RESEARCH ARTICLE

Prevalence and Characteristics of Metabolic Syndrome in 111 Royal Jordanian Air Force Pilots Nawaf Salem Khazale and Fares Haddad

KHAZALE NS, HADDAD F. Prevalence and characteristics of metabolic syndrome in 111 Royal Jordanian Air Force pilots. Aviat Space Environ Med 2007; 78:968–72. Introduction: Metabolic syndrome is associated with development of cardiovascular disease, stroke, and diabetes mellitus, conditions that are disabling for military aircrew members. Prevalence of metabolic syndrome varies in different geographic areas and is of concern in the Middle East. Methods: Data were collected for 111 Royal Jordanian Air Force pilots (mean age 32.5 6 7.2 yr) during routine annual medical examinations, with an added assessment for metabolic syndrome according to the third report of the National Cholesterol Education Program (NCEP) Adult Treatment Panel (ATP III) criteria. Measurements included height, weight, waist and hip circumference, and blood pressure. Blood was drawn in a fasting state for measurement of kidney function, liver function, lipid profile, and fasting blood sugar (FBS). Results: There were 17 subjects who were found to have 3 or more components of metabolic syndrome. The crude prevalence was 15.3%; the age adjusted prevalence was 18.0%. Prevalence increased with age, from 11.5% for those younger than 30 yr to 26.7% for those over 40 yr of age. There were significant differences between metabolic syndrome and non-metabolic syndrome groups with respect to lipid profile, systolic and diastolic blood pressure, waist circumference, and FBS. Subjects with metabolic syndrome had the following distribution of characteristics: 35.3% had waist circumference ⱖ102cm; 71.4% were hypertensive (blood pressure ⱖ130/85); 100% had triglyceride ⱖ150 mg z dl21; 88.2% had high density lipoprotein , 40 mg z dl21; and 23.5% had FBS ⱖ110 mg z d21. Discussion: The prevalence of metabolic syndrome in this population was sufficiently high to be a matter of medical concern, especially since military pilots are generally regarded as healthy and fit. Keywords: metabolic syndrome, ATPIII criteria, Royal Jordanian Air Force.

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ETABOLIC SYNDROME is a widely prevalent and multifactorial disorder that presents in a distinct, albeit heterogeneous phenotype (24). This constellation of risk factors constitutes a growing problem in modern societies (9,14,15) and is considered an established predictor for the development of Type 2 diabetes mellitus and cardiovascular disease (18,24). While there is no universally accepted definition of, nor criteria for, metabolic syndrome (4,12), the third report of the National Cholesterol Education Program (NCEP) Adult Treatment Panel (ATP III) included clinical diagnosis guidelines for metabolic syndrome that are applicable to clinical practice (12,24). The prevalence of metabolic syndrome depends on age, ethnic background, and gender. It rises linearly from age 20 to 50 yr, and plateaus thereafter. The prevalence for a population from 20 to 25 yr of age and up-

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wards varies from 8% (India) to 24% (United States) in men, and from 7% (France) to 46% (India) in women (9,13,14) and is highest in South Asians and Africans and lowest in European women (15,23). In Arabs, the metabolic syndrome rate ranges from 23–48% (1,2,7,16), being higher in more affluent Arab countries (6,21). In Jordan the exact prevalence was not studied, but obesity is a prime component of metabolic syndrome and is considered a significant health burden. Obesity is estimated to be 32.7–37.9% in males and 33.7–59.8% in females (3,10). There is evidence that military populations are affected as well, which imposes an additional health hazard, and pilots are no exception (7,8). We investigated the current extent of the problem by assessing the prevalence and the demographic characteristics of metabolic syndrome that had been added to the standard routine annual physical exam for a cohort of pilots in the Royal Jordanian Air Force (RJAF), representing a homogenous group of the Jordanian male population. We hope to recommend a future training program for this cohort. METHODS During a routine annual physical for RJAF pilots, we assessed the presence of three or more of the following components of metabolic syndrome according to ATPIII criteria: waist circumference of 102 cm or higher in men and 88 cm or higher in women; systolic/diastolic blood pressure of 130/85 mmHg or higher; HDL-C levels less than 40 mg z dl21 in men and less than 45 mg z dl21 in women; triglyceride levels of 150 mg z dl21 or higher; and blood glucose level of 110 mg z dl21 or higher (12). The study was conducted at the Air Force Medical Center, Aviation Medicine, Royal Medical Services in From the Royal Jordanian Air Force Medical Center, Aviation Medicine, Royal Medical Services (N. S. Khazale); and Endocrine Division, Department of Internal Medicine, King Hussein Medical Center (F. Haddad), Amman, Jordan. This manuscript was received for review in March 2007. It was accepted for publication in July 2007. Address reprint requests to: Fares Haddad, M.D., JBED, FRCP, who is a consultant physician, P.O. Box 967, Amman 11118, Jordan; haddf@ hotmail.com. Reprint & Copyright © by Aerospace Medical Association, Alexandria, VA. DOI: 10.3357/ASEM.2097.2007

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METABOLIC SYNDROME IN PILOTS—KHAZALE & HADDAD TABLE I. CHARACTERISTICS OF RESPONDING PILOTS (MEAN 6 SD).

Age (yr) Height (cm) Weight (kg) Smokers, N (%) Cigarettes/day Duration of smoking (yr) No. of pilots doing exercise, N (%) No. of exercise sessions/week Mean duration of exercise (minutes/exercise session) Regular alcohol intake SBP (mmHg) DBP (mmHg) Waist circumference (cm) Hip circumference (cm)

All (N $ 111)

Metabolic Syndrome (N $ 17)

Non-Metabolic Syndrome (N $ 94)

P-value

32.5 6 7.2 177.7 6 4.9 81.5 6 9.2 72(65%) 17.3 6 5.4 10.3 6 6.7 58(52.2%) 3.1 6 2.0 46.4 6 17.8 13(11.7%) 123.7 6 9.4 80.6 6 6.4 93.5 6 6.8 110.1 6 6.1

34.35 6 7.1 175.2 6 4.8 83.9 6 12.2 10(58.8%) 18.5 6 3.4 13.4 6 7.6 12(70.6%) 3.15 6 2.1 48.3 6 19.3 2(11.8%) 131.2 6 8.6 83.8 6 7.0 96.9 6 8.1 111.8 6 6.3

32.2 6 7.1 178.1 6 4.9 81 6 8.4 62(66%) 17.15 6 5.6 9.8 6 6.4 46(48.9%) 3.1 6 1.9 46.2 6 17.3 11(11.7%) 122.2 6 8.9 80 6 6.3 92.8 6 6.4 109.8 6 6.1

0.12 0.012 0.1 0.57 0.23 0.057 0.1 0.42 0.36 0.62 0.0001 0.012 0.01 0.11

Amman, Jordan, between January and December 2006. All pilots who presented on Sunday and Tuesday of the first week of the month were randomized and assessed. This study was approved by the Directorate of Study and Research of the RJAF and the informed consent of the subjects was obtained. Medical histories of diabetes (DM), hypertension (HTN), smoking, alcohol consumption, and exercise habits were assessed by direct questioning and completion of a predefined questionnaire. A total of 111 pilots who completed the questionnaires and had their blood test results readily available were assessed for the components of metabolic syndrome. The type, duration, and frequency of exercise per week were also stated. Waist circumference, hip circumference, and height were assessed to the nearest centimeter using a non-stretch tape measure, and bodyweight was measured to the nearest kilogram while barefoot and wearing a fatigue suit. Blood pressure from the right arm was assessed by standard sphygmomanometer after 10 min of seated rest. Blood was withdrawn after 12 h of fast for lipid profile: high-density lipoprotein (HDL-C), low-density lipoprotein (LDL-C), triglyceride (TG), total cholesterol (TC), and fasting blood sugar (FBS), kidney function test (KFT), liver function test (LFT), and uric acid. Blood was separated and analyzed immediately at the RJAF Medical Center using an automated Hitachi 927 device for the lipid profile, KFT, LFT, and free thyroxin level (T4) and thyroid stimulating hormone (TSH) to rule out secondary causes of hyperlipidemia. The crude and age-adjusted prevalence of metabolic syndrome and its components were assessed. The group with metabolic syndrome was compared with those without metabolic syndrome with regard to demographic features, habits, and biochemical profile. Statistical analysis using descriptive statistics, Student’s t-test, were employed to compare means using XP Excel and Epinfo 6 programs.

(6 SD) age was 32.3 (7.2) yr. The mean height was 177.7 (4.5) cm, and weight was 81.5 (9.2) kg. Of the cohort, 65% were smokers who smoked 17.3 (5.4) cigarettes/ day for a duration of 10.3 (6.7) years. Over half (52.2%) of the cohort were performing regular exercise of 3.1 (2) sessions/week, with the mean duration of each session being 46.4 (17.8) min. Only 11.7% of the cohorts drank alcohol socially on an irregular basis (Table I). Of the cohort, 27% did not have any of the metabolic syndrome features, 29.7% had one component, 27.9% had two components, and 14.4% and 0.9% had three and four components, respectively. The crude metabolic syndrome prevalence was 15.3% (Fig. 1). The mean metabolic syndrome components were 3.1 6 0.24 in the metabolic syndrome cohort (N 5 17) vs. 0.97 6 0.8 for the non-metabolic syndrome cohort (N 5 94, P , 0.000). The age adjusted prevalence was 18%. The prevalence of metabolic syndrome by age decades in the group of , 30 yr was 11.5%, for those between 31 and 40 yr it was 15.9%, and for those over 41 yr it was 26.7% (Fig. 2, Table II). Waist circumference: Waist circumference ⱖ 102 cm was found in a total of 10 subjects [6 (35.3%) in the metabolic syndrome group and 4 (4.2%) in the non-metabolic syndrome group]. The mean waist circumference was 93.5 6 6.8 cm (96.09 6 8.1 cm vs. 92.8 6 6.4 cm for metabolic syndrome vs. non-metabolic syndrome groups, respectively; P 5 0.01). No difference in hip circumference between the two groups was found.

RESULTS A total of 111 male pilots were assessed, none of whom were known to have diabetes or hypertension. The mean Aviation, Space, and Environmental Medicine x Vol. 78, No. 10 x October 2007

Fig. 1. Prevalence of each component of metabolic syndrome.

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METABOLIC SYNDROME IN PILOTS—KHAZALE & HADDAD 10.3 mg z dl21 for the whole cohort (103.5 6 18 in the metabolic syndrome group vs. 97.1 6 8 for the nonmetabolic syndrome group; P 5 0.0088). Thyroids factions tests, uric acid, and KFT: There was no significant difference in T4 level or TSH level between the two groups; however, three pilots had TSH below the reference range of 0.40 uIU z ml-1 and two had TSH between 4.4–8 uIU z ml-1, with normal free thyroxin levels. None of them had clinical symptoms and all were referred for further endocrine evaluation. There was no difference in the mean uric acid for either group (6.1 6 1.1 mg z dl21; P 5 0.14). The levels of creatinine, blood urea nitrogen, electrolytes, and protein are given in Table III.

Fig. 2. Prevalence of metabolic syndrome per decade of age.

DISCUSSION Hypertension: Hypertension was statistically higher in the metabolic syndrome group: 29.4% of metabolic syndrome group and 5.3% of the non-metabolic syndrome group had high systolic blood pressure (SBP) and 47% of the metabolic syndrome group vs. 16% of the non-metabolic syndrome group had high diastolic blood pressure (DBP). Mean SBP was 123.7 6 9.4 mmHg for the whole group (131.2 6 8.6 for the metabolic syndrome group vs. 122.2 6 8.9 for the non-metabolic syndrome group; P 5 0.0001); mean DBP was 80.6 6 6.4 mmHg (83.8 6 7 vs. 80 6 6.3 mmHg; P 5 0.012). Lipid profile: All patients with metabolic syndrome and 43.1% of the non-metabolic syndrome group had high TG . 150 mg z dl21, and 88.2% of the metabolic syndrome group vs. 29.8% of the non-metabolic syndrome group had low HDL , 40 mg z dl21. The mean TG level was 159.7 6 88.4 mg z dl21 for the cohort group (the metabolic syndrome group had a significantly higher TG level than the non-metabolic syndrome group; 240.4 6 93.5 vs. 145.1 6 79.6 mg z dl21; P , 0.001). The mean HDL-C for the whole group was 44.3 6 11.3 mg z dl21 (36.2 6 9.2 vs. 45.8 6 11.1 for the metabolic syndrome vs. non-metabolic syndrome group, respectively; P 5 0.00056). The metabolic syndrome group also had a higher LDL-C level vs. the non-metabolic syndrome group (155.3 6 99.6 vs. 108 6 32.6; P 5 0.0001). Diabetes, fasting blood sugar: None of the cohort was known to have diabetes or to be on medication for diabetes. Only six subjects (6.4%) in the non-metabolic syndrome group had FBS . 110 mg vs. 23.5% in the metabolic syndrome group. The mean FBS was 98 6

This was a pilot study carried out in a cohort of RJAF pilots as part of their annual physical for licensure. The exact prevalence of metabolic syndrome in Jordan has not been studied previously. Obesity as determined by body mass index is estimated to be 50% (3). In a crosssectional study by the Ministry of Health, overweight was found to be 38% in males and 34% in females, and obesity 14.4% in males vs. 23.4% in females (10). Diabetes is another major health problem in Jordan, with 32.5% of the population affected with either impaired glucose tolerance or overt diabetes (19). We believe that the westernization of the Jordanian diet has contributed to the increased prevalence of diabetes and obesity in Jordan, as well as to metabolic syndrome. This study looked at metabolic syndrome according to NCEP, ATP III criteria and found that the crude prevalence of metabolic syndrome was 15.3% in a group of highly physically trained subjects. This figure is higher than that in a military group in Greece who eat a similar Mediterranean diet (8); however, it is slightly lower than a similar study of a military cohort in neighboring Saudi Arabia, where metabolic syndrome in soldiers was 20.8% (7). Our findings are also lower than those in some of the neighboring Arab and Muslim countries. For example, in the adult Turkish population, the prevalence of metabolic syndrome was 33.4%, and is more common in women than in men (39.1% vs. 23.7%; P , 0.0001) (20). In Kuwait, metabolic syndrome was 34% overall with 55% of those males and 45% females (21).The prevalence of metabolic syndrome in Saudi Arabia is 39.3%; the age

TABLE II. PREVALENCE OF METABOLIC SYNDROME COMPONENTS [N (%)]. Whole Cohort (N $ 111) Waist circumference . 102 cm SBP . 130 mmHg DBP . 85 mmHg Triglyceride . 150 mg z dl21 HDL-C < 40 mg z dl21 Fasting blood glucose . 110 mg z dl21

970

10 (9.3%) 10 (9.6%) 23 (23.1%) 58 (52.2%) 43 (38.7%) 10 (9.6%)

Metabolic Syndrome Group (N $ 17) 6 (35.3%) 5 (29.4%) 8 (47%) 17 (100%) 15 (88.2%) 4 (23.5%)

Non-Metabolic Syndrome Group (N $ 94) 4 (4.2%) 5 (5.3%) 15 (16%) 41 (43.1%) 28 (29.8%) 6 (6.4%)

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METABOLIC SYNDROME IN PILOTS—KHAZALE & HADDAD TABLE III. BIOCHEMICAL PROFILE OF BOTH METABOLIC SYNDROME AND NON-METABOLIC SYNDROME (MEAN 6 SD).

BUN (mg z dl21) Creatinine (mg z dl21) Uric acid (mg z dl21) FBS (mg z dl21) TG (mg z dl21) Cholesterol (mg z dl21) HDL-C (mg z dl21) LDL-C (mg z dl21) Sodium (mEq z L-1) Potassium (mEq z L-1) Total protein (mg z dl21) Albumin (mg z dl21) Thyroxin (ng z ml21) TSH (mIU z ml-1)

All (N $ 111)

Metabolic Syndrome (N $ 17)

13.9 6 3.4 0.9 6 0.2 6.1 6 1.1 98 6 10.3 159.7 6 88.4 186.6 6 43.5 44.3 6 11.3 114.8 6 49.2 135.5 6 18.6 4.3 6 0.3 7.3 6 0.5 4.8 6 0.4 1.3 6 0.3 1.9 6 1.0

13.7 6 3.1 0.8 6 0.2 5.9 6 1.0 103.47 6 18 240.4 6 93.5 207.2 6 77.1 36.25 6 9.2 155.3 6 94.6 128.9 6 32.5 4.3 6 0.3 7.25 6 0.5 5.05 6 0.2 1.38 6 0.3 1.98 6 1.3

adjusted prevalence in males is 37.2% and crude prevalence is 40.9% (6). The results of this study are similar to that of an Omani study where the age-adjusted prevalence of metabolic syndrome was 21%, while the crude prevalence was 17.0%. The age-adjusted prevalence was 19.5% among men (5). Hypertriglyceridemia was present in 52% of the cohort tested after 12 h of fasting; it was present in all patients with metabolic syndrome and in 43.6% of the nonmetabolic syndrome group. Hypertriglyceridemia is considered among the strongest indicators of metabolic syndrome (17). Our findings coincide with those from a study in Turkey (22), and contrast with Omani and Hispanic studies that found that low HDL was the most prevalent component of metabolic syndrome (5,12). Low HDL was found in second place for the whole group (38.7%) and for subgroups as well (88.2% for the metabolic syndrome group and 29.8% for the non-metabolic syndrome group). The rest of the metabolic syndrome components in decreasing percentages were: DBP (47%), high waist circumference . 102 cm (35.3%), SBP (29.4%), and FBS (23.5%), respectively. The prevalence of metabolic syndrome in this cohort increased with age from 11.5% for those , 30 yr, to . 26.7% for those . 41 yr of age (13), and is consistent with many other studies (4,9,21) (Fig. 1). Metabolic syndrome is a predictor as well as a risk factor for CAD; therefore, therapy should be instituted to prevent these complications (11,18,22,24). This study, however, did not investigate rates or correlations between metabolic syndrome and ischemic heart disease or cerebrovascular disease, since none of this cohort’s subjects were experiencing any of these. One important limitation is that despite the assurance that the results of this study would not affect a pilot’s career, we believe that some pilots may have exaggerated the number of their weekly training sessions and under-reported their smoking habits. Drinking alcohol was also under-reported due to both career and socioreligious considerations, since Islam prohibits drinking alcohol.

Non-Metabolic Syndrome (N $ 94) 13.9 6 3.5 0.92 6 0.2 6.2 6 1.1 97.1 6 8 145.1 6 79.6 183 6 33.5 45.8 6 11.1 108 6 32.6 136.7 6 14.7 4.35 6 0.5 7.3 6 0.5 4.8 6 0.4 1.3 6 0.3 1.9 6 0.9

P-value 0.4 0.01 0.14 0.0088 ,0.0001 0.016 0.00056 0.0001 0.055 0.24 0.42 0.0038 0.22 0.36

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