Biomedical subjects

S S Harris

Publications and source records attributed to S S Harris.

At least 19 recordsLinked to original sources

PubMed2005

Convective flow increases lipoplex delivery rate to in vitro cellular monolayers.

The mass transport characteristics of cationic, nonviral liposome-DNA plasmid complexes (lipoplexes) were evaluated over a range of fluid shear stresses. The typical case of stagnant flow transfection was expanded to include controlled fluid convection provided by constant flow through a parallel plate flow chamber. Equations describing the transport of lipoplex by sedimentation and convection were derived from theory and solved numerically. Instantaneous lipoplex delivery rate and total lipoplex surface delivery during a 72-h transfection were estimated for two shear stress levels and for static conditions. Theory predicted that lipoplex is delivered to the cell surface more than 12- to 19-fold faster through the addition of convection, at least for physiologic shear stresses of 2.3-9.7 dyn/cm2, respectively. These calculations were tested experimentally using a cell line (ECV-304) transfected with fluorescently labeled plasmid DNA formulated into a lipoplex. Transfections were conducted during cellular exposure to the same known, uniform levels of fluid shear stress presumed in theoretical calculations. Lipoplex delivery was increased by more than nine-fold at 2.3 dyn/cm2 compared to the static case as assessed by flow cytometric measurement. Lipoplex delivery was modestly reduced at the highest fluid shear stress, to six-fold of the static case, consistent with the disruption of lipoplex-cell binding mediated by hydrodynamic forces. The complicated relationship between fluid convection and lipoplex delivery has important implications for nonviral gene therapy.

Animals↗

PubMed2003

Leptin, body composition and bone mineral density in premenopausal women.

Body weight is known to be associated with bone mass, however, it is unclear whether body composition, as reflected by the percent of total weight that is fat tissue (%fat), is associated with bone mass independently of weight. Fat tissue is metabolically active, and hormonal factors may mediate an association of %fat with bone mass. Leptin, a hormone produced in fat tissue, has recently been shown to be inversely related to bone mass in mice, but whether it is related to human bone mass is uncertain. We sought to investigate the associations of %fat and of serum leptin concentration with bone mineral density (BMD) in a cohort of 153 premenopausal women. BMD measurements of the total hip, lumbar spine and total body as well as body composition were measured by dual energy X-ray absorptiometry (DXA). Serum leptin levels were established using a commercial competitive binding assay. Individually, body weight, %fat and leptin were each positively associated with BMD at all three sites. However, when we examined BMD either as a function of both body weight and %fat together, or as a function of both body weight and leptin together, we found that for a given body weight, BMD appeared to be inversely associated with %fat and similarly appeared to be inversely associated with leptin. When BMD was examined as a function of %fat and leptin together, we found that for a given %fat, leptin appeared to be inversely associated with BMD. In summary, the results of this study suggest that for a given body weight, a higher proportion of fat and a higher serum leptin concentration have negative associations with bone mass in premenopausal women.

Absorptiometry, Photon↗

PubMed2002

Calcium supplement and bone medication use in a US Medicare health maintenance organization.

This study was conducted to determine the prevalence of the use of calcium supplements and of prescription medications to prevent or treat osteoporosis in men and women in a large New England Medicare Health Maintenance Organization (HMO). A two-page diet, medication use and medical history questionnaire was sent to a random sample of 9000 out of 82 985 members and 2932 (32.6%) responded. Over 97% of the participants were Caucasian and 64.7% were female. The mean ages of the men and women were 74.4+/-5.8 and 74.6+/-6.2 years, respectively. Sixty-nine percent of the men and 59% of the women consumed two or fewer servings of dairy foods per day. Calcium supplement use was more prevalent among the women than the men (66.8% vs 24.9%, p<0.001). Men and women with higher dairy food intakes were more likely to take calcium supplements than were those with lower dairy intakes. Prescription bone medications (including bisphosphonates, raloxifene and calcitonin) were used currently by 17.5% of the women and 2.3% of the men ( p<0.001). An additional 16.2% of the women currently took estrogen. Among the women, bone medication use did not change with age but estrogen use declined with increasing age. Among women age 80+ years, 15.6% used bone medications and 4.9% took estrogen. According to a national survey, more than half the US Caucasian female population over age 80 years has bone density low enough to warrant treatment under current guidelines. Based on the results of this survey, many elderly men and women may benefit from increased utilization of calcium supplements and bone-active medications.

Aged↗

PubMed2002

Household tobacco smoke exposure is negatively associated with premenopausal bone mass.

Subjects exposed to environmental tobacco smoke have been found to be at increased risk for several health problems. Whether exposure to passive tobacco smoke is associated with reduced bone mineral density (BMD) is unknown. In order to examine this, we measured BMD in 154 healthy premenopausal women (age range 40-45 years). BMD of the total hip, femoral neck, lumbar spine and total body was measured by dual-energy X-ray absorptiometry (DXA). Data were collected on exposure to household tobacco smoke from age 10 years to the present as well as on other lifestyle factors related to bone mass. We found that 67.5% of the subjects had a history of household tobacco smoke exposure. Subjects exposed to household tobacco smoke had a mean adjusted BMD that was significantly lower at the total hip ( p = 0.021) and femoral neck ( p = 0.018) compared with subjects who were not exposed. In addition, duration of household tobacco smoke exposure was negatively associated with BMD at the total hip ( p = 0.010), femoral neck ( p = 0.004), lumbar spine ( p = 0.037) and total body ( p = 0.031). Subjects exposed to household tobacco smoke for 15 years or more had mean adjusted BMD that was 4% lower at the total body, and more than 8% lower at the total hip, femoral neck and lumbar spine, compared with subjects who were not exposed. In conclusion, household tobacco smoke exposure during adolescence and young adulthood was found to be negatively associated with BMD at the total hip and femoral neck, and duration of exposure was negatively associated with BMD at the total hip, femoral neck, lumbar spine and total body in premenopausal women.

Absorptiometry, Photon↗

PubMed2001

Calcium and vitamin D supplements reduce tooth loss in the elderly.

PURPOSE: Oral bone and tooth loss are correlated with bone loss at nonoral sites. Calcium and vitamin D supplementation slow the rate of bone loss from various skeletal sites, but it is not known if intake of these nutrients affects oral bone and, in turn, tooth retention. SUBJECTS AND METHODS: Tooth loss was examined in 145 healthy subjects aged 65 years and older who completed a 3-year, randomized, placebo-controlled trial of the effect of calcium and vitamin D supplementation on bone loss from the hip, as well as a 2-year follow-up study after discontinuation of study supplements. Teeth were counted at 18 months and 5 years. A comprehensive oral examination at 5 years included assessment of caries, oral hygiene, and periodontal disease. The odds ratio (OR) and 95% confidence interval (CI) of tooth loss were estimated by stepwise multivariate logistic regression. Initial age (mean +/- SD) of subjects was 71 +/- 5 years, and the number of teeth remaining was 22 +/- 7. RESULTS: During the randomized trial, 11 of the 82 subjects (13%) taking supplements and 17 of the 63 subjects (27%) taking placebo lost one or more teeth (OR = 0.4; 95% CI: 0.2 to 0.9). During the 2-year follow-up period, 31 of the 77 subjects (40%) with total calcium intake of at least 1000 mg per day lost one or more teeth compared with 40 of the 68 subjects (59%) who consumed less (OR = 0.5; 95% CI: 0.2 to 0.9). CONCLUSION: These findings suggest that intake levels of calcium and vitamin D aimed at preventing osteoporosis have a beneficial effect on tooth retention.

Aged↗

PubMed2001

Weight and body mass index at menarche are associated with premenopausal bone mass.

Adolescence is a critical time for skeletal growth and mineralization. Exposure to protective or detrimental factors during this period may influence peak bone mass attainment and subsequent development of osteoporosis. In order to evaluate the association of body size during adolescence with subsequent adult bone mass, we conducted a follow-up study of a community-based cohort of girls who participated in a growth and sexual maturation study 30 years ago. Data from the original study included age at menarche, height at menarche and weight at menarche. Follow-up evaluation of 119 subjects, now premenopausal women ages 40-45 years, included bone mineral density (BMD) measurements of the total body, lumbar spine, femoral neck, total hip, and ultradistal radius by dual-energy X-ray absorptiometry. After adjustment for current adult weight and other factors related to bone mass, weight at menarche was found to be positively associated with subsequent adult BMD. Similarly, body mass index (BMI) at menarche was positively associated with adult BMD. In contrast, age at menarche was not found to predict adult BMD. When the subjects were divided into quartiles based on their BMI at menarche, subjects in the lowest quartile of BMI at menarche had adult mean BMD that was 8-15% lower at the measured sites compared with subjects in the highest quartile of BMI at menarche. In conclusion, low body weight and low BMI at menarche appear to be significant predictors of reduced bone mass in healthy premenopausal women ages 40-45 years.

Adult↗

PubMed2001

Vitamin D status of an outpatient clinic population.

Vitamin D insufficiency contributes to bone loss and fracture risk. Low 25-hydroxyvitamin D (25OHD) levels are common in elderly people and in housebound and hospitalized patients. This study was conducted to assess wintertime 25OHD levels in relation to self-reported vitamin D supplement use in an outpatient thyroid clinic population. We assessed the medical history, vitamin D intake from milk and supplements, and serum 25OHD levels in 231 women and 41 men who attended a Thyroid Clinic between January and March, 1999. Of the 272 outpatients, 13.6% had 25OHD levels <40 nmol/l and 53.3% had levels below 80 nmol/l. Fewer than 15% of the patients consumed more than 200 IU per day of vitamin D from milk. Vitamin D supplement use was a positive determinant of serum 25OHD concentration (P < 0.001). For example, among the largest homogenous subset of patients, Caucasian women (n = 137), 30% of the unsupplemented women, and 65% of those taking 400 lU/day of vitamin D had levels of 25OHD as high as 80 nmol/l. Other significant determinants of 25OHD levels were race, weight, milk intake, and recent southern travel. Thyroid disorder, serum TSH level, and age were not predictors of serum 25OHD concentration. In conclusion, at their current dietary vitamin D intake levels, most patients at this latitude will need vitamin D supplements in the wintertime.

Adult↗

PubMed2001

Secondary hyperparathyroidism and bone turnover in elderly blacks and whites.

This study was undertaken to describe the prevalence of secondary hyperparathyroidism in African-American and Caucasian participants in the Boston Low-Income Elderly Osteoporosis Study and to examine and compare associations of hyperparathyroidism with biochemical markers of bone turnover and bone density in the two racial groups. Serum osteocalcin and serum cross-linked N-telopeptides of type I collagen, and calcaneal bone mineral density were measured in February or March in 255 men and women, 64 yr of age and older. Subjects were categorized as normal or as having hyperparathyroidism, based on a serum PTH concentration below or above the top of the normal range (6.9 pmol/liter), respectively. The prevalence of hyperparathyroidism was 38% in the 144 black subjects and 20% in the 111 white subjects. Serum osteocalcin and cross-linked N-telopeptides of type I collagen were significantly higher in both black and white hyperparathyroid subjects (P < 0.05), and the hyperparathyroid-related difference in osteocalcin was greater among black than white subjects. Hyperparathyroidism was significantly associated with reduced heel bone mineral density in blacks (P = 0.008) but not in whites. This study provides evidence that secondary hyperparathyroidism is prevalent in elderly adults, both black and white, and that it should not be viewed as a benign condition in either group. Recent public health efforts to promote higher calcium and vitamin D intakes, targeted predominantly to older Caucasians, should also be directed to older African-Americans.

Black or African American↗

PubMed2000

Associations of the collagen type Ialpha1 Sp1 polymorphism with five-year rates of bone loss in older adults.

The collagen type Ialpha1 Sp1 (ColIA1) polymorphism has been associated with reduced bone mineral density (BMD) and increased prevalence of osteoporosis. This study examines associations of the ColIA1 genotype with BMD and 5-year rates of change in BMD in elderly men and women. The 243 subjects, aged 65 years and older, were participants in two consecutive studies lasting a total of 5-years. BMD of the total body, femoral neck, and lumbar spine were made by dual-energy X-ray absorptiometry (DXA). The distribution of the genotypes (155 in the SS genotype, 79 in Ss, and 9 in ss) was proportionately similar to those reported by others. Baseline BMD did not differ significantly at any skeletal site. Unadjusted 5-year percent changes in BMD differed significantly by genotype only at the total body (P = 0.009), where the change was -0.29+/-0.21 (SEM) in the SS genotype, -0.60+/-0.25 in the Ss genotype, and -3.01+/-0.72 in the ss genotype. This 9.4% increase in bone loss of the ss genotype relative to the SS genotype was reduced to an 8.9% increase after adjustment for sex, age, weight, and supplementation group. Results at the femoral neck were directionally similar, but not statistically significant. No effect of genotype on change in spine BMD was observed. In conclusion, bone loss from the total body was significantly greater in elderly men and women who were homozygous for the s allele compared with heterozygotes and SS homozygotes. This finding suggests a possible explanation for the association of the ColIA1 polymorphism with increased rates of osteoporotic fracture, but should be interpreted with caution because of the small number of subjects in the unfavorable ss genotype.

Absorptiometry, Photon↗

PubMed2000

Effect of withdrawal of calcium and vitamin D supplements on bone mass in elderly men and women.

BACKGROUND: Supplementation with calcium and vitamin D reduces bone loss and prevents fractures in elderly people, but it is not known whether any lasting benefit remains if the supplements are discontinued. OBJECTIVE: The objective was to determine whether gains in bone mineral density (BMD) induced by calcium and vitamin D supplementation persist after supplement withdrawal. DESIGN: Two-hundred ninety-five healthy, elderly men and women (aged >/=68 y) who had completed a 3-y randomized, placebo-controlled trial of calcium and vitamin D supplementation were followed for an additional 2 y during which no study supplements were given. BMD was measured by dual-energy X-ray absorptiometry, and biochemical variables related to calcium metabolism and bone turnover were measured. RESULTS: In the 128 men, supplement-induced increases in spinal and femoral neck BMD were lost within 2 y of supplement discontinuation, but small benefits in total-body BMD remained. In the 167 women, there were no lasting benefits in total-body BMD or at any bone site. Consistent with the observations on BMD, the bone turnover rates in both men and women (as measured by serum osteocalcin concentrations) returned to their original higher concentrations within the same 2-y period. CONCLUSION: Discontinued calcium and vitamin D supplementation has limited cumulative effect on bone mass in men and women aged >/=68 y.

Absorptiometry, Photon↗

PubMed2000

Vitamin D insufficiency and hyperparathyroidism in a low income, multiracial, elderly population.

This report examines the wintertime vitamin D and PTH status of 308 participants in the Boston Low Income Elderly Osteoporosis Study of noninstitutionalized low income elderly men and women (age, 64-100 yr) living in subsidized housing in Boston, MA. Twenty-one percent of the 136 black subjects and 11% of the 110 whites had very low plasma 25-hydroxyvitamin D (25OHD) concentrations (<25 nmol/L), and 73% of the blacks and 35% of the whites had 25OHD concentrations less than 50 nmol/L. The mean 25OHD levels of the smaller Hispanic and Asian subsets were generally similar to those of the white subjects. In addition to race, significant predictors of 25OHD included vitamin D intake (positive association) and smoking (inverse association), but not sex or age. Low 25OHD concentrations were associated with increased PTH and reduced serum calcium. The PTH level in the black subjects was substantially higher than that in the white subjects, and this difference was only partially explained by the racial difference in 25OHD. Elderly individuals who live in northern areas, particularly African-Americans, should be strongly encouraged to increase their vitamin D intake, especially in winter.

Activities of Daily Living↗

PubMed1999

Plasma 25-hydroxyvitamin D responses of younger and older men to three weeks of supplementation with 1800 IU/day of vitamin D.

OBJECTIVE: The objective of this study was to compare changes in plasma 25-hydroxyvitamin D (25(OH)D) levels of younger and older men after three weeks of oral vitamin D supplementation. METHODS: Nine younger men (22 to 28 years) and nine older men (65 to 73 years) with self-reported vitamin D intakes below 200 IU/d were enrolled in February and randomized to 1800 IU/d of ergocalciferol (vitamin D2, n=11) or to a control group (n=7) and followed for three weeks. Blood was collected at baseline, and after one, two and three weeks for measurement of plasma concentrations of total 25(OH)D, 25(OH)D2 and 25(OH)D3. RESULTS: In both the younger and older supplemented men, 25(OH)D2 and total 25(OH)D concentrations increased significantly during the study, whereas values of these metabolites did not change in younger or older control subjects. No group showed significant changes in 25-hydroxyvitamin D3. There was a significant interaction between age group and supplement group, suggesting that the effect of vitamin D2 supplementation on changes in 25(OH)D2 changes with age. The mean increase in 25(OH)D2 was greater in the younger supplemented men than in the older supplemented men (37+/-9 nmol/L vs. 19.5 nmol/L, p=0.027), and this accounted for their significantly greater increase in total 25(OH)D. CONCLUSION: These data are consistent with an age-related decline in the absorption, transport or liver hydroxylation of orally-consumed vitamin D.

Absorption↗

PubMed1998

The association of oral contraceptive use with plasma 25-hydroxyvitamin D levels.

OBJECTIVE: This analysis was conducted to compare wintertime 25-hydroxyvitamin D (25OHD) levels of young women who did and did not use oral contraceptives (OC). METHODS: The subjects were 66 Caucasian women aged 20 through 40 recruited from the Boston area. Plasma 25OHD was measured in February or March and again 1 year later. Other measurements included height, weight and vitamin D intake from diet and supplements. RESULTS: The initial mean 25OHD level of the 26 OC users was 41% higher than those of nonusers before adjustment for age and vitamin D intake (83 +/- 40 (sd) nmol/L compared with 59 +/- 22), and 39% higher after adjustment (p = 0.003). Five women who discontinued OC use during the year following their initial measurement all had decreases in their 25OHD levels (mean change was -25.5 +/- 17.7 (SD) nmol/L), whereas levels in women whose OC use or non-use was constant did not change. CONCLUSION: OC use increases circulating levels of 25OHD, and should be considered when interpreting values obtained for clinical evaluation or nutrition research.

Adult↗

PubMed1998

Seasonal changes in plasma 25-hydroxyvitamin D concentrations of young American black and white women.

Seasonal changes in 25-hydroxyvitamin D concentrations were studied in 51 black and 39 white women aged 20-40 y from Boston. Individual measurements were made in February or March (February-March), June or July (June-July), October or November (October-November), and the following February or March (February-March). Samples from the four visits were analyzed in batches at the end of the study. Plasma 25-hydroxyvitamin D was substantially lower in black than in white women at all the time points, including February-March when values were lowest (30.2 +/- 19.7 nmol/L in black and 60.0 +/- 21.4 nmol/L in white women) and June-July when they were highest (41.0 +/- 16.4 nmol/L in black and 85.4 +/- 33.0 nmol/L in white women). Although both groups showed seasonal variation in 25-hydroxyvitamin D concentrations, the mean increase between February-March and June-July was smaller in black women (10.8 +/- 14.0 nmol/L compared with 25.4 +/- 29.8 nmol/L in white women, P = 0.006) and their overall amplitude of seasonal change was lower (P = 0.001). Concentrations of serum parathyroid hormone in February-March were significantly higher (P < 0.005) in black women (5.29 +/- 2.32 pmol/L) than in white women (4.08 +/- 1.41 pmol/L) and were significantly inversely correlated with 25-hydroxyvitamin D in blacks (r = -0.42, P = 0.002) but not in whites (r = -0.19, P = 0.246). Although it is well established that blacks have denser bones and lower fracture rates than whites, elevated parathyroid hormone concentrations resulting from low 25-hydroxyvitamin D concentrations may have negative skeletal consequences within black populations.

Adult↗

PubMed1997

Effect of calcium and vitamin D supplementation on bone density in men and women 65 years of age or older.

BACKGROUND: Inadequate dietary intake of calcium and vitamin D may contribute to the high prevalence of osteoporosis among older persons. METHODS: We studied the effects of three years of dietary supplementation with calcium and vitamin D on bone mineral density, biochemical measures of bone metabolism, and the incidence of nonvertebral fractures in 176 men and 213 women 65 years of age or older who were living at home. They received either 500 mg of calcium plus 700 IU of vitamin D3 (cholecalciferol) per day or placebo. Bone mineral density was measured by dual-energy x-ray absorptiometry, blood and urine were analyzed every six months, and cases of nonvertebral fracture were ascertained by means of interviews and verified with use of hospital records. RESULTS: The mean (+/-SD) changes in bone mineral density in the calcium-vitamin D and placebo groups were as follows: femoral neck, +0.50+/-4.80 and -0.70+/-5.03 percent, respectively (P=0.02); spine,+2.12+/-4.06 and +1.22+/-4.25 percent (P=0.04); and total body, +0.06+/-1.83 and -1.09+/-1.71 percent (P<0.001). The difference between the calcium-vitamin D and placebo groups was significant at all skeletal sites after one year, but it was significant only for total-body bone mineral density in the second and third years. Of 37 subjects who had nonvertebral fractures, 26 were in the placebo group and 11 were in the calcium-vitamin D group (P=0.02). CONCLUSIONS: In men and women 65 years of age or older who are living in the community, dietary supplementation with calcium and vitamin D moderately reduced bone loss measured in the femoral neck, spine, and total body over the three-year study period and reduced the incidence of nonvertebral fractures.

Aged↗

PubMed1997

Plasma calcidiol, season, and serum parathyroid hormone concentrations in healthy elderly men and women.

Wintertime declines in vitamin D lead to increased concentrations of parathyroid hormone (PTH) and accelerated bone loss in postmenopausal women. We conducted this study to compare calcidiol (25-hydroxyvitamin D) concentrations of men and women, to examine the influence of season, travel, vitamin D intake, and other variables on these concentrations, and to compare associations between calcidiol and PTH concentrations in elderly men and women. In this cross-sectional study of 182 men and 209 women aged > 65 y, mean calcidiol concentrations were higher in men than in women overall (mean +/- SD: 82.4 +/- 35.8 compared with 68.9 +/- 32.1 nmol/L, P < 0.001). In the subset measured in winter (February-May), plasma calcidiol concentrations were lower and not significantly different in men (59.4 +/- 21.8, n = 52) and women (57.7 +/- 23.4 nmol/L, n = 83). In a multiple-regression model, calcidiol concentrations were positively influenced by wintertime travel (P = 0.012), vitamin D intake (P = 0.002), and time spent outdoors (P = 0.096) and negatively influenced by weight (P < 0.001) and age (P = 0.039). Plasma calcidiol and serum PTH concentrations were inversely related, with PTH rising slowly as calcidiol concentrations declined below 110 nmol/L (95 CI: 60, 168 nmol/L). More than 90% of the men and women had calcidiol concentrations below this value in the wintertime. The high prevalence of lower wintertime calcidiol values may increase risk of bone loss in elderly men and women.

Aged↗

PubMed1997

The vitamin D receptor start codon polymorphism (FokI) and bone mineral density in premenopausal American black and white women.

This study examines the association between bone mineral density (BMD) and a start codon polymorphism (SCP) at the translation initiation site of the vitamin D receptor (VDR) gene. The thymine/cytosine (T/C) polymorphism in the first of two start (ATG) codons can be detected by a restriction fragment length polymorphism (RFLP) using the endonuclease FokI, which recognizes ATG as part of its restriction site. F indicates absence of the first ATG and a VDR that is shorter by three amino acids. The FokI genotype was determined in 154 premenopausal American women (72 black and 82 white) who were 20-40 years old. BMD of the total body, femoral neck, and lumbar spine were measured by dual-energy X-ray absorptiometry. The distribution of the SCP genotypes differed significantly by race (p < 0.001): 4% of blacks versus 18% of whites were ff homozygous and 65% of blacks versus 37% of whites were FF homozygous. There was no statistically significant interaction between race and SCP genotype in analyses of BMD at any skeletal site. In the group as a whole, the ff women had femoral neck BMD that was 7.4% lower than that of the FF women. The ff white women had total body BMD values that were 4.3% lower and femoral neck values that were 12.1% lower than FF white women. Total body and femoral neck BMD did not differ significantly by genotype in black women, and spine BMD did not differ by genotype in either race. Addition of the SCP genotype to analysis of covariance models comparing BMD of the black and white women reduced estimated differences in femoral neck BMD between the two groups by about 35%. In conclusion, the SCP polymorphism, detected with the endonuclease FokI, appears to influence peak bone density, particularly at the femoral neck. Racial differences in its distribution may explain some of the racial difference in femoral neck BMD.

Adult↗

PubMed1996

Weight, body composition, and bone density in postmenopausal women.

Associations of body weight and body composition with bone mineral density (BMD) were examined in 261 postmenopausal women. BMD, body fat, and body nonfat soft tissue (NFST) were measured by dual-energy X-ray absorptiometry (DXA). A height-independent BMD variable (HIBMD) was calculated to correct for differences among individuals in bone thickness, a dimension that is ignored by DXA scanners. HIBMD was calculated as BMD divided by height at the spine and femoral neck, and BMD divided by the square root of height at the total body. Weight, fat, and nonfat soft tissue were all positively correlated with both BMD and HIBMD, but the magnitudes of regression and correlation coefficients were lower when HIBMD was the dependent variable. The weight-independent associations of body composition with HIBMD were examined by including weight and % NFST together in linear models. In these analyses, weight was positively associated with HIBMD at all three skeletal sites (r = 0.22-0.26, P < 0.05), % NFST was not associated with HIBMD at the spine or femoral neck (r = 0.01-0.02), and there was only a weak inverse correlation of % NFST with total body BMD (r = -0.12, P < 0.05). These findings are consistent with those of previous studies demonstrating positive associations between body weight and BMD. In addition, they demonstrate that once bone thickness and body weight are taken into account, body composition appears to have little if any independent effect on bone density at the skeletal sites measured. This finding is consistent with the hypothesis that the protective effect of body weight is brought about predominantly through its mechanical force on the skeleton.

Aged↗