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

Abstract

ObjectivesThe 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.MethodsWe 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.ResultsSouth 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.ConclusionDifferences 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.

Performance of a Framingham cardiovascular risk model among Indians and Europeans in New Zealand and the role of body mass index and social deprivation

“…However, the Framingham score overestimated risk substantially in Indian women with predicted risk values of about 6% and above, and in European men and women in all but the two lowest deciles of predicted risk. Despite Indians being around 6–8 years younger than Europeans in the cohort, their observed 5-year CVD event rates were very similar to the observed 5-year CVD event rates in Europeans, consistent with the previously documented high burden of CVD in South Asians in New Zealand 22 and other countries. 1 23 We also found a positive association between increasing BMI (from BMI≥18.5) and the risk of CVD in both ethnic groups which remained statistically significant in all the subgroups except European women after adjustment for the Framingham risk score.…”

“…The UK study found that Framingham underestimated risk in South Asian women and performed reasonably well in South Asian men after a factor of 1.4 was added to the score. 26 Based on these findings, 26 the previously documented high burden of CVD in South Asians 22 and New Zealand guidelines recommendations to add 5% to the risk score for South Asians, 2 we would expect the Framingham risk score to underestimate risk among Indians in New Zealand. Instead, we found that Framingham overestimated the risk in Indian women and in Europeans of both genders.…”

Diet quality and risk factors for cardiovascular disease among South Asians in Alberta

“…A recent longitudinal cohort study involving individuals with low 10-year heart risk score found that trends of elevated low-density lipoprotein (LDL) and non-high-density lipoprotein (HDL) cholesterol (≥160 mg/dL) were independently associated with a 50%-80% increased relative risk of CVD mortality (Abdullah et al 2018). A comparison of risks of CVD events between SAs and Europeans from Norway who had no previous CVD events indicated that SAs had 87%-92% higher age-adjusted risk (Rabanal et al 2017). The differences in baseline total cholesterol/ LDL ratio and diabetes prevalence explained the excess CVD risk in this cohort.…”

“…Individuals of South Asian (SA) descent are either born in or can trace their ancestry to India, Pakistan, Nepal, Bangladesh, or Sri Lanka. SAs have significantly higher risk for early onset of cardiovascular diseases (CVD) (Joshi et al 2007), hyperinsulinemia, and dyslipidemia compared with other Asians and individuals of European descent (Ahmed and El-Menyar 2014;Rabanal et al 2017;Volgman et al 2018). Also, the mortality risk associated with CVD is higher in SAs compared with Europeans, Americans, other Asians (Ahmed and El-Menyar 2014), or Africans (Chaturvedi 2003).…”

Validation of the cardiovascular risk model NORRISK 2 in South Asians and people with diabetes

“…In 2019, immigrants and Norwegianborn to immigrant parents with a country background from South Asia living in Norway counted 75,227 individuals [12]. We previously reported that immigrants from South Asia have an increased risk of CVD compared to ethnic Norwegians after adjustment for traditional risk factors [13].…”