Circulating sclerostin associated with vertebral bone marrow fat in older men but not women.

CONTEXT: Osteocyte activity is crucial to the maintenance of bone quality. Sclerostin, an osteocyte product, inhibits bone formation, yet higher circulating sclerostin is associated with higher bone density. Bone marrow fat (MF) is associated with osteoporosis, but little is known about the relationship between osteocyte activity and MF. OBJECTIVE: Our objective was to assess the relationships between circulating sclerostin, vertebral MF, volumetric bone mineral density (vBMD), and other fat depots in older adults. DESIGN, SETTING, AND PARTICIPANTS: We conducted a cross-sectional study in the Age Gene/Environment Susceptibility-Reykjavik cohort. MAIN OUTCOME MEASURES: Outcome measures included vertebral MF (L1-L4) measured with magnetic resonance spectroscopy and vBMD (spine and hip) and abdominal fat measured with quantitative computed tomography. RESULTS: After excluding subjects with bone-active medication use (n = 50), inadequate serum (n = 2), or inadequate magnetic resonance spectroscopy (n = 1), analyses included 115 men and 134 women (mean age 79 y, mean body mass index 27.7 kg/m(2)). In men, but not women, vertebral MF was greater in those with higher serum sclerostin levels. MF was 52.2 % in the lowest tertile of serum sclerostin and 56.3% in the highest tertile in men (P for trend <.01) in models adjusted for age, body mass index, and diabetes. Sclerostin was positively associated with cortical and trabecular total hip vBMD, weight in men and women, and total fat mass in men but was not associated with total lean mass or abdominal fat depots. CONCLUSION: Circulating sclerostin levels are associated with higher vertebral marrow fat in men, suggesting a relationship between osteocyte function and marrow adipogenesis.

Vertebral bone marrow fat associated with lower trabecular BMD and prevalent vertebral fracture in older adults.

CONTEXT: Bone marrow fat (BMF) and bone mineral density (BMD) by dual x-ray energy absorptiometry (DXA) are negatively correlated. However, little is known about the association of BMF with fracture or with separate trabecular and cortical bone compartments. OBJECTIVE: Our objective was to assess the relationships between vertebral BMF, BMD by quantitative computed tomography, and fracture in older adults. DESIGN, SETTING, AND PARTICIPANTS: We conducted a cross-sectional study in the Age Gene/Environment Susceptibility-Reykjavik cohort. MAIN OUTCOME MEASURES: Outcomes measures included vertebral BMF (L1-L4) measured with magnetic resonance spectroscopy, quantitative computed tomography and DXA scans of the hip and spine, and DXA vertebral fracture assessments. Previous clinical fracture was determined from medical records. RESULTS: In 257 participants without recent bone-active medication use, mean age was 79 (SD 3.1) years. Mean BMF was 53.5% ± 8.1% in men and 55.0% ± 8.4% in women. Those with prevalent vertebral fracture (21 men, 32 women) had higher mean BMF in models adjusted for BMD. In separate models by sex, the difference was statistically significant only in men (57.3% vs 52.8%, P = 0.02). BMF was associated with lower trabecular volumetric BMD (vBMD) at the spine (-10.5% difference for each 1 SD increase in BMF, P < 0.01), total hip, and femoral neck, but not with cortical vBMD, in women. In men, BMF was marginally associated with trabecular spine vBMD (-6.1%, P = 0.05). Total hip and spine areal BMD (aBMD) were negatively correlated with BMF in women only. CONCLUSION: Higher marrow fat correlated with lower trabecular, but not cortical, BMD in older women but not men. Higher marrow fat was associated with prevalent vertebral fracture in men, even after adjustment for BMD.

Risk factors for bone loss in the hip of 75-year-old women: a 4-year follow-up study.

Risk factors for bone loss among the elderly are largely unknown. The objective of the study was to examine longitudinal bone loss in the hip in one-hundred and sixty-two 75-year-old women. Bone mineral density (BMD, g/cm(2)) was measured with dual X-ray absorptiometry (DXA) at baseline and after 4 years. The relationship between changes in BMD during follow-up and the following factors; baseline BMD, baseline weight, weight change, baseline lean and fat body mass (measured with DXA), serum values of biochemical markers and hormones, nutritional and lifestyle factors according to a questionnaire was assessed. The annual mean (SD) change in femoral neck BMD was -0.31% (1.38) in total trochanter -0.35% (1.15) and total hip -0.34% (1.10) and did not differ significantly between measurement sites. Bisphosphonate users had a 2.9%, 1.7% and 1.9% mean adjusted increase in femoral neck, total trochanter and total hip BMD respectively, different from none-users (p<0.05). Subjects with more than three weekly physical activity sessions had less femoral neck bone loss than less active women (p<0.05). The proportion of the variance in BMD changes explained by multivariate models (R(2)) was 12-13%. Women gaining weight had less loss of BMD than those losing weight in the trochanter and the total hip (p<0.001), and in the femoral neck (p=0.055). Elderly women should be advised to maintain their body weight and participate in physical activity. Despite the large number of variables examined in this study, bone loss occurring with increased age is not thoroughly explained.

[The relationship between physical activity, body mass index, body composition and grip strength in an Icelandic population.].

OBJECTIVE: To study physical activity among Icelandic adults and the relationship with anthropometric factors and grip strength. MATERIAL AND METHODS: Randomly selected participants, 30-85 years of age, answered questions regarding exercise and diet. Body composition was measured with DXA, which detects the proportions of different body tissues. Height, weight and grip strength were measured and the body mass index (kg/m(2)) was calculated. The prevalence of regular physical activity was studied for men and women in the age groups of 30-45 years, 50-65 years and 70-85 years and the relationship to body mass index, body composition and grip strength examined. The possible preventive effect of exercise on overweight and obesity was also studied. RESULTS: Of 2310 invited, 1630 subjects (70.6%) participated. Mean participation in regular physical activity was 3-4 times a week but 19% of the women and 24% of the men did no exercise at all. In general, swimming, walking and calisthenics of various types and intensities were the most common forms of exercise and in the age group 30-45 year old 16% of the women and 8% of the men did strength training. 50.4% of women 30-45 years of age and 68.2% of 50-65 year old men were overweight or obese. Mean fat mass was highest in 70-85 year old women (38%) and men (27%). Occupational activity was not related to body mass index, body composition or grip strength. Significant negative relationship was found between frequency of exercise and fat mass. The relationship between grip strength and lean mass or exercise was non-significant. The odds ratio of being overweight or obesity was 0.5 (CI was 0.37-0.77 for women and 0.37-0.94 for men) for those who exercised five or more days per week compared to those who exercised less frequently. CONCLUSION: One of four Icelandic men and one of five women do not participate in regular physical activity despite of strong scientific indications of various positive health effects of exercise. More than half of adult Icelanders are overweight or obese but the risk is halved among those who exercise at least five days per week, compared to those who exercise less frequently. Sedentary lifestyle is more common amongst Icelanders than in the neighboring countries and realistic goals need to be set to increase the participation in regular physical activity.

[Bone mineral density and physical activity in 70-year-old Icelandic women.].

OBJECTIVE: It is generally believed that exercise positively influences bone mineral density (BMD). Athletes have been found to have higher BMD than controls but it has proven difficult to reproduce these findings in the general population. RESULTS from cross-sectional studies on the relationship between exercise and BMD in postmenopausal women have been contradictory. In most studies the age range of subjects has been quite large. Few studies have concentrated on this relationship in elderly women, the largest risk group for osteoporosis and little is known if, and in that case what kind of, exercise has positive effects on BMD in these women. The purpose of this study was to examine the relation of BMD to exercise and current and lifetime occupational activity in 70-year-old Icelandic women. MATERIAL AND METHODS: 248 women, all inhabitants in Reykjavik were investigated. BMD in the lumbar spine, femoral neck, total hip and total body was measured with dual energy X-ray absorptiometry (DXA) and the women filled out a questionnaire regarding general health issues, leisure time and occupational activity. Questions included number of leisure walks per week, frequency of other exercises and an attempt was made to estimate the intensity of the activities. Occupational activity was evaluated at ages 20-29 years, 30-44 years, 45-65 years as well as currently, and defined in four grades, from "mostly sedentary" to "hard work including walking". RESULTS: No relationship was found between number of walks and BMD. Significant positive correlation was found between number of other exercise sessions per week and total body BMD (b=0.008, p=0.01), but not total hip (p=0.09), femoral neck (p=0.15) or lumbar spine (p=0.07). Significant negative correlation was found between number of leisure walks and height loss from the age of 25 years (r=-0.211, p=0.001). No significant relationship was found between occupational activity and BMD. CONCLUSION: RESULTS indicate that leisure time exercise can bring on some bone density benefits for elderly women. Leisure walking alone may not provide high enough stimuli to influence BMD but increasing number of other exercise sessions per week has positive relations to total body and possibly total hip and lumbar spine BMD. A randomized controlled study on the relationship between exercise and BMD in this age group should be conducted.