Eliassen et al. BMC Public Health 2012, 12:948 http://www.biomedcentral.com/1471-2458/12/948 Confounding The overall comparability in this study is somewhat reduced as the populations differ with regard to living condition and the distribution of general risk factors; comparing the associations between acculturation and SRH may be flawed if the Inuit and Sami differ with re- gard to the distribution of confounding factors. This may however be statistically corrected for by adjusting for known and relevant confounding variables [67]. We have assessed and accounted for several potential major confounders, but not all. The notion that acculturation is synonymous with ill health may arise from failure to control for the negative effects of discrimination and SES, which often co-exist with acculturation [32,47,48,68]. Low SES may in some instances even work as a dimension of acculturation and in other function as an effect modifier [68]. We found no evidence of education confounding or modifying the effect of acculturation. Nevertheless, using education as a proxy for SES in this study is indeed challenging as ac- cess to education and the educational systems differ among the Inuit and the Sami, and it is likely that educa- tion is a more appropriate proxy in Norway than in Alaska and Greenland. Studies show that conventional SES such as education attainment cannot be directly ap- plied to Inuit populations [36]. Residual SES confound- ing may therefore be an issue in our study, which may damage the internal validity. However, it is important to note that education levels among the Inuit are improv- ing rapidly [9], thus strengthening the validity of educa- tion as a proxy for SES. Nevertheless, one still knows little about how SES plays into the relationship of accul- turation and health. More research is needed to assess possible confounding, mediating or modifying effects. As information on discrimination was not included in the questionnaire, we have been unable to control for its assumed effect. Our estimates may in this regard be biased away from the [68]. The association between acculturation and health sta- tus is conceptually thought to be mediated by health care use [69]. The Inuit of Alaska and Greenland, and the Sami are provided publicly funded health care [70,71]. What first and foremost distinguish Alaska and Greenland from Norway in terms of health care, are the enormous distances, poorly developed infrastructure, and the climatic conditions. A study in Canada among Inuit showed that education and remoteness are import- ant factors in terms of access to health care [72]. We have thus controlled for these variables; education and remoteness however do not exclusively explain variation in health care use. Residual confounding in this regard may also limit our analysis. Furthermore, language-based and culture sensitive health care service is offered to a varying degree in these countries which of course affect Page 9 of 11 both access to services but also the degree to which people are inclined to use them. Overall, because of bias due to discrepancies in word- ing, categorisation and cultural conceptualisation of SRH, and potential confounding, we cannot conclude convincingly on the relative strength of the effect esti- mates. It is plausible that residual confounding is influ- ential in these analyses; we are however convinced that enough confounding is accounted for in terms of con- trolling any distortion of qualitative character potentially affecting the direction of the associations. Also, compari- son of effect sizes in this study is not recommended as study efficiency and precision is affected by small sample sizes. Conclusions This study shows that aggregate acculturation is a strong risk factor for poorer SRH among the Kalaallit of Greenland and female Iñupiat of Alaska, but our cross- sectional study design does not allow any conclusion with regard to causality. Limitations with regard to wording, categorisations, assumed cultural differences in the conceptualisation of SRH, and confounding effects of health care use, SES and discrimination, make it diffi- cult to appropriately assess how strong this effect is though. Acculturation is indeed a process that takes place over time [3]; longitudinal research and large sam- ples are therefore required to examine the effect of ac- culturation on SRH within multiple dimensions among these populations, while simultaneously exploring how SES may play into this relationship. Abbreviations IASSA: International Arctic Social Science Association; IRB: University of Alaska Institutional Review Board; MI: Multiple Imputations; OR: Odds Ratio; SES: Socioeconomic Status; SILA: Spoken Indigenous Language Ability; SLiCA: Survey of Living Conditions in the Arctic: Inuit, Sami and the indigenous peoples of Chukotka; SRH: Self-Rated Health; STATA: STATA: Data Analysis and Statistical Software; 95% CI: 95% Confidence Interval. Competing interests The authors declare that they have no competing interests. Authors’ contributions BME carried out the statistical analysis and drafted the manuscript. TB executed the multiple imputation of missing data and participated in the statistical analysis. MM, KLH and ARB helped to draft the manuscript, while also MM assisted the statistical analysis. All authors read and approved the final manuscript. Acknowledgments The authors thank the Kalaallit of Greenland, the Iñupiat of Alaska and the Sami of Norway, who participated in the study. The authors also thank all project workers who participated in the data collection and processing in Greenland, Alaska and Norway. Finally, they thank Vigdis Stordahl and Jack Kruse for their constructive comments on an earlier version of this article. Author details 1Department of Community Medicine, Centre for Sami Health Research, University of Tromsø, Tromsø N-9037, Norway. 2Department of Community