Kojima Gotaro, Iliffe Steve, Tanabe Marianne
Department of Primary Care and Population Health, University College London (Royal Free Campus), Rowland Hill Street, London, NW3 2PF, UK.
Veterans Affairs Pacific Islands Health Care System, Honolulu, Hawaii, USA.
BMC Geriatr. 2017 Oct 16;17(1):236. doi: 10.1186/s12877-017-0631-0.
A recent controversy in vitamin D research is a "U-shaped association", with elevated disease risks at both high and low 25-hydroxyvitamin D (25 (OH) D) levels.
This is a cross-sectional study of 238 male nursing home veterans in Hawaii. Classification and regression tree (CART) analysis identified groups based on 25 (OH) D and vitamin D supplementation for frailty risk. Characteristics were examined and compared across the groups using logistic regression and receiver operating characteristic (ROC) curve analyses.
CART analysis identified three distinct groups: vitamin D supplement users (n = 86), non-users with low vitamin D (n = 55), and non-users with high vitamin D (n = 97). Supplement users were the most frail, but had high mean 25 (OH) D of 26.6 ng/mL, which was compatible with 27.1 ng/mL in non-users with high vitamin D, while mean 25 (OH) D of non-users with low vitamin D was 11.7 ng/mL. Supplement users and non-users with low vitamin D were significantly more likely to be frail (odds ratio (OR) = 9.90, 95% CI = 2.18-44.86, p = 0.003; OR = 4.28, 95% CI = 1.44-12.68, p = 0.009, respectively), compared with non-users with low vitamin D. ROC curve analysis showed the three groups significantly predicted frailty (area under the curve = 0.73), with sensitivity of 64.4% and specificity of 76.7%, while 25 (OH) D did not predict frailty.
In these nursing home veterans, vitamin D supplement users were the most frail but with high 25 (OH) D. This can potentially be a cause of U-shaped associations between vitamin D levels and negative health outcomes.
维生素D研究中最近的一个争议点是“U型关联”，即25-羟基维生素D（25(OH)D）水平过高和过低时疾病风险都会升高。
这是一项对夏威夷238名男性疗养院退伍军人的横断面研究。分类与回归树（CART）分析根据25(OH)D和维生素D补充情况确定了衰弱风险组。使用逻辑回归和受试者工作特征（ROC）曲线分析对各组的特征进行了检查和比较。
CART分析确定了三个不同的组：维生素D补充剂使用者（n = 86）、维生素D水平低的非使用者（n = 55）和维生素D水平高的非使用者（n = 97）。补充剂使用者最虚弱，但平均25(OH)D为26.6 ng/mL，与维生素D水平高的非使用者的27.1 ng/mL相当，而维生素D水平低的非使用者的平均25(OH)D为11.7 ng/mL。与维生素D水平低的非使用者相比，补充剂使用者和维生素D水平低的非使用者更有可能虚弱（优势比（OR）分别为9.90，95%置信区间为2.18 - 44.86，p = 0.003；OR = 4.28，95%置信区间为1.44 - 12.68，p = 0.009）。ROC曲线分析表明，这三组显著预测了衰弱（曲线下面积 = 0.73），敏感性为64.4%，特异性为76.7%，而25(OH)D不能预测衰弱。
在这些疗养院退伍军人中，维生素D补充剂使用者最虚弱，但25(OH)D水平较高。这可能是维生素D水平与不良健康结果之间U型关联的一个原因。
