glucose and cholesterol oxidase for total cholesterol)." [35] "Absorption were read utilizing (Visible Light Spectrophotometer) instrument [35]." Health risk behaviour variables included current and past smoking, past months passive smoking in home and/or at closed spaces at work, ever alcohol use, inadequate fruit and vegetable intake (<5 servings/day) and based on the "Global Physical Activity Questionnaire" low, moderate or high physical activity and sedentary behavior/s (≥8 h/day) [35].

Data analysis
Statistical analyses were done with the STATA software version 15.0 (Stata Corporation, College Station, TX, USA), taking into account the complex study design. The data were weighted to make the sample representative of the target population in Iraq (by sex and by age group, 18-39, 40-59, 60 and over). [35] Prior to data analyses, the normal distribution of the study variables was examined. The P-P-plot analyses and K-S tests of normal distribution showed that the study variables fulfilled the postulation of normal distribution. Chi-square tests were used to test for differences in proportions. Unadjusted and adjusted logistic regression was used to assess predictors of MetS and linear regression for the number of MetS components. Covariates were included based on a previous literature review [12,13,16,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. Explanatory variables are statistically significant at p<0.05 and are free from multicollinearity as measured by the variance inflation factor (VIF < 1.8). Missing values (<1.2% for any study variable) were excluded from the statistical analysis. p<0.05 was accepted as significant.

Sample and MetS status characteristics
The sample comprised of 3703 18-108-year-old persons (32 years median age, 22 years interquartile range) with complete MetS measurements. More than one in five of the participants (59.5%) were female, 37.6% had more than primary education and 75.9% lived in urban areas. More than one in ten participants (21.3%) reported current smoking, 7.3% past smoking, 60.3% past month passive smoking, 2.5% ever alcohol use, 79.5% inadequate fruit and vegetable intake, 52.3% low physical activity, 26.3% sedentary behaviour and 34.0% obesity. The prevalence of MetS was 39.4%, 39.8% among women and 39.0% among men, and the mean number of MetS components was 2.4 (SD=1.4), 2.4 (SD=1.4) among women and 2.5 (SD=1.4) among men (see Table 1).

MetS components
Overall, high WC was 43.8%, high BP 51.0%, high FBC 31.8%, high TG 35.4% and low HDL 54.5%. Low HDL was significantly higher in women than in men, and high TG was significantly higher among men than women, while high WC, high BP and high FBG did not differ significantly between the sexes. All five MetS components did not significantly differ by residence status. Between both sexes, all five MetS components significantly increased with age. Among men, high WC, high BP and high FBG increased with age, high TG increased from the 18-39 year-old age group to the 40-59 year-old age group and decreased among the 60 years and older age group. Low HDL did not significantly differ among age groups in men. Among men, high BP, high FBG, high TG and low HDL increased with age, while high WC increased from the 18-39-year-old age group to the 40 to 59-year-old age groups and slightly decreased among the 60 years and older age group (see Table 3).

Discussion
The investigation aimed to estimate the prevalence and correlates of MetS in a national population-based survey among 18-108year-old persons in Iraq. The prevalence of MetS (harmonized definition) (39.4%) in 2015 seems higher than global estimates (25%) [2,6], and similar to different local studies in Iraq, in different institutions in Erbil City (30.6%, ATP IV criteria) [9], in a hospital outpatient sample (30-75 years) in Baghdad (42%, IDF criteria) [10] and among outpatients (25-85 years) in Baghdad (37.8%, ATP III criteria) [11], and probably similar to national estimates in 2004-2005 in Tunisia (30.0%, NCEP-ATPIII definition) [12], in 2012 in Qatar (37%, IDF definition) [13], in 2007 in Iran (24-64 years) (37.4%, IDF definition) [14], and higher than in 2005 in Saudi Arabia (28.3%, IDF definition) [15], in 2009 in China (21.3%, Revised NCEP ATPIII definition) [16] and in 2015 in Ethiopia (4.8%, IDF definition) [17]. Some of the country differences in the prevalence of MetS may be related to the different definitions used for MetS, different age groups are analysed and some studies are older with probably having lower rates of MetS. For example, in a recent study (2017) among adults (18-100 years) in Morocco, the prevalence of MetS (using the harmonized definition) was 40.0% [37], similar to our study in Iraq (39.4%). The high prevalence of MetS may be attributed to "improvement in economic situation, increased urbanization, nutrition transition, and reduced physical activity." [7].
The study found that the most prevalent MetS components were low HDL, high BP and high WC. Similar results were found in national surveys in Iran [14] and in Nepal [19]. In this study, we saw a decline of two MetS components (high WC among women and high TG among men) in persons 60 years and older. One possible explanation for this could be mortality prior to 60 years [18]. Consistent with former research [18,19,12,13,21], this investigation showed an association between older age and MetS. While several studies found a higher prevalence of MetS among women than men [18,19,20,21], this study did not show any significant sex differences. In fact, men seemed to have a greater number of MetS components than women in this study. Several studies showed an increased risk of MetS in people with lower education [13,15], which was confirmed in our study in unadjusted analysis and in the adjusted analysis in terms of a greater number of MetS components. Persons with lower education may have lesser knowledge on health risk behavior/s that are implicated in the development of MetS [10]. While several previous research studies showed an association between urban residence and MetS [12,18,19], this survey did not find significant ruralurban differences. This could mean that MetS risk behavior/s (sedentary lifestyle, stress and diet changes) have penetrated rural areas as well as urban areas.
In agreement with previous research findings [19,20], this survey showed that having general overweight or obesity increased the odds for MetS. Consistent with previous studies [20][21][22][23], this investigation showed in unadjusted analysis an inverse association between high physical activity and MetS. Several studies and reviews [25][26][27][28] found a significant association between inadequate fruit and vegetable consumption and MetS, while this survey did not find any significant association between the two.
This study found in unadjusted analysis that ever alcohol use and in the adjusted analysis that current and past smoking were associated with MetS. Regarding alcohol use, our findings confirm former research conducted in China [16]. Since the proportion of current alcohol users was too small in this study population, we are not able to distinguish heavy from moderate alcohol users. In terms of smoking, our findings are in line with former research showing a positive association between active and past smoking and MetS [16,[29][30][31]. In a recent review, the following lifestyle changes are recommended to prevent and manage MetS: stop smoking, engage in physical activity (30-60 min daily), moderate intake of red wine and beer, a healthy diet for weight loss and fruit and vegetable consumption as part of a healthy diet [38].

Study limitations
The strength of the study was to cover a nationally representative adult sample in Iraq, but was limited because of its cross-sectional design as well as the self-report of the interview data. The variable of household income was not available on the publically available dataset and could therefore not be included in the analysis.

Conclusion
The 2015 Iraq STEPS survey found among a nationally representative population of adults that two in five participants had MetS. Several risk factors for MetS were identified, including older age, current and past smoking and general overweight and obesity, which can facilitate in aiding interventions to prevent and control MetS in the general population in Iraq. High WC waist circumference (waist ≥89 cm in men, ≥91 cm in women), High BP blood pressure (systolic BP ≥130 or diastolic BP ≥85 mmHg and or on anti-hypertensive medication), High FBG fasting blood glucose (≥100 mg/dL or on antidiabetic medication), High TG triglycerides (≥150 mg/dL and/or on anti-cholesterol medication), Low HDL highdensity lipoprotein cholesterol (<40 mg/dL in men; <50 mg/dL in women and/or on anti-cholesterol medication)