The association between oral contraceptive use, bone mineral density and fractures in women aged 50-80 years.

BACKGROUND: The associations between oral contraceptive (OC) use, bone mineral density (BMD) and the risk of fractures remain controversial. STUDY DESIGN: A cross-sectional study of 491 women aged 50-80 years was performed. We assessed OC use and fractures by questionnaire, and BMD and vertebral deformity by dual-energy x-ray absorptiometry. RESULTS: Ever use of OC was associated with significantly higher BMD at the total body (6%, p<.001) and spine (4%; p=.05) (but not hip) after adjustment for confounders. There was also a significant association between duration of OC use and total body and spine BMD. Use of OCs for 5-10 years was associated with reduced vertebral deformity (adjusted odds ratio 0.46, 95% confidence interval 0.22-0.94). CONCLUSIONS: Oral contraceptive use and duration were associated with higher total body and spine BMD and a consistent reduction in vertebral deformities, although most associations did not reach significance.

Tracking of bone mass from childhood to adolescence and factors that predict deviation from tracking.

It has been hypothesized that bone density tracks but long term studies in children are lacking. As such, the aim of this study was to describe tracking of dual X-ray absorptiometry measures from age 8 to age 16 years, whether this was independent of change in body size and whether deviation from tracking could be predicted. 116 males and 67 females had anthropometric (height and weight), questionnaire (medication use, sports, breastfeeding), fitness (PWC(170)) and DXA measures (bone free lean mass [LM], fat mass [FM] and bone mass) at baseline and follow-up. BMC and aBMD were assessed at the spine and hip and total body and bone mineral apparent density (BMAD) at the spine and hip. We found all DXA measures tracked significantly after adjustment for change in height and change in weight (males: R(2): BMC 24-62%; aBMD 41-48%; BMAD 30-37%, females: R(2): BMC 45-72%; aBMD 36-56%; BMAD 30-48%). Factors that predicted subjects would deviate positively, that is improve in tertile or remain in the highest tertile of spine and hip aBMD included having been breastfed, increase in LM, PWC(170) at age 8 and sport participation in males. LM at age 8 was beneficial in males while in females; FM at age 8 predicted subjects would deviate positively. Boys who gained absolute and percent FM and girls who gained percent FM, were more likely to deviate negatively, that is, decrease in tertile or remain in the lowest tertile of spine and hip aBMD. ICS use at age 8 also predicted subjects, particularly males would not improve in bone mass relative to their peers. In conclusion, DXA measures track moderately to strongly from childhood to adolescence. This was independent of linear growth and sex indicating bone development and physical growth are under largely separate mechanistic control. Body composition was the main predictor of altered tracking but environmental factors also appear important.

Increasing stair usage in a professional workplace: a test of the efficacy of positive and negative message prompts to change pedestrian choices.

ISSUE ADDRESSED: This study investigated the effectiveness of positive and negative-themed message prompts encouraging stair use at the point of choice between an elevator and stairwell in a professional workplace. METHODS: A simple time series design using two control periods assessed the efficacy of positive and negative messages on the pedestrian choice between stairs and an elevator in a restricted-entry, four-story building. Traffic volume was restricted to employees. Their movements were measured at two sites within the building - ground floor access doors and stairwell entry - by small infrared motion-sensing devices (MSD) linked to incremental LCD counters. RESULTS: A positive or negative poster prompt did not significantly modify employees' stair usage when compared with baseline levels. Odds ratios (OR) for stair usage in the workplace were OR=0.6, 95% CI=0.3- 1.1 for the positive and OR=1.0 (95% CI=0.5-1.9) for the negative poster prompts.

Measures of childhood fitness and body mass index are associated with bone mass in adulthood: a 20-year prospective study.

The long-term effects of childhood exercise and body mass index (BMI) on bone mass remain uncertain. We measured 1434 children, 7-15 yr of age, as part of the Australian Schools Health and Fitness Survey in 1985 and approximately 20 yr later (mean age, 31 yr). Fitness measures included a 1.6-km run and a 50-m sprint (childhood only), leg strength, standing long jump, and physical work capacity at 170 beats/min (PWC(170); childhood and adulthood). BMI was assessed at both time points. A single Sahara bone ultrasound densitometer was used to determine heel bone mass. We found, in females, there were modest but significant beneficial relationships between the childhood 1.6-km run, 50-m sprint, standing long jump, and adult bone mass. In both sexes, PWC(170) at 9 yr of age had a greater influence on adult bone mass (r(2) = 5-8%, all p < 0.05) than it did for 15 yr olds (r(2) = <1%, all p > 0.05), independent of adult performance. In the 12 yr olds, childhood PWC(170) was also associated with female adult bone mass (broadband ultrasound attenuation: r(2) = 6%, p = 0.045). In males, childhood BMI (but no performance measures) was positively associated with adult bone mass after adjustment for adult BMI. In conclusion, childhood fitness levels, particularly in females and in the early pubertal years, are predictive of adult skeletal status as measured by quantitative ultrasound, whereas BMI is predictive in males only. These results suggest that increased skeletal loading in childhood leads to an increase in peak bone mass independent of current loading.

Physical activity and knee structural change: a longitudinal study using MRI.

INTRODUCTION: Exercise therapy is effective in improving symptoms of knee osteoarthritis, but its effect on structural change remains unclear. PURPOSE: To describe the associations between physical activity and structural changes of the knee joint as assessed by magnetic resonance imaging (MRI) in adult male and female subjects. METHODS: A convenience sample of 325 subjects (mean age 45 yr, range 26-61) was measured at baseline and approximately 2 yr later. Measures of physical activity included questionnaire items, physical work capacity (PWC(170)), and lower-limb muscle strength. Knee cartilage volume, tibial plateau area, and cartilage defect score (0-4) were determined using T1-weighted fat saturation MRI. RESULTS: Lower-limb muscle strength at baseline was positively associated with both percent-per-year changes in total cartilage volume (r = 0.13) and lateral and total tibial plateau area (r = 0.15 and 0.17) but not other sites. Change in muscle strength was negatively associated with annual changes in lateral and total tibial plateau area (r = -0.13 and -0.17). In females only, PWC170 at baseline was negatively associated with percent-per-year changes in lateral and total cartilage volume (r = -0.16 and -0.17) and positively for lateral and total tibial plateau area (r = 0.18 and 0.16). Conversely, change in PWC(170) was positively associated with changes in cartilage volume at all sites (r = 0.24-0.26). For all associations, P < 0.05. CONCLUSIONS: Overall, these associations were modest in magnitude, but they suggest that knee cartilage volume and tibial plateau area are dynamic structures that can respond to physical stimuli. Greater muscle strength and endurance fitness, especially in women, may be protective against cartilage loss, but it also may result in a maladaptive enlargement of subchondral bone in both sexes, suggesting that physical activity may have both good and bad effects on the knee.

Can BMD assessed by DXA at age 8 predict fracture risk in boys and girls during puberty?: an eight-year prospective study.

UNLABELLED: This study reports on the association between DXA at age 8 and subsequent fractures in both male and female children. Bone densitometry at the total body and spine (but not hip) is a strong predictor of fracture (especially upper limb) during puberty. INTRODUCTION: The aim of this study was to determine if prepubertal DXA can predict fracture risk during puberty. MATERIALS AND METHODS: We studied 183 children who were followed for 8 yr (1460 person-years). Bone densitometry was measured at the total body, hip, and spine by DXA and reported as BMC, BMD, and bone mineral apparent density (BMAD). Fractures were self-reported at age 16 with X-ray confirmation, RESULTS: There were a total of 63 fractures (43 upper limb). In unadjusted analysis, only total body BMD showed an inverse relationship with upper limb fracture risk (p = 0.03). However, after adjustment for height, weight, age (all at age 8), and sex, total body BMC (HR/SD, 2.47; 95% CI, 1.52-4.02), spine BMC (HR/SD, 1.97: 95% CI, 1.30-2.98), total body BMD (HR/SD, 1.67; 95% CI, 1.18-2.36), total body BMAD (HR/SD, 1.54; 95% CI, 1.01-2.37), and spine BMD (HR/SD, 1.53; 95% CI, 1.10, 2.22) were all significantly associated with upper limb fracture risk. Similar, but weaker associations were present for total fractures. There was a trend for overweight/obesity to be associated with increased upper limb fracture risk (HR, 1.53/category; p = 0.08). CONCLUSIONS: Measurement of bone mass by DXA is a good predictor of upper limb fracture risk during puberty. Although we did not measure true BMD, the constancy of fracture prediction after a single measure suggests bone strength remains relatively constant during puberty despite the large changes in bone size.