2008-Issue1.indd ABSTRACT Objectives: Evaluation of some of the leading risk factors for coronary heart disease (CHD) among males in Oman. Methods: We conducted a hospital-based pair-wise matched case-control study among Omani CHD patients admitted in the Sultan Qaboos University Hospital and the Royal Hospital located in Muscat, Oman. The cases were matched with an equal number of controls in respect of age and hospital. The information was collected from the cases and controls based on an interview and review of the medical records of the admitted CHD patients. The odds ratios (ORs) were estimated under univariate as well as multivariate situations using conditional multiple binary logistic regression model. Results: The analysis revealed that 74 percent of the cases were of angina pectoris. The majority of the cases (96%) were above 40 years of age. The prevalence of sedentary life style was predominant (88.0%). Hypertension, diabetes, family history of CHD and a sedentary occupation were the most significant risk factors for the development of the disease. The estimated values of the adjusted ORs were found to be 9.98, 2.74, 28.9 and 3.00 respectively (p<0.05). Conclusion: Individuals with hypertension, diabetes mellitus, a family history of CHD and with sedentary occupations are to be considered at high risk of developing CHD. Such individuals should be provided with appropriate health education along with close monitoring for symptoms and signs of CHD. Key words: Coronary heart disease; Risk factors; Males; Case-control study; Oman. Some Risk Factors for Coronary Heart Disease among Omani Males A matched case-control study Shyam S Ganguly, Mohammed AAl-Shafaee, Abdullah A Al-Maniri Department of Family Medicine & Public Health, College of Medicine & Health Sciences, Sultan Qaboos University, Muscat, Sultanate of Oman *To whom correspondence should be addressed. Email: ganguly@squ.edu.om : الذكور العمانيني عند التاجي القلب ملرض االختطار عوامل بعض د توافقية واهِ وشَّ حاالَتِ ةُ دِراسَ املنيري اهللا عبد ، الشافعي محمد ، شيام جنجلي التوافقية ــواهد والش احلاالت ــة دراس . الطريقة: أجرينا في عمان عند الذكور التاجي القلب ملرض االختطار عوامل بعض امللخص: الهدف: تقييم بني بعمل توافق قمنا . ــلطاني الس ــفى واملستش قابوس ــلطان الس جامعة ــفى مستش من في كل والراقدين القلب التاجي املصابني مبرض للمرضى املعنيني ــطة مقابلة بواس الضابطة العينة في وأقرانهم املرضى من املعلومات أخذت . ــفى واملستش العمر حيث من الضابطة والعينة املرضى عدد الثنائي اللوجستي باستخدام برنامج االنحدار املتغيرات وذلك ومتعدد أحادي من كال بواسطة األرجحية ــبة نس قدرت . ــجالت الطبية الس ومراجعة فوق كان (96%) احلاالت أغلب في املرضى وأن عمر ، الصدرية من الذبحة تعاني احلاالت كانت %74 من بني التحليل أن . النتائج: ــرطي الش املتعدد هي إحصائيا معتدة بصورة التاجي القلب مبرض ــببة املتس عوامل االختطار كانت .(88%) كبيرا احلركة اخلالي من احلياة منط ــار انتش و كان األربعني لنسب املصححة املقدرة القيم كانت . من احلركة العمل اخلالي وطبيعة األسرة في التاجي القلب مرض حاالت السكر ووجود وداء الدم ارتفاع ضغط في توجد والتي ، ــكر الس وداء ضغط الدم بارتفاع املصابون ــخاص اخلالصة: يعتبر األش .(p<0.05) (3.00 , 28.19 ,2.74 هي: (9.98, االختطار األمور الضرورية من . التاجي القلب مبرض لإلصابة اختطارا أكثر احلركة وقلة بالركود تتميز أعماال يزاولون والذين ، التاجي مرض القلب حاالت أسرهم . التاجي لديهم القلب مرض وعالمات أعراض لظهور دقيقة مراقبة عمل وكذلك األشخاص هؤالء ملثل بالتثقيف الصحي القيام عمان. ، وشواهد ، دراسة حاالت االختطار عوامل ، التاجي القلب مرض الكلمات: مفتاح SULTAN QABOOS UNIVERSITY MEDICAL JOURNAL MARCH 2008, VOLUME 8, ISSUE 1, P. 45-51 SULTAN QABOOS UNIVERSITY© SUBMITTED - 5TH AUGUST 2007 ACCEPTED - 13TH FEBRUARY 2008 C L I N I C A L A N D B A S I C R E S E A R C H Advances in Knowledge • The findings of the article have important implications in the primary prevention of CHD. • The study indicated major risk factors for CHD among males in Oman. • The hypertension, diabetes mellitus, family history of CHD and sedentary type of occupation were found to be the most contributing factors in the causation of CHD. S H YA M S G A N G U LY, M O H A M M E D A A L -S H A FA E E , A B D U L L A H A A L - M A N I R I 46 AN ESTIMATED 16.7 MILLION OR 29.2% OF total global deaths result from the various forms of cardiovascular disease, many of which are preventable. Out of the 16.7 million deaths, 7.2 million are due to coronary heart disease (CHD). Moreover, 56% of these deaths occur before the age of 75 years.1 At least twenty million people survive heart attacks and strokes every year, their treatment requir- ing costly clinical care and so placing a huge financial burden on the individual as well as on the nation.1 Heart disease has no geographic, gender or socio eco- nomic boundaries.1, 2 The World Health Organization (WHO) has drawn attention to the fact that (CHD) is a modern epidemic. In the Eastern Mediterranean region, cardiovascular diseases (CVD) and stroke ac- count for 31% of mortality.3 In Oman, chronic non-communicable diseases related to lifestyle, namely coronary heart diseases, hypertension, diabetes mellitus and cancer, are now emerging as new health challenges for the country.4 The CHD made up nearly 10.5% of all deaths for adults aged 45–60 years and 31.5% for these above 60 years. In various studies carried out in the Omani pop- ulation, hypertension, diabetes, dyslipidaemia, seden- tary occupations and smoking have been reported to be the major cardiovascular risk factors.5, 6 Moreover, consanguinity is quite common with 34 percent of women married to first cousins and 20% married to other relations.7 This cultural practice may have re- sulted in an increased prevalence of hypertension and diabetes.8, 9 Although there are many risk factors relat- ed to CHD in our population, we focused on some of the leading risk factors, namely hypertension, diabetes mellitus, sedentary occupations, lack of physical exer- cise and a family history of CHD and diabetes. As the prevalence of CHD risk factors in the Omani popula- tion is high, so the present study aimed to quantify the degree and extent of association between CHD and such risk factors in terms of ORs under univariate and multivariate situations. M E T H O D S A hospital-based pair-wise matched case control study was carried out among the Omani male CHD patients admitted and treated in the Cardiac Care Units (CCU) of Sultan Qaboos University Hospital (SQUH) and the Royal Hospital, Muscat. Patients were identified from the CCU register and information was extracted from the medical records. An equal number of controls (i.e. either noncoronary patients or any asymptomatic in- dividual) were matched in respect of the confounding variables namely, age (± 2yrs) and hospital. Following the method as described by Schlesselman,10 a total of 100 case-control pairs con- stituted an adequate sample size for carrying out the study. A questionnaire was developed and pilot test- ing was conducted with 20 subjects. After the pre- testing, the relevant information on the risk factors of interest (including level of physical activity) in 200 subjects was recorded based on interviews. The study subjects gave informed consent before participation in the study. The study was conducted based on the necessary permission from the concerned authorities of both hospitals. The various levels/degrees of CHD risk factors used in this study were as follows: H Y PE RTE N SI O N The standard definition of hypertension was consid- ered as systolic blood pressure ≥ 140 mm Hg and/or diastolic blood pressure ≥ 90 mm Hg or current use of any hypertensive medicines.11 D I A BE TE S ME L L I T US Individuals who were on anti diabetic drugs or having fasting blood glucose level ≥ 7.0 mmol/L were consid- ered havings diabetes.12 FA MI LY H I STO RY O F C H D Individuals who responded to a history of angina on exertion, myocardial infarction, diagnosis of CHD or sudden death among first degree relatives were con- sidered to have a positive family history of CHD. SE D E N TA RY O C C UPATI O N The individuals who were working in an office at a job without much movement were classified as sedentary. FA MI LY H I STO RY O F D I A BE TE S Individuals who responded to a history of diagnosis of diabetes among first degree relatives were considered Applications to Patient Care • Data could be used for appropriate health education to patients as well as the community in Oman. S O M E R I S K FA C T O R S F O R C O R O N A R Y H E A R T D I S E A S E A M O N G O M A N I M A L E S 47 to have a positive family history of diabetes. L A C K O F PH Y SI C A L E X E R C I SE This was classified as individuals who were not do- ing at least 150 minutes of moderate intensity aerobic physical activities or at least 90 minutes of vigorous exercise per week. SMO K I N G The matched pairs were classified into ever smoker and non-smoker groups. The ever smokers were indi- viduals who were irregular or regular were considered at risk. STATI STI C A L A N A LY SI S The percentages were calculated to summarize the various socio-demographic characteristics of the pa- tients. The data on all the risk factors included in the study were coded “1” if the respondent was found to be in the exposure category and “0’ if the individual was not in the exposure category. The McNemar chi- square test13 was used for testing the significance of as- sociation under univariate analysis. The data were en- tered and the univariate analysis was carried out using the Statistical Package for the Social Sciences (SPSS) software version 10.0. To estimate the ORs for each of the risk factors, a 2x2 table was formed representing the results of matched case-control study designed to assess the relationship between a single dichotomous risk factor and CHD. Denoting an exposed individual by (+) and an unexposed individual by (-), we obtained the discordant pairs of observations in the resulting cells of the table corresponding to (+ -) and (- +). Con- sidering b and c as the discordant pairs, the estimated values of the ORs were obtained by the relation OR= b/c and their 95% confidence limits were obtained by: OR x exp [± 1.96 x √{(1/b)+(1/c)}] TH E C O N D I TI O N A L L O GI STI C R E GR E S SI O N ME TH O D Consider X= (X1,……., X7) a vector of risk factor vari- ables for an individual under study. Each of the vari- ables entering in the conditional logistic regression analysis is defined in Table 1. The parameters βj (j = 1…,7) and their asymptotic standard errors were es- timated using conditional likelihood procedure.14, 15 Variable Definition Disease Status (D) 0 1 Noncoronary patient/asymptomatic individual A case of CHD Hypertension (X1) 0 1 <140mm Hg systolic and < 90mm diastolic ≥ 140mm Hg systolic and/or ≥90mm Hg diastolic Diabetes mellitus (X2) 0 1 < 7.0 mmol/L ≥ 7.0 mmol/L Family history of CHD (X3) 0 1 Absence of family history Presence of family history Type of occupation (X4) 0 1 Active Sedentary Family history of diabetes (X5) 0 1 Absence of family history Presence of family history Physical exercise (X6) 0 1 At least 90 minutes vigorous exercise weekly Less than the above Smoking (X7) 0 1 Nonsmoker Smoker Table 1: Summary of variables used in the analysis of Coronary Heart Disease data S H YA M S G A N G U LY, M O H A M M E D A A L -S H A FA E E , A B D U L L A H A A L - M A N I R I 48 The ORs for each of the risk factors were estimated by Ψj=exp(βj), j=1,… ,7. The asymptotic variances of the estimated ORs were obtained by the use of delta method 16 and is given by v(Ψj)=[Ψj] 2 v[βj], j= 1, ……, 7 The tests of significance of the parameters involved in the model were carried out using the Wald test. The conditional multiple logistic regression model was fit- ted using EGRET, version 2.0.31 software. The level of p <0.05 was considered as cut-off value of statistical significance. R E S U L T S Table 2 shows that the mean age was 56.24 years (± 10.37) with 96 percent above 40 years of age. The lit- eracy rate was 39 percent. The majority (73%) was married. The prevalence of a sedentary life style was very high (88.0%). The break-up of the 100 cases ac- cording to the type of CHD diagnosed revealed that the largest number of cases were of angina pectoris (74%) followed by acute myocardial infarction (15%) and chronic CHD (11%). UN I VA R I ATE A N A LY SI S The results from univariate analysis for each risk fac- tor are shown in Table 3. It is evident that an individ- ual with a history of hypertension has 7 times more chance of developing CHD as compared to a person without hypertension (p< 0.01). The risk of develop- ing CHD was 3 times higher for a diabetic patient as compared to a nondiabetic person (p<0.05). A family history of CHD was found more frequent among the cases as compared to controls with an OR of 5.0, but this was not statistically significant (p>0.05). The ORs of suffering from CHD for a person with a sedentary type of occupation as compared to an individual with a non-sedentary occupation was found to be 3.14 (p<0.01). A family history of diabetes, lack of physical exercise and the smoking habits of the individual also contributed to the incidence of the disease, with ORs of 1.71, 1.43 and 1.15 respectively, but these were not statistically significant (p>0.05). MULTI VA R I ATE A N A LY SI S The pair-wise matched case-control data set, for which the univariate analysis was carried out, was also considered for multivariate analysis. For this, condi- tional logistic regression analysis was used. All seven risk factors, which were entered in the analysis, pro- vided the estimated values of ORs controlled for other variables included in the model. The maximum likeli- hood estimates of the parameters, the standard errors of the estimates and the estimated values of ORs with their standard errors under the model, are shown in Table 4. It is observed that, out of the seven risk factors, hypertension status, diabetes mellitus, a family his- tory of CHD and sedentary type of occupation of the individual are the main modifiable factors in the de- velopment of CHD in this community (p<0.05). The estimated odds of developing CHD for an individual with hypertension, after adjusting the effect of other risk factors, was about 10 times higher as compared to a normal person. The adjusted OR for CHD due to diabetes mellitus was found to be 2.74. The odds of suffering from the disease for an individual with the presence of family history of CHD after adjusting the effect of other factors, was found to be very high as compared to an individual who did not have a family history (p<0.05). Moreover, the analysis also revealed that an indi- Characteristics n % Age range < 40 40 – 49 50 – 59 ≥ 60 4 21 32 43 4.0 21.0 32.0 43.0 Education Illiterate Koran Elementary & above 61 28 11 61.0 28.0 11.0 Marital Status Single Married Divorced Widowed 2 73 3 22 2.0 73.0 3.0 22.0 Type of occupation Active Sedentary 12 88 12.0 88.0 Category of CHD Acute Chronic Angina Pectoris 15 11 74 15.0 11.0 74.0 Table 2: Distribution of 100 cases according to the socio-demographic characteristics and type of coronary heart disease diagnosed S O M E R I S K FA C T O R S F O R C O R O N A R Y H E A R T D I S E A S E A M O N G O M A N I M A L E S 49 vidual with a sedentary occupation had 3 times the risk of developing CHD as compared to a person with an occupation involving physical activity (p<0.05). The chance of developing CHD among the individuals with the family history of diabetes was found to be about 2.7 times more as compared to the individuals with- out family history of diabetes mellitus but this was not statistically significant (p>0.05). In the case of the other two risk factors, namely lack of physical exercise and smoking, the risk of developing the disease were found to be approximately the same as found under the univariate analysis. D I S C U S S I O N By the end of twentieth century, most developing countries, including Oman, experienced a major surge in life expectancy due to a decline in various mortal- ity indicators and an improvement in overall socio- economic development. The demographic shift has increased the number of older adults thus providing longer exposure to risk factors of CHD. The medical and socioeconomic consequences of an increase in the burden of CHD will be disastrous for most of the countries as costly interventions and drugs may not be affordable.17 Strategies to prevent the acquisition or augmentation of CHD risk factors will be a combina- tion of primordial prevention and primary preventive action to reverse and reduce the elevation of risk fac- tors. Most researchers suggest that overweight/obesity increased serum total cholesterol, low density lipo- protein cholesterol and decreased high density lipo- protein cholesterol are well established risk factors for coronary heart diseases.18, 19 In our study, we excluded these factors since they have been well uninvesigated in this part of the world. Our study has reported that the average age of the patients was 56.2 ±10.4 years ranging from 36 years to 80 years. Al Adsani et al20, in their study carried out in Kuwait on a similar population to ours, found that the average age of male patients of CHD was 52.4 ± 10.4. The results from both univariate and multivariate analyses indicate that hypertension, diabetes mellitus and sedentary occupations contributed significantly to the development of CHD (p< 005). Yusuf et al21 in their INTERHEART study in 52 countries reported the strength of association between hypertension and acute myocardial infarction in men and women after adjustment for age, sex, and geographical region with an OR of 2.95 (95% CI 2.59, 3.39). In the present study, it was found that hypertension was present in 61% of the cases against 23% in the control (p<0.001). A fam- ily history of CVD reflects genetic, environmental and behavioural elements and interactions between them. The relative risk ranges from 2.0 to 9.0 among persons who report a family history of CVD, depending on the type and number of relatives considered.22 In this study, the family history of CHD is associated with the development of the disease (p<0.05). Ganguly et al23 in their study reported that smok- Sl. No. Risk factor No. of discordant pairs Odds ratio 95% Confidence limits p (+ -) (- +) 1 Hypertension 44 6 7.33 3.12, 17.20 0.008 2 Diabetes mellitus 23 7 3.29 1.34, 8.40 0.010 3 Family history of CHD 5 1 5.00 0.58, 42.79 0.230 4 Sedentary occupation 22 7 3.14 1.50, 6.58 0.006 5 Family history of diabetes 12 7 1.71 0.67, 4.34 0.359 6 Lack of physical exercise 10 7 1.43 0.54, 3.78 0.630 7 Smoking habit 15 13 1.15 0.55, 2.52 0.850 Table 3: The estimated values of odds ratios and their 95 percent confidence limits for the various risk factors S H YA M S G A N G U LY, M O H A M M E D A A L -S H A FA E E , A B D U L L A H A A L - M A N I R I 50 ing increases by threefold the chances of developing CHD as compared to nonsmokers (p<0.001). In this study, no significant association between smoking his- tory and development of disease was found (p>0.05). This may be due to reluctance to provide a correct his- tory of smoking habits because of religious and cul- tural taboos. It can be observed that the ORs computed using univariate analysis and multivariate analysis differ. In univariate analysis, we estimate the ORs for each factor independently, whereas, under the conditional logistic regression model, the estimation of ORs de- pends upon the regression coefficients, which in turn were estimated by simultaneously considering all the factors included in the model. Thus we can always ex- pect differences in conclusions based on the two pro- cedures. C O N C L U S I O N From the above study, it can be concluded that individ- uals above 40 years of age with hypertension, diabetes mellitus, a family history of CHD and a sedentary life style should be considered at high risk for developing CHD. They should be provided with intensive health education along with close monitoring to detect the emergence of the symptoms and signs of CHD. 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