Sex-specific height-correction of weight in a population with ethnic groups that differ in stature - the SAMINOR 1 Survey: a cross-sectional study

Abstract

Background: Body mass index (BMI, weight/height2) is a common proxy for body fatness, but it is negatively correlated with height. In Norway, the ethnic Sami people have had higher BMI and lower height than their non-Sami peers. This article aimed to examine if previous findings of higher obesity measures in Sami compared to non-Sami persist when applying an adequately height-corrected weight index.

Methods: We estimated a sex-specific height-corrected weight index—the Benn index—that is, weight/heightp where p is estimated from log(weight)-log(height) regression. We used data on 15 717 men and women aged 30 and 36–79 years who participated in the SAMINOR 1 Survey (2003–2004). Correlations between height and weight and the indices BMI and Benn index were calculated using Pearson’s correlation coefficient.

Results: BMI and height had a modest, negative correlation. Analyses were stratified by sex due to a statistically significant interaction (sex * log(height), p<0.001). There was no interaction with ethnicity (ethnicity * log(height), p=0.07 in women and p=0.24 in men). The p (95% confidence interval) in Benn index (weight/heightp) was estimated to 1.29 (1.21, 1.38) in women and 1.90 (1.83, 1.98) in men. Higher BMI in Sami compared to non-Sami was most evident in women, but Benn index did not differ by ethnicity in either sex.

Conclusion: Previous findings of higher obesity measures in Sami than in non-Sami may be biased. Future studies should take into account the marked height differences between these groups when comparing obesity indices.