Rod214 Portable Stadiometer, Seca) and weight was measured to the nearest 0.1 kg using an electronic scale. BMI-for-age z-score (BAZ), height-for-age z-score (HAZ) and weight-for-age z-score (WAZ) were calculated and interpreted using the World health organization (WHO) Child Growth Charts for children (21). The non-dominant calcaneus was measured using ultrasound Sahara Sonometer (Hologic, Bedford, MA, USA). Mea- surement of the os calcis consisted of BUA (expressed in decibels per megahertz, Ddb/DMHz) and SoS (expressed in meters per second, m/s). The quantitative ultrasound device measures BUA and SoS and the results are combined to estimate BMD. Ultrasound bone densito- metry was shown to be sensitive enough to detect physiological bone development in childhood (22) and compromised bone health in diseased children (16). At the start of each clinical day, the sonometer was quality checked according to the manufacturer’s instructions. Briefly, the machine was checked using a control bone also known as a ‘‘phantom’’. These assessments were recorded in a quality control log and tracked to ensure the machine was working consistently. Laboratory analysis Plasma Alkaline Phosphatase (ALP) and total calcium were measured by Beckman Coulter D C 800 (Beckman Coulter Inc., Mississauga, Ontario, Canada) at the Royal Victoria Hospital. The Laboratory participated in exter- nal validation and received a proficiency certificate for 2009 2010 from DigitalPT. High sensitivity C-reactive protein (CRP) was measured in the serum using Enzyme Linked Immunosorbance Assay. Plasma 25(OH)D and parathyroid hormone (PTH) concentrations were mea- sured using LIAISON total 25(OH)D and N-tact PTH assays (DiaSorin Inc., Stillwater, MN, USA) at McGill University. The inter-assay and the intra-assay coefficient of variation (CV) were 4.5 and 11.1% for the low 25(OH)D control (38.2 nmol/L) and 6.2 and 5.3% for the high 25(OH)D control (127.2 nmol/L); the accuracy using the mid-range of the manufacturer’s specifications was 95%. For the PTH low control, the inter-assay CV% was 19.1 (5.2 pmol/L) and 8.7 for the high PTH control (52.1 pmol/L). The accuracy using the mid-range of manufacture specifications was 86.7%. The labora- tory (HW) that measured 25(OH)D participated in the Vitamin D External Quality Assessment Scheme program and obtained a certificate of proficiency for 2009 2010, which reflects that ]80% of the reported results fell within 30% of the All-Laboratory Trimmed Mean. Statistical analysis Questionnaires and clinical information were entered into a Microsoft Access Database and 24-h dietary recall data were entered using CANDAT (Godin London). For outliers, all dietary variables exceeding mean 3 standard deviations (SD) were substituted with mean 3 SD. Bone mineral density of Inuit preschoolers in the Arctic For all other variables, values exceeding mean 3 SD were excluded. All variables were tested for norma- lity prior to statistical analysis using Shapiro Wilk test. Since variables were skewed, spearman correlations were used to identify correlations between BUA or SoS and different continuous characteristics. ANOVA, followed by Bonferroni post-hoc tests whenever appropriate, were used to determine whether dietary, anthropometric, biochemical and lifestyle factors were different by BUA or SoS quartiles when variables were continuous and Chi- square was used when variables were categorical. Prior to ANOVA, all skewed variables were log transformed or square rooted. Multivariable linear regression was used to identify predictors of SoS or BUA. SoS and BUA measurements were available for 285 children and full multivariable analysis was possible for 211 children, because data on food intake, accurate anthropometry measures, the number of hours spent outside or 25(OH)D concentration were missing. Various models were con- structed. Normality of residuals was ensured using the Kolmogorov Smirnov test along with visual examination of residual-normal quantile plot, and heteroskedasticity was evaluated using the Breusch Pagan/Cook Weisberg test. Variance inflation factors were examined post- regression to ensure the absence of multicollinearity. For all tests, p B0.05 was considered significant. Values in the text are percent (95% CI), means9SD, or medians with interquartile ranges (IQR). All statistical analyses were completed using Stata 10 (Stata Corp). Results Although 388 children participated in the health survey, not all children had BMD measures. Children with available SoS and BUA measures (n 285) were similar to those with unavailable values (n 103) for age, gender, BMI percentile, number of hours spent outside, amount of TF consumed the previous day, milk intake, calcium intake, vitamin D intake, carbohydrates intake, protein intake, fat intake, PUFA intake, monounsaturated fatty acids (MUFA) intake, saturated fatty acids (SFA) intake, plus concentrations of CRP, ALP, total calcium, PTH, and 25(OH)D. Thus, results are presented for only the 285 children with available BMD measures (Table I). The average latitude of communities participating in the study was 65.2 [95% CI: 64.8 65.68N]. Median plasma total calcium, ALP, CRP, and PTH concentra- tions of Inuit preschoolers fell in the normal range. However, median 25(OH)D concentration was below 50 nmol/L (Table I) with 57.5% [95% CI: 50.9 64.1%] of the children below this cut off and 82.2% were below 75 nmol/L. Of Inuit preschoolers, 60.9% met the EAR of 800 mg/d for calcium while 10.5% met the EAR of 10 mg/d for vitamin D. Since correlation coefficients were similar between boys and girls, all participants were analyzed together. Citation: Int J Circumpolar Health 2012, 71: 18999 - http://dx.doi.org/10.3402/ijch.v71i0.18999 3 (page number not for citation purpose)