Cardiovascular risk factors and predicted risk of cardiovascular disease among Sri Lankans living in Kandy, Sri Lanka and Oslo, Norway

Background: South Asians living in western countries are known to have unfavourable cardiovascular risk profiles. Studies indicate migrants are worse off when compared to those living in country of origin. The purpose of this study was to compare selected cardiovascular risk factors between migrant Sri Lankans living in Oslo, Norway and Urban dwellers from Kandy, Sri Lanka. Methods: Data on non fasting serum lipids, blood pressure, anthropometrics and socio demographics of Sri Lankan Tamils from two almost similar population based cross sectional studies in Oslo, Norway between 2000 and 2002 (1145 participants) and Kandy, Sri Lanka in 2005 (233 participants) were compared. Combined data were analyzed using linear regression analyses. Results: Men and women in Oslo had higher HDL cholesterol. Men and women from Kandy had higher Total/HDL cholesterol ratios. Mean waist circumference and body mass index was higher in Oslo. Smoking among men was low (19.2% Oslo, 13.1% Kandy, P = 0.16). None of the women smoked. Mean systolic and diastolic blood pressure was significantly higher in Kandy than in Oslo. Conclusions: Our comparison showed unexpected differences in risk factors between Sri Lankan migrants living in Oslo and those living in Kandy Sri Lanka. Sri Lankans in Oslo had favorable lipid profiles and blood pressure levels despite being more obese. Background Cardiovascular disease (CVD) risk profile of South Asians living in western countries is characterized by low High Density Lipoprotein (HDL) cholesterol, central obesity and increased diabetes mellitus together with higher rates of myocardial infarctions, re-infarctions and higher mortality rates from Coronary Heart Disease (CHD) [1-4]. By grouping South Asians together, some studies may have overlooked inherent differences amongst them [2]. At present South Asia is experiencing a rapid increase in CVD particularly in the urban areas and among higher socioeconomic classes [5-10]. Studies comparing migrant Indians in UK and USA with those living in India observe migrants having higher mean total cholesterol, triglycerides and Body Mass Index (BMI) but no consistent difference in HDL [11,12]. In Sri Lanka coronary heart disease (CHD) is a main cause of morbidity and mortality [13,14]. Sri Lankan stu- dies suggest concentration of risk factors in urban areas and higher socioeconomic classes with an increasing pre- valence among younger people [8-10,15]. A diet rich in carbohydrates and saturated fats (coconut is the major supplier of fat energy) but low in protein may contribute to the worsening burden of CVD and diabetes [9,16]. It has been previously reported from Oslo, Norway that Sri Lankan migrants have lower HDL cholesterol and higher triglycerides compared to Vietnamese, Iranians and eth- nic Norwegians[17]. The prevalence of central obesity was highest among Sri Lankan and Pakistani women in Oslo and both men and women had higher Waist to Hip ratios for any given BMI compared to other immigrant groups [18]. To our knowledge, no studies comparing Sri Lankan migrants and a native group in Sri Lanka have been published. Our study compares cardiovascular risk factors from a population based study in Kandy Sri Lanka * Correspondence: sampathte@yahoo.com † Contributed equally Department of General Practice and Community Medicine, University of Oslo, Oslo, Norway Full list of author information is available at the end of the article Tennakoon et al. BMC Public Health 2010, 10:654 http://www.biomedcentral. com/1471-2458/10/654 © 2010 Tennakoon et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. with data from Sri Lankans participating in the Oslo Immigrant Health Study. The study design and imple- mentation in Kandy was as similar as possible to the Oslo study to facilitate the comparison. Methods Study population Oslo, Norway The population based, cross sectional Oslo health study (HUBRO) and Oslo immigrant health study were con- ducted between 2000 and 2002 by the Norwegian Institute of Public Health and the University of Oslo [17]. Both stu- dies used the same protocol. In HUBRO, all Oslo residents born in 1924, 1925, 1940, 1941, 1955, 1960 and 1970 were invited. In the Oslo immigrant health study, all those born between 1942 and 1971in Sri Lanka, Turkey, Iran Vietnam and a 30% random sample of Pakistanis living in Oslo were invited, except for those who previously had been invited to HUBRO [19]. An invitation and the main ques- tionnaire were sent to participants 2 weeks before the screening followed by a reminder to non responders. In both studies the questionnaires were also available in the appropriate languages of the five immigrant groups. Here we have included participants from both studies born in Sri Lanka between 1940 and 1971, and in this group the response rate was 50% in HUBRO (143 participants) and 50.9% in the Oslo immigrant health study (1002 partici- pants) [19]. The majority of the Sri Lankans (99%) in Oslo belonged to the Tamil ethnic group. Study population Kandy, Sri Lanka The population based cross sectional study in Kandy was conducted in the municipal council area between August and December 2005 among ethnic Tamils. The target was 300 men and women between the ages of 30 and 60 years. The government electoral list for 2004 in which those above 18 years are required to register was the sampling frame [8-10,20]. Tamils were identified by their family names and selected through simple random sampling. All the selected persons were then invited at house visits after verification of ethnicity and age. Of those invited, 74 per- cent of the men and 92 percent of the women participated. Data collection Data collection in Kandy followed the Oslo study with a very similar protocol. In Oslo, participants completed a questionnaire, with or without assistance, while partici- pants in Kandy were interviewed using a structured ques- tionnaire. In both studies years of education, personal history of chronic diseases and medication and smoking habits were recorded. The Norwegian population register provided information on age and gender and country of birth which was taken as the county of origin [19]. In Kandy date of birth was recorded at the interview while gender was provided by the electoral list. Body weight and height were measured with electronic Height and Weight Scale in Oslo and a Salter medical scale and a Statometer in Kandy, with the participants wearing light clothing without shoes. BMI (kg/m) was calculated accordingly [19]. Waist circumference, at the midpoint between the iliac crest and lower margin of ribs was mea- sured with the subject standing and breathing normally to the nearest 0.1 cm with the same steel measuring tape utilised in both studies. Systolic and diastolic blood pressures were measured three times at one-minute intervals in mmHg by an automatic device (DINAMAP, Criticon, Tampa, USA) in Oslo and with a mercury sphygmomanometer in Kandy. The mean of the last two recordings were used in this paper. Hypertension was defined as systolic blood pres- sure ≥ 140 mmHg or diastolic blood pressure ≥ 90 mmHg or being on blood pressure lowering drugs. Non-fasting blood samples were collected and serum total cholesterol, serum HDL cholesterol and serum tri- glycerides were measured directly by an enzymatic method. This was done at the Department of Clinical Chemistry, Ulleval University Hospital, Oslo, Norway which was the reference laboratory, (Hitachi 917 auto analyzer, Roche Diagnostic, Switzerland) and ESPEE laboratory Kandy Sri Lanka (COBAS MIRA 36-3122 auto analyzer). Cross calibration of serum analysis For purposes of comparison, serum from a random sample of 14 persons from the Kandy study was re- analyzed at the reference laboratory in Oslo. As the Kandy results for total cholesterol and HDL cho- lesterol showed systematic differences from the Oslo results a further 182 samples were re-analyzed at the refer- ence laboratory, including 8 of the initial 14. Adjustments in total cholesterol and HDL cholesterol values from the Kandy study were thus made according to the reference laboratory scale. Triglyceride values did not differ between the two laboratories. Ethical considerations The Higher Degrees and Research Ethics committee of the University of Peradeniya, Sri Lanka approved the Kandy study. HUBRO and the Oslo Immigrant Health Study were approved by the Norwegian Data Inspecto- rate and cleared by the Regional Committee for Medical Research Ethics. Data analysis Combined data were analyzed by SPSS version 16 using linear regression and UNIANOVA methods with all variables adjusted for age, except age. Triglycerides were also adjusted for time since last meal. Regression ana- lyses assumptions (linearity and similar variance over Tennakoon et al. BMC Public Health 2010, 10:654 http://www.biomedcentral. com/1471-2458/10/654 Page 2 of 7