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1.  The Hip Impact Protection Project: Design and Methods 
Nearly 340,000 hip fractures occur each year in the U.S. With current demographic trends, the number of hip fractures is expected to double at least in the next 40 years.
The Hip Impact Protection Project (HIP PRO) was designed to investigate the efficacy and safety of hip protectors in an elderly nursing home population. This paper describes the innovative clustered matched-pair research design used in HIP PRO to overcome the inherent limitations of clustered randomization.
Three clinical centers recruited 37 nursing homes to participate in HIP PRO. They were randomized so that the participating residents in that home received hip protectors for either the right or left hip. Informed consent was obtained from either the resident or the resident's responsible party. The target sample size was 580 residents with replacement if they dropped out, had a hip fracture, or died. One of the advantages of the HIP PRO study design was that each resident was his/her own case and control, eliminating imbalances, and there was no confusion over which residents wore pads (or on which hip).
Generalizability of the findings may be limited. Adherence was higher in this study than in other studies because of: (1) the use of a run-in period, (2) staff incentives, and (3) the frequency of adherence assessments. The use of a single pad is not analogous to pad use in the real world and may have caused unanticipated changes in behavior. Fall assessment was not feasible, limiting the ability to analyze fractures as a function of falls. Finally, hip protector designs continue to evolve so that the results generated using this pad may not be applicable to other pad designs. However, information about factors related to adherence will be useful for future studies.
The clustered matched-pair study design avoided the major problem with previous cluster-randomized investigations of this question – unbalanced risk factors between the experimental group and the control group. Because each resident served as his/her own control, the effects of unbalanced risk factors on treatment effect were virtually eliminated. In addition, the use of frequent adherence assessments allowed us to study the effect of various demographic and environmental factors on adherence, which was vital for the assessment of efficacy.
PMCID: PMC3725461  PMID: 18697849
2.  Adherence to Hip Protectors and Implications for U.S. Long-Term Care Settings 
Determine nursing home characteristics related to adherence to use of a hip protector (HP) to prevent fracture; also describe adherence and related resident characteristics.
A multi-center, randomized controlled trial of a HP in which adherence to wearing the HP was monitored by research staff three times a week for up to 21 months; data were collected by interviews and chart review.
Thirty-five nursing homes in Boston, St. Louis, and Baltimore.
A total of 797 eligible residents, 633 (79%) of whom passed the run-in period, 397 (63%) of whom remained in the study until the end of follow-up.
Residents wore a single HP on their right or left side.
In addition to regular monitoring of adherence, data were collected regarding facility characteristics, staffing, policies and procedures, perception of HPs and related experience, and research staff ratings of environmental and overall quality; and also resident demographic characteristics, and function, health, and psychosocial status.
Facility characteristics related to more adherence were not being chain-affiliated; less Medicaid case-mix; fewer residents wearing HPs; more paraprofessional staff training; more rotating workers; and having administrators who were less involved in meetings.
Efforts to increase adherence to the use of HPs should focus on facilities with more Medicaid case-mix to reduce disparities in care, and those that have less of a culture of training. Staff may need support to increase adherence, and when adherence cannot be maintained, HP use should be targeted to those who remain adherent.
PMCID: PMC2846526  PMID: 20142065
hip fracture; nursing homes; compliance
3.  Vitamin D Deficiency Is Associated With Worse Cognitive Performance and Lower Bone Density in Older African Americans 
Vitamin D deficiency is common in older adults and is more prevalent among persons with darker pigmented skin. The detrimental effects of vitamin D deficiency on the bone are widely known; however, recent data suggest that vitamin D deficiency may contribute to other disorders, including low mood, cognitive impairment, and impaired mobility.
The purpose of this study was to determine whether nonskeletal diseases such as depression, cognitive impairment, and physical disability, which have been associated with vitamin D deficiency, are more commonly seen in older African Americans.
In a cross-sectional study of 60 older adults (30 African Americans and 30 European Americans), vitamin D status, cognitive performance, physical performance, and bone mineral density (BMD) were assessed. Differences between groups and differences between those with vitamin D deficiency and those with normal vitamin D levels were tested.
African Americans had a lower mean 25-hydroxyvitamin D level (17.98 ng/ml; SD, 6.9) compared to European Americans (25.20 ng/ml; SD, 7.0; p < .0001). Participants with vitamin D deficiency performed worse on a measure of cognitive performance, the Short Blessed Test (10.87 vs 6.31; p = .016); the Physical Performance Test (PPT) (27.00 vs 28.96; p = .039); and had lower BMD (0.823 vs 0.914; p = .005) and t scores (−1.29 vs −0.72; p = .008) of the hip. Among African Americans, vitamin D deficiency was associated with worse cognitive performance and lower BMD of the hip.
Vitamin D deficiency in older African Americans was associated with worse cognitive performance and lower BMD of the hip.
PMCID: PMC2801439  PMID: 19397226
vitamins and minerals; African Americans; cognitive functioning; bone
4.  The Role of Phosphate in the Action of Vitamin D on the Intestine 
Journal of Clinical Investigation  1977;60(5):980-988.
The response of chick intestine to vitamin D and its metabolites was studied in an organ culture preparation of chick ileum explants. Both 25-hydroxycholecalciferol (25-OHD3) at a concentration of 20 ng/ml or greater and 1,25-dihydroxycholecalciferol [1,25-(OH)2D3] at a concentration of 50 pg/ml or greater stimulated the rate of accumulation of [32P]phosphate and 45Ca by the explants and the incorporation of [3H]thymidine into DNA. The accumulation of [32P]phosphate by the explants was against a concentration gradient and inhibited by ouabain and dinitrophenol. Two saturable mechanisms appeared to mediate the cellular accumulation of phosphate with Ka of 0.0047 and 0.125 mM, respectively. The Vmax of the lower affinity transport mechanism was accelerated by 1,25-(OH)2D3. Actinomycin D (5.0 μg/ml) did not block the intestinal response to 1,25-(OH)2D3 stimulation of both [32p]phosphate and 45Ca accumulation. Significant stimulation of [32P]phosphate accumulation was observed 30 min after the addition of 1,25-(OH)2D3, preceding the sterol-induced increase in the rate of 45Ca uptake by 30 min and the sterol-induced increase in [3H]thymidine incorporation into DNA by 150 min. Increasing extracellular phosphate concentration to 3.0 mM increased [3H]thymidine incorporation into DNA and the rate of 45Ca uptake by the explants. Reducing extracellular phosphate concentration to 0.05 mM attenuated the response of the explants to 1,25-(OH)2D3. From these observations it is postulated that the primary action of vitamin D sterols in the intestine is to enhance the ability of the mucosal cell to accumulate phosphate. The data suggest that restoration of intracellular phosphate levels may then permit expression of the cells' response to vitamin D sterols.
PMCID: PMC372449  PMID: 908762
5.  Identification of an Intestinal Sodium and Calcium-Dependent Phosphatase Stimulated by Parathyroid Hormone 
Journal of Clinical Investigation  1974;54(3):710-717.
Previous reports suggest that the site of the energy-dependent intestinal calcium transport against an electropotential and concentration gradient is located along the basal-lateral membrane of the mucosal cell. Accordingly, basal-lateral membranes were prepared from rat intestinal homogenates in order to identify the enzyme mediating this step in the transport process. An alkaline phosphatase was delineated which utilized ATP as a substrate and was dependent on both Na- and Ca++ with optimum enzyme activity at 200 mM and 0.04 mM, respectively. Furthermore, the activity of the enzyme was demonstrated to decrease with the advance in age of the animal and to decrease with removal of the parathyroid glands, consistent with a decreased rate of 45Ca release from mucosal cells under the same experimental conditions. Calcium binding to basal-lateral membrane fragments was also sodium dependent and enhanced by the prior administration of parathyroid extract. The consistent correlation between the rate of calcium transport across the basal-lateral membrane of the mucosal cell and the activity of this Na, Ca-dependent phosphatase under a variety of experimental conditions suggest that this enzyme may mediate the parathyroid hormone-sensitive active transport of calcium across the intestine.
PMCID: PMC301605  PMID: 4852407
6.  Influence of Sodium and Parathyroid Hormone on Calcium Release from Intestinal Mucosal Cells 
Journal of Clinical Investigation  1974;54(3):702-709.
The uptake and release of 45Ca from the intestinal mucosal epithelium were investigated under a variety of conditions. The initial rate of uptake characterized a calcium pool with a half-time of saturation of less than 2 min. The entry of 45Ca into this pool was inhibited by NaCN and ethacrynic acid and was stimulated by the removal of Cl- from the incubation. The initial rate of 45Ca release was also inhibited by NaCN and removal of Na+ from the incubation. Parathyroid hormone administration enhanced the release of 45Ca from cells prepared from parathyroid-ectomized animals. These observations suggest that calcium transport across the brush border and basallateral membranes are identifiable components of the kinetics of 45Ca uptake and release and that parathyroid hormone stimulates a sodium-dependent mechanism of calcium transport across the basal-lateral membranes.
PMCID: PMC301604  PMID: 4852449
7.  Study of calcium absorption in man: a kinetic analysis and physiologic model 
Journal of Clinical Investigation  1969;48(9):1705-1713.
A physical model of calcium absorption was developed from analysis of data obtained on 23 subjects, including 13 patients having a variety of abnormalities of calcium metabolism. The model was tested and found consistent in all subjects studied. This technique provides a quantitative description of the rate of entry of oral dose of 47Ca into the circulation as a function of time by analysis of serum or forearm radioactivity in response to intravenous and oral administration of 47Ca. The kinetics of the absorption process as proposed by the model are characterized by an initial delay phase of 15-20 min, by a maximal rate of absorption at 40-60 min after ingestion, and by 95% completion of the absorption within 2½ hr. Partial identification of the physiological counterparts of the model was possible by introduction of the isotope at various levels of the gut. Although the region of the duodenum was found to have the greatest rate of absorption per unit length in normal subjects, it was least responsive to stimulation by parathyroid hormone and suppression by calcium loading. Furthermore, the response of the gut to parathyroid hormone was delayed, whereas the suppression of absorption by intravenous or oral calcium loading was rapid and dramatic. The implications of these observations are discussed.
PMCID: PMC535742  PMID: 5822579

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