Vitamin D, falls, fractures and function in community-dwelling older adults

描述（由申请人提供）：NHANES III的预测表明，大约12，000，000名60岁的美国成年人患有维生素D不足（血清25（OH）D < 50 nmol/L）。越来越多的证据表明，维生素D不足和/或其相关的继发性甲状旁腺功能亢进不仅通过对骨密度和骨折的影响，而且通过对肌肉功能的直接影响加速残疾过程，我们假设这会导致更高的活动受限率和福尔斯。由于维生素D不足即使在社区居住的老年人中也很常见，并且补救次优水平的成本很低，因此更好地了解老年人维生素D状态和功能之间的关系具有重要的公共卫生意义。为了促进我们对维生素D在功能和骨骼健康中的作用的理解，研究人员建议测量来自健康、衰老和身体组成（健康ABC）研究的存档样本中的循环25（OH）D和甲状旁腺激素（PTH）水平，该研究是一项由3，075名黑人和白色功能良好的社区居住男性和女性组成的队列，基线年龄为70-79岁。将讨论三个具体目标：具体目标1。确定通过循环25（OH）D和PTH确定的维生素D状态是否影响6年内活动受限的发生率;具体目标2。确定维生素D状态是否影响6年以上的福尔斯率;具体目标3。确定维生素D状态在6年内骨折风险中的作用。我们还将研究维生素D在这些重要结果的近端介质轨迹中的作用（即，力量、平衡、步行速度和骨矿物质密度）。作为次要目的，我们将评估：1）替代临界点，以告知老年人维生素D充足性的辩论; 2）PTH独立于维生素D的作用; 3）膳食和补充维生素D摄入对功能和骨骼的影响。我们将专门研究非裔美国人的相关性，这是一个维生素D不足的高风险群体。健康ABC具有关于重要功能结局（活动受限、福尔斯和骨折）和近端介质（力量、平衡、步行速度和骨矿物质密度）的纵向数据，是以具有成本效益和高效的方式推进这一高度优先领域科学知识的理想研究。

DESCRIPTION (provided by applicant): Projections from NHANES III indicate that approximately 12,000,000 US adults 60 years of age have vitamin D insufficiency (serum 25(OH)D < 50 nmol/L). A growing body of evidence suggests that vitamin D insufficiency and/or its associated secondary hyperparathyroidism accelerates the disablement process not only through effects on bone density and fractures but also through direct effects on muscular function which we hypothesize lead to higher rates of mobility limitation and falls. Since vitamin D insufficiency is common even in community-dwelling elderly, and the cost of remediating suboptimal levels is low, a better understanding of the relationship between vitamin D status and function in older adults is of significant public health importance. To advance our understanding of the role of vitamin D in function and bone health, the investigators propose to measure circulating 25(OH)D and parathyroid hormone (PTH) levels in archived samples from the Health, Aging and Body Composition (Health ABC) Study, a cohort of 3,075 black and white well-functioning community-dwelling men and women aged 70-79 yrs at baseline. Three specific aims will be addressed: Specific Aim 1. Determine whether vitamin D status as determined by circulating 25(OH)D and PTH affects the rate of incident mobility limitation over 6 years; Specific Aim 2. Determine whether vitamin D status affects the rate of falls over 6 years; Specific Aim 3. Determine the role of vitamin D status in fracture risk over 6 years. We will also examine vitamin D's role in trajectories of proximal mediators of these important outcomes (i.e., strength, balance, walking speed and bone mineral density). As secondary aims, we will evaluate: 1) alternative cut-points to inform the debate on vitamin D adequacy in older adults; 2) the role of PTH independent from vitamin D; and 3) the effects of dietary and supplementary vitamin D intake on function and bone. We will specifically examine the associations in African-Americans, a group at high risk for vitamin D insufficiency. Health ABC, with longitudinal data on important functional outcomes (mobility limitation, falls and fractures) and proximal mediators (strength, balance, walking speed and bone mineral density) is the ideal study to advance scientific knowledge in this area of high priority in a cost-effective and efficient manner.