Open access Cardiac risk factors and prevention Open Heart: first published as 10.1136/openhrt-2019-001213 on 12 May 2020. Downloaded from Coronary heart disease and stroke in the Sami and non- Sami populations in rural Northern and Mid Norway—the SAMINOR Study Susanna R A Siri ,1 Bent M Eliassen,2 Ann R Broderstad,1,3 Marita Melhus,1 Vilde L Michalsen,1 Bjarne K Jacobsen,1 Luke J Burchill,4 Tonje Braaten1 ► Additional material is ABSTRACT Key questions published online only. To view Background Previous studies have suggested that Sami please visit the journal online have a similar risk of myocardial infarction and a possible (http:// dx. doi. org/ 10. 1136/ What is already known about this subject? higher risk of stroke compared with non-Sami living in the openhrt- 2019- 001213). Previous studies have found similar risk of coronary same geographical area. ► heart disease and a possible higher risk of stroke in Design Participants in the SAMINOR 1 Survey (2003– To cite: Siri SRA, Eliassen BM, Sami compared to non-Sami populations. Broderstad AR, et al. Coronary 2004) aged 30 and 36–79 years were followed to the heart disease and stroke in the 31 December 2016 for observation of fatal or non- fatal What does this study add? Sami and non- Sami populations events of acute myocardial infarction (AMI), coronary ► In the SAMINOR 1 Survey (2003–2004), the Sami in rural Northern and Mid heart disease (CHD), ischaemic stroke (IS), stroke and a population has a higher risk of stroke and isch- Norway—the SAMINOR Study. composite endpoint (fatal or non-fa tal AMI or stroke). aemic stroke compared with non-Sami. Differences 2020;7:e001213. Open Heart Aim Compare the risk of AMI, CHD, IS, stroke and the in height explained more than conventional risk doi:10.1136/ composite endpoint in Sami and non-Sami populations, openhrt-2019-001213 factors. and identify intermediate factors if ethnic differences in risks are observed. How might this impact on clinical practice? Received 28 November 2019 Methods Cox regression models. ► Our findings have predominantly public health rel- Revised 27 February 2020 Results The sex-adjusted and age-adjusted risks of AMI evance. The clinical relevance depend on the inter- Accepted 26 March 2020 (HR for Sami versus non-Sami 0.99, 95% CI: 0.83 to 1.17), pretation of height and ethnicity as risk predictors of CHD (HR 1.03, 95% CI: 0.93 to 1.15) and of the composite ischemic stroke and stroke. http://openheart.bmj.com/ endpoint (HR 1.09, 95% CI: 0.95 to 1.24) were similar in Sami and non-Sami populations. Sami ethnicity was, 3 however, associated with increased risk of IS (HR 1.36, cardiovascular risk factors ; for fatal CHD, 95% CI: 1.10 to 1.68) and stroke (HR 1.31, 95% CI: 1.08 to fewer out- of- hospital sudden deaths and © Author(s) (or their 1.58). Height explained more of the excess risk observed hospitalisations with severe myocardial infarc- 2 employer(s)) 2020. Re- use in Sami than conventional risk factors. tion (MI) contributed to the decline. permitted under CC BY- NC. No Conclusions The risk of IS and stroke were higher The Sami people live across Norway, commercial re- use. See rights in Sami and height was identified as an important Sweden, Finland and on the Kola Penin- and permissions. Published intermediate factor as it explained a considerable on October 2, 2021 by guest. Protected copyright. by BMJ. sula in the Russian Federation. In Norway, proportion of the ethnic differences in IS and stroke. The 1Department of Community the Sami are acknowledged as indigenous risk of AMI, CHD and the composite endpoint was similar Medicine, Centre for Sami people, and the majority live in Northern in Sami and non-Sami populations. Health Research, Faculty of Norway, together with the Kven people and Health Sciences, UiT The Arctic Norwegian majority population. The Kven University of Norway, Tromso, people are descendants of Finnish-speaking Norway 2Faculty of Nursing and Health INTRODUCTION immigrants who arrived in the 1700s and 4 Sciences, Nord University, Bodo, Through 2001 to 2014, the incidence of 1800s from northern Sweden and Finland. Nordland, Norway non- fatal acute myocardial infarction (AMI) As with other indigenous people, the Norwe- 3 Department of Medicine, and fatal coronary heart disease (CHD) gian government imposed harsh assimilation University Hospital of North declined in Norway in both sexes,1 even policies on the Sami from 1850 until 1960,5 Norway, Harstad, Troms, Norway 1 4Department of Medicine, among people aged 25–44 years. Between when a revitalisation of Sami culture and Royal Melbourne Hospital, 1994 and 2012, a decline was observed in the languages began, but many had already given The University of Melbourne, incidence of CHD2 and stroke3 in the largest up using Sami languages. In the 1970 popu- Melbourne, Victoria, Australia city in Northern Norway, which is close to the lation census, information on Sami and Kven Correspondence to regions included in the present study. The ethnicities was collected in selected areas of Susanna R A Siri; susanna. r. decline in the incidence of CHD and stroke Northern Norway, and it was estimated that 6 siri@ uit. no was mainly driven by the improvement of around 40 000 people in Norway were Sami. Siri SRA, et al. Open Heart 2020;7:e001213. doi:10.1136/openhrt-2019-001213 1 Open Heart Open Heart: first published as 10.1136/openhrt-2019-001213 on 12 May 2020. Downloaded from Unlike other indigenous populations,7 the somatic health weight scale (DS-102, Dongsahn Jenix, Seoul, Korea) to in Sami has been shown to be similar to that in the non- the nearest 0.1 decimal, with the participant standing Sami population in the same geographical areas.8 and wearing no shoes. A digital oscillometric device Two studies regarding CHD mortality in Sami, covering (DINAMAP- R, Critikon, Tampa, Florida, USA) was used roughly the same time period but different geograph- to measure blood pressure three times at 1- minute inter- ical areas, show contradicting mortality rates,9 10 whereas vals, and the average of the last two measurements was similar incidence of MI was observed in Sami and non- reported. Those who used antihypertensive medications Sami in 1973/1974 through 1989 in Finnmark County, or had systolic or diastolic blood pressure ≥140/90 mm in Northern Norway.11 With regards to stroke, higher Hg, respectively, were categorised as hypertensive. Non- mortality9 and possibly higher incidence11 12 were fasting venous blood samples were taken while partici- observed in Sami compared with their reference popu- pants were resting. The samples were centrifuged within lations in the years 1974–1998. Moreover, several studies 30 min, separated within 2 hours and sent by overnight observed lower average heights in Sami than in non-Sami post to Ullevål University Hospital in Oslo, Norway, populations,10 13 14 and a possible inverse association where total cholesterol, high-density lipoprotein (HDL) between height and degree of Sami affiliation.13 More- cholesterol, glucose and triglycerides were measured with over, an increase in height has been found to be inversely an enzymatic method (Hitachi 917 autoanalyser, Roche associated with CHD and stroke,15 16 which has also been Diagnostics, Switzerland). observed in Finnmark,12 however, for MI, this was only found in women.11 Self-administered questionnaires We have previously reported overall similar levels of There is no registry on ethnicity in Norway and health cardiovascular risk factors in Sami and non- Sami popu- surveys rely on self- reported ethnic information. There lations in rural Northern Norway.17 18 However, it is not is no consensus on how ethnicity should be operation- known whether the incidence of cardiovascular disease alised in health research except that it is recommended (CVD) differs in Sami and non- Sami in this population. that several markers of ethnicity are applied, as ethnicity Thus, the aim of this study was to compare the risk of is a multifaceted concept.20–22 The following 11 questions fatal or non- fatal AMI, CHD, ischaemic stroke (IS), stroke provided information about ethnicity: (1) What language and a composite endpoint (AMI or stroke) in Sami and do/did you, (2) your mother, (3) your father, (4–7) your grand- non- Sami populations, and identify intermediate factors parents (all four) speak at home? (8) What is your, (9) your if ethnic differences in risks are observed. mother’s, (10) your father’s ethnic background? (11) What do you consider yourself to be? To each of the questions, one or more of the following alternatives could be ticked: Sami, METHODS Kven, Norwegian and other (specify). Participants who The SAMINOR 1 Survey (SAMINOR 1) was conducted (1) considered themselves as Sami or ticked ‘Sami’ as http://openheart.bmj.com/ in 2003–2004 and was the first of three population- based their own ethnic background, and (2) either spoke the cross- sectional surveys, which together constitute the Sami language themselves, or had at least one parent SAMINOR Study. The SAMINOR 1 was initiated due to or grandparent who used it at home, were categorised limited knowledge about the health of the Sami popula- as Sami. All others were categorised as non-Sami. Sensi- tion, and it was conducted by the Centre for Sami Health tivity analyses were performed using an alternative ethnic Research at UiT the Arctic University of Norway, together categorisation: (1) high Sami affiliation, that is, reported with the Norwegian Institute of Public Health. There Sami to all 11 questions (n=1385), (2) some Sami affilia- is no registry of ethnicity in Norway; thus, SAMINOR 1 tion, that is, reported Sami in 1–10 questions (n=3168), on October 2, 2021 by guest.