Forearm bone mineral density varies as a function of adiposity in inuit women 40-90 years of age during the vitamin D-synthesizing period.

Abstract

Aging Inuit women are at increased risk for low vitamin D status due to habitation at higher latitudes, darker skin, and ongoing nutrition transition. Lower serum 25-hydroxyvitamin D (25[OH]D) concentration and higher risk of fracture have been separately reported in Inuit women, with particular relevance to postmenopausal women. We evaluated vitamin D status, forearm bone mineral density (fBMD), and nutrition in Inuit women ≥40 years. Women (n = 568) were randomly selected to participate in the 2007-2008 International Polar Year Inuit Health Survey from 36 Arctic communities. fBMD was measured using peripheral dual-energy X-ray absorptiometry. Dietary intakes were derived from 24 h recall and food-frequency questionnaires. Fasting serum 25(OH)D, parathyroid hormone, and osteocalcin (OC) were measured using a LIAISON(®) automated analyzer. The weighted prevalence of women having 25(OH)D concentration below 37.5, 50, and 75 nmol/L was 7.2 %, 17.6 %, and 48.6 %, respectively, with older women having better status. The dietary density of most nutrients increased with age, as did traditional food intake. fBMD was low in 3 (1.4 %) premenopausal (Z score < -2) and 107 (29.6 %) postmenopausal (T score < -1.5) women. Regression revealed that either weight, body mass index, or percent body fat significantly predicted fBMD in premenopausal women, in addition to age and OC in postmenopausal women. Women ≥50 years have higher vitamin D status and more nutrient-dense diets than women 40-49 years. While measures of adiposity predicted fBMD in all women, additional predictors after menopause included age and bone turnover.