Year: 2014
Type: dissertation
Study design: Observational Study
Abstract: Measurement of bone mineral density (BMD, g/cm 2 ) by dual-energy X-ray absorptiometry (DXA) is the clinical golden standard technique with which to diagnose osteoporosis.In general, overweight is considered to confer protection against from osteoporosis and conversely underweight is considered as a major risk factor for osteoporosis and lowenergy fractures.Many biological mechanisms have been proposed to explain this positive relationship between adiposity and bone tissue.However, the strong connection between DXA-measured BMD and anthropometric parameters has been called into some question due to the systematic errors inherent in planar DXA technology.The present thesis evaluated the effects of adiposity on DXA and quantitative ultrasound (QUS) measurements in postmenopausal women.This study population consisted of stratified samples from both the Kuopio Osteoporosis Risk Factor and Prevention study (OSTPRE) and its Fracture Prevention substudy (OSTPRE-FPS) study cohorts.Eighty-nine women were measured twice with two different DXA devices in a cross-calibration study.In addition 139 women were measured cross-sectionally with QUS, peripheral DXA (pDXA) and central DXA devices.The effect of central obesity on BMD values was studied on a sample of 198 women.The association between progress of bone loss and obesity was studied in a sample of 300 women, who underwent BMD and body mass index (BMI) measurements three times during a mean follow-up of 10.5 years.There were systematic differences between the measurement values of two pencil-beam DXA densitometers (DPX and DPX-IQ) from the same manufacturer, although their correlation was high.The DPX measured BMD values were higher for lumbar spine and Ward's triangle, whereas femoral neck BMD results were lower compared to DPX-IQ.In all regions of interests (ROI), the regression slope was significantly different from unity, thus demonstrating the need for cross-calibration between the two densitometers.With most ROI's, except for lumbar spine, the performance of the two devices was also found to depend on BMI or weight, thus affecting correction equations during cross-calibration.A positive trend, although not always statistically significant, was found between the body size (height) and most of the measured QUS and DXA bone parameters.DXA, pDXA and QUS parameters were differently affected by adiposity.Thus, higher heel and lumbar spine BMD values were observed with increasing adiposity, whereas femoral neck BMD values and some of the QUS parameters were less affected by adiposity.There were inconsistencies between the study population-based normalized values (z-scores) and the manufacturer provided T-score values between the different devices.DXA measured trunk fat and weight were the strongest determinants of postmenopausal lumbar spine and femoral neck BMD, respectively.DXA-measured trunk fat was positively
Author: J. Saarelainen
Language: English
Subfield: Orthopedics and Sports Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W3095297637