The Association Between BMI and QCT-Derived Proximal Hip Structure and Strength in Older Men: A Cross-Sectional Study

Abstract

Although higher body mass index (BMI) is associated with higher bone mineral density, recent evidence indicates that increased BMI may not be consistently associated with reduced hip fracture risk. Moreover, substantial proportions of hip fractures occur among overweight and obese men and women. The role of increased BMI and obesity on bone density, structure, and strength at the hip is not well understood. We conducted cross-sectional analyses between BMI and various density and structure measures derived from quantitative computed tomography (QCT)-scans of the proximal femur, in 3067 men (mean age: 73 y) from the Osteoporotic Fractures in Men Study (MrOS). Finite element (FE) analysis of hip QCT scans was performed for a subcohort of 672 men to provide a measure of femoral strength for a simulated sideways fall. The impact force was estimated using patient-specific weight and height information. Multivariable general linear models were used to examine the associations between BMI and hip QCT measures. The relationship of BMI with hip QCT measures was significantly different between men categorized as non-obese and obese (P for interaction ≤ 0.014). For non-obese men (BMI < 30), increasing BMI was associated with higher integral, cortical and trabecular vBMD, integral volume, cross-sectional area, and percent cortical volume (all p< 0.001). For obese men (BMI ≥30), increasing BMI was not associated with any of those parameters. In addition, compared to non-obese men, obese men had a higher hip strength, but also a higher ratio of impact force to strength (P < 0.0001), in theory increasing their risk of hip fracture despite their increased strength. These results provide a better understanding of hip fracture risk in obese men.

Body composition predictors of skeletal integrity in obesity

“…This is consistent with studies that have shown adaptive increase in hip BMD in response to increasing BMI [41, 42], while relative to BMI, obese subjects had impaired hip structure compared to normal-weight subjects [41–43], suggesting that hip structure is insufficient to compensate for increasing BMI. However, in a study of older (>65 years) individuals this did not translate into increased risk of developing a major osteoporotic fracture over a follow-up time of 6.2 ± 3.7 years in women and 4.7 ± 3.4 6.2 ± 3.7 years in women and 4.7 ± 3.4 years [43].…”

<p>The Relation Between Calcaneus Stiffness Index as a Measure of Bone Density and Body Mass Index in an Egyptian Cohort</p>

“…30 These data are also supported by Shen et al who linked BMI to a higher integral, trabecular and cortical BMD and percent cortical volume. 31 Similarly, Scott et al 7 found a positive impact of BMI on BMD in older subjects. Furthermore, muscle mass measures adjusted for height was associated with less incident osteoporosis in postmenopausal women, as reported by Papageorgiou et al 32 Some studies have shown conflicting evidence; a wide based study among women with mean age of 62.08 years found no strong association between BMI and BMD.…”

The relationship of maximal oxygen consumption to bone mineral density in Iranian young women

“…In fact, low body weight is considered a risk factor for osteoporosis (Bonjour et al, ; Rizzoli, Bianchi, Garabedian, HA, & Moreno, ). It seems that the relationship between BMI and BMD is affected by the following factors: the accumulation of vitamin D in fat tissue, an increase of PTH, increased stimulation of osteoblast proliferation, the roles of IGF‐1 and leptin, and the conversion of androgens to estrogen in fat tissue (Reid, ; Shen et al, ).…”