Serum level of under-carboxylated osteocalcin and bone mineral density in early menopausal Norwegian women

Observational and some experimental data suggest that low intake of vitamin K may be associated with an increased risk of fracture. To assess whether oral vitamin K (phytonadione and menaquinone) supplementation can reduce bone loss and prevent fractures. The search included the following electronic databases: MEDLINE (1966 to June 2005), EMBASE (1980 to June 2005), the Cochrane Library (issue 2, 2005), the ISI Web of Science (1945 to June 2005), the National Research Register (inception to the present), Current Controlled Trials, and the Medical Research Council Research Register. Randomized controlled trials that gave adult participants oral phytonadione and menaquinone supplements for longer than 6 months were included in this review. Four authors extracted data on changes in bone density and type of fracture. All articles were double screened and double data extracted. Thirteen trials were identified with data on bone loss, and 7 reported fracture data. All studies but 1 showed an advantage of phytonadione and menaquinone in reducing bone loss. All 7 trials that reported fracture effects were Japanese and used menaquinone. Pooling the 7 trials with fracture data in a meta-analysis, we found an odds ratio (OR) favoring menaquinone of 0.40 (95% confidence interval [CI], 0.25-0.65) for vertebral fractures, an OR of 0.23 (95% CI, 0.12-0.47) for hip fractures, and an OR of 0.19 (95% CI, 0.11-0.35) for all nonvertebral fractures. This systematic review suggests that supplementation with phytonadione and menaquinone-4 reduces bone loss. In the case of the latter, there is a strong effect on incident fractures among Japanese patients.

To determine the magnitude and importance of the relation between smoking, bone mineral density, and risk of hip fracture according to age. Meta-analysis of 29 published cross sectional studies reporting the difference in bone density in 2156 smokers and 9705 non-smokers according to age, and of 19 cohort and case-control studies recording 3889 hip fractures reporting risk in smokers relative to non-smokers. In premenopausal women bone density was similar in smokers and non-smokers. Postmenopausal bone loss was greater in current smokers than non-smokers, bone density diminishing by about an additional 2% for every 10 year increase in age, with a difference of 6% at age 80. In current smokers relative to non-smokers the risk of hip fracture was similar at age 50 but greater thereafter by an estimated 17% at age 60, 41% at 70, 71% at 80, and 108% at 90. These estimates of relative risk by age, derived directly from a regression analysis of the studies of smoking and hip fracture, were close to estimates using the difference in bone density between smokers and non-smokers and the association between bone density and risk of hip fracture. The estimated cumulative risk of hip fracture in women in England was 19% in smokers and 12% in non-smokers to age 85; 37% and 22% to age 90. Among all women, one hip fracture in eight is attributable to smoking. Limited data in men suggest a similar proportionate effect of smoking as in women. The association was not explained by smokers being thinner, younger at menopause, and exercising less nor by actions of smoking on oestrogen, but smoking may have a direct action on bone. Hip fracture in old age is a major adverse effect of smoking after the menopause. The cumulative excess bone loss over decades is substantial, increasing the lifetime risk of hip fracture by about half.

Studies of the effect of exercise programs on bone mass appear inconsistent. Our objective was to systematically review and meta-analyze randomized trials of the effect of exercise on bone mass in pre- and postmenopausal women. A computerized MEDLINE search was conducted for the years 1966-1997. Thirty-five randomized trials were identified. Meta-analytic methods were used to statistically pool results of studies of the effect of impact (e.g., aerobics) and non-impact (e.g., weight training) exercise on the lumbar spine and femoral neck. The most studied bone site was the lumbar spine in postmenopausal women (15 studies), where both impact [1.6% bone loss prevented, 95% confidence intervals (CI): 1.0%-2.2%] and non-impact (1.0%, 95% CI: 0.4%-1.6%) exercise programs had a positive effect. Results for the lumbar spine in premenopausal women (eight studies) were similar: 1.5% (95% CI: 0.6%-2.4%) less bone loss (or net gain) after impact exercise and 1.2% (95% CI: 0.7%-1.7%) after non-impact exercise. Impact exercise programs appeared to have a positive effect at the femoral neck in postmenopausal women (five studies), 1.0% (95% CI: 0.4%-1.6%) bone loss prevented, and possibly in premenopausal women, 0.9% (95% CI: -0.2%-2.0%) bone loss prevented. There were too few trials to draw conclusions from meta-analyses of the effect of non-impact exercise on the neck of femur. This systematic review of randomized trials shows that both impact and non-impact exercise have a positive effect at the lumbar spine in pre- and postmenopausal women. Impact exercise probably has a positive effect at the femoral neck. More studies are required to determine the optimal intensity and type of exercise.