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Biomedical subjects

Vasi Naganathan

Publications and source records attributed to Vasi Naganathan.

10 recordsLinked to original sources
PubMed2005

Gender differences in relationships between body composition components, their distribution and bone mineral density: a cross-sectional opposite sex twin study.

Numerous studies indicate that bone mineral density (BMD) is closely related to body mass and its components. Most studies have examined these relationships in women with little attention given to how these relationships differ by gender. The aims of the present study were to use the opposite sex twin model to determine if there were gender differences in the relationship between body composition and its relation to BMD and how any such differences were influenced by age. We measured body composition and bone mass by dual energy X-ray absorptiometry in 93 pairs of opposite sex twins. To examine the effect of age, they were divided into two age groups: under 50 years old (45 pairs) and over 50 years old (48 pairs). Lean mass (LM) had stronger positive relationships with the most bone variables than fat mass in both genders at all ages. Fat mass (FM) had positive relationships with total body and hip BMD in women under age 50, but not over 50. There was no significant relationship between FM and total or regional BMD in men under age 50, but men over 50 showed positive relationships between FM measures and total and some regional BMD measures. Central adiposity showed a positive relationship with BMD in men over 50 and women under 50. Fat mass (FM) and lean mass (LM) and their distribution in the body have different relationships with regional BMD in men and women that differ by age.

Absorptiometry, Photon↗
PubMed2004

Prescribing in older people.

BACKGROUND: Prescribing medications to older people is difficult due to comorbidity, limited evidence for efficacy, increased risk of adverse drug reactions, polypharmacy, and altered pharmacokinetics. OBJECTIVE: This article describes the principles underlying clinical geriatric pharmacology including approaches to evaluating the evidence for risk and benefit, and adjusting dose for age related pharmacokinetic changes. DISCUSSION: The challenge for the general practitioner is to balance an incomplete evidence base for efficacy in frail, older people against the problems related to adverse drug reactions without denying older people potentially valuable pharmacotherapeutic interventions.

Aged↗
PubMed2003

Relationship between pretreatment bone resorption and vertebral fracture incidence in postmenopausal osteoporotic women treated with risedronate.

UNLABELLED: It is unclear whether the antifracture efficacy of bisphosphonates depends on pretreatment bone turnover. We analyzed the risedronate phase III clinical programs using the urinary excretion of deoxypyridinoline (uDPD) as an index of pretreatment bone resorption rates. Risedronate reduced incident vertebral fractures in women with postmenopausal osteoporosis independent from pretreatment bone resorption. INTRODUCTION: Earlier studies on postmenopausal osteoporosis have suggested that the therapeutic efficacy of antiresorptive therapies might be influenced by pretreatment bone turnover. Because all of these studies have used bone mineral density (BMD) as the primary endpoint, it remains unclear whether this association holds true for incident fractures. MATERIALS AND METHODS: This study aims to answer this question in a post hoc analysis of a subset of the risedronate phase III clinical programs, using the urinary excretion of deoxypyridinoline (uDPD) as an index of pretreatment bone resorption (PBR). A total of 1593 women with postmenopausal osteoporosis that had baseline uDPD values and paired spinal radiographs available were pooled, in similar proportions, from the risedronate multinational and North American VERT, and from the risedronate HIP trials. Patients from treatment and placebo groups were stratified by the uDPD premenopausal normative median. The four resulting groups were balanced for age, years since menopause, body mass index, baseline femoral neck BMD, and number of prevalent fractures, but baseline lumbar spine BMD was significantly higher in patients with low PBR rates. RESULTS: In all groups, the proportion of patients with new vertebral fractures was higher in patients with baseline uDPD levels above the normative median. The incidence of vertebral fracture was significantly lower in groups assigned to risedronate compared with placebo. This effect was independent of PBR: in patients with high PBR, the relative risk (RR) of vertebral fracture after 1 year of risedronate was 0.28 (p = 0.03 compared with controls, absolute risk reduction 7.1%). In patients with low PBR, the RR of fracture after 1 year was 0.33 (p < 0.001, absolute risk reduction 4%). After 3 years, the RR of fracture was 0.52 (p = 0.042, absolute risk reduction 8.3%) in patients with high PBR, and 0.54 (p = 0.002, absolute risk reduction 7.1%) in patients with low PBR. Results were similar after adjusting for age, baseline lumbar spine BMD, and prevalent fractures. The number needed to treat to avoid one vertebral fracture at 12 months was 15 in the group of patients with high PBR and 25 in patients with low PBR. Risedronate significantly increased lumbar spine BMD. During the first year of treatment, women with high PBR gained lumbar spine BMD at a faster rate than patients with low PBR. Treatment-by-PBR status interactions were not significantly different over time. CONCLUSION: The efficacy of risedronate to reduce incident vertebral fractures in women with postmenopausal osteoporosis is largely independent of pretreatment bone resorption rates.

Aged↗
PubMed2003

Gender differences in volumetric bone density: a study of opposite-sex twins.

Gender difference in bone size is a potential confounder when comparing bone density between males and females. A comparison of volumetric BMD (vBMD) between men and women, which is a measure of bone mass relative to three-dimensional bone volume (g/cm(3)) as opposed to areal bone density (g/cm(2)), may be a more accurate reflection of gender differences in bone density. The aims of this study were to examine gender differences in bone mass (BMC), areal BMD (aBMD), volumetric BMD (vBMD) by comparing twins of opposite sex in whom the effects of age, genes and environment are partially controlled for. DEXA derived BMC, aBMD, vBMD at the third lumbar vertebra (L3), femoral neck (FN) and forearm (1/3 radius) were compared between 82 opposite sex pairs aged 18-80. BMC was significantly higher in males at all three sites (26-45.5%). For aBMD the gender differences remained significant at all sites except the spine. The average differences in aBMD were not as great as the differences in BMC (2.2-20.5%). The differences in vBMD, however, followed a different pattern. FN and L3 vBMD were significantly higher in females (4.8 and 0.6%, respectively), while radial BMD was not significantly different between the sexes. Comparing aBMD values between males and females, when females in general have a smaller skeleton than males may not be a true indication of gender differences in bone density. A comparison of vBMD between men and women shows only small differences in bone density between the sexes.

Adult↗
PubMed2003

Prevention and treatment of glucocorticoid-induced osteoporosis: a comparison of calcitriol, vitamin D plus calcium, and alendronate plus calcium.

High-dose corticosteroids, used for many medical conditions, are associated with rapid bone loss from sites such as the vertebrae, and compression fractures can be observed within months. Recent trials suggest treatment with bisphosphonates or active vitamin D analogs can reduce bone loss and the risk of fracture associated with glucocorticoids, but few studies have directly compared such agents. We conducted a randomized, multicenter, open-label trial to compare the efficacy of alendronate, calcitriol, and simple vitamin D in prevention and treatment of glucocorticoid-induced bone loss. A total of 195 subjects (134 females and 61 males) commencing or already taking glucocorticoids were randomized to one of three groups: calcitriol, 0.5 to 0.75 microg/day; simple vitamin D (ergocalciferol, 30,000 IU weekly) plus calcium carbonate (600 mg daily); or alendronate, 10 mg/day plus calcium carbonate (600 mg daily). Over 2 years, mean lumbar bone mineral density change was +5.9% with alendronate, -0.5% with ergocalciferol, and -0.7% with calcitriol (p < 0.001). At the femoral neck, there was no significant difference in bone mineral density change between the treatments over 2 years: alendronate (+0.9%), ergocalciferol (-3.2%), and calcitriol (-2.2%). Lumbar bone loss varied according to whether patients were starting or receiving chronic glucocorticoids, and there was a significant treatment x prior glucocorticoid use interaction effect. Six of 66 calcitriol subjects, 1 of 61 ergocalciferol subjects, and 0 of 64 alendronate subjects sustained new vertebral fractures. These data do not suggest any difference between simple vitamin D and calcitriol but do show that alendronate was superior to either treatment for glucocorticoid induced bone loss.

Absorptiometry, Photon↗
PubMed2002

Gender differences in the genetic factors responsible for variation in bone density and ultrasound.

Although genetic factors are thought to explain a large proportion of the variation in bone density in women, few studies have been conducted in men. Therefore, it is unclear whether the individual differences in bone strength between men and women are a reflection of gender differences in the relative influence of genetic and environmental factors on bone density variance. The aim of this study was to determine if there were gender differences in the genetic components of variance for bone density and ultrasound. In addition, the study aimed to explore the hypothesis that there are unique gender-specific genetic determinants of these traits. Bone mineral density (BMD) of the hip, distal forearm, and lumbar spine were measured by dual-energy X-ray absorptiometry (DXA) as well as quantitative ultrasound (QUS) at the calcaneus in healthy female twin pairs (286 identical [MZ] and 265 nonidentical [DZ]), male twin pairs (72 MZ and 65 DZ), and 82 opposite-sex (OS) pairs aged between 18 and 80 years. For hip BMD, distal forearm, and QUS measurements, the differences between MZ correlations and like-sex DZ correlations were similar for both sexes, suggesting little difference in the component of total variance explained by genetic factors between male and female twin pairs. However, correlations between OS twin pairs were lower than that of like-sex twin pairs, suggesting the possibility of unique gender-specific genetic effects. At the forearm, model fitting suggested a small gender difference in the magnitude of genetic variance as well as the presence of a unique gender-specific genetic variance component. Hip, lumbar spine, and QUS measurements were better explained by models that assumed no gender differences in genetic variance between the sexes, but the study had insufficient power to detect small differences in the genetic components of variance. The results of this study suggest that the proportion of bone strength variance explained by genetic factors is similar for men and women. However, at some regions there is evidence to suggest a gender-specific genetic component to the overall genetic variance.

Absorptiometry, Photon↗