Abstract
Objectives: To assess whether smoking,
alcohol intake and exercise cofounders have an impact on the development of
metabolic syndrome in a Jordanian cohort of air pilots.
Methods:
A random sample of 111 subjects serving at Royal Jordanian Air Force were
recruited at the routine annual examination. Complete history and physical exam
was done. The criteria of the National Cholesterol Education Program-Adult
Treatment Panel III were used to define features of metabolic syndrome. Waist
and hip circumference and height were measured to nearest centimeter, body
weight to the nearest kilogram. Blood
pressure was taken after 10 minutes of rest. Blood was drawn in fasting state
for complete kidney function test, liver function test, lipid profile and fasting
blood sugar. The cohort was divided into
groups according to exercise, alcohol intake and smoking habit and comparison
among groups was performed. Metabolic syndrome in Jordan ranges from 19-36% in
different studies. The prevalence of metabolic syndrome in air pilots was 15.3%.
Result:
Mean age was 32.5 ± 7.2 years. There were 72 smokers of 17.3± 5.4 cigarettes/day
for a duration of 10.3+ 6.7 years. Thirteen subjects consume alcohol on
social basis and 58 subjects who do regular excises of a mean of 3 sessions per
week. There was no difference in the
prevalence of metabolic syndrome among all groups studied as well as for
components of metabolic syndrome. Smokers
were having a statistically significant higher rates of low HDL-C vs.
non smokers (47.2% vs. 23.1%, p=0.0012; OR=2.98(95% CI : 1.15-7.9)RR =2.05 (95% CI
:1.1-3.81) and their mean HDL-C level was lower (42.3±10.1 vs. 48.1± 12.5) for non smokers (p=
0.0041).The systolic blood pressure and body weight were significantly lower in the smoker group.
Conclusion: Smoking,
alcohol intake and exercise as confounders did not affect the prevalence of metabolic
syndrome in this cohort. Smoking has a
significant impact on low HDL-C rates and levels in smokers. Further, larger studies are needed to elicit
differences and significant results of these confounders.
Key word: Air pilots, Alcohol, Confounders,
Metabolic syndrome, Smoking
JRMS
March 2011; 18(1): 34-38
Introduction
The metabolic syndrome (MS),
characterized by a clustering of abdominal obesity, hypertrigly-ceridaemia, low
high-density lipoprotein (HDL) cholesterol, elevated blood pressure (BP), and
high fasting glucose, has been associated with an increased risk for the development
of diabetes and CVD as well as an increased mortality from CVD and from all
other causes.(1)
The age-adjusted prevalence of
the Metabolic Syndrome in West Bank of
Jordan as defined by the WHO was 17%.(2) The estimated
prevalence of MS in a small military cohort in Jordan using the ATP III is 15.3
% and increases with age being 26.7% in subjects >40 years.(3) In a cross-sectional study in North of Jordan
that included a random sample of 1121 aged ≥25 years to estimate the prevalence
of metabolic syndrome using the ATPIII criteria, the prevalence was 36.3%; the
prevalence being higher in females (40.9%) than males (28.7%) the study also
showed that the prevalence increased significantly with age.(4)
In a previous study by our group
we showed an increased prevalence of cardiovascular disease in a cohort of
patients with MS; this prevalence being higher in the diabetic subgroup.(5,6)
A Chinese study in men showed that physical activity was associated with a
lower prevalence of metabolic syndrome, whereas drinking more than three drinks
per day was associated with a higher risk of metabolic syndrome regardless of
the criteria employed. The association between smoking and the prevalence of
metabolic syndrome in this population failed to reach significance.(7)
In a Swedish cross sectional
study, authors showed that education, physical activity at leisure time,
moderate intensity of physical activity at work, alcohol intake and smoking had
strong association with MS.(8)
In a study from Taiwan, the
higher risk of development of metabolic syndrome, high triglyceride level, and
low HDL-C level was insignificant in former smokers. In the
same study, current
smokers who smoke ≥ 20 pack-years have a significantly increased risk of
developing metabolic syndrome, high triglyceride level, and low HDL-C level.(9)
The study concluded that this community-based study supports the view that
smoking is associated with metabolic syndrome and its individual components.
Smoking cessation is beneficial to metabolic syndrome and its individual
components. (9)
The crude prevalence of metabolic
syndrome in the sedentary, low active, active and very active groups was 9.7%,
6.9%, 5.6% and 4.9% respectively.(10) After adjusting for the
effect of other risk factors, the higher the physical activity level, the lower
the relative risk of metabolic syndrome as well as the individual metabolic
abnormalities.(10,11)
In the NCEP III report,(12)
the relationship between current smoking and ex-smoking and metabolic syndrome
was statistically significant while there was no correlation between
non-smokers and the metabolic syndrome.(12)
In this
study we aim to see the effect of smoking, alcohol intake and exercise on the
prevalence of metabolic syndrome defined according to NCEP ATP III and the
biochemical profiles among a group of air pilots at one of the air bases of the
Royal Jordanian Air Force.
Methods
In a routine annual medical
checkup of military air pilots of Jordan armed forces, we assessed the presence
of three or more of the following components of the metabolic syndrome
according to National Cholesterol Education Program (NCEP); Adult Treatment
Panel III (ATPIII) criteria: waist circumference of 102 cm or higher in men and
88 cm or higher in women, SBP/DBP of 130/85 mm Hg or higher, HDL-C levels less
than 40mg/dl in men and less than 45 mg/dl in women, triglyceride levels of 150
mg/dl or higher, and blood glucose level
of 110mg/dl or higher.(12)
The study took place at the Air
Force Medical Center- Aviation Medicine, Royal Medical Services between January
and December 2006; all pilots who presented on Sunday and Tuesday of the first
week of the month were randomized and assessed.
Medical history of
diabetes (DM) hypertension (HTN), smoking, alcohol and exercise habits were
assessed by direct questioning and completion of predefined questionnaire. A total of 111 pilots who
completed the questionnaires and had their blood test were assessed for the components. The
type, duration and frequency of exercise per week were also stated. Complete physical examination
including the waist circumference, hip circumference and height were assessed
by a non-stretchable tape meter to
nearest centimeter (cm) and body weight was measured bare feet in fatigue suit
to nearest kilogram (kg). Blood pressure
was assessed in a sitting position after 10 minutes of rest from right arm by
standard sphygmomanometer. Blood was withdrawn after 12 hours 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 tests
(KFT), liver function tests (LFT), and uric acid. Blood was separated and analysed immediately at the
RJAF medical center using automated Hitachi 927 device for
lipid profile, KFT, LFT as
well as free thyroxin level (T4) and thyroid stimulating hormone (TSH) to rule out secondary causes of hyperlipidemia.
Table I. Rates of metabolic syndrome and its components in each subgroup studied
|
Confounders
|
Smoking
|
Exercise
|
Alcohol
|
|
MS components
|
Yes n=72
|
No n=39
|
Yes n=59
|
No n=52
|
Yes n=13
|
No n= 98
|
|
Metabolic Syndrome
|
11(15.3%)
|
8(20.5%)
|
13(22%)
|
6(11.5%)
|
3(23.7%)
|
16(16.3%)
|
|
Hypertriglyceridemia
|
36(50%)
|
22(56.4%)
|
33(56%)
|
25(48%)
|
8(61.5%)
|
50(51%)
|
|
Hyperglycemia(>110mg/dl)
|
5(6.9%)
|
5(12.8%)
|
7(11.8%)
|
3(5.8%)
|
1(7.7%)
|
9(9.2%)
|
|
Hypertension(>130/85)
|
15(20.8%)
|
10(25.6%)
|
13(22%)
|
12(23%)
|
2(15.4%)
|
23(23.5%)
|
|
Low HDL(<40 mg/dl)
|
34(47.2%)*
|
9(23%)*
|
22(37.3%)
|
21(40%)
|
3(23%)
|
40(40.8%)
|
|
High waist circumference (>102)
|
6(8.3%)
|
5(12.8%)
|
5(8.5%)
|
6(11.5%)
|
2(15.4%)
|
9(9.2%)
|
*p=0.0012; OR=2.98(95% CI: 1.15-7.9).RR =2.05 (95% CI: 1.1-3.81)
Table II. Showing the demographic and biochemical profile of all
group studied with statistical significance
|
Smoking
|
Exercise
|
Alcohol
|
|
mean ±SD
|
Yes n=72
|
No n=39
|
p value
|
Yes n=59
|
No n=52
|
P value
|
Yes n=13
|
No n=98
|
p value
|
|
Age (yr)
|
33.2
(7.6)
|
32.9
(6.4)
|
0.35
|
33.7
(8.04)
|
31.2
(5.8)
|
0.033
|
36.7
(8.1)
|
31.9
(6.9)
|
0.01
|
|
Waist
circumference
|
92.4
(7.04)
|
95.5
(5,8)
|
0.012
|
92.9
(7)
|
92.2
(6.3)
|
0.15
|
94.1
(8.3)
|
93.4
(6.6)
|
0.37
|
|
SBP(mmHg)
|
122.2
(9.2)
|
126.7
(9.2)
|
0.009
|
122.3
(9.1)
|
125.5
(9.6)
|
0.039
|
122.7
(10.1)
|
123.8
(9.4)
|
0.35
|
|
DBP(mmHg)
|
80.2
(6.3)
|
81.4
(6.7)
|
0.18
|
80.2
(6.6)
|
81.1
(6.3)
|
0.25
|
80.4
(6.5)
|
80.6
(6.5)
|
0.46
|
|
FBS (mg/dl)
|
97.2
(9.8)
|
99.6
(11.2)
|
0.12
|
99.2
(11.8)
|
96.7
(8.2)
|
0.104
|
98.1
(8.2)
|
98
(10.6)
|
0.48
|
|
TG (mg/dl)
|
155.4
(78)
|
167.7
(105.7)
|
0.24
|
161.2
(85.2)
|
158
(92.8)
|
0.42
|
177.5
(92.9)
|
157.3
(88)
|
0.22
|
|
Cholesterol (mg/dl)
|
182.5
(34.1)
|
194.3
(56.6)
|
0.08
|
190.4
(49.8)
|
182.4
(34.9)
|
0.16
|
202
(35.3)
|
184.6
(44.2)
|
0.08
|
|
HDL-C (mg/dl)
|
42.3
(10.1)
|
48.1
(12.5)
|
0.004
|
44.4
(11.1)
|
44.2
(11.6)
|
0.47
|
48.8
(12.6)
|
43.7
(11.1)
|
0.065
|
|
LDL-C (mg/dl)
|
109.5
(33.4)
|
124.5
(68.8)
|
0.06
|
115.8
(47.7)
|
113.8
(51.3)
|
0.41
|
123.8
(43)
|
113.6
(50.1)
|
0.24
|
|
T4 ng/ml
|
1.36
(0.29)
|
1.26
(0.22)
|
0.028
|
1.4
(0.27)
|
1.3
(0.3)
|
0.019
|
1.34
(0.3)
|
1.33
(0.27)
|
0.38
|
|
T3 ng/ml
|
3.3
(0.77)
|
3.07
(0.66)
|
0.044
|
3.2
(0.74)
|
3.2
(0.75)
|
0.4
|
3.2
(0.6)
|
3.2
(0.76)
|
0.39
|
|
TSH mIU/ml
|
1.86(
1.03)
|
1.98
(0.97)
|
0.27
|
1.8
(1.1)
|
1.97
(0.87)
|
0.25
|
1.67
(1)
|
1.93
(1)
|
0.19
|
This
study was approved by the Directorate of Study and Research of the RJAF and
informed consent of the subjects involved in the study was taken.
The cohort was divided into smokers
vs. non-smokers, alcohol intake vs. none and subject doing
exercise vs. none. These groups
were compared among each other with regards to prevalence of MS components and
differences between rates of each MS component in each group. The RR and OD were
calculated, the anthropometric and the biochemical profile of each group
expressed as mean (±SD) were reported for each group.
Statistical analyses using
descriptive statistics, Student’s t-test to compare means using XP excel
program and Epinfo 6 program.
Results
A total of 111 male pilots were
assessed, none of them were known to have diabetes or hypertension. The mean age
was 32.3±7.2 years. The mean height was 177.7±4.5 cm and weight 81.5±9.2 kg.
Sixty five percent of the cohort were smokers of 17.3±5.4 cigarettes per day
for a duration of 10.3±6.7 years, 52.2% of the cohort were doing regular
exercise of 3.1±2 sessions per week, the mean duration of each session was 46.4±17.8
minutes. Alcohol consumption on social irregular basis was reported in 11.7% of
the cohort.
The
overall prevalence of MS was shown in previous study to be 15.3%.(3) There were
no statistically significant differences in the prevalence of metabolic
syndrome in smokers (Yes vs. No:15.3% vs. 20.5%, p=0.3), exercise (22% vs.11.5%
p=0.14) or alcohol subgroups (23.7% vs.16.3% p=0.39) (Table I).
There
were no statistically significant differences in the prevalence of MS
components between all groups studied. Smokers were having a statistically
higher rate of low HDL-C than non smokers (47.2% vs. 23%; p=0.0012)
giving an Odds Ratio of 2.98 (95% CI: 1.15-7.9), the Relative Risk was 2.05
(95% CI: 1.1-3.81) (Table I).
The
demographic and biochemical profile of all groups are shown in Table II. Smokers were having lower body weight and
lower systolic blood pressure (122.2 (9.2) vs. 126.7 (9.2) p= 0.009). The HDL-C level was significantly lower than
non-smokers and the levels of thyroxin and triiodtyronine were higher in the
non smokers (Table II).
The
exercising group was older and had lower body weight, the systolic blood
pressure being again lower than the non exercising group (122.3(9.1) vs.
126.5(9 .6); p=0.039).
The
alcohol consumers were older, consumed less than 14 units per week on social
bases. Their HDL-C level was not
significantly higher than non consumers; (48.8(12.6) vs. 43.7(11.1) p=0.065) (Table
II).
The kidney function test, liver function tests
and electrolytes were normal in all studied groups; the free T3 and T4 were
significantly higher in the smoker group (Table II)
Discussion
This
study looked into MS in a small cohort of air pilots; in a previous study of
same cohort we showed the prevalence to be 15.3%,(3) here we
tried to analyze the effect of some important confounders that were showing
conflicting effects on MS prevalence.
Many
studies have shown high prevalence of MS in smokers than non smokers,(9) in this study we failed to show
any effect neither on MS prevalence nor on any of its components except on
rates and levels of low HDL-C in smokers (Table I).
Fisher et al. found that
current smokers have higher thyroxin levels and lower thyroid stimulating
hormone levels than never smokers and former smokers. They also found that
heavy smokers had a smaller increase in thyroxin levels than did light smokers,
when compared to non-smokers.(13)
Leisure-time physical activity
was inversely related to the metabolic syndrome. Smoking more than 20
cigarettes per day was associated with an increased risk compared to
non-smokers. The hazard ratios (95% confidence intervals) were 1.27 (1.04-1.54)
and 1.40 (1.02-1.92) in men and women, respectively. Alcohol intake and
education were inversely associated with metabolic syndrome in women but not in
men. Physical inactivity and heavy smoking increased the metabolic syndrome
incidence in men and women. Low or no intake of alcohol was also associated
with increased risk, but in women only.(6,14)
In a study by Santos et al.
from Brazil(15)
on the effect of certain confounders and their effect on metabolic syndrome
prevalence revealed that, after adjustment, higher total physical activity and
work activity levels in females were significantly associated with lower
prevalence of the metabolic syndrome. More sleeping hours were positively
associated with metabolic syndrome. Regarding smoking, the only statistically
significant association was found in women that smoked less than 10 cigarettes
per day. No statistically significant association was found between ethanol
intake and metabolic syndrome. The study concluded that there is an association
between decreased physical activity, increased sleeping hours and metabolic
syndrome but no association was found between cigarette smoking, alcohol intake
and the metabolic syndrome. This was further supported by an Irish study.(15,16)
This study did not show any difference
in the prevalence of MS, rather there were more subjects with MS in the
exercise group than non- exercise group but this did not reach statistical
significance (Table I). The presence of
multiple components in metabolic syndrome made most of the studied subject
exercise more to keep fit and to obtain licensure for flying.
Studies have shown that alcohol
intake increases the HDL level and reduce the rates of MS.(15,16) In this study there was no difference in the
prevalence of MS, the mean level of HDL-C was not statistically significantly
higher in the group that consumed some alcohol than non consumers and less
subjects with low HDL-C were found in this group but the difference did not
reach statistical significance. (23% vs. 40%; p=0.09 Table II). However, the
number of subjects that consume alcohol is small enough to draw a significant
impact on the components of metabolic syndrome. No protective effect of alcohol
on the occurrence of metabolic syndrome was found supporting the study by
Kawada et al.(10)
Limitation of the Study
This
study has some limitations that might have exerted an effect on the results as
a whole. There were under reported rates
of smoking habits and alcohol consumption due to the fear that this might
affect the pilots’ career and the social and religious prohibition of alcohol
intake.
Conclusions
This
study concludes that smoking, alcohol intake and exercise as confounders did
not exert any deleterious or beneficial effects on the prevalence of metabolic
syndrome or its components. The most prevalent components of MS are
dyslipidemia in all groups. Smoking has
a significant impact on low HDL-C rates and levels in smokers. The total number
of subjects studied is small so further larger studies are needed to elicit
differences and significant results of these confounders.
References
1. Reynolds
K, He J.
Epidemiology of metabolic syndrome. Am J Med Sci 2005; 330: 273–279
2. Abdul-Rahim
HF, Husseini A, Bjertness E, et al. The Metabolic Syndrome in the West Bank Population. An urban-rural comparison. Diabetes
Care 2001;24:275–279,
3. Khazaleh NS, Haddad FH. Prevalence and
characteristics of metabolic syndrome in 111 Royal Jordanian Air Force pilots. Aviat Space Environ Med 2007; 78(10):968-972.
4. Khader
Y, Bateiha A, El-Khateeb M, et al. High prevalence of the metabolic
syndrome among northern Jordanians. Diabetes Complications 2007; 21(4):214-219
5. Mahafza
S, Khazaalah N, Wraikat A, et al. Metabolic syndrome in a Jordanian
cohort; demography, complications and predictors of cardiovascular disease. Journal
of The Royal Medical Services 2009; 16(2): 5-11.
6.Haddad FH, Mahafza SM.
Impact of metabolic syndrome's components on thedevelopment of cardiovascular disease in a Jordanian cohort with metabolic
syndrome. Saudi Med J 2008 Sep; 29(9):1299-1305.
7.Villegas
R, Xiang YB, Yang G, Cai Q, et al. Prevalence and Determinants of
Metabolic Syndrome According to Three Definitions in Middle-Aged Chinese Men. Metab
Syndr Relat Disord 2009 Feb; 7(1):37-45
8.Qader
SS, Shakir YA, Nyberg P, Samsioe G. Sociodemographic risk factors of metabolic
syndrome in middle-aged women: results from a population-based study of Swedish
women, The Women's Health in the Lund Area (WHILA) Study. Climacteric
2008; 11(6):475-482.
9.Chen CC, Li TC, Chang PC, Liu CS, et al. Association
among cigarette smoking, metabolic syndrome, and its individual components: the
metabolic syndrome study in Taiwan.
Metabolism 2008; 57(4):544-548.
10. Kawada
T, Okada K. The
metabolic syndrome: prevalence and associated lifestyles in Japanese workingmen.
J Cardiometab Syndr 2006; 1(5):313-317.
11. Ma
G, Luan D, Li Y, Liu A, Hu X, Cui Z, Zhai F, Yang X. Physical
activity level and its association with metabolic syndrome among an employed
population in China. Obes Rev 2008; 9 Suppl 1:113-118.
12. Expert
Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in
Adults.
Executive Summary of the Third Report of the National Cholesterol Education
Program (NCEP III) Expert Panel on Detection, Evaluation, and Treatment of High
Blood Cholesterol in Adults (Adult Treatment Panel III). JAMA 2001; 285:
2486-2497.
13. Fisher
CL, Mannino DM, Herman WH, Frumkin H. Cigarette smoking and thyroid hormone
levels in males. Int J Epidemiol 1997 Oct; 26(5):972-977.
14. Wilsgaard
T, Jacobsen BK. Lifestyle factors and incident metabolic
syndrome. The Tromsø Study 1979-2001. Diabetes Res Clin Pract 2007;
78(2): 212-217
15. Santos
AC, Ebrahim S, Barros H. Alcohol intake, smoking, sleeping hours, physical
activity and the metabolic syndrome. Prev
Med 2007 Apr; 44(4):328-334.
16. Villegas
R, Creagh D, Hinchion R, O'Halloran D, Perry IJ. Prevalence and
lifestyle determinants of the metabolic syndrome. Ir Med J 2004;
97(10):300-303.