Correction to: The factor-of-risk biomechanical approach predicts hip fracture in men and women: the Framingham Study

The original version of this article, published 23 February 2011, unfortunately contained a mistake. The following correction has therefore been made in the original.

The factor-of-risk biomechanical approach predicts hip fracture in men and women: the Framingham Study

SUMMARY

We examined the relation between a biomechanical measure, factor-of-risk, and hip fracture risk in 1,100 men and women from the Framingham Study and found that it predicted hip fracture (men, ORs of 1.8; women, 1.2-1.4).

INTRODUCTION

Alternative methods of predicting hip fracture are needed since 50% of adults who fracture do not have osteoporosis by bone mineral density (BMD) measurements. One method, factor-of-risk (Φ), computes the ratio of force on the hip in a fall to femoral strength. We examined the relation between Φ and hip fracture in 1,100 subjects from the Framingham Study with measured hip BMD, along with weight, height, and age, collected in 1988-1989.

METHODS

We estimated both peak and attenuated force applied to the hip in a sideways fall from standing height, where attenuated force incorporated cushioning effects of trochanteric soft tissue. Femoral strength was estimated from femoral neck BMD, using cadaveric femoral strength data. Sex-specific, age-adjusted survival models were used to calculate hazard ratios (HR) and 95% confidence intervals for the relation between Φ (peak), Φ (attenuated), and their components with hip fracture.

RESULTS

In 425 men and 675 women (mean age, 76 years), 136 hip fractures occurred over median follow-up of 11.3 years. Factor-of-risk, Φ, was associated with increased age-adjusted risk for hip fracture. One standard deviation increase in Φ (peak) and Φ (attenuated) was associated with HR of 1.88 and 1.78 in men and 1.23 and 1.41 in women, respectively. Examining components of Φ, in women, we found fall force and soft tissue thickness were predictive of hip fracture independent of femoral strength (was estimated from BMD).

CONCLUSIONS

Thus, both Φ (peak) and Φ (attenuated) predict hip fracture in men and women. These findings suggest additional studies of Φ predicting hip fracture using direct measurements of trochanteric soft tissue.

Reliability of vertebral fracture assessment using multidetector CT lateral scout views: the Framingham Osteoporosis Study

Two radiologists evaluated images of the spine from computed tomography (CT) scans on two occasions to diagnose vertebral fracture in 100 individuals. Agreement was fair to good for mild fractures, and agreement was good to excellent for more severe fractures. CT scout views are useful to assess vertebral fracture.

INTRODUCTION

We investigated inter-reader agreement between two radiologists and intra-reader agreement between duplicate readings for each radiologist, in assessment of vertebral fracture using a semi-quantitative method from lateral scout views obtained by CT.

METHODS

Participants included 50 women and 50 men (age 50-87 years, mean 70 years) in the Framingham Study. T4-L4 vertebrae were assessed independently by two radiologists on two occasions using a semi-quantitative scale as normal, mild, moderate, or severe fracture.

RESULTS

Vertebra-specific prevalence of grade ≥ 1 (mild) fracture ranged from 3% to 5%. We found fair (κ = 56-59%) inter-reader agreement for grade ≥ 1 vertebral fractures and good (κ = 68-72%) inter-reader agreement for grade ≥ 2 fractures. Intra-reader agreement for grade ≥ 1 vertebral fracture was fair (κ = 55%) for one reader and excellent for another reader (κ = 77%), whereas intra-reader agreement for grade ≥ 2 vertebral fracture was excellent for both readers (κ = 76% and 98%). Thoracic vertebrae were more difficult to evaluate than the lumbar region, and agreement was lowest (inter-reader κ = 43%) for fracture at the upper (T4-T9) thoracic levels and highest (inter-reader κ = 76-78%) for the lumbar spine (L1-L4).

CONCLUSIONS

Based on a semi-quantitative method to classify vertebral fractures using CT scout views, agreement within and between readers was fair to good, with the greatest source of variation occurring for fractures of mild severity and for the upper thoracic region. Agreement was good to excellent for fractures of at least moderate severity. Lateral CT scout views can be useful in clinical research settings to assess vertebral fracture.

Does dietary protein reduce hip fracture risk in elders? The Framingham Osteoporosis Study

Association between dietary protein and fracture risk is unclear. We examined association between energy-adjusted protein intake and hip fracture risk in elders. The risk of hip fracture was reduced in upper quartiles of protein intake when compared with lowest quartile.

INTRODUCTION

Studies of the association between dietary protein intake and hip fracture risk are conflicting. Therefore, we examined protein intake and hip fracture risk in a population-based group of elderly men and women.

METHODS

Five hundred seventy-six women and 370 men from the Framingham Osteoporosis Study with no previous history of hip fracture completed Food Frequency Questionnaires. Energy-adjusted protein intake was evaluated as a continuous variable and as quartiles. Incidence rates and hazard ratios were calculated, adjusting for age, BMI, sex, and energy intake.

RESULTS

Among 946 participants (mean age 75 years), mean protein intake was found to be 68 gm/d. Increased protein intake was associated with a decreased risk of hip fracture compared to those in the lowest quartile of protein intake (Q2 HR = 0.70, Q3 HR = 0.56, and Q4 HR = 0.63; all p values ≥ 0.044), p for trend was 0.07. When a threshold effect was considered (Q2-4 vs Q1), intakes in the higher quartiles combined were associated with a significantly lower risk for hip fracture (HR = 0.63; p = 0.04).

CONCLUSION

Our results are consistent with reduced risk of hip fracture with higher dietary protein intake. Larger prospective studies are needed to confirm and extend this finding in elderly men and women.

Association of dietary and biochemical measures of vitamin K with quantitative ultrasound of the heel in men and women

INTRODUCTION

Low vitamin K nutritional status is associated with increased fracture risk but is inconsistently related to bone mineral density (BMD), suggesting that vitamin K may affect components of bone strength not measured by BMD, such as microarchitecture. Quantitative ultrasound (QUS) may assess trabecular orientation, providing information on the mechanical properties of bone and may serve as a potential alternative to BMD for gaining insight to the relation between vitamin K and bone strength. We therefore examined the association of vitamin K nutritional status measured in several different ways with QUS in men and women who participated in the Framingham Osteoporosis Study.

METHODS

From 1996 to 2001, broadband ultrasound attenuation (BUA) and speed of sound (SOS) of the calcaneus (heel) were measured in 583 men and 768 women (mean age 59 years). Vitamin K nutritional status was assessed between 1995 and 1998 by three separate measures: plasma phylloquinone concentration, serum percent undercarboxylated osteocalcin (%ucOC) and dietary vitamin K intake. Multiple linear regression analyses were used to calculate regression coefficients in order to evaluate the associations between both measures of QUS and each measure of vitamin K nutritional status. Regression analyses were conducted separately for subgroups of participants defined by gender, menopause status and current use of estrogen replacement medication.

RESULTS

Among the men, plasma phylloquinone concentration was positively associated with both BUA (P<0.01) and SOS (P=0.02) of the heel. Neither serum %ucOC nor dietary vitamin K intake, however, was associated with QUS measures. Among women, none of the three measures of vitamin K nutritional status were associated with either BUA or SOS, regardless of menopause status or use of estrogen. Although QUS is associated with vitamin K nutritional status in men, the observed relation was not consistent among subgroups of participants.

CONCLUSION

These findings suggest that QUS may not be the best method for elucidating the role of vitamin K on the skeleton.

Insulin-like growth factor binding proteins 4 and 5 and bone mineral density in elderly men and women

Insulin-like growth factor-1 (IGF-I) plays a central role in the maintenance of bone mass. To test whether two major IGF-I binding proteins, IGFBP-4 and IGFBP-5, are related to bone mineral density (BMD), we studied a sample of the Framingham Offspring Cohort participants (99 men and 101 women, ages 60-87). Serum levels of IGF-I, IGFBP-4, and IGFBP-5 were measured by previously validated radioimmunoassays (CVs approximately 10%). BMDs of the proximal femur and lumbar spine were measured using a Lunar DPX-L densitometer. In males, but not females, IGF-I and IGFBP-5 were inversely associated with age (r = 0.34 and r = -0.28, respectively; P <0.01), while IGFBP-4 levels were positively associated with age (P <0.01). Multivariate means for BMD (adjusted for age, body mass index, height, smoking, and in women, estrogen use) were computed across quartiles of IGFBP-4 and IGFBP-5 and IGFBP-4/IGFBP-5 ratio. In women, but not men, IGFBP-5 was positively associated with femoral neck BMD (P = 0.03), however, after statistical adjustment for IGF-I, this association was no longer significant. No other associations were observed for BMD at any other site. Further study is necessary for elucidation of the gender differences in the possible influence of IGF system components on bone mass.

Can metacarpal cortical area predict the occurrence of hip fracture in women and men over 3 decades of follow-up? Results from the Framingham Osteoporosis Study

The purpose of this study was to determine if a single measurement of metacarpal cortical area could predict the subsequent risk of hip fracture over a long-term follow-up period. Thirteen hundred eighty-six women and 1014 men (mean age [+/- SD] 61 +/- 8 years) underwent posteroanterior hand radiography between 1966 and 1970 as part of the Framingham Study. Measurements of cortical bone width (external width and medullary width) were made at the midpoint of the second metacarpal with a digital caliper to the nearest 0.1 mm. Hip fracture occurrence was ascertained on all survivors through December 1995. Surprisingly, in women, there was no significant increase in hip fracture according to metacarpal cortical area measurements (per SD decrease) in either age-adjusted (hazard ratio [HR] = 1.13; 95% CI, 0.94-1.35) or multivariate-adjusted models (HR = 1.06; 95% CI, 0.88-1.27). The same results were seen when considering only those women who were > or = 65 years of age at the time of their X-ray or when considering only the first 10 years of follow-up. When the type of hip fracture was considered in women, after adjustment for other risk factors, there appeared to be an association between metacarpal cortical area and intertrochanteric fracture risk (HR = 1.24; 95% CI, 0.91-1.71) but not femoral neck fracture risk (HR = 0.93; 95% CI, 0.71-1.22). In men, the age-adjusted risk of hip fracture was increased modestly per SD decrease in metacarpal cortical area (HR = 1.38; 95% CI, 1.02-1.87), and this remained true after adjustment for potential confounders. In this prospective cohort study with up to 30 years of follow-up, metacarpal cortical area in men predicted hip fracture risk. In women, the only association between metacarpal cortical area and fracture risk was observed for intertrochanteric fractures and was not significant when adjusting for multiple potential confounders. We conclude that this peripheral measure of bone status is not a potent predictor of hip fracture over a long period of follow-up.

Predicting fractures using bone mineral density: a prospective study of long-term care residents

Bone mineral density (BMD) has been shown to predict fracture risk in community-dwelling older persons; however, no comparable prospective study has been performed in the long-term care setting where the role of BMD testing is uncertain. To determine the ability of a single BMD measurement to predict the risk of subsequent fracture in long-term care residents, we designed a prospective study in a 725-bed long-term care facility. A total of 252 Caucasian nursing home residents (mean age 88 years, 74% women) were recruited between 1992 and 1998. BMD of the hip, radius or both sites was measured using dual-energy X-ray absorptiometry. Participants were followed through September 1999 for the occurrence of fracture. Cox proportional hazards regression models were constructed to determine the relationship between BMD and the risk of fracture controlling for potentially confounding variables. Sixty-three incident osteoporotic fractures occurred during a median follow-up time of 2.3 years. The multivariate-adjusted risk of fracture for each standard deviation decrease in BMD was 2.82 (95% CI 1.81-4.42) at the total hip, 2.79 (95% CI 1.69-4.61) at the femoral neck, 2.26 (95% CI 1.51-3.38) at the trochanter, 1.83 (95% CI 1.14-2.94) at the radial shaft and 1.84 (95% CI 1.21-2.80) at the ultradistal radius. Subjects in the lowest age-specific quartile of femoral neck BMD had over 4 times the incidence of fracture compared with those in the highest quartile. BMD at either hip or radius was a predictor of osteoporotic fracture, although in women, radial BMD did not predict fracture. Knowledge of BMD in long-term care residents provides important information on subsequent fracture risk.