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Bone architecture as well as size and shape is important for bone strength and risk of fracture. Most bone loss is cortical and occurs by trabecularization of the inner part of the cortex. We therefore wanted to identify determinants of the bone architecture, especially the area and porosity of the transitional zone, an inner cortical region with a large surface/matrix volume available for intracortical remodeling. In 211 postmenopausal women aged 54 to 94 years with nonvertebral fractures and 232 controls from the Tromsø Study, Norway, we quantified femoral subtrochanteric architecture in CT images using StrAx1.0 software, and serum levels of bone turnover markers (BTM, procollagen type I N-terminal propeptide and C-terminal cross-linking telopeptide of type I collagen). Multivariable linear and logistic regression analyses were used to quantify associations of age, weight, height, and bone size with bone architecture and BTM, and odds ratio (OR) for fracture. Increasing age, height, and larger total cross-sectional area (TCSA) were associated with larger transitional zone CSA and transitional zone CSA/TCSA (standardized coefficients [STB] = 0.11 to 0.80, p ≤ 0.05). Increasing weight was associated with larger TCSA, but smaller transitional zone CSA/TCSA and thicker cortices (STB = 0.15 to 0.22, p0.01). Increasing height and TCSA were associated with higher porosity of the transitional zone (STB = 0.12 to 0.46, p0.05). Increasing BTM were associated with larger TCSA, larger transitional zone CSA/TCSA, and higher porosity of each of the cortical compartments (p0.01). Fracture cases exhibited larger transitional zone CSA and higher porosity than controls (p0.001). Per SD increasing CSA and porosity of the transitional zone, OR for fracture was 1.71 (95% CI, 1.37 to 2.14) and 1.51 (95% CI, 1.23 to 1.85), respectively. Cortical bone architecture is determined mainly by bone size as built during growth and is modified by lifestyle factors throughout life through bone turnover. Fracture cases exhibited larger transitional zone area and porosity, highlighting the importance of cortical bone architecture for fracture propensity.

Bone mineral density (BMD) is a reflection of bone strength and lifestyles that preserve bone mass and may reduce fracture risk in old age. This study examined the effect of combined profiles of smoking, physical activity, and body mass index (BMI) on lifetime bone loss. Data were collected from the population-based Tromsø Study. BMD was measured as g/cm(2) by dual-energy X-ray absorptiometry (DXA) at the total hip and femoral neck in 2580 women and 2084 men aged 30 to 80 years in the 2001-02 survey, and repeated in 1401 women and 1113 men in the 2007-08 survey. Height and weight were measured and lifestyle information was collected through questionnaires. Data were analyzed using linear mixed models with second-degree fractional polynomials. From the peak at the age around 40 years to 80 years of age, loss rates varied between 4% at the total hip and 14% at femoral neck in nonsmoking, physically active men with a BMI of 30 kg/m(2) to approximately 30% at both femoral sites in heavy smoking, physically inactive men with a BMI value of 18 kg/m(2) . In women also, loss rates of more than 30% were estimated in the lifestyle groups with a BMI value of 18 kg/m(2) . BMI had the strongest effect on BMD, especially in the oldest age groups, but a BMI above 30 kg/m(2) did not exert any additional effect compared with the population average BMI of 27 kg/m(2) . At the age of 80 years, a lifestyle of moderate BMI to light overweight, smoking avoidance, and physical activity of 4 hours of vigorous activity per week through adult life may result in 1 to 2 standard deviations higher BMD levels compared with a lifestyle marked by heavy smoking, inactivity, and low weight. In the prevention of osteoporosis and fracture risk, the effect of combined lifestyles through adult life should be highlighted. © 2014 American Society for Bone and Mineral Research.

The risk of subsequent fracture is increased after initial fractures; however, proper understanding of its magnitude is lacking. This population-based study examines the subsequent fracture risk in women and men by age and type of initial incident fracture. All incident nonvertebral fractures between 1994 and 2009 were registered in 27,158 participants in the Tromsø Study, Norway. The analysis included 3108 subjects with an initial incident fracture after the age of 49 years. Subsequent fracture (n = 664) risk was expressed as rate ratios (RR) and absolute proportions irrespective of death. The rates of both initial and subsequent fractures increased with age, the latter with the steepest curve. Compared with initial incident fracture rate of 30.8 per 1000 in women and 12.9 per 1000 in men, the overall age-adjusted RR of subsequent fracture was 1.3 (95% CI, 1.2-1.5) in women, and 2.0 (95% CI, 1.6-2.4) in men. Although the RRs decreased with age, the absolute proportions of those with initial fracture who suffered a subsequent fracture increased with age; from 9% to 30% in women and from 10% to 26% in men, between the age groups 50-59 to 80+ years. The type of subsequent fracture varied by age from mostly minor fractures in the youngest to hip or other major fractures in the oldest age groups, irrespective of type and severity of initial fracture. In women and men, 45% and 38% of the subsequent hip or other major fractures, respectively, were preceded by initial minor fractures. The risk of subsequent fracture is high in all age groups. At older age, severe subsequent fracture types follow both clinically severe and minor initial incident fractures. Any fragility fracture in the elderly reflects the need for specific osteoporosis management to reduce further fracture risk.

Despite reported bone loss during pregnancy and lactation, no study has shown deleterious long-term effects of parity or breastfeeding. Studies have shown higher bone mineral density and reduced risk for fracture in parous than in nulliparous women or no effect of parity and breastfeeding, so long-term effects are uncertain. We studied the effect of parity and breastfeeding on risk for hip, wrist and non-vertebral fragility fractures (hip, wrist, or proximal humerus) in 4681 postmenopausal women aged 50 to 94 years in the Tromso Study from 1994-95 to 2010, using Cox's proportional hazard models. During 51 906 person-years, and a median of 14.5 years follow-up, 442, 621, and 1105 of 4681 women suffered incident hip, wrist, and fragility fractures, and the fracture rates were 7.8, 11.4, and 21.3 per 1000 person-years, respectively. The risk for hip, wrist, and fragility fracture did not differ between parous (n = 4230, 90.4%) and nulliparous women (n = 451, 9.6%). Compared with women who did not breast-feed after birth (n = 184, 4.9%), those who breastfed (n = 3564, 95.1%) had 50% lower risk for hip fracture (HR 0.50; 95% CI 0.32 to 0.78), and 27% lower risk for fragility fracture (HR 0.73; 95% CI 0.54 to 0.99), but similar risk for wrist fracture, after adjustment for age, BMI, height, physical activity, smoking, a history of diabetes, previous fracture of hip or wrist, use of hormone replacement therapy, and length of education. Each 10 months longer total duration of breastfeeding reduced the age-adjusted risk for hip fracture by 12% (HR 0.88; 95% CI 0.78 to 0.99, p for trend = 0.03) before, and marginally after, adjustment for BMI and other covariates (HR 0.91; 95% CI 0.80 to 1.04). In conclusion, this data indicates that pregnancy and breastfeeding has no long-term deleterious effect on bone fragility and fractures, and that breastfeeding may contribute to a reduced risk for hip fracture after menopause.

Higher rates of hip fracture and all fractures combined have been observed in urban compared with rural areas, but whether there are urban-rural differences in distal forearm fracture rates is less studied. The aim of this longitudinal study was to compare the incidence of forearm fracture in postmenopausal women in urban and rural areas in Norway and to investigate risk factors that could explain potential fracture differences. The study included data from 11,209 women aged 65 years or more who participated in two large health studies, the Tromso Health Study in 1994–1995 and the Nord-Trondelag Health Study in 1995–1997. Forearm bone mineral density (BMD) was measured by single-energy X-ray absorptiometry in a subsample of women (n = 7333) at baseline. All women were followed with respect to hospital-verified forearm fractures (median follow-up 6.3 years). A total of 9249 and 1960 women lived in areas classified as rural and urban, respectively. Urban women had an increased forearm fracture risk [relative risk (RR) = 1.29, 95% confidence interval (CI) 1.09–1.52] compared with women in rural areas. Rural women had higher body mass index (BMI) than urban women, and the RR was moderately reduced to 1.21 (95% CI 1.02–1.43) after BMI adjustments. Rural women had the highest BMD. In the subgroup with measured BMD, adjustments for BMD changed the urban versus rural RR from 1.21 (95% CI 0.96–1.52) to 1.05 (95% CI 0.83–1.32), suggesting that BMD is an important explanatory factor. In conclusion, higher rates of forearm fractures was found in urban compared with rural women. © 2011 American Society for Bone and Mineral Research.