Physical activity and mortality under Arctic conditions – impact of ethnicity

Movement and health are inherently interconnected. The beneficial associations between regular physical activity (PA) or physical fitness and almost any health outcome have been scrutinized in numerous previous studies. Physical activity is considered beneficial for both primary and secondary health prevention strategies.^1–3 Sub segments of physical activity – such as leisure time physical activity (LTPA), exercise and even different types of exercise (running, yoga, Thai Chi) are all favourable in terms of health outcome.⁴ Persistence or increases in LTPA over time adds to these benefits.⁵ A possible benefit of physical activity during working hours, that is, occupational physical activity (OPA), has been harder to prove and the evidence has been conflicting.⁶

Indigenous people may, however, be different from the majority of attendees in such studies in several ways, and their health has been subjected to several challenges.⁷ The Sami are the indigenous ethnic population of northern Scandinavia and their health condition is poorly known.⁸

Epidemiological data has shown increased occurrence of cardiovascular disease (CVD), arrhythmias and sudden deaths in winter climate and there is suggested causation by identifiable triggers.⁹ Indeed, detailed and specific knowledge of both fixed and modifiable risk factors are needed to tailor preventive measures and educational strategies in people with higher risk of disease.

The paper by Hermansen et al.¹⁰ addresses the association between different measures of physical activity and fitness (measured as resting heart rate (RHR)) and mortality (all-cause and cardiovascular). This study adds to the current knowledge in two ways: i) it compares findings across ethnic groups from a large Sami- and non-Sami population, and ii) it provides data from a population living in arctic climate (in Finnmark, the northernmost county of Norway).

The authors followed 17,821 (78%) study attendees over 26 years, in itself a strength of the study. They found confirming evidence that LTPA was inversely associated with all-cause mortality, and RHR was positively associated with both CVD and all-cause mortality. As observed in several other studies, the association between OPA, CVD- and all-cause mortality was U-shaped. In contrast with other studies the authors could not confirm any association between LTPA and CVD-mortality, despite adjustments for several recorded confounding factors.

The Finnmark County has a higher prevalence of CVD than the rest of Norway. In addition to the increased prevalence of traditional CVD risk factors in this region, the cold climate, disturbed circadian rhythms (polar nights) as well as other unmeasured, detrimental, confounding variables, might have contributed to deflate the association between LTPA and CVD-mortality.

LTPA was recorded only once, but persistence and non-persistence in LTPA over time also impacts CVD- and all-cause mortality.⁵ Also, the attendees were skewed towards more women and older age groups. The attendance rate of the Sami versus non-Sami was not reported, but is expected to only marginally influence the results. All in all, however, the findings are largely robust and in line with current evidence about the benefits of LTPA.

Somewhat surprisingly, the results were similar in the Sami and the non-Sami population. There are, however, no validated criteria or definition of what it means to be Sami. The Sami Parliament has agreed upon a set of rules to qualify for their elections,¹¹ but there is neither a phenotype nor specific genes defining the Sami people. Only a small minority of the Sami people (<5%) are still holding on to a traditional life-style based on fishing, hunting and reindeer-herding and many previous health disparities are largely based on findings from these sub-groups of occupation. Like other ethnic minorities, the Sami people have suffered from discrimination and marginalization and data on Sami origin might have been underreported, contributing to dilution of the results. Also, due to migration, mixed ethnicity is now more prevalent, making ethnic classes more difficult to evaluate. Hence, studies of indigenous populations today might find that health disparities in general are decreasingly evident. In addition, the baseline health of the Sami has been demonstrated to be good, and there is no evidence of low life-expectancy or increased alcohol- or substance abuse being a serious health problem among other indigenous populations.⁸

It still seems convincing that movement is beneficial to health. The general conflicting findings for OPA might be mainly due to confounding factors, especially interconnecting lower socioeconomic status and hard occupational physical activity.^6,12 Recent evidence also indicates that occupational inactivity (in terms of longer occupational sitting time) is significantly associated with higher mortality.³ As almost any movement seems to be beneficial, it might not be the working hour movements in themselves that are futile, even if such and other hypotheses have been suggested, as referred by the authors.

The present study provides new and important knowledge about the association between physical activity and mortality in arctic climate and confirms the benefits of physical activity in a non-indigenous and an indigenous population such as the Sami people.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

References