John D. Wark
Royal Melbourne Hospital
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Featured researches published by John D. Wark.
The New England Journal of Medicine | 2012
Heike A. Bischoff-Ferrari; Walter C. Willett; Endel John Orav; Paul Lips; Pierre J. Meunier; Ronan Lyons; Leon Flicker; John D. Wark; Rebecca D. Jackson; Jane A. Cauley; Haakon E. Meyer; Michael Pfeifer; Kerrie M. Sanders; Hannes B. Stähelin; Robert Theiler; Bess Dawson-Hughes
BACKGROUND The results of meta-analyses examining the relationship between vitamin D supplementation and fracture reduction have been inconsistent. METHODS We pooled participant-level data from 11 double-blind, randomized, controlled trials of oral vitamin D supplementation (daily, weekly, or every 4 months), with or without calcium, as compared with placebo or calcium alone in persons 65 years of age or older. Primary end points were the incidence of hip and any nonvertebral fractures according to Cox regression analyses, with adjustment for age group, sex, type of dwelling, and study. Our primary aim was to compare data from quartiles of actual intake of vitamin D (including each individual participants adherence to the treatment and supplement use outside the study protocol) in the treatment groups of all trials with data from the control groups. RESULTS We included 31,022 persons (mean age, 76 years; 91% women) with 1111 incident hip fractures and 3770 nonvertebral fractures. Participants who were randomly assigned to receive vitamin D, as compared with those assigned to control groups, had a nonsignificant 10% reduction in the risk of hip fracture (hazard ratio, 0.90; 95% confidence interval [CI], 0.80 to 1.01) and a 7% reduction in the risk of nonvertebral fracture (hazard ratio, 0.93; 95% CI, 0.87 to 0.99). By quartiles of actual intake, reduction in the risk of fracture was shown only at the highest intake level (median, 800 IU daily; range, 792 to 2000), with a 30% reduction in the risk of hip fracture (hazard ratio, 0.70; 95% CI, 0.58 to 0.86) and a 14% reduction in the risk of any nonvertebral fracture (hazard ratio, 0.86; 95% CI, 0.76 to 0.96). Benefits at the highest level of vitamin D intake were fairly consistent across subgroups defined by age group, type of dwelling, baseline 25-hydroxyvitamin D level, and additional calcium intake. CONCLUSIONS High-dose vitamin D supplementation (≥800 IU daily) was somewhat favorable in the prevention of hip fracture and any nonvertebral fracture in persons 65 years of age or older. (Funded by the Swiss National Foundations and others.).
Journal of Bone and Mineral Research | 1997
Fiona L. Morris; Geraldine Naughton; Joanne L. Gibbs; John Carlson; John D. Wark
Enhancement of bone mineral acquisition during growth may be a useful preventive strategy against osteoporosis. The aim of this study was to explore the lean mass, strength, and bone mineral response to a 10‐month, high‐impact, strength‐building exercise program in 71 premenarcheal girls, aged 9–10 years. Lean body mass, total body (TB), lumbar spine (LS), proximal femur (PF), and femoral neck (FN) bone mineral were measured using the Hologic QDR 2000+ bone densitometer. Strength was assessed using a grip dynamometer and the Cybex isokinetic dynamometer (Cybex II). At baseline, no significant difference in body composition, pubertal development, calcium intake, physical activity, strength, or bone mineral existed between groups. At completion, there were again no differences in height, total body mass, pubertal development, calcium intake, or external physical activity. In contrast, the exercise group gained significantly more lean mass, less body fat content, greater shoulder, knee and grip strength, and greater TB, LS, PF, and FN BMD (exercise: TB 3.5%, LS 4.8%, PF 4.5%, and FN 12.0%) compared with the controls (controls: TB 1.2%, LS 1.2%, PF 1.3%, and FN 1.7%). TB bone mineral content (BMC), LS BMC, PF BMC, FN BMC, LS bone mineral apparent density (BMAD), and FN bone area also increased at a significantly greater rate in the exercise group compared with the controls. In multiple regression analysis, change in lean mass was the primary determinant of TB, FN, PF, and LS BMD accrual. Although a large proportion of bone mineral accrual in the premenarcheal skeleton was related to growth, an osteogenic effect was associated with exercise. These results suggest that high‐impact, strength building exercise is beneficial for premenarcheal strength, lean mass gains, and bone mineral acquisition.
Scandinavian Journal of Medicine & Science in Sports | 2000
Bd Coleman; Km Khan; Nicola Maffulli; Jl Cook; John D. Wark
Patellar tendinopathy is often treated surgically after failure of conservative treatment but clinical experience suggests that results are not uniformly excellent. The aim of this review was to (i) identify the different surgical techniques that have been reported and compare their success rates, and (ii) critically assess the methodology of studies that have reported surgical outcomes. Twenty‐three papers and two abstracts were included in the review. Surgical procedures were categorized and outcomes summarized. Using ten criteria, an overall methodology score was derived for each paper. Criteria for which scores were generally low (indicating methodological deficiency) concerned the type of study, subject selection process and outcome measures. We found a negative correlation between papers’ reported success rates and overall methodology scores (r=−0.57, P<0.01). There was a positive correlation between year of publication and overall methodology score (r=0.68, P<0.001). We conclude that study methodology may influence reported surgical outcome. We suggest practical guidelines for improving study design in this area of clinical research, as improved study design would provide clinicians with a more rigorous evidence‐base for treating patients who have recalcitrant patellar tendinopathy.
American Journal of Sports Medicine | 1996
Kim L. Bennell; Susan Malcolm; Shane A. Thomas; Sally J. Reid; Peter Brukner; Peter R. Ebeling; John D. Wark
The aim of this 12-month prospective study was to investigate risk factors for stress fractures in a cohort of 53 female and 58 male track and field athletes, aged 17 to 26 years. Total bone mineral content, regional bone density, and soft tissue composition were meas ured using dual-energy x-ray absorptiometry and an thropometric techniques. Menstrual characteristics, current dietary intake, and training were assessed us ing questionnaires. A clinical biomechanical assess ment was performed by a physical therapist. The inci dence of stress fractures during the study was 21.1%, with most injuries located in the tibia. Of the risk factors evaluated, none was able to predict the occurrence of stress fractures in men. However, in female athletes, significant risk factors included lower bone density, a history of menstrual disturbance, less lean mass in the lower limb, a discrepancy in leg length, and a lower fat diet. Multiple logistic regression revealed that age of menarche and calf girth were the best independent predictors of stress fractures in women. This bivariate model correctly assigned 80% of the female athletes into their respective stress fracture or nonstress frac ture groups. These results suggest that it may be pos sible to identify female athletes most at risk for this overuse bone injury.
American Journal of Sports Medicine | 1996
Kim L. Bennell; Susan Malcolm; Shane A. Thomas; John D. Wark; Peter Brukner
The incidence and distribution of stress fractures were evaluated prospectively over 12 months in 53 female and 58 male competitive track and field athletes (age range, 17 to 26 years). Twenty athletes sustained 26 stress fractures for an overall incidence rate of 21.1%. The incidence was 0.70 for the number of stress frac tures per 1000 hours of training. No differences were observed between male and female rates (P > 0.05). Twenty-six stress fractures composed 20% of the 130 musculoskeletal injuries sustained during the study. Although there was no difference in stress fracture incidence among athletes competing in different events (P > 0.05), sprints, hurdles, and jumps were associated with a significantly greater number of foot fractures; middle- and long-distance running were as sociated with a greater number of long bone and pelvic fractures (P < 0.05). Overall, the most common sites of bone injuries were the tibia with 12 injuries (46%), followed by the navicular with 4 injuries (15%), and the fibula with 3 injuries (12%). The high incidence of stress fractures in our study suggests that risk factors in track and field athletes should be identified.
Journal of Science and Medicine in Sport | 1998
Paul J. Visentini; Karim M. Khan; Jill Cook; Z. S. Kiss; Peter Harcourt; John D. Wark
Symptoms of jumpers knee (patellar tendinosis) are not easily quantified and this may explain why there are no evidence-based guidelines for managing the condition. A simple, practical questionnaire-based index of severity would facilitate jumpers knee research and subsequently, clinical management. Thus we devised and tested the Victorian Institute of Sport Assessment (VISA) questionnaire. The brief questionnaire assesses (i) symptoms, (ii) simple tests of function and (iii) ability to play sport. Six of the eight questions are scored on a visual analogue scale from 0-10 with 10 representing optimal health. The maximal VISA score for an asymptomatic, fully performing individual is 100 points and the theoretical minimum is 0 points. We found the VISA scale to have excellent short-term test-retest, and inter-tester reliability (both, r>0.95) as well as good short-term (one week) stability (r=0.87). Mean (SD) of the VISA scores ranged from 95 (8) points in asymptomatic control subjects to 55 (12) points in patients who presented to a sports medicine clinic with jumpers knee and 22 (17) points in patients before surgery for chronic jumpers knee. Six- and twelve-months after surgery VISA scores returned to 49 (15) and 75 (17) points respectively, mirroring clinical recovery. We conclude that the VISA score is a reliable index of the severity of jumpers knee that has potential to aid clinicians and researchers.
Journal of the American Geriatrics Society | 2005
Leon Flicker; Robert J. MacInnis; Mark S. Stein; Sam C. Scherer; Kate E. Mead; Caryl Nowson; Jenny Thomas; Chris Lowndes; John L. Hopper; John D. Wark
Objectives: To determine whether vitamin D supplementation can reduce the incidence of falls and fractures in older people in residential care who are not classically vitamin D deficient.
Bone | 1995
E. Newman; A.S. Turner; John D. Wark
There is a great need to develop an animal model for postmenopausal osteoporosis; a model that will be useful for the understanding of the pathogenesis of the disease as well as the investigation of new therapies. The requirements for such an animal model are discussed and ones that have been used in the past include nonhuman primates, dogs, cats, rodents, rabbits, guinea pigs, and minipigs. Advantages and disadvantages of these models are briefly reviewed. Sheep are a promising model for various reasons; they are docile, easy to handle and house, relatively inexpensive, available in large numbers, spontaneously ovulate, and have hormone profiles similar to women. Ovariectomy results in a slight loss of bone from the ovine iliac crest, and biochemical markers such as osteocalcin are well characterized. Physiological disadvantages are lack of natural menopause, that normal estrus cycles are restricted to fall and winter and that they have a different gastrointestinal system. Sheep have cortical bone that is plexiform in structure although haversian remodeling is seen in older animals. When and if biomechanical incompetence of bone follows ovariectomy is presently unknown. There is no ideal model for the study of postmenopausal osteoporosis; all have advantages and disadvantages. Researchers in this field must recognize the limitations of the model they choose, and select one that will fulfill their needs.
Journal of Medical Internet Research | 2012
Yeshe Fenner; Suzanne M. Garland; Elya E. Moore; Yasmin Jayasinghe; Ashley Fletcher; Sepehr N. Tabrizi; Bharathy Gunasekaran; John D. Wark
Background Recruitment of young people for health research by traditional methods has become more expensive and challenging over recent decades. The Internet presents an opportunity for innovative recruitment modalities. Objective To assess the feasibility of recruiting young females using targeted advertising on the social networking site Facebook. Methods We placed an advertisement on Facebook from May to September 2010, inviting 16- to 25-year-old females from Victoria, Australia, to participate in a health study. Those who clicked on the advertisement were redirected to the study website and were able to express interest by submitting their contact details online. They were contacted by a researcher who assessed eligibility and invited them to complete a health-related survey, which they could do confidentially and securely either at the study site or remotely online. Results A total of 551 females responded to the advertisement, of whom 426 agreed to participate, with 278 completing the survey (139 at the study site and 139 remotely). Respondents’ age distribution was representative of the target population, while 18- to 25-year-olds were more likely to be enrolled in the study and complete the survey than 16- to 17-year-olds (prevalence ratio = 1.37, 95% confidence interval 1.05–1.78, P = .02). The broad geographic distribution (major city, inner regional, and outer regional/remote) and socioeconomic profile of participants matched the target population. Predictors of participation were older age, higher education level, and higher body mass index. Average cost in advertising fees per compliant participant was US
PLOS Genetics | 2011
Emma L. Duncan; Patrick Danoy; John P. Kemp; Paul Leo; Eugene McCloskey; Geoffrey C. Nicholson; Richard Eastell; Richard L. Prince; John A. Eisman; Graeme Jones; P. Sambrook; Ian R. Reid; Elaine M. Dennison; John D. Wark; J.B. Richards; A.G. Uitterlinden; Tim D. Spector; C. Esapa; Roger D. Cox; Steve D.M. Brown; Rajesh V. Thakker; K. Addison; Linda A. Bradbury; C Cooper; C. Cremin; Karol Estrada; Dieter Felsenberg; Claus-C. Glüer; Johanna Hadler; Margaret J. Henry
20, making this highly cost effective. Conclusions Results demonstrate the potential of using modern information and communication technologies to engage young women in health research and penetrate into nonurban communities. The success of this method has implications for future medical and population research in this and other demographics.