Can traditional risk factors explain the higher risk of cardiovascular disease in South Asians compared to Europeans in Norway and New Zealand? Two cohort studies.

OBJECTIVES: The objective was to prospectively examine potential differences in the risk of first cardiovascular disease (CVD) events between South Asians and Europeans living in Norway and New Zealand, and to investigate whether traditional risk factors could explain any differences. METHODS: We included participants (30-74 years) without prior CVD in a Norwegian (n=16 606) and a New Zealand (n=129 449) cohort. Ethnicity and cardiovascular risk factor information was linked with hospital registry data and cause of death registries to identify subsequent CVD events. We used Cox proportional hazards regression to investigate the relationship between risk factors and subsequent CVD for South Asians and Europeans, and to calculate age-adjusted HRs for CVD in South Asians versus Europeans in the two cohorts separately. We sequentially added the major CVD risk factors (blood pressure, lipids, diabetes and smoking) to study their explanatory role in observed ethnic CVD risk differences. RESULTS: South Asians had higher total cholesterol (TC)/high-density lipoprotein (HDL) ratio and more diabetes at baseline than Europeans, but lower blood pressure and smoking levels. South Asians had increased age-adjusted risk of CVD compared with Europeans (87%-92% higher in the Norwegian cohort and 42%-75% higher in the New Zealand cohort) and remained with significantly increased risk after adjusting for all major CVD risk factors. Adjusted HRs for South Asians versus Europeans in the Norwegian cohort were 1.57 (95% CI 1.19 to 2.07) in men and 1.76 (95% CI 1.09 to 2.82) in women. Corresponding figures for the New Zealand cohort were 1.64 (95% CI 1.43 to 1.88) in men and 1.39 (95% CI 1.11 to 1.73) in women. CONCLUSION: Differences in TC/HDL ratio and diabetes appear to explain some of the excess risk of CVD in South Asians compared with Europeans. Preventing dyslipidaemia and diabetes in South Asians may therefore help reduce their excess risk of CVD.

Ethnic inequalities in acute myocardial infarction and stroke rates in Norway 1994-2009: a nationwide cohort study (CVDNOR).

BACKGROUND: Immigrants to Norway from South Asia and Former Yugoslavia have high levels of cardiovascular disease (CVD) risk factors. Yet, the incidence of CVD among immigrants in Norway has never been studied. Our aim was to study the burden of acute myocardial infarction (AMI) and stroke among ethnic groups in Norway. METHODS: We studied the whole Norwegian population (n = 2,637,057) aged 35-64 years during 1994-2009. The Cardiovascular Disease in Norway (CVDNOR) project provided information about all AMI and stroke hospital stays for this period, as well as deaths outside hospital through linkage to the Cause of Death Registry. The direct standardization method was used to estimate age standardized AMI and stroke event rates for immigrants and ethnic Norwegians. Rate ratios (RR) with ethnic Norwegians as reference were calculated using Poisson regression. RESULTS: The highest risk of AMI was seen in South Asians (men RR = 2.27; 95 % CI 2.08-2.49; women RR = 2.10; 95 % CI 1.76-2.51) while the lowest was seen in East Asians (RR = 0.38 in both men (95 % CI 0.25-0.58) and women (95 % CI 0.18-0.79)). Immigrants from Former Yugoslavia and Central Asia also had increased risk of AMI compared to ethnic Norwegians. South Asians had increased risk of stroke (men RR = 1.26; 95 % CI 1.10-1.44; women RR = 1.58; 95 % CI 1.32-1.90), as did men from Former Yugoslavia, Sub-Saharan Africa and women from Southeast Asia. CONCLUSIONS: Preventive measures should be aimed at reducing the excess numbers of CVD among immigrants from South Asia and Former Yugoslavia.

Ethnic differences in risk factors and total risk of cardiovascular disease based on the Norwegian CONOR study.

BACKGROUND: Risk of cardiovascular disease varies between ethnic groups and the aim of this study was to investigate differences in cardiovascular risk factors, and total cardiovascular risk between ethnic groups in Norway. DESIGN: Cross-sectional study using data from the Cohort of Norway (CONOR). METHODS: A sample of 62,145 participants, 40-65 years of age, originating from 11 geographical regions, were included in our study. Self-reported variables, blood samples and physical measurements were used to estimate age- and time-adjusted mean values of cardiovascular risk factors for different ethnic groups. The 10-year risks of cardiovascular mortality and cardiovascular events were calculated using the Framingham and NORRISK risk models. RESULTS: We observed differences between ethnic groups for cardiovascular risk factors and both Framingham and NORRISK risk scores. NORRISK showed significant differences by ethnicity in women only. Immigrants from the Indian subcontinent had the lowest high-density lipoprotein (HDL) levels, the highest levels of blood glucose, triglycerides, total cholesterol/HDL ratio, waist hip ratio and diabetes prevalence. Immigrants from the former Yugoslavia had the highest Framingham scores, high blood pressure, high total cholesterol/HDL ratio, overweight measures and smoking. Low cardiovascular risk was observed among East Asian immigrants. CONCLUSION: The previously reported excess cardiovascular risk among immigrants from the Indian subcontinent was supported in this study. We also showed that immigrants from the former Yugoslavian countries had a higher total 10-year risk of cardiovascular events than other ethnic groups. This study adds information about ethnic groups in Norway which needs to be addressed in further research and targeted prevention strategies.