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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
  1. Kjersti S Rabanal1,
  2. Haakon E Meyer1,2,
  3. Grethe S Tell3,4,
  4. Jannicke Igland4,
  5. Romana Pylypchuk5,
  6. Suneela Mehta5,
  7. Bernadette Kumar6,
  8. Anne Karen Jenum7,
  9. Randi M Selmer1,
  10. Rod Jackson5
  1. 1 Division for Mental and Physical Health, Norwegian Institute of Public Health, Oslo, Norway
  2. 2 Department of Community Medicine, Institute of Health and Society, University of Oslo, Oslo, Norway
  3. 3 Division for Health Data and Digitalisation, Norwegian Institute of Public Health, Bergen, Norway
  4. 4 Department of Global Public Health and Primary Care, University of Bergen, Norway
  5. 5 School of Population Health, University of Auckland, Auckland, New Zealand
  6. 6 Norwegian Center for Minority Health Research, Oslo, Norway
  7. 7 Faculty of Health and Society, Institute of Health and Society, University of Oslo, Oslo, Norway
  1. Correspondence to Kjersti S Rabanal; kjersti.stormark.rabanal{at}fhi.no

Abstract

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.

  • cardiovascular disease
  • risk factors
  • South Asians
  • ethnicity
  • prospective
  • cohort

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Footnotes

  • Contributors HEM, RJ and GST contributed to the conception and design of the work. RJ, BK, AKJ and GST contributed to the collection of data. JI, RP and SM contributed to data preparations and definition of endpoints. KSR drafted the paper and carried out the data analyses. All authors contributed to the interpretation of data as well as critical reading and revision of the draft.

  • Funding This work was supported by the Norwegian Extra-Foundation for Health and Rehabilitation (grant number 2012-2-0129).

  • Competing interests All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf. RJ and SM report grants from Health Research Council of New Zealand. All other coauthors have no competing interests to declare.

  • Ethics approval For the Norwegian cohort: the Regional Committee for Medical Research Ethics, Health Region West, Norway. For the New Zealand cohort: the Northern Region Ethics Committee Y in 2003, and later annually approved by the National Multi Region Ethics Committee since 2007.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement No additional data are available.

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